A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it runs out of water, or only flow during certain seasons. Rivers are regulated by the water cycle, the processes by which water moves around the Earth. Water first enters rivers through precipitation, whether from rainfall, the runoff of water down a slope, the melting of glaciers or snow, or seepage from aquifers beneath the surface of the Earth.
Rivers flow in channeled watercourses and merge in confluences to form drainage basins, areas where surface water eventually flows to a common outlet. Rivers have a great effect on the landscape around them. They may regularly overflow their banks and flood the surrounding area, spreading nutrients to the surrounding area. Sediment or alluvium carried by rivers shapes the landscape around it, forming deltas and islands where the flow slows down. Rivers rarely run in a straight line, instead, they bend or meander; the locations of a river’s banks can change frequently. Rivers get their alluvium from erosion, which carves rock into canyons and valleys.
Rivers have sustained human and animal life for millennia, including the first human civilizations. The organisms that live around or in a river such as fish, aquatic plants, and insects have different roles, including processing organic matter and predation. Rivers have produced abundant resources for humans, including food, transportation, drinking water, and recreation. Humans have engineered rivers to prevent flooding, irrigate crops, perform work with water wheels, and produce hydroelectricity from dams. People associate rivers with life and fertility and have strong religious, political, social, and mythological attachments to them.
Rivers and river ecosystems are threatened by water pollution, climate change, and human activity. The construction of dams, canals, levees, and other engineered structures has eliminated habitats, has caused the extinction of some species, and lowered the amount of alluvium flowing through rivers. Decreased snowfall from climate change has resulted in less water available for rivers during the summer. Regulation of pollution, dam removal, and sewage treatment have helped to improve water quality and restore river habitats.
A river is a natural flow of freshwater that flows on or through land towards another body of water downhill.[1] This flow can be into a lake, an ocean, or another river.[1] A stream refers to water that flows in a natural channel, a geographic feature that can contain flowing water.[2] A stream may also be referred to as a watercourse.[2] The study of the movement of water as it occurs on Earth is called hydrology, and their effect on the landscape is covered by geomorphology.[2]
Source and drainage basin
The major drainage basins in North America
Rivers are part of the water cycle, the continuous processes by which water moves about Earth.[3] This means that all water that flows in rivers must ultimately come from precipitation.[3] The sides of rivers have land that is at a higher elevation than the river itself, and in these areas, water flows downhill into the river.[4] The headwaters of a river are the smaller streams that feed a river, and make up the river’s source.[4] These streams may be small and flow rapidly down the sides of mountains.[5] All of the land uphill of a river that feeds it with water in this way is in that river’s drainage basin or watershed.[4] A ridge of higher elevation land is what typically separates drainage basins; water on one side of a ridge will flow into one set of rivers, and water on the other side will flow into another.[4] One example of this is the Continental Divide of the Americas in the Rocky Mountains. Water on the western side of the divide flows into the Pacific Ocean, whereas water on the other side flows into the Atlantic Ocean.[4]
Not all precipitation flows directly into rivers; some water seeps into underground aquifers.[3] These, in turn, can still feed rivers via the water table, the groundwater beneath the surface of the land stored in the soil. Water flows into rivers in places where the river’s elevation is lower than that of the water table.[3] This phenomenon is why rivers can still flow even during times of drought.[3] Rivers are also fed by the melting of snowglaciers present in higher elevation regions.[3] In summer months, higher temperatures melt snow and ice, causing additional water to flow into rivers. Glacier melt can supplement snow melt in times like the late summer, when there may be less snow left to melt, helping to ensure that the rivers downstream of the glaciers have a continuous supply of water.[3]
The flow of rivers
Rivers flow downhill, with their direction determined by gravity.[6] A common misconception holds that all or most rivers flow from North to South, but this is not true.[6] As rivers flow downstream, they eventually merge to form larger rivers. A river that feeds into another is a tributary, and the place they meet is a confluence.[4] Rivers must flow to lower altitudes due to gravity.[3] The bed of a river is typically within a river valley between hills or mountains. Rivers flowing through an impermeable section of land such as rocks will erode the slopes on the sides of the river.[7] When a river carves a plateau or a similar high-elevation area, a canyon can form, with cliffs on either side of the river.[8][4] Areas of a river with softer rock weather faster than areas with harder rock, causing a difference in elevation between two points of a river. This can cause the formation of a waterfall as the river’s flow falls down a vertical drop.[9]
A river in a permeable area does not exhibit this behavior and may even have raised banks due to sediment.[7] Rivers also change their landscape through their transportation of sediment, often known as alluvium when applied specifically to rivers.[10][7] This debris comes from erosion performed by the rivers themselves, debris swept into rivers by rainfall, as well as erosion caused by the slow movement of glaciers. The sand in deserts and the sediment that forms bar islands is from rivers.[10] The particle size of the debris is gradually sorted by the river, with heavier particles like rocks sinking to the bottom, and finer particles like sand or silt carried further downriver. This sediment may be deposited in river valleys or carried to the sea.[7]
The sediment yield of a river is the quantity of sand per unit area within a watershed that is removed over a period of time.[11] The monitoring of the sediment yield of a river is important for ecologists to understand the health of its ecosystems, the rate of erosion of the river’s environment, and the effects of human activity.[11]
The Nile in Egypt is known for its fertile floodplains, which flood annually.
Rivers rarely run in a straight direction, instead preferring to bend or meander.[10] This is because any natural impediment to the flow of the river may cause the current to deflect in a different direction. When this happens, the alluvium carried by the river can build up against this impediment, redirecting the course of the river. The flow is then directed against the opposite bank of the river, which will erode into a more concave shape to accommodate the flow. The bank will still block the flow, causing it to reflect in the other direction. Thus, a bend in the river is created.[7]
Rivers may run through low, flat regions on their way to the sea.[12] These places may have floodplains that are periodically flooded when there is a high level of water running through the river. These events may be referred to as “wet seasons’ and “dry seasons” when the flooding is predictable due to the climate.[12] The alluvium carried by rivers, laden with minerals, is deposited into the floodplain when the banks spill over, providing new nutrients to the soil, allowing them to support human activity like farming as well as a host of plant and animal life.[12][4] Deposited sediment from rivers can form temporary or long-lasting fluvial islands.[13] These islands exist in almost every river.[13]
Non-perennial rivers
About half of all waterways on Earth are intermittent rivers, which do not always have a continuous flow of water throughout the year.[14] This may be because an arid climate is too dry depending on the season to support a stream, or because a river is seasonally frozen in the winter (such as in an area with substantial permafrost), or in the headwaters of rivers in mountains, where snowmelt is required to fuel the river.[14] These rivers can appear in a variety of climates, and still provide a habitat for aquatic life and perform other ecological functions.[14]
Subterranean rivers
The Blue Water Cave in Quezon, Philippines features an underground river.
Subterranean rivers may flow underground through flooded caves.[15] This can happen in karst systems, where rock dissolves to form caves. These rivers provide a habitat for diverse microorganisms and have become an important target of study by microbiologists.[15] Other rivers and streams have been covered over or converted to run in tunnels due to human development.[16] These rivers do not typically host any life, and are often used only for stormwater or flood control.[16] One such example is the Sunswick Creek in New York City, which was covered in the 1800s and now exists only as a sewer-like pipe.[16]
The terminus
The Lena river delta in Russia is formed from the river’s sediment.
While rivers may flow into lakes or man-made features such as reservoirs, the water they contain will always tend to flow down toward the ocean.[3] However, if human activity siphons too much water away from a river for other uses, the riverbed may run dry before reaching the sea.[3] The outlets mouth of a river can take several forms. Tidal rivers (often part of an estuary) have their levels rise and fall with the tide.[3] Since the levels of these rivers are often already at or near sea level, the flow of alluvium and the brackish water that flows in these rivers may be either upriver or downriver depending on the time of day.[7]
Rivers that are not tidal may form deltas that continuously deposit alluvium into the sea from their mouths.[7] Depending on the activity of waves, the strength of the river, and the strength of the tidal current, the sediment can accumulate to form new land.[17] When viewed from above, a delta can appear to take the form of several triangular shapes as the river mouth appears to fan out from the original coastline.[17]
A diagram of a possible river with the Strahler number of each tributary labeled.
In hydrology, a stream order is a positive integer used to describe the level of river branching in a drainage basin.[18] Several systems of stream order exist, one of which is the Strahler number. In this system, the first tributaries of a river are 1st order rivers. When two 1st order rivers merge, the resulting river is 2nd order. If a river of a higher order and a lower order merge, the order is incremented from whichever of the previous rivers had the higher order.[18] Stream order is correlated with and thus can be used to predict certain data points related to rivers, such as the size of the drainage basin (drainage area), and the length of the channel.[18]
Ecology
Models
River Continuum Concept
The headwaters of the River Wey in England provide organic matter for organisms to process.
The ecosystem of a river includes the life that lives in its water, on its banks, and in the surrounding land.[19] The width of the channel of a river, its velocity, and how shaded it is by nearby trees. Creatures in a river ecosystem may be divided into many roles based on the River Continuum Concept. “Shredders” are organisms that consume this organic material. The role of a “grazer” or “scraper” organism is to feed on the algae that collects on rocks and plants. “Collectors” consume the detritus of dead organisms. Lastly, predators feed on living things to survive.[19]
The river can then be modeled by the availability of resources for each creature’s role. A shady area with deciduous trees might experience frequent deposits of organic matter in the form of leaves. In this type of ecosystem, collectors and shredders will be most active.[19] As the river becomes deeper and wider, it may move slower and receive more sunlight. This supports invertebrates and a variety of fish, as well as scrapers feeding on algae.[20] Further downstream, the river may get most of its energy from organic matter that was already processed upstream by collectors and shredders. Predators may be more active here, including fish that feed on plants, plankton, and other fish.[20]
Flood pulse concept
This marsh is a floodplain of the Narew in Poland.
The flood pulse concept focuses on habitats that flood seasonally, including lakes and marshes. The land that interfaces with a water body is that body’s riparian zone. Plants in the riparian zone of a river help stabilize its banks to prevent erosion and filter alluvium deposited by the river on the shore, including processing the nitrogen and other nutrients it contains. Forests in a riparian zone also provide important animal habitats.[19]
Fish zonation concept
River ecosystems have also been categorized based on the variety of aquatic life they can sustain, also known as the fish zonation concept.[21] Smaller rivers can only sustain smaller fish that can comfortably fit in its waters, whereas larger rivers can contain both small fish and large fish. This means that larger rivers can host a larger variety of species.[21] This is analogous to the species-area relationship, the concept of larger habitats being host to more species. In this case, it is known as the species-discharge relationship, referring specifically to the discharge of a river, the amount of water passing through it at a particular time.[21]
Movement of organisms
The flow of a river can act as a means of transportation for plant and animal species, as well as a barrier. For example, the Amazon River is so wide in parts that the variety of species on either side of its basin are distinct.[19] Some fish may swim upstream to spawn as part of a seasonal migration. Species that travel from the sea to breed in freshwater rivers are anadromous. Salmon are an anadromous fish that may die in the river after spawning, contributing nutrients back to the river ecosystem.[19]
This levee protects the city of Honghu in the Hubei province of China from flooding.
Modern river engineering involves a large-scale collection of independent river engineering structures that have the goal of flood control, improved navigation, recreation, and ecosystem management.[22] Many of these projects have the effect of normalizing the effects of rivers; the greatest floods are smaller and more predictable, and larger sections are open for navigation by boats and other watercraft.[22] A major effect of river engineering has been a reduced sediment output of large rivers. For example, the Mississippi River produced 400 million tons of sediment per year.[22] Due to the construction of reservoirs, sediment buildup in man-made levees, and the removal of natural banks replaced with revetments, this sediment output has been reduced by 60%.[22]
The most basic river projects involve the clearing of obstructions like fallen trees. This can scale up to dredging, the excavation of sediment buildup in a channel, to provide a deeper area for navigation.[22] These activities require regular maintenance as the location of the river banks changes over time, floods bring foreign objects into the river, and natural sediment buildup continues.[22] Artificial channels are often constructed to “cut off” winding sections of a river with a shorter path, or to direct the flow of a river in a straighter direction.[22] This effect, known as channelization, has made the distance required to traverse the Missouri River in 116 kilometres (72 mi) shorter.[22]
Dikes are channels built perpendicular to the flow of the river beneath its surface. These help rivers flow straighter by increasing the speed of the water at the middle of the channel, helping to control floods.[22] Levees are also used for this purpose. They can be thought of as dams constructed on the sides of rivers, meant to hold back water from flooding the surrounding area during periods of high rainfall. They are often constructed by building up the natural terrain with soil or clay.[22] Some levees are supplemented with floodways, channels used to redirect floodwater away from farms and populated areas.[22]
Dams restrict the flow of water through a river. They can be built for navigational purposes, providing a higher level of water upstream for boats to travel in. They may also be used for hydroelectricity, or power generation from rivers.[22] Dams typically transform a section of the river behind them into a lake or reservoir. This can provide nearby cities with a predictable supply of drinking water. Hydroelectricity is desirable as a form of renewable energy that does not require any inputs beyond the river itself.[23] Dams are very common worldwide, with at least 75,000 higher than 6 feet (1.8 m) in the U.S. Globally, reservoirs created by dams cover 193,500 square miles (501,000 km2).[23] Dam-building reached a peak in the 1970s, when between two or three dams were completed every day, and has since begun to decline. New dam projects are primarily focused in China, India, and other areas in Asia.[24]
History
The Sumerian civilization was made possible by the floodplains of the Tigris and Euphrates rivers.
Pre-industrial era
The first civilizations of Earth were born on floodplains between 5,500 and 3,500 years ago.[19] The freshwater, fertile soil, and transportation provided by rivers helped create the conditions for complex societies to emerge. Three such civilizations were the Sumerians in the Tigris–Euphrates river system, the Ancient Egyptian civilization in the Nile, and the Indus Valley Civilization on the Indus River.[19][25] The desert climates of the surrounding areas made these societies especially reliant on rivers for survival, leading to people clustering in these areas to form the first cities.[26] It is also thought that these civilizations were the first to organize the irrigation of desert environments for growing food.[26] Growing food at scale allowed people to specialize in other roles, form hierarchies, and organize themselves in new ways, leading to the birth of civilization.[26]
The counterweight system of the shadoof is an early example of the engineering of river water.
In pre-industrial society, rivers were a source of transportation and abundant resources.[19][26] Many civilizations depended on what resources were local to them to survive. Shipping of commodities, especially the floating of wood on rivers to transport it, was especially important. Rivers also were an important source of drinking water. For civilizations built around rivers, fish were an important part of the diet of humans.[26] Some rivers supported fishing activities, but were ill-suited to farming, such as those in the Pacific Northwest.[26] Other animals that live in or near rivers like frogs, mussels, and beavers could provide food and valuable goods such as fur.[19]
Humans have been building infrastructure to use rivers for thousands of years.[19] The Sadd el-Kafara dam near Cairo, Egypt, is an ancient dam built on the Nile 4,500 years ago. The Ancient Roman civilization used aqueducts to transport water to urban areas. Spanish Muslims used mills and water wheels beginning in the seventh century. Between 130 and 1492, larger dams were built in Japan, Afghanistan, and India, including 20 dams higher than 15 metres (49 ft).[19] Canals began to be cut in Egypt as early as 3000 BC, and the mechanical shadoof began to be used to raise the elevation of water.[26] Drought years harmed crop yields, and leaders of society were incentivized to ensure regular water and food availability to remain in power. Engineering projects like the shadoof and canals could help prevent these crises.[26] Despite this, there is evidence that floodplain-based civilizations may have been abandoned occasionally at a large scale. This has been attributed to unusually large floods destroying infrastructure; however, there is evidence that permanent changes to climate causing higher aridity and lower river flow may have been the determining factor in what river civilizations succeeded or dissolved.[26]
The Cochecho mill in Dover, New Hampshire, United States was a textile mill powered by the pictured hydroelectric dam.
Water wheels began to be used at least 2,000 years ago to harness the energy of rivers.[19] Water wheels turn an axle that can supply rotational energy to move water into aqueducts, work metal using a trip hammer, and grind grains with a millstone. In the Middle Ages, water mills began to automate many aspects of manual labor, and spread rapidly. By 1300, there were at least 10,000 mills in England alone. A medieval watermill could do the work of 30–60 human workers.[19] Water mills were often used in conjunction with dams to focus and increase the speed of the water.[19] Water wheels continued to be used up to and through the Industrial Revolution as a source of power for textile mills and other factories, but were eventually supplanted by steam power.[19]
Industrial era
The barge is one of the primary means of shipping goods on the Mississippi and other rivers.The Tiber river in Rome near the Ponte Sant’Angelo, Italy
Rivers became more industrialized with the growth of technology and the human population.[19] As fish and water could be brought from elsewhere, and goods and people could be transported via railways, pre-industrial river uses diminished in favor of more complex uses. This meant that the local ecosystems of rivers needed less protection as humans became less reliant on them for their continued flourishing. River engineering began to develop projects that enabled industrial hydropower, canals for the more efficient movement of goods, as well as projects for flood prevention.[19][24]
River transportation has historically been significantly cheaper and faster than transportation by land.[19] Rivers helped fuel urbanization as goods such as grain and fuel could be floated downriver to supply cities with resources.[27] River transportation is also important for the lumber industry, as logs can be shipped via river. Countries with dense forests and networks of rivers like Sweden have historically benefited the most from this method of trade. The rise of highways and the automobile has made this practice less common.[19]
The Canal du Midi was one of the first large canal projects in the world.
One of the first large canals was the Canal du Midi, connecting rivers within France to create a path from the Atlantic Ocean to the Mediterranean Sea.[24] The nineteenth century saw canal-building become more common, with the U.S. building 4,400 miles (7,100 km) of canals by 1830. Rivers began to be used by cargo ships at a larger scale, and these canals were used in conjunction with river engineering projects like dredging and straightening to ensure the efficient flow of goods.[24] One of the largest such projects is that of the Mississippi River, whose drainage basin covers 40% of the contiguous United States. The river was then used for shipping crops from the American Midwest and cotton from the American South to other states as well as the Atlantic Ocean.[24]
The role of urban rivers has evolved from when they were a center of trade, food, and transportation to modern times when these uses are less necessary.[27] Rivers remain central to the cultural identity of cities and nations. Famous examples include the River Thames‘s relationship to London, the Seine to Paris, and the Hudson River to New York City.[27] The restoration of water quality and recreation to urban rivers has been a goal of modern administrations. For example, swimming was banned in the Seine for over 100 years due to concerns about pollution and the spread of E. coli, until cleanup efforts to allow its use in the 2024 Summer Olympics.[28] Another example is the restoration of the Isar in Munich from being a fully canalized channel with hard embankments to being wider with naturally sloped banks and vegetation.[29] This has improved wildlife habitat in the Isar, and provided more opportunities for recreation in the river.[29]
As a natural barrier, rivers are often used as a border between countries, cities, and other territories.[25] For example, the Lamari River in New Guinea separates the Angu and the Fore people in New Guinea. The two cultures speak different languages and rarely mix.[19] 23% of international borders are large rivers (defined as those over 30 meters wide).[25] The traditional northern border of the Roman Empire was the Danube, a river that today forms the border of Hungary and Slovakia. Since the flow of a river is rarely static, the exact location of a river border may be called into question by countries.[19] The Rio Grande between the United States and Mexico is regulated by the International Boundary and Water Commission to manage the right to fresh water from the river, as well as mark the exact location of the border.[19]
Up to 60% of fresh water used by countries comes from rivers that cross international borders.[19] This can cause disputes between countries that live upstream and downstream of the river. A country that is downstream of another may object to the upstream country diverting too much water for agricultural uses, pollution, as well as the creation of dams that change the river’s flow characteristics.[19] For example, Egypt has an agreement with Sudan requiring a specific minimum volume of water to pass into the Nile yearly over the Aswan Dam, to maintain both countries access to water.[19]
The Ogun River in Nigeria is sacred to the Yoruba.
The importance of rivers throughout human history has given them an association with life and fertility. They have also become associated with the reverse, death and destruction, especially through floods. This power has caused rivers to have a central role in religion, ritual, and mythology.[19]
In Greek mythology, the underworld is bordered by several rivers.[19] Ancient Greeks believed that the souls of those who perished had to be borne across the River Styx on a boat by Charon in exchange for money.[19] Souls that were judged to be good were admitted to Elysium and permitted to drink water from the River Lethe to forget their previous life.[19] Rivers also appear in descriptions of paradise in Abrahamic religions, beginning with the story of Genesis.[19] A river beginning in the Garden of Eden waters the garden and then splits into four rivers that flow to provide water to the world. These rivers include the Tigris and Euphrates, and two rivers that are possibly apocryphal but may refer to the Nile and the Ganges.[19] The Quran describes these four rivers as flowing with water, milk, wine, and honey, respectively.[19]
The book of Genesis also contains a story of a great flood.[19] Similar myths are present in the Epic of Gilgamesh, Sumerian mythology, and in other cultures.[19][30] In Genesis, the flood’s role was to cleanse Earth of the wrongdoing of humanity. The act of water working to cleanse humans in a ritualistic sense has been compared to the Christian ritual of baptism, famously the Baptism of Jesus in the Jordan River.[19] Floods also appear in Norse mythology, where the world is said to emerge from a void that eleven rivers flowed into. Aboriginal Australian religion and Mesoamerican mythology also have stories of floods, some of which contain no survivors, unlike the Abrahamic flood.[19]
The ghats along the Ganges river are the steps that allow people to bathe and release the ashes of the dead.[31]
Along with mythological rivers, religions have also cared for specific rivers as sacred rivers.[19] The Ancient Celtic religion saw rivers as goddesses. The Nile had many gods attached to it. The tears of the goddess Isis were said to be the cause of the river’s yearly flooding, itself personified by the goddess Hapi. Many African religions regard certain rivers as the originator of life. In Yoruba religion, Yemọja rules over the Ogun River in modern-day Nigeria and is responsible for creating all children and fish.[19] Some sacred rivers have religious prohibitions attached to them, such as not being allowed to drink from them or ride in a boat along certain stretches. In these religions, such as that of the Altai in Russia, the river is considered a living being that must be afforded respect.[19]
Rivers are some of the most sacred places in Hinduism.[19] There is archeological evidence that mass ritual bathing in rivers at least 5,000 years ago in the Indus river valley.[19] While most rivers in India are revered, the Ganges is most sacred.[31] The river has a central role in various Hindu myths, and its water is said to have properties of healing as well as absolution from sins.[19] Hindus believe that when the cremated remains of a person is released into the Ganges, their soul is released from the mortal world.[31]
Threats
The Colorado River now runs dry in the deserts of Mexico, rather than running to the sea, due to diversion of water for agricultural uses.[32]
Freshwater fish make up 40% of the world’s fish species, but 20% of these species are known to have gone extinct in recent years.[33] Human uses of rivers make these species especially vulnerable.[33] Dams and other engineered changes to rivers can block the migration routes of fish and destroy habitats.[34] Rivers that flow freely from headwaters to the sea have better water quality, and also retain their ability to transport nutrient-rich alluvium and other organic material downstream, keeping the ecosystem healthy.[34] The creation of a lake changes the habitat of that portion of water, and blocks the transportation of sediment, as well as preventing the natural meandering of the river.[23] Dams block the migration of fish such as salmon for which fish ladder and other bypass systems have been attempted, but these are not always effective.[23]
Pollution from factories and urban areas can also damage water quality.[33][27] “Per- and polyfluoroalkyl substances (PFAS) is a widely used chemical that breaks down at a slow rate.[35] It has been found in the bodies of humans and animals worldwide, as well as in the soil, with potentially negative health effects.[35] Research into how to remove it from the environment, and how harmful exposure is, is ongoing.[35]Fertilizer from farms can lead to a proliferation of algae on the surface of rivers and oceans, which prevents oxygen and light from dissolving into water, making it impossible for underwater life to survive in these so-called dead zones.[22]
Urban rivers are typically surrounded by impermeable surfaces like stone, asphalt, and concrete.[19] Cities often have storm drains that direct this water to rivers. This can cause flooding risk as large amounts of water are directed into the rivers. Due to these impermeable surfaces, these rivers often have very little alluvium carried in them, causing more erosion once the river exits the impermeable area.[19] It has historically been common for sewage to be directed directly to rivers via sewer systems without being treated, along with pollution from industry. This has resulted in a loss of animal and plant life in urban rivers, as well as the spread of waterborne diseases such as cholera.[19] In modern times, sewage treatment and controls on pollution from factories have improved the water quality of urban rivers.[19]
Climate change can change the flooding cycles and water supply available to rivers.[33] Floods can be larger and more destructive than expected, causing damage to the surrounding areas. Floods can also wash unhealthy chemicals and sediment into rivers.[34]Droughts can be deeper and longer, causing rivers to run dangerously low.[33] This is in part because of a projected loss of snowpack in mountains, meaning that melting snow can’t replenish rivers during warm summer months, leading to lower water levels.[34] Lower-level rivers also have warmer temperatures, threatening species like salmon that prefer colder upstream temperatures.[34]
Attempts have been made to regulate the exploitation of rivers to preserve their ecological functions.[33] Many wetland areas have become protected from development. Water restrictions can prevent the complete draining of rivers. Limits on the construction of dams, as well as dam removal, can restore the natural habitats of river species.[23] Regulators can also ensure regular releases of water from dams to keep animal habitats supplied with water.[23] Limits on pollutants like pesticides can help improve water quality.[33]
Extraterrestrial rivers
A dried out network of river valleys on Mars
Today, the surface of Mars does not have liquid water. All water on Mars is part of permafrost ice caps, or trace amounts of water vapor in the atmosphere.[36] However, there is evidence that rivers flowed on Mars for at least 100,000 years.[37] The Hellas Planitia is a crater left behind by an impact from an asteroid. It has sedimentary rock that was formed 3.7 billion years ago, and lava fields that are 3.3 billion years old.[37] High resolution images of the surface of the plain show evidence of a river network, and even river deltas.[37][38] These images reveal channels formed in the rock, recognized by geologists who study rivers on Earth as being formed by rivers,[37] as well as “bench and slope” landforms, outcroppings of rock that show evidence of river erosion. Not only do these formations suggest that rivers once existed, but that they flowed for extensive time periods, and were part of a water cycle that involved precipitation.[37]
The term flumen, in planetary geology, refers to channels on Saturn‘s moon Titan that may carry liquid.[39][40] Titan’s rivers flow with liquid methane and ethane. There are river valleys that exhibit wave erosion, seas, and oceans.[40] Scientists hope to study these systems to see how coasts erode without the influence of human activity, something that isn’t possible when studying terrestrial rivers.[40]
The first settlers of Australia, New Guinea, and the large islands just to the east arrived more than 60,000 years ago.[13] Oceania was first explored by Europeans from the 16th century onward. Portuguese explorers, between 1512 and 1526, reached the Tanimbar Islands, some of the Caroline Islands and west New Guinea. Spanish and Dutch explorers followed, then British and French. On his first voyage in the 18th century, James Cook, who later arrived at the highly developed Hawaiian Islands, went to Tahiti and followed the east coast of Australia for the first time.[14] The arrival of European settlers in subsequent centuries resulted in a significant alteration in the social and political landscape of Oceania. The Pacific theatre saw major action during the First and Second World Wars.
Definitions of Oceania vary.[17][18][7] The broadest definition encompasses the many islands between mainland Asia and the Americas.[6][19][20] The island nation of Australia is the only piece of land in the area which is large enough to typically be considered a continent.[21][22][better source needed] The culture of the people who lived on these islands was often distinct from that of Asia and pre-Columbian America.[23] Before Europeans arrived in the area, the sea shielded Australia and south central Pacific islands from cultural influences that spread through large continental landmasses and adjacent islands.[23][24] The islands of the Malay Archipelago, north of Australia, mainly lie on the continental shelf of Asia, and their inhabitants had more exposure to mainland Asian culture as a result of this closer proximity.[23]
Mercator Planisphere by A.-H. Brué (1816), showing Océanie, the Grand Océan and Polynésie including all the islands of the Pacific Ocean
The geographer Conrad Malte-Brun coined the French expression Terres océaniques (Oceanic lands) c. 1804.[25] In 1814 another French cartographer, Adrien-Hubert Brué, coined from this expression the shorter “Océanie”,[26] which derives from the Latin word oceanus, and this from the Greek word ὠκεανός (ōkeanós), “ocean”. The term Oceania is used because, unlike the other continental groupings, it is the ocean that links the parts of the region together.[27] John Eperjesi’s 2005 book The Imperialist Imaginary says that it has “been used by Western cartographers since the mid-19th century to give order to the complexities of the Pacific area.”[28]
In the 19th century, many geographers divided Oceania into mostly racially based subdivisions: Australasia, Malesia (encompassing the Malay Archipelago), Melanesia, Micronesia and Polynesia. The 2011 book Maritime Adaptations of the Pacific, by Richard W. Casteel and Jean-Claude Passeron, states that, “for the purpose of anthropology, Oceania has long been a continent like Africa, Asia and America.”[29] Scottish geographer John Bartholomew wrote in 1873 that, “the New World consists of North America, and the peninsula of South America attached to it. These divisions [are] generally themselves spoken as continents, and to them has been added another, embracing the large island of Australia and numerous others in the [Pacific] Ocean, under the name of Oceania. There are thus six great divisions of the earth — Europe, Asia, Africa, North America, South America and Oceania.”[30] American author Samuel Griswold Goodrich wrote in his 1854 book History of All Nations that, “geographers have agreed to consider the island world of the Pacific Ocean as a third continent, under the name Oceania.” In this book, the other two continents were categorized as being the New World (the Americas) and the Old World (Afro-Eurasia).[31] In his 1879 book Australasia, British naturalist Alfred Russel Wallace commented that, “Oceania is the word often used by continental geographers to describe the great world of islands we are now entering upon” and that “Australia forms its central and most important feature.”[32] He did not explicitly label Oceania a continent in the book, but did note that it was one of the six major divisions of the world.[32]The Oxford Handbook of World History (2011) describes the areas encompassed in Oceania as being “afterthoughts in world history texts, lumped together and included at the end of global surveys as areas largely marginal to the main events of world history”.[33]
In most non-English-speaking countries Oceania is treated as a continent in the sense that it is “one of the parts of the world”, and Australia is only seen as an island nation. In other non-English-speaking countries Australia and Eurasia are thought of as continents, while Asia, Europe, and Oceania are regarded as “parts of the world”.[34][35] Nevertheless, various writers from English-speaking countries have described Oceania as a continent over the years.[36][37][38][39][40][41][42] Prior to the 1950s, before the popularization of the theory of plate tectonics, Antarctica, Australia, and Greenland were sometimes described as island continents, but none were usually taught as one of the world’s continents in the English-speaking countries.[43][44][45] In his 1961 book The United States and the Southwest Pacific, American author Clinton Hartley Grattan commented that, “the use of the word Oceania to cover Australia, New Zealand, and the [Pacific] islands now has a slightly old-fashioned flavor.”[46] Australia is a founding member of the Pacific Islands Forum in 1971, and at times has been interpreted as the largest Pacific island.[47][48] Some geographers group the Australian tectonic plate with others in the Pacific to form a geological continent.[49]National Geographic states that the term Oceania “establishes the Pacific Ocean as the defining characteristic of the continent.”[50] Others have labelled it as the “liquid continent”.[51][52][53] The Pacific Ocean itself has been labelled as a “continent of islands”, and contains approximately 25,000, which is more than all the other major oceans combined.[54][55] In a 1991 article, American archeologist Toni L. Carrell wrote, “the immensity of and great distances within the Pacific Basin often make it difficult to conceptualize the basin as a single earth feature.”[56] Oceania’s subregions of Australasia, Melanesia, Micronesia, and Polynesia cover two major plates; the Australian Plate (also known as the Indo-Australian Plate) and the Pacific Plate, in addition to two minor plates; the Nazca Plate and the Philippine Sea Plate.[57][58] The Australian Plate includes Australia, Fiji, New Caledonia, Papua New Guinea, Vanuatu, and parts of New Zealand.[57][58] The Pacific Plate covers the Solomon Islands and parts of New Zealand, as well as Micronesia (excluding the westernmost islands near the Philippine Sea Plate) and Polynesia (excluding Easter Island).[57][58] The Nazca Plate, which includes Easter Island, neighbours the South American Plate, and is still considered to be a separate tectonic plate, despite only containing a handful of islands.[57][58]
The new terms Near Oceania and Remote Oceania were proposed in 1973 by anthropologists Roger Green and Andrew Pawley. By their definition, Near Oceania consists of New Guinea, the Bismarck Archipelago and the Solomon Islands, with the exception of the Santa Cruz Islands.[59] They are designed to dispel the outdated categories of Melanesia, Micronesia, and Polynesia; many scholars now replace those categories with Green’s terms since the early 1990s, but the old categories are still used in science, popular culture and general usage.[60]
The United Nations (UN) has used its own geopolitical definition of Oceania since its foundation in 1947, which utilizes four of the five subregions from the 19th century: Australasia, Melanesia, Micronesia, and Polynesia. This definition consists of discrete political entities, and so excludes the Bonin Islands, Hawaii, Clipperton Island and the Juan Fernández Islands, along with Easter Island — which was annexed by Chile in 1888.[68] It is used in statistical reports, by the International Olympic Committee, and by many atlases.[69] The UN categorizes Oceania, and by extension the Pacific area, as one of the major continental divisions of the world, along with Africa, Asia, Europe and the Americas. Their definition includes American Samoa, Australia and their external territories, the Cook Islands, Federated States of Micronesia, French Polynesia, Fiji, Guam, Kiribati, the Marshall Islands, Nauru, New Caledonia, New Zealand, Niue, the Northern Mariana Islands, Palau, Papua New Guinea, Pitcairn Islands, Samoa, the Solomon Islands, Tokelau, Tonga, Tuvalu, Vanuatu, Wallis and Futuna, and the United States Minor Outlying Islands (Baker Island, Howland Island, Jarvis Island, Midway Atoll, Palmyra Atoll, and Wake Island).[68] The original UN definition of Oceania from 1947 included these same countries and semi-independent territories, which were mostly still colonies at that point.[70] Hawaii had not yet become a U.S. state in 1947, and as such was part of the original UN definition of Oceania. The island states of Indonesia, Japan, the Philippines, Singapore and Taiwan, all located within the bounds of the Pacific or associated marginal seas, are excluded from the UN definition. The states of Hong Kong and Malaysia, located in both mainland Asia and marginal seas of the Pacific, are also excluded, as are Brunei, East Timor and Indonesian New Guinea/Western New Guinea.[71][72]The CIA World Factbook also categorizes Oceania as one of the major continental divisions of the world, but the name “Australia and Oceania” is used. Their definition does not include all of Australia’s external territories, but is otherwise the same as the UN’s definition, and is also used for statistical purposes.[73] The Pacific Islands Forum expanded during the early 2010s, and areas that were already included in the UN definition of Oceania, such as French Polynesia, gained membership.[74]
A German map of Oceania from 1884, showing the region to encompass Australia and all islands between Asia and Latin America
French writer Gustave d’Eichthal remarked in 1844 that, “the boundaries of Oceania are in reality those of the great ocean itself.”[75]Conrad Malte-Brun in 1824 defined Oceania as covering Australia, New Zealand, the islands of Polynesia (which then included all the Pacific islands) and the Malay Archipelago.[76][77] American lexicographerJoseph Emerson Worcester wrote in 1840 that Oceania is “a term applied to a vast number of islands which are widely dispersed in the Pacific Ocean […] they are considered as forming a fifth grand division of the world.” He also viewed Oceania as covering Australia, New Zealand, the Malay Archipelago and the islands of Melanesia, Micronesia, and Polynesia.[78] In 1887, the Royal Asiatic Society of Great Britain and Ireland referred to Australia as the area’s westernmost land,[79] while in 1870, British Reverend Alexander Mackay identified the Bonin Islands as its northernmost point, and Macquarie Island as its southernmost point.[80] The Bonin Islands at that time were a possession of Britain; Macquarie Island, to the south of Tasmania, is a subantarctic island in the Pacific. It was politically associated with Australia and Tasmania by 1870.[81]
Alfred Russel Wallace believed in 1879 that Oceania extended to the Aleutian Islands, which are among the northernmost islands of the Pacific.[32] The islands, now politically associated with Alaska, have historically had inhabitants that were related to Indigenous Americans, in addition to having non-tropical biogeography similar to that of Alaska and Siberia.[82][83] Wallace insisted while the surface area of this wide definition was greater than that of Asia and Europe combined, the land area was only a little greater than that of Europe.[32] American geographer Sophia S. Cornell claimed that the Aleutian Islands were not part of Oceania in 1857.[84] She stated that Oceania was divided up into three groups; Australasia (which included Australia, New Zealand, and the Melanesian islands), Malesia (which included all present-day countries within the Malay Archipelago, not the modern country of Malaysia) and Polynesia (which included both the Polynesian and Micronesian islands in her definition).[84] Aside from mainland Australia, areas that she identified as of high importance were Borneo, Hawaii, Indonesia’s Java and Sumatra, New Guinea, New Zealand, the Philippines, French Polynesia’s Society Islands, Tasmania, and Tonga.[84]
American geographer Jesse Olney‘s 1845 book A Practical System of Modern Geography stated that it “comprises the numerous isles of the Pacific, lying south east of Asia.” Olney divided up Oceania into three groups; Australasia (which included Australia, New Guinea, and New Zealand), Malesia and Polynesia (which included the combined islands of Melanesia, Micronesia, and Polynesia in his definition).[85] Publication Missionary Review of the World claimed in 1895 that Oceania was divided up into five groups; Australasia, Malesia, Melanesia, Micronesia, and Polynesia. It did not consider Hawaii to be part of Polynesia, due to its geographic isolation, commenting that Oceania also included, “isolated groups and islands, such as the Hawaiian and Galápagos.”[86] In 1876, French geographer Élisée Reclus labelled Australia’s flora as “one of the most characteristic on the globe”, adding that “the Hawaiian archipelago also constitutes a separate vegetation zone; of all tropical insular groups it possesses the relatively largest number of endemic plants. In the Galápagos group also more than half of the species are of local origin.”[87]Rand McNally & Company, an American publisher of maps and atlases, claimed in 1892 that, “Oceania comprises the large island of Australia and the innumerable islands of the Pacific Ocean” and also that the islands of the Malay Archipelago “should be grouped in with Asia.”[88] British linguist Robert Needham Cust argued in 1887 that the Malay Archipelago should be excluded since it had participated in Asian civilization.[89] Cust considered Oceania’s four subregions to be Australasia, Melanesia, Micronesia and Polynesia.[89] New Zealand was categorized by him as being in Polynesia; and the only country in his definition of Australasia was Australia.[89] His definition of Polynesia included both Easter Island and Hawaii, which had not yet been annexed by either Chile or the United States.[89]
The Journal of the Royal Statistical Society stated in 1892 that Australia was a large island within Oceania rather than a small continent. It additionally commented:
It is certainly not necessary to consider the Hawaiian Islands and Australia as being in the same part of the world, it is however permissible to unite in one group all the islands which are scattered over the great ocean. It should be remarked that if we take the Malay Archipelago away from Oceania, as do generally the German geographers, the insular world contained in the great ocean is cut in two, and the least populated of the five parts of the world is diminished in order to increase the number of inhabitants of the most densely populated continent.[90]
Regarding Australia and the Pacific, Chambers’s New Handy Volume American Encyclopædia observed in 1885 that, “the whole region has sometimes been called Oceania, and sometimes Australasia—generally, however, in modern times, to the exclusion of the islands in the [Malay] archipelago, to which certain writers have given the name of Malesia.”[91] It added there was controversy over the exact limits of Oceania, saying that, “scarcely any two geographers appear to be quite agreed upon the subject”.[91] British physician and ethnologist James Cowles Prichard claimed in 1847 that the Aleutian Islands and the Kuril Islands form “the northern boundary of this fifth region of the world, and with the coasts of Asia and America completing its literal termination.” However, he wrote that these islands “are not usually reckoned as belonging to it, because they are known to be inhabited by races of people who came immediately from the adjacent continents and are unconnected with those tribes of the human race who peopled the remote islands of this great ocean.” He added that Hawaii was the most northerly area to be inhabited by races associated with Oceania.[92]
The 1926 book Modern World History, 1776–1926, by Alexander Clarence Flick, considered Oceania to include all islands in the Pacific, and associated the term with the Malay Archipelago, the islands of Melanesia, Micronesia, and Polynesia, the Aleutian Islands, Japan’s Ryukyu Islands, Taiwan and the Kuril Islands.[93] He further included in his definition Sakhalin, an island which is geologically part of the Japanese Archipelago, but that has been administered by Russia since World War II. Hong Kong, partly located in another marginal sea of the Pacific (the South China Sea) was also included in his definition. Australia and New Zealand were grouped together by Flick as Australasia, and categorized as being in the same area of the world as the islands of Oceania. Flick estimated this definition of Oceania had a population of 70,000,000, and commented that, “brown and yellow races constitute the vast majority” and that the minority of whites were mainly “owners and rulers”.[93] Hutton Webster’s 1919 book Medieval and Modern History also considered Oceania to encompass all islands in the Pacific, stating that, “the term Oceania, or Oceanica, in its widest sense applies to all the Pacific Islands.” Webster broke Oceania up into two subdivisions; the continental group, which included Australia, the Japanese archipelago, the Malay Archipelago and Taiwan, and the oceanic group, which included New Zealand and the islands of Melanesia, Micronesia and Polynesia.[94]
Charles Marion Tyler’s 1885 book The Island World of the Pacific Ocean considered Oceania to ethnographically encompass Australia, New Zealand, the Malay Archipelago, and the islands of Melanesia, Micronesia, and Polynesia. However, Tyler included other Pacific islands in his book as well, such as the Aleutian Islands, the Bonin Islands, the Japanese archipelago, the Juan Fernández Islands, the Kuril Islands, the Ryukyu Islands, Taiwan, California‘s Channel Islands and Farallon Islands, Canada‘s Vancouver Island and Queen Charlotte Islands (now known as Haida Gwaii), Chile’s Chiloé Island, Ecuador’s Galápagos Islands, Mexico’s Guadalupe Island, Revillagigedo Islands, San Benito Islands and Tres Marías Islands, and Peru’s Chincha Islands.[95] Islands in marginal seas of the Pacific were also covered in the book, including Alaska’s Pribilof Islands and China’s Hainan. Tyler additionally profiled the Anson Archipelago, which during the 19th century was a designation for a widely scattered group of purported islands in the Northwestern Pacific Ocean between Japan and Hawaii. The Anson archipelago included phantom islands such as Ganges Island and Los Jardines which were proven to not exist, as well as real islands such as Marcus Island and Wake Island.[96][97] Tyler described Australia as “the leviathan of the island groups of the world”.[95] In his 1857 book A Treatise on Physical Geography, Francis B. Fogg commented that “the Pacific and its dependencies may be said to contain that portion of the globe termed Oceanica or ‘the Maritime World’, which is divided into Australasia, Malesia and Polynesia.” Fogg defined Polynesia as covering the combined islands of Melanesia, Micronesia and Polynesia, as well as the Ryukyu Islands. He added that, “besides the proceeding, the Pacific contains many other islands, of which the most important are Hainan and Formosa, on the coast of China, the Japan isles, the Kuriles, the Aleutian Islands (stretching from the New World to the Old), Vancouver Island, the Galápagos, Juan Fernández and Chiloé.”[98] Scottish academic John Merry Ross in 1879 considered Polynesia to cover the entire South and Central Pacific area, not just islands ethnographically within Polynesia. He wrote in The Globe Encyclopedia of Universal Information that, “literally interpreted, the name would include all the groups from Sumatra to the Galápagos, together with Australia.”[99] Ross further wrote, “and to this vast region the term Oceania has been applied. It is more usual at the present time, however, to exclude the [Malay] archipelago.”[99]
In a 1972 article for the Music Educators Journal titled Musics of Oceania, author Raymond F. Kennedy wrote:
Many meanings have been given to the word Oceania. The most inclusive–but not always the most useful–embraces about 25,000 land areas between Asia and the Americas. A more popular and practical definition excludes Indonesia, East Malaysia (Borneo), the Philippines, Taiwan, Japan, and other islands closely related to the Asian mainland, as well as the Aleutians and the small island groups situated near the Americas. Thus, Oceania most commonly refers to the land areas of the South and Central Pacific.[100]
Kennedy defined Oceania as including Australasia, Melanesia, Micronesia, and Polynesia.[100] The U.S. Government Publishing Office‘s Area Handbook for Oceania from 1971 states that Australia and New Zealand are the principal large sovereignties of the area. It further states:
In its broadest definition Oceania embraces all islands and island groups of the Pacific Ocean that lie between Asia and the two American continents. In popular usage, however, the designation has a more restricted application. The islands of the North Pacific, such as the Aleutians and the Kuriles, usually are excluded. In addition, the series of sovereign island nations fringing Asia (Japan, Taiwan, the Philippines, East Malaysia, the Republic of Indonesia) are not ordinarily considered to be part of the area.[101]
In 1948, American military journal Armed Forces Talk broke the islands of the Pacific up into five major subdivisions; Indonesia, Melanesia, Micronesia, Polynesia and the non-tropical Islands. The Indonesia subdivision consisted of the islands of the Malay Archipelago, while the non-tropical islands were categorized as being North Pacific islands such as Alaska’s Kodiak archipelago, the Aleutian Islands, Japan, the Kuril Islands, and Sakhalin. Japan’s Bonin and Ryukyu Islands are also considered to be subtropical islands, with the main Japanese archipelago being non-tropical.[102] The journal associated the term Oceania with the Melanesian, Micronesian, and Polynesian subdivisions, but not with the Indonesian or non-tropical subdivisions.[103] The Pacific Islands Handbook (1945), by Robert William Robson, stated that, “Pacific Islands generally are regarded as Pacific islands lying within the tropics. There are a considerable number of Pacific Islands outside the tropics. Most of them have little economic or political importance.” He noted the political significance of the Aleutian Islands, which were invaded by the Japanese military in World War II, and categorized New Zealand’s Antipodes Islands, Auckland Islands, Bounty Islands, Campbell Islands, Chatham Island and Kermadec Islands as being non-tropical islands of the South Pacific, along with Australia’s Lord Howe Island and Norfolk Island. The Kermadec Islands, Lord Howe Island and Norfolk Island are also considered to be subtropical islands. Other non-tropical areas below the equator, such as Chiloé Island, Macquarie Island, Tasmania, and the southern portions of mainland Australia and New Zealand, were not included in this category.[104]
According to the 1998 book Encyclopedia of Earth and Physical Sciences, Oceania refers to Australasia, Melanesia, Micronesia, Polynesia, and more than 10,000 islands scattered across the Pacific Ocean. It notes that, “the term [has] also come under scrutiny by many geographers. Some experts insist that Oceania encompasses even the cold Aleutian Islands and the islands of Japan. Disagreement also exists over whether or not Indonesia, the Philippines and Taiwan should be included in Oceania.”[105] The Japanese Archipelago, the Malay Archipelago and Taiwan and other islands near China are often deemed as a geological extension of Asia, since they do not have oceanic geology, instead being detached fragments of the Eurasian continent that were once physiographically connected.[106][107][108] Certain Japanese islands off the main archipelago are not geologically associated with Asia.[109][110] The book The World and Its Peoples: Australia, New Zealand, Oceania (1966) asserts that, “Japan, Taiwan, the Aleutian Islands, Indonesia, the Philippines and Malaysia [and] the Pacific archipelagos bordering upon the Far East Asian mainland are excluded from Oceania”, and that “all the islands lying between Australia and the Americas, including Australia, are part of Oceania.”[111] Furthermore, the book adds that Hawaii is still within Oceania, despite being politically integrated into the U.S., and that the Pacific Ocean “gives unity to the whole” since “all these varied lands emerge from or border upon the Pacific.”[111]
The 1876 book The Countries of the World, by British scientist and explorer Robert Brown, labelled the Malay Archipelago as Northwestern Oceania, but Brown still noted that these islands belonged more to the Asian continent. They are now often referred to as Maritime Southeast Asia, with Indonesia, Malaysia, the Philippines and Singapore being founding members of the ASEAN regional organization for Southeast Asia in 1967 (Brunei and East Timor did not exist as independent nations at that point).[67][112] Brown also categorized Japan and Taiwan as being in the same part of the world as the islands of Oceania, and excluded them from The Countries of the World: Volume 5, which covered mainland Asia and Hong Kong.[67] However, Brown did not explicitly associate Japan or Taiwan with the term Oceania.[67] He divided Oceania into two subregions: Eastern Oceania, which included the islands of Melanesia, Micronesia and Polynesia, and Southwestern Oceania, which included Australia and New Zealand.[67] The Galápagos Islands, the Juan Fernández Islands and the Revillagigedo Islands were identified as the easternmost areas of Oceania in the book. Brown wrote, “they lie nearest the American continent of all oceanic islands, and though rarely associated with Polynesia, and never appearing to have been inhabited by any aboriginal races, are, in many ways, remarkable and interesting.”[67] Brown went on to add, “the small islands lying off the continent, like the Queen Charlotte’s in the North Pacific, the Farallones off California, and the Chinchas off Peru are—to all intents and purposes, only detached bits of the adjoining shores. But in the case of the Galápagos, at least, this is different.”[67] The Juan Fernández Islands and the neighbouring Desventuradas Islands are today seen as the easternmost extension of the Indo-West Pacific biogeographic region. The islands lie on the Nazca Plate with Easter Island and the Galápagos Islands, and have a significant south central Pacific component to their marine fauna.[113][114][61] According to scientific journal PLOS One, the Humboldt Current helps create a biogeographic barrier between the marine fauna of these islands and South America.[113] Chile’s government have occasionally considered them to be within Oceania along with Easter Island.[115] Chile’s government also categorize Easter Island, the Desventuradas Islands and the Juan Fernández Islands as being part of a region titled Insular Chile. They further include in this region Salas y Gómez, a small uninhabited island to the east of Easter Island. PLOS One describe Insular Chile as having “cultural and ecological connections to the broader insular Pacific.”[113]
A map of member states for the Pacific Islands Forum, the member states are depicted in blue. The PIF is a governing organization for the Pacific, and all of its members are seen as being politically within Oceania. Territories ethnographically associated with Oceania, but not politically associated with Oceania, such as Easter Island, Hawaii, and Western New Guinea, have considered gaining representation in the PIF. The Pacific island nations of Indonesia, Japan, Malaysia, the Philippines, Singapore and Taiwan are dialogue partners, but none have full membership. East Timor, located in marginal seas of the Pacific and Indian Oceans, also have observer status.An exclusive economic zone map of the Pacific which includes areas not politically associated with Oceania, that may be considered geographically or geologically within Oceania
In her 1997 book Australia and Oceania, Australian historian Kate Darian-Smith defined the area as covering Australia, New Zealand and the islands of the Melanesia, Micronesia and Polynesia. She excluded Hawaii from her definition, but not Easter Island.[116] The International Union for Conservation of Nature stated in a 1986 report that they include Easter Island in their definition of Oceania “on the basis of its Polynesian and biogeographic affinities even though it is politically apart”, further noting that other oceanic islands administered by Latin American countries had been included in definitions of Oceania.[117] In 1987, The Journal of Australasian Cave Research described Oceania as being “the region from Irian Jaya (Western New Guinea, a province of New Guinea) in the west to Galápagos Islands (Equador) and Easter Island (Chile) in the east.”[118] In a 1980 report on venereal diseases in the South Pacific, the British Journal of Venereal Diseases categorized the Desventuradas Islands, Easter Island, the Galápagos Islands and the Juan Fernández Islands as being in an eastern region of the South Pacific, along with areas such as Pitcairn Islands and French Polynesia, but noted that the Galápagos Islands were not a member of the South Pacific Commission, like other islands in the South Pacific.[119] The South Pacific Commission is a developmental organization formed in 1947 and is currently known as the Pacific Community; its members include Australia and other Pacific Islands Forum members. In a 1947 article on the formation of the South Pacific Commission for the Pacific Affairs journal, author Roy E. James stated the organization’s scope encompassed all non-self governing islands below the equator to the east of Papua New Guinea (which itself was included in the scope and then known as Dutch New Guinea). Easter Island and the Galápagos Islands were defined by James as falling within the organization’s geographical parameters.[120] The 2007 book Asia in the Pacific Islands: Replacing the West, by New Zealand Pacific scholar Ron Crocombe, defined the term “Pacific Islands” as being islands in the South Pacific Commission, and stated that such a definition “does not include Galápagos and other [oceanic] islands off the Pacific coast of the Americas; these were uninhabited when Europeans arrived, then integrated with a South American country and have almost no contact with other Pacific Islands.” He adds, “Easter Island still participates in some Pacific Island affairs because its people are Polynesian.”[18]
Thomas Sebeok‘s two volume 1971 book Linguistics in Oceania defines Easter Island, the Galápagos Islands, the Juan Fernández Islands, Costa Rica‘s Cocos Island and Colombia‘s Malpelo Island (all oceanic)[121] as making up a Spanish language segment of Oceania.[122] Cocos Island and Malpelo Island are the only landmasses located on the Cocos Plate, which is to the north of the Nazca Plate. The book observed that a native Polynesian language was still understood on Easter Island, unlike with the other islands, which were uninhabited when discovered by Europeans and mostly being used as prisons for convicts.[122] Additionally, the book includes Taiwan and the entire Malay Archipelago as part of Oceania.[123] While not oceanic in nature, Taiwan and Malay Archipelago countries like Indonesia and the Philippines share Austronesian ethnolinguistic origins with Melanesia, Micronesia and Polynesia, hence their inclusion in the book.[124][123] Hainan, which neighbours Taiwan, also has Austronesian ethnolinguistic origins, although it was not included in the book.[125] The book defined Oceania’s major subregions as being Australia, Indonesia (which included all areas associated with the Malay Archipelago), Melanesia, Micronesia, and Polynesia. In 2010, Australian historian Bronwen Douglas claimed in The Journal of Pacific History that “a strong case could be made for extending Oceania to at least Taiwan, the homeland of the Austronesian language family whose speakers colonized significant parts of the region about 6,000 years ago.”[126] For political reasons, Taiwan was a member of the Oceania Football Confederation during the 1970s and 1980s, rather than the Asian Football Confederation.[127][128]
Ian Todd’s 1974 book Island Realm: A Pacific Panorama also defines oceanic Latin American islands as making up a Spanish language segment of Oceania, and included the Desventuradas Islands, Easter Island, the Galápagos Islands, Guadalupe Island, the Juan Fernández Islands, the Revillagigedo Islands and Salas y Gómez. Cocos Island and Malpelo Island were not explicitly referenced in the book, despite being areas which would fall within this range. All other islands associated with Latin American countries were excluded, as they are continental in nature, unlike Guadalupe Island and the Revillagigedo Islands (both situated on the Pacific Plate) and the oceanic islands situated on the Cocos Plate and Nazca Plate. Todd defined the oceanic Bonin Islands as making up a Japanese language segment of Oceania, and excluded the main Japanese archipelago.[65] Todd further included the Aleutian Islands in his definition of Oceania. The island chain borders both the Pacific Plate and the North American Plate, and is geologically a partially submerged volcanic extension of the Aleutian Range on the Alaskan mainland.[129][130][131] He did not include the volcanic Kuril Islands and Ryukyu Islands, which similarly border both the Eurasian Plate and the Pacific Plate,[132][133] nor did he include the neighbouring Kodiak archipelago in the North Pacific Ocean, which is firmly situated on the North American Plate.[134]The Stockholm Journal of East Asian Studies stated in 1996 that Oceania was defined as Australia and an ensemble of various Pacific Islands, “particularly those in the central and south Pacific [but] never those in the extreme north, for example the Aleutian chain.”[135] In the Pacific Ocean Handbook (1945), author Eliot Grinnell Mears claimed, “it is customary to exclude the Aleutians of the North Pacific, the American coastal islands and the Netherlands East Indies“, and that he included Australia and New Zealand in Oceania for “scientific reasons; Australia’s fauna is largely continental in character, New Zealand’s are clearly insular; and neither Commonwealth realm has close ties with Asia.”[136] In his 2002 book Oceania: An Introduction to the Cultures and Identities of Pacific Islanders, Andrew Strathern excluded Okinawa and the rest of the Ryukyu Islands from his definition of Oceania, but noted that the islands and their indigenous inhabitants “show many parallels with Pacific island societies.”[137]
In the 2006 book Extinction and Biogeography of Tropical Pacific Birds, American paleontologist David Steadman wrote, “no place on earth is as perplexing as the 25,000 islands that make Oceania.” Steadman viewed Oceania as encompassing Melanesia, Micronesia and Polynesia (including Easter Island and Hawaii). He excluded from his definition the larger islands of New Guinea and New Zealand, and argued that Cocos Island, the Galápagos Islands, the Revillagigedo Islands and other oceanic islands nearing the Americas were not part of Oceania, due to their biogeographical affinities with that area and lack of prehistoric indigenous populations.[57] In his 2018 book Regionalism in South Pacific, Chinese author Yu Changsen wrote that some “stress a narrow vision of the Pacific as those Pacific Islands excluding Australia and even sometimes New Zealand”, adding that the term Oceania “promotes a broader concept that has room for Australia and New Zealand.”[138]
American marine geologist Anthony A. P. Koppers wrote in the 2009 book Encyclopedia of Islands that, “as a whole, the islands of the Pacific Region are referred to as Oceania, the tenth continent on earth. Inherent to their remoteness and because of the wide variety of island types, the Pacific Islands have developed unique social, biological and geological characteristics.” Koppers considered Oceania to encompass the entire 25,000 islands of the Pacific Ocean. In this book, he included the Aleutian Islands, the Galápagos Islands, the Japanese archipelago, the Kuril Islands and continental islands off the coast of the Americas such as the Channel Islands, the Farallon Islands and Vancouver Island;[139] all of these islands lie in or close to the Pacific Ring of Fire, as is the case with New Guinea and New Zealand, which were also included. In the 2013 book The Environments of the Poor in Southeast Asia, East Asia and the Pacific, Paul Bullen critiqued the definition of Oceania in Encyclopedia of Islands, and wrote that since Koppers included areas such as Vancouver Island, it is “not clear what the referents of ‘Pacific Region’, ‘Oceania’ or ‘Pacific Islands’ are.” Bullen added that, “Asia, Europe and the Maritime Continent are not literal geographic continents. The ‘Asia–Pacific region’ would comprise two quasi-continents. ‘The Pacific’ would not refer to the Pacific Ocean and everything in it e.g., the Philippines.”[140]The Concise Oxford Dictionary of World Place Names (2017), by John Everett-Heath, states that Oceania is “a collective name for more than 10,000 islands in the Pacific Ocean” and that “it is generally accepted that Indonesia, Japan, the Philippines, Taiwan, and the islands north of Japan (the Kurils and Aleutians) are excluded.”[141] In his 1993 book A New Oceania: Rediscovering Our Sea of Islands, New Guinea-born Fijian scholar Epeli Hauʻofa wrote that, “Pacific Ocean islands from Japan, through the Philippines and Indonesia, which are adjacent to the Asian mainland, do not have oceanic cultures, and are therefore not part of Oceania.”[23]
The Oxford Handbook of Prehistoric Oceania (2018) defined Oceania as only covering Austronesian-speaking islands in Melanesia, Micronesia and Polynesia, with this definition including New Guinea and New Zealand. Other Austronesian areas such as Indonesia and the Philippines were not included, due to their closer cultural proximity to mainland Asia. Australia was also not included, as it was settled several thousands of years before the arrival of Austronesian-speaking peoples in Melanesia, Micronesia and Polynesia. The book stated, “this definition of Oceania might seem too restrictive: Why not include Australia, for example, or even too broad, for what does Highland New Guinea have to do with Hawai’i?”, further noting that, “a few other islands in the Pacific such as those of Japan or the Channel Islands off the southern California coast are not typically considered Oceania as the indigenous populations of these places do not share a common ancestry with Oceanic groups, except for a time far before humans sailed Pacific waters.”[142] It has been theorized that the indigenous Jōmon people of the Japanese archipelago are related to Austronesians, along with the indigenous inhabitants of the Ryukyu Islands. Some also theorize that Indigenous Australians are related to the Ainu people, who are the original inhabitants of Japan’s Hokkaido, the Kuril Islands and the southern part of Sakhalin.[143][144] In their 2019 book Women and Violence: Global Lives in Focus, Kathleen Nadeau and Sangita Rayamajhi wrote:
the Philippines, Malaysia, Brunei, and most of Indonesia are not usually considered to be part of the region of Oceania as it is understood today. These regions are usually considered to be part of Maritime Southeast Asia. Although these regions, as well as the large East Asian islands of Taiwan, Hainan and the Japanese archipelago, have varying degrees of cultural connections.[145]
In Reptiles and Amphibians of the Pacific Islands: A Comprehensive Guide (2013), George R. Zug claimed that “a standard definition of Oceania includes Australia, Papua New Guinea, the Solomon Islands, New Caledonia, and New Zealand and the oceanic islands of Polynesia, Micronesia, and Melanesia.” He went on to write that his preferred definition of Oceania emphasizes islands with oceanic geology, stating that oceanic islands are, “islands with no past connections to a continental landmass” and that, “these boundaries encompass the Hawaiian and Bonin Islands in the north and Easter Island in the south, and the Palau Islands in the west to the Galápagos Islands in the east.”[121] Australia, New Guinea, New Zealand and New Caledonia (which is geologically associated with New Zealand) were all excluded, as these areas are descendants of the ancient Pangaea supercontinent, along with landmasses such as the Americas and Afro-Eurasia. Volcanic islands which are geologically associated with continental landmasses, such as the Aleutian Islands, Japan’s Izu Islands, the Kuril Islands, the Ryukyu Islands and most of the Solomon Islands, were also excluded from his definition. Unlike the United Nations, the World Factbook defines the still-uninhabited Clipperton Island as being a discrete political entity, and they categorize it as part of North America, presumably due to its relative proximity (situated 1,200 kilometres off Mexico on the Pacific Plate). Clipperton is not politically associated with the Americas, as is the case with other oceanic islands nearing the Americas, having had almost no interaction with the continent throughout its history.[146][147] From the early 20th century to 2007, the island was administratively part of French Polynesia, which itself was known as French Oceania up until 1957.[148][149] In terms of marine fauna, Clipperton shares similarities with areas of the Pacific which are much farther removed from the Americas.[150][151] Scottish author Robert Hope Moncrieff considered Clipperton to be the easternmost point of Oceania in 1907, while Ian Todd also included it in his definition of Oceania in Island Realm: A Pacific Panorama.[152]
Other uninhabited Pacific Ocean landmasses have been explicitly associated with Oceania,[153] including the highly remote Baker Island and Wake Island (now administered by the U.S. military).[68] This is due to their location in the centre of the Pacific, their biogeography and their oceanic geology. Less isolated oceanic islands that were once uninhabited, such as the Bonin Islands, the Galápagos Islands and the Juan Fernández Islands, have since been sparsely populated by citizens of their political administrators.[65][122] Archaeological evidence suggests that Micronesians may have lived on the Bonin Islands c. 2,000 years ago, but they were uninhabited at the time of European discovery in the 16th century.[154]
Depending on the definition, New Zealand could be part of Polynesia, or part of Australasia with Australia.[155] New Zealand was originally settled by the Polynesian Māori, and has long maintained a political influence over the subregion.[156][157] Through immigration and high Māori birth rates, New Zealand has attained the largest population of Polynesians in the world,[158] while Australia has the third largest Polynesian population (consisting entirely of immigrants). Modern-day Indigenous Australians are loosely related to Melanesians,[159][160] and Australia maintains political influence over Melanesia,[157] which is mostly located on the same tectonic plate.[57][58] Despite this, Australia is rarely seen as a part of the subregion.[161][162] As with Australia and New Zealand, Melanesia’s New Caledonia has a significant non-indigenous European population, numbering around 71,000.[163] Conversely, New Caledonia has still had a similar history to the rest of Melanesia, and their French-speaking Europeans make up only 27% of the total population.[163][164] As such, it is not also culturally considered a part of the predominantly English-speaking Australasia.[165] Some cultural and political definitions of Australasia include most or all of Melanesia, due to its geographical proximity to Australia and New Zealand, but these are rare.[166] Australia, New Zealand and the islands of Melanesia are more commonly grouped together as part of the Australasian biogeographical realm.[167] Papua New Guinea is geographically the closest country to Australia, and is often geologically associated with Australia as it was once physiologically connected.[68] Australia’s Indian Ocean external territories of Christmas Island and Cocos (Keeling) Islands are situated within the bounds of the Australian Plate and have been geographically associated with Southeast Asia, due to their proximity to western Indonesia.[168][169][170][171][172] Both were uninhabited when discovered by Europeans during the 17th century. Approximately half of the population on these islands are European Australian mainlanders (with smaller numbers being European New Zealanders), while the other half are immigrants from China or the nearby Malay Archipelago.[173][174] Australia’s Indian Ocean external territory Heard Island and McDonald Islands lie on the Antarctic Plate and are also thought of as being in Antarctica or no region at all, due to their extreme geographical isolation.[175][68] The World Factbook define Heard Island and McDonald Islands as part of Antarctica, while placing Christmas Island and Cocos (Keeling) Islands as the westernmost extent of Oceania.[176][177]
Norfolk Island, an external territory of Australia, was inhabited in prehistoric times by either Melanesians or Polynesians, and is geographically adjacent to the islands of Melanesia. The current inhabitants are mostly European Australians, and the UN categorize it as being in the Australasia subregion.[68] The 1982 edition of the South Pacific Handbook, by David Stanley, groups Australia, New Zealand, Norfolk Island, and Hawaiʻi together under an “Anglonesia” category. This is in spite of the geographical distance separating these areas from Hawaiʻi, which technically lies in the North Pacific.[178] The 1985 edition of the South Pacific Handbook also groups the Galápagos Islands as being in Polynesia, while noting that they are not culturally a part of the subregion.[179] The islands are typically grouped with others in the southeastern Pacific that were never inhabited by Polynesians.[180][181]
The Bonin Islands are in the same biogeographical realm as the geographically adjacent Micronesia, and are often grouped in with the subregion because of this.[182][181]
A 19th-century engraving of an Aboriginal Australian encampment
Indigenous Australians are the original inhabitants of the Australian continent and nearby islands who migrated from Africa to Asia c. 70,000 years ago[183] and arrived in Australia c. 50,000 years ago.[184] They are believed to be among the earliest human migrations out of Africa.[185] Although they likely migrated to Australia through Southeast Asia, they are not demonstrably related to any known Asian or Polynesian population.[186] There is evidence of genetic and linguistic interchange between Australians in the far north and the Austronesian peoples of modern-day New Guinea and the islands, but this may be the result of recent trade and intermarriage.[187]
It is estimated that 4% to 6% of the genome in Melanesians (e.g. Papua New Guinean and Bougainville Islander) derives from the Denisova hominin, an ancient human species discovered in 2010, while no Eurasians or Africans displayed contributions of the Denisovan genes.[192]
The original inhabitants of the group of islands now named Melanesia were likely the ancestors of the present-day Papuan-speaking people. Migrating from Southeast Asia, they appear to have occupied these islands as far east as the main islands in the Solomon Islands archipelago, including Makira and possibly the smaller islands farther to the east.[193]
Particularly along the north coast of New Guinea and in the islands north and east of New Guinea, the Austronesian people, who had migrated into the area somewhat more than 3,000 years ago, came into contact with these pre-existing populations of Papuan-speaking peoples. In the late 20th century, some scholars theorized a long period of interaction, which resulted in many complex changes in genetics, languages, and culture among the peoples.[194]
Stone money transport to Yap Island in Micronesia (1880)Chronological dispersal of Austronesian people across the Pacific (per Bellwood in Chambers, 2008)
Micronesia began to be settled several millennia ago, although there are competing theories about the origin and arrival of the first settlers. There are numerous difficulties with conducting archaeological excavations in the islands, due to their size, settlement patterns and storm damage. As a result, much evidence is based on linguistic analysis.[195]
The earliest archaeological traces of civilization have been found on the island of Saipan, dated to 1500 BCE or slightly before. The ancestors of the Micronesians settled there over 4,000 years ago. A decentralized chieftain-based system eventually evolved into a more centralized economic and religious culture centred on Yap and Pohnpei.[196] The prehistories of many Micronesian islands such as Yap are not known very well.[197]
The first people of the Northern Mariana Islands navigated to the islands and discovered it at some period between 4000 BCE to 2000 BCE from Southeast Asia. They became known as the Chamorros. Their language was named after them. The ancient Chamorro left a number of megalithic ruins, including Latte stone. The Refaluwasch or Carolinian people came to the Marianas in the 1800s from the Caroline Islands. Micronesian colonists gradually settled the Marshall Islands during the 2nd millennium BCE, with inter-island navigation made possible using traditional stick charts.[198]
The Polynesian people are considered to be by linguistic, archaeological and human genetic ancestry a subset of the sea-migrating Austronesian people and tracing Polynesian languages places their prehistoric origins in the Malay Archipelago, and ultimately, in Taiwan. Between c. 3000 and 1000 BCE, speakers of Austronesian languages began spreading from Taiwan into Island Southeast Asia,[199][200][201] as tribes whose natives were thought to have arrived through South China c. 8,000 years ago to the edges of western Micronesia and on into Melanesia.
In the archaeological record there are well-defined traces of this expansion which allow the path it took to be followed and dated with some certainty. It is thought that by roughly 1400 BCE,[202] “Lapita Peoples”, so-named after their pottery tradition, appeared in the Bismarck Archipelago of north-west Melanesia.[203][204]
Easter Islanders claimed that a chief Hotu Matuꞌa[205] discovered the island in one or two large canoes with his wife and extended family.[206] They are believed to have been Polynesian. Around 1200, Tahitian explorers discovered and began settling the area. This date range is based on glottochronological calculations and on three radiocarbon dates from charcoal that appears to have been produced during forest clearance activities.[207] Moreover, a recent study which included radiocarbon dates from what is thought to be very early material suggests that the island was discovered and settled as recently as 1200.[208]
On 23 April 1770, British explorer James Cook made his first recorded direct observation of Aboriginal Australians at Brush Island near Bawley Point.[213] On 29 April, Cook and crew made their first landfall on the mainland of the continent at a place now known as the Kurnell Peninsula. It is here that James Cook made first contact with an aboriginal tribe known as the Gweagal. His expedition became the first recorded Europeans to have encountered its eastern coastline of Australia.[214]
New Guinea from 1884 to 1919. The Netherlands controlled the western half of New Guinea, Germany the north-eastern part, and Britain the south-eastern part.
In 1789, the mutiny on the Bounty against William Bligh led to several of the mutineers escaping the Royal Navy and settling on Pitcairn Islands, which later became a British colony. Britain also established colonies in Australia in 1788, New Zealand in 1840 and Fiji in 1872, with much of Oceania becoming part of the British Empire. The Gilbert Islands (now known as Kiribati) and the Ellice Islands (now known as Tuvalu) came under Britain’s sphere of influence in the late 19th century.[215][216]
French Catholic missionaries arrived on Tahiti in 1834; their expulsion in 1836 caused France to send a gunboat in 1838. In 1842, Tahiti and Tahuata were declared a French protectorate, to allow Catholic missionaries to work undisturbed.[217] On 24 September 1853, under orders from Napoleon III, Admiral Febvrier Despointes took formal possession of New Caledonia.[218]
The Spanish explorer Alonso de Salazar landed in the Marshall Islands in 1529. They were named by Krusenstern, after English explorer John Marshall, who visited them together with Thomas Gilbert in 1788, en route from Botany Bay to Canton (two ships of the First Fleet). In 1905, the British government transferred some administrative responsibility over southeast New Guinea to Australia (which renamed the area “Territory of Papua“); and in 1906, transferred all remaining responsibility to Australia. The Marshall Islands were claimed by Spain in 1874. Germany established colonies in New Guinea in 1884, and Samoa in 1900. The United States also expanded into the Pacific, beginning with Baker Island and Howland Island in 1857, and with Hawaiʻi becoming a US territory in 1898. Disagreements between the US, the UK, and Germany over Samoa led to the Tripartite Convention of 1899.[219]
One of the first land offensives in Oceania was the Occupation of German Samoa in August 1914 by New Zealand forces. The campaign to take Samoa ended without bloodshed after over 1,000 New Zealanders landed on the German colony. Australian forces attacked German New Guinea in September 1914. A company of Australians and a British warship besieged the Germans and their colonial subjects, ending with a German surrender.[220]
Australia and New Zealand became dominions in the 20th century, adopting the Statute of Westminster Act in 1942 and 1947 respectively. In 1946, Polynesians were granted French citizenship and the islands’ status was changed to an overseas territory; the islands’ name was changed in 1957 to Polynésie Française (French Polynesia). Hawaii became a U.S. state in 1959. Fiji and Tonga became independent in 1970. On 1 May 1979, in recognition of the evolving political status of the Marshall Islands, the United States recognised the constitution of the Marshall Islands and the establishment of the government of the Republic of the Marshall Islands. The South Pacific Forum was founded in 1971, which became the Pacific Islands Forum in 2000.[220]
Oceanian islands are of four basic types: continental islands, high islands, coral reefs and uplifted coral platforms. High islands are of volcanic origin, and many contain active volcanoes. Among these are Bougainville, Hawaiʻi, and Solomon Islands.[227]
Oceania is one of eight terrestrial biogeographic realms, which constitute the major ecological regions of the planet. Related to these concepts are Near Oceania, that part of western Island Melanesia which has been inhabited for tens of millennia, and Remote Oceania which is more recently settled. Although the majority of the Oceanian islands lie in the South Pacific, a few of them are not restricted to the Pacific Ocean – Kangaroo Island and Ashmore and Cartier Islands, for instance, are situated in the Southern Ocean and Indian Ocean, respectively, and Tasmania’s west coast faces the Southern Ocean.[228] The coral reefs of the South Pacific are low-lying structures that have built up on basaltic lava flows under the ocean’s surface. One of the most dramatic is the Great Barrier Reef off northeastern Australia with chains of reef patches. A second island type formed of coral is the uplifted coral platform, which is usually slightly larger than the low coral islands. Examples include Banaba (formerly Ocean Island) and Makatea in the Tuamotu group of French Polynesia.[229][230]
Australasia comprises Australia, New Zealand, and neighbouring islands in the Pacific Ocean. Along with India most of Australasia lies on the Indo-Australian Plate with the latter occupying the Southern area. It is flanked by the Indian Ocean to the west and the Southern Ocean to the south.[235][236]
The Pacific Plate, which makes up most of Oceania, is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres (40,000,000 sq mi), it is the largest tectonic plate. The plate contains an interior hot spot forming the Hawaiian Islands.[237] It is almost entirely oceanic crust.[238] The oldest member disappearing by way of the plate tectonics cycle is early-Cretaceous (145 to 137 million years ago).[239]
Australia became part of the Indo-Australian Plate 45 to 40 million years ago and this is in the process of separating again with the Australian Plate being relevant to Oceania.[240] It is the lowest, flattest, and oldest landmass on Earth[241] and it has had a relatively stable geological history. Geological forces such as tectonic uplift of mountain ranges or clashes between tectonic plates occurred mainly in Australia’s early history, when it was still a part of Gondwana. Australia is situated in the middle of the tectonic plate, has occasional middle-sized earthquakes, and currently has no active volcanism (but some volcanoes in southeast Australia erupted within the last 10,000 years).[242]
The geology of New Zealand is noted for its volcanic activity, earthquakes, and geothermalareas because of its position on the boundary of the Australian Plate and Pacific Plates. Much of the basement rock of New Zealand was once part of the super-continent of Gondwana, along with South America, Africa, Madagascar, India, Antarctica and Australia. The rocks that now form the continent of Zealandia were nestled between Eastern Australia and Western Antarctica.[243]
The Australia-New Zealand continental fragment of Gondwana split from the rest of Gondwana in the late Cretaceous time (95–90 Ma). By 75 Ma, Zealandia was essentially separate from Australia and Antarctica, although only shallow seas might have separated Zealandia and Australia in the north. The Tasman Sea, and part of Zealandia then locked together with Australia to form the Australian Plate (40 Ma), and a new plate boundary was created between the Australian Plate and Pacific Plate.
The most diverse country of Oceania when it comes to the environment is Australia, with tropical rainforests in the north-east, mountain ranges in the south-east, south-west and east, and dry desert in the centre.[247]Desert or semi-arid land commonly known as the outback makes up by far the largest portion of land.[248] The coastal uplands and a belt of Brigalow grasslands lie between the coast and the mountains, while inland of the dividing range are large areas of grassland.[249] The northernmost point of the east coast is the tropical-rainforested Cape York Peninsula.[250][251][252][253][254]
New Zealand’s landscape ranges from the fjord-like sounds of the southwest to the tropical beaches of the far north. South Island is dominated by the Southern Alps. There are 18 peaks of more than 3000 metres (9800 ft) in the South Island. All summits over 2,900 m are within the Southern Alps, a chain that forms the backbone of the South Island; the highest peak of which is Aoraki / Mount Cook, at 3,754 metres (12,316 ft). Earthquakes are common, though usually not severe, averaging 3,000 per year.[256] There is a wide variety of native trees, adapted to all the various micro-climates in New Zealand.[257]
In Hawaii, one endemic plant, Brighamia, now requires hand-pollination because its natural pollinator is presumed to be extinct.[258] The two species of Brighamia – B. rockii and B. insignis – are represented in the wild by around 120 individual plants. To ensure these plants set seed, biologists rappel down 910-metre (3,000 ft) cliffs to brush pollen onto their stigmas.[259]
The birds of New Zealand evolved into an avifauna that included a large number of endemic species. As an island archipelago New Zealand accumulated bird diversity and when Captain James Cook arrived in the 1770s he noted that the bird song was deafening. The mix includes species with unusual biology such as the kākāpō which is the world’s only flightless, nocturnal, lek-breeding parrot, but also many species that are similar to neighbouring land areas. Some of the more well known and distinctive bird species in New Zealand are the kiwi, kea, takahē, Kākāpō, mohua, tūī, and the bellbird.[277] The tuatara is a notable reptile endemic to New Zealand.[278]
Australia, New Zealand, New Guinea, Wallacea, and the islands of the Pacific Ocean collectively possess 42% of the world’s parrot species, including half of all Critically Endangered parrots, many of which are endemic to the region.[279]
Hawaii, although being in the tropics, experiences many different climates, depending on latitude and its geography. The island of Hawaii for example hosts 4 (out of 5 in total) climate groups on a surface as small as 10,430 km2 (4,028 sq mi) according to the Köppen climate types: tropical, arid, temperate and polar. The Hawaiian Islands receive most of their precipitation during the winter months (October to April).[288] A few islands in the northwest, such as Guam, are susceptible to typhoons in the wet season.[289]
The highest recorded temperature in Oceania occurred in Oodnadatta, South Australia (2 January 1960), where the temperature reached 50.7 °C (123.3 °F).[290] The lowest temperature ever recorded in Oceania was −25.6 °C (−14.1 °F), at Ranfurly in Otago in 1903, with a more recent temperature of −21.6 °C (−6.9 °F) recorded in 1995 in nearby Ophir.[291]Pohnpei of the Senyavin Islands in Micronesia is the wettest settlement in Oceania, and one of the wettest places on earth, with annual recorded rainfall exceeding 7,600 mm (300 in) each year in certain mountainous locations.[292]The Big Bog on the island of Maui is the wettest place, receiving an average 10,271 mm (404.4 in) each year.[293]
Köppen climate classification of selected regions in Oceania
The linked map below shows the exclusive economic zones (EEZs) of the islands of Oceania and neighbouring areas, as a guide to the following table (there are few land boundaries that can be drawn on a map of the Pacific at this scale).
Australia and New Zealand are the only highly developed independent nations in the region, although the economy of Australia is by far the largest and most dominant economy in the region and one of the largest in the world. New Caledonia, Hawaiʻi, and French Polynesia are highly developed too but are not sovereign states. Australia’s per-capita GDP is higher than that of the UK, Canada, Germany, and France in terms of purchasing power parity.[311] New Zealand is also one of the most globalised economies and depends greatly on international trade.[312][313]
The majority of people living in Australia work in health care, retail and education sectors.[323] Australia boasts the largest amount of manufacturing in the region, producing cars, electrical equipment, machinery and clothes.
New Zealand has a large GDP for its population of 5.2 million, and sources of revenue are spread throughout the large island nation. The country has one of the most globalised economies and depends greatly on international trade – mainly with Australia, Canada, China, the European Union, Japan, Singapore, South Korea and the United States. New Zealand’s 1983 Closer Economic Relations agreement with Australia means that the economy aligns closely with that of Australia. In 2005, the World Bank praised New Zealand as the most business-friendly country in the world.[326][327] The economy diversified and by 2008, tourism had become the single biggest generator of foreign exchange.[328] The New Zealand dollar is the 10th-most traded currency in the world.[329]
The overwhelming majority of people living in the Pacific islands work in the service industry which includes tourism, education and financial services. Oceania’s largest export markets include Japan, China, the United States and South Korea. The smallest Pacific nations rely on trade with Australia, New Zealand and the United States for exporting goods and for accessing other products. Australia and New Zealand’s trading arrangements are known as Closer Economic Relations. Australia and New Zealand, along with other countries, are members of Asia–Pacific Economic Cooperation (APEC) and the East Asia Summit (EAS), which may become trade blocs in the future particularly EAS.
Endowed with forest, mineral, and fish resources, Fiji is one of the most developed of the Pacific island economies, though it remains a developing country with a large subsistence agriculture sector.[330] Agriculture accounts for 18% of gross domestic product, although it employed some 70% of the workforce as of 2001. Sugar exports and the growing tourist industry are the major sources of foreign exchange. Sugar cane processing makes up one-third of industrial activity. Coconuts, ginger, and copra are also significant.
The history of Hawaii’s economy can be traced through a succession of dominant industries; sandalwood,[331]whaling,[332] sugarcane, pineapple, the military, tourism and education.[333] Hawaiian exports include food and clothing. These industries play a small role in the Hawaiian economy, due to the shipping distance to viable markets, such as the West Coast of the contiguous U.S. The state’s food exports include coffee, macadamia nuts, pineapple, livestock, sugarcane and honey.[334] As of 2015, Honolulu was ranked high on world livability rankings, and was also ranked as the 2nd safest city in the U.S.[335][336]
Tourists mostly come from Japan, the United Kingdom and the United States. Fiji currently attracts almost half a million tourists each year, more than a quarter of whom come from Australia. This has contributed $1 billion or more to Fiji’s economy since 1995, but the Government of Fiji likely underestimates these figures due to the invisible economy inside the tourism industry.
Vanuatu is widely recognised as one of the premier vacation destinations for scuba divers wishing to explore coral reefs of the South Pacific region. Tourism has been promoted, in part, by Vanuatu being the site of several reality-TV shows. The ninth season of the reality TV series Survivor was filmed on Vanuatu, entitled Survivor: Vanuatu – Islands of Fire. Two years later, Australia’s Celebrity Survivor was filmed at the same location used by the U.S. version.[337]
Tourism in New Zealand contributes NZ$7.3 billion (or 4%) of the country’s GDP in 2013, as well as directly supporting 110,800 full-time equivalent jobs (nearly 6% of New Zealand’s workforce). International tourist spending accounted for 16% of New Zealand’s export earnings (nearly NZ$10 billion). International and domestic tourism contributes, in total, NZ$24 billion to New Zealand’s economy every year. Tourism New Zealand, the country’s official tourism agency, is actively promoting the country as a destination worldwide.[341]Milford Sound in South Island is acclaimed as New Zealand’s most famous tourist destination.[342]
In 2003 alone, according to state government data, there were over 6.4 million visitors to the Hawaiian Islands with expenditures of over $10.6 billion.[343] Due to the mild year-round weather, tourist travel is popular throughout the year. In 2011, Hawaiʻi saw increasing arrivals and share of foreign tourists from Canada, Australia, and China increasing 13%, 24% and 21% respectively from 2010.[344]
The demographic table below shows the subregions and countries of geopolitical Oceania. The countries and territories in this table are categorised according to the scheme for geographic subregions used by the United Nations. The information shown follows sources in cross-referenced articles; where sources differ, provisos have been clearly indicated. These territories and regions are subject to various additional categorisations, depending on the source and purpose of each description.
The predominant religion in Oceania is Christianity (73%).[362][363] A 2011 survey found that 92% in Melanesia,[362] 93% in Micronesia[362] and 96% in Polynesia described themselves as Christians.[362] Traditional religions are often animist, and prevalent among traditional tribes is the belief in spirits (masalai in Tok Pisin) representing natural forces.[364] In the 2018 census, 37% of New Zealanders affiliated themselves with Christianity and 48% declared no religion.[365] In the 2016 Census, 52% of the Australian population declared some variety of Christianity and 30% stated “no religion”.[366]
In recent Australian and New Zealand censuses, large proportions of the population say they belong to “no religion” (which includes atheism, agnosticism, deism, and secular humanism). In Tonga, everyday life is heavily influenced by Polynesian traditions and especially by the Christian faith. The Ahmadiyya mosque in Marshall Islands is the only mosque in Micronesia.[367] Another one in Tuvalu belongs to the same sect. The Baháʼí House of Worship in Tiapapata, Samoa, is one of seven designations administered in the Baháʼí Faith.
Hinduism is a minority faith in Oceania. Fiji has the highest percentage of Hindus in Oceania at 29.7%[368] In absolute numbers, Australia has the largest population of Hindus in Oceania constituting 2.7% of the country’s population.[369] In New Zealand, Hindus form 2.65% of the population of.[370]Samoa also has a significant Hindu population.[371]
Dutch immigrants arriving in Melbourne, Australia in 1954
The most multicultural areas in Oceania, which have a high degree of immigration, are Australia, New Zealand, and Hawaii. Since 1945, more than 7 million people have settled in Australia. From the late 1970s, there was a significant increase in immigration from Asian and other non-European countries, making Australia a multicultural country.[377]
Sydney is the most multicultural city in Oceania, having more than 250 different languages spoken with about 40% of residents speaking a language other than English at home.[378] Furthermore, 36 percent of the population reported having been born overseas, with top countries being Italy, Lebanon, Vietnam and Iraq, among others.[379][380]Melbourne is also fairly multicultural, having the largest Greek-speaking population outside of Europe,[381] and the second largest Asian population in Australia after Sydney.[382][383][384]
European migration to New Zealand provided a major influx following the signing of the Treaty of Waitangi in 1840. Subsequent immigration has been chiefly from the British Isles, but also from continental Europe, the Pacific, The Americas and Asia.[385][386]Auckland is home to over half (51.6 percent) of New Zealand’s overseas born population, including 72 percent of the country’s Pacific Island-born population, 64 percent of its Asian-born population, and 56 percent of its Middle Eastern and African born population.[387]
Hawaii is a majority-minority state.[388]Chinese workers on Western trading ships settled in Hawaii starting in 1789. In 1820, the first American missionaries arrived to preach Christianity and teach the Hawaiians Western ways.[389] As of 2015, a large proportion of Hawaii’s population have Asian ancestry – especially Filipino, Japanese, Korean and Chinese. Many are descendants of immigrants brought to work on the sugarcane plantations in the mid-to-late 19th century. Almost 13,000 Portuguese immigrants had arrived by 1899; they also worked on the sugarcane plantations.[390]Puerto Rican immigration to Hawaii began in 1899 when Puerto Rico’s sugar industry was devastated by two hurricanes, causing a worldwide shortage of sugar and a huge demand for sugar from Hawaii.[391]
Archaeology, linguistics, and existing genetic studies indicate that Oceania was settled by two major waves of migration. The first migration of Australo-Melanesians took place c. 40 to 80 thousand years ago, and these migrants, Papuans, colonised much of Near Oceania. Approximately 3.5 thousand years ago, a second expansion of Austronesian speakers arrived in Near Oceania, and the descendants of these people spread to the far corners of the Pacific, colonising Remote Oceania.[393]
Mitochondrial DNA (mtDNA) studies quantify the magnitude of the Austronesian expansion and demonstrate the homogenising effect of this expansion. With regards to Papuan influence, autochthonous haplogroups support the hypothesis of a long history in Near Oceania, with some lineages suggesting a time depth of 60 thousand years. Santa Cruz, a population located in Remote Oceania, is an anomaly with extreme frequencies of autochthonous haplogroups of Near Oceanian origin.[393]
Large areas of New Guinea are unexplored by scientists and anthropologists due to extensive forestation and mountainous terrain. Known indigenous tribes in Papua New Guinea have very little contact with local authorities aside from the authorities knowing who they are. Many remain preliterate and, at the national or international level, the names of tribes and information about them is extremely hard to obtain. The Indonesian provinces of Papua and West Papua on the island of New Guinea are home to an estimated 44 uncontacted tribal groups.[394]
Australia is also known for its cafe and coffee culture in urban centres.[407] Australia and New Zealand were responsible for the flat white coffee. Most Indigenous Australian tribal groups subsisted on a simple hunter-gatherer diet of native fauna and flora, otherwise called bush tucker.[408] The first settlers introduced British food to the continent, much of which is now considered typical Australian food, such as the Sunday roast.[409][410] Multicultural immigration transformed Australian cuisine; post-World War II European migrants, particularly from the Mediterranean, helped to build a thriving Australian coffee culture, and the influence of Asian cultures has led to Australian variants of their staple foods, such as the Chinese-inspired dim sim and Chiko Roll.[411]
The ʻIolani Palace in Honolulu, formerly the residence of the Hawaiian monarch, was restored and opened to the public as a museum in 1978.
The music of Hawaii includes traditional and popular styles, ranging from native Hawaiian folk music to modern rock and hip hop. Hawaii’s musical contributions to the music of the United States are out of proportion to the state’s small size. Styles such as slack-key guitar are well known worldwide, while Hawaiian-tinged music is a frequent part of Hollywood soundtracks. Hawaii also made a major contribution to country music with the introduction of the steel guitar.[412] The Hawaiian religion is polytheistic and animistic, with a belief in many deities and spirits, including the belief that spirits are found in non-human beings and objects such as animals, the waves, and the sky.[413]
New Zealand as a culture is a Western culture, which is influenced by the cultural input of the indigenous Māori and the various waves of multi-ethnic migration which followed the British colonisation of New Zealand. The Māori people constitute one of the major cultures of Polynesia. The country has been broadened by globalisation and immigration specifically from Oceania, Europe, and Asia.[416] New Zealand marks two national days of remembrance, Waitangi Day and ANZAC Day, and also celebrates many holidays such as the King’s Birthday, Labour Day, and Christmas Day, as well as public anniversaries of the founding dates of most regions.[417] The New Zealand recording industry began to develop from 1940 onwards and many New Zealand musicians have obtained success in Britain and the United States.[418] Some artists release Māori language songs and the Māori tradition-based art of kapa haka (song and dance) has made a resurgence.[419] The country’s diverse scenery and compact size, plus government incentives,[420] have encouraged some producers to film big budget movies in New Zealand, including Avatar, The Lord of the Rings, The Hobbit, The Chronicles of Narnia, King Kong and The Last Samurai.[421]
The national cuisine has been described as Pacific Rim, incorporating the native Māori cuisine and diverse culinary traditions introduced by settlers and immigrants from Europe, Polynesia and Asia.[422] New Zealand yields produce from land and sea – most crops and livestock, such as maize, potatoes and pigs, were gradually introduced by the early European settlers.[423] Distinctive ingredients or dishes include lamb; salmon; koura (crayfish);[424]whitebait; shellfish including dredge oysters, pāua, mussels, scallops, pipi and tuatua;[425]kumara (sweet potato); kiwifruit; tamarillo; and pavlova (considered a national dish).[426][422]
The fa’a Samoa, or traditional Samoan way, remains a strong force in Samoan life and politics. Despite centuries of European influence, Samoa maintains its historical customs, social and political systems, and language. Cultural customs such as the Samoa ‘ava ceremony are significant and solemn rituals at important occasions including the bestowal of matai chiefly titles. Items of great cultural value include the finely woven ‘ie toga.
The Samoan word for dance is siva, which consists of unique gentle movements of the body in time to music and which tell a story. Samoan male dances can be more snappy.[427] The sasa is also a traditional dance where rows of dancers perform rapid synchronised movements in time to the rhythm of wooden drums (pate) or rolled mats. Another dance performed by males is called the fa’ataupati or the slap dance, creating rhythmic sounds by slapping different parts of the body. As with other Polynesian cultures (Hawaiian, Tahitian and Māori) with significant and unique tattoos, Samoans have two gender specific and culturally significant tattoos.[428]
The artistic creations of native Oceanians varies greatly throughout the cultures and regions. The subject matter typically carries themes of fertility or the supernatural. Petroglyphs, tattooing, painting, wood carving, stone carving, and textile work are other common art forms.[429] Art of Oceania properly encompasses the artistic traditions of the people indigenous to Australia and the Pacific Islands.[430] These early peoples lacked a writing system, and made works on perishable materials, so few records of them exist from this time.[431]
Indigenous Australian rock art is the oldest and richest unbroken tradition of art in the world, dating as far back as 60,000 years and spread across hundreds of thousands of sites.[432][433] These rock paintings served several functions. Some were used in magic, others to increase animal populations for hunting, while some were simply for amusement.[434] Sculpture in Oceania first appears on New Guinea as a series of stone figures found throughout the island, but mostly in mountainous highlands. Establishing a chronological timeframe for these pieces in most cases is difficult, but one has been dated to c. 1500 BCE.[435]
By 1500 BCE the Lapita culture, descendants of the second wave, would begin to expand and spread into the more remote islands. At around the same time, art began to appear in New Guinea, including the earliest examples of sculpture in Oceania. Beginning c. 1100 CE, the people of Easter Island would begin construction of nearly 900 moai (large stone statues). At c. 1200 CE, the people of Pohnpei, a Micronesian island, would embark on another megalithic construction, building Nan Madol, a city of artificial islands and a system of canals.[436] Hawaiian art includes wood carvings, feather work, petroglyphs, bark cloth (called kapa in Hawaiian and tapa elsewhere in the Pacific), and tattoos. Native Hawaiians had neither metal nor woven cloth.[437]
Rugby union is one of the region’s most prominent sports,[438] and is the national sport of New Zealand, Samoa, Fiji and Tonga. The most popular overall sport in Australia is cricket, with their national team having won the Cricket World Cup a record five times.[439] The most popular sport among Australian women is netball, while Australian rules football garners the highest spectatorship numbers and television ratings.[440][441][442][443] Rugby union is the most popular sport among New Zealanders,[444] and they are tied with South Africa for the most Rugby World Cup titles, having won the tournament three times.[445] Australia’s team the Wallabies have won the World Cup twice, despite Rugby union being less popular among Australians.[446] In Papua New Guinea, the most popular sport is Rugby league.[447][448]Fiji’s sevens team is one of the most successful in the world, as is New Zealand’s.[449]
Australian rules football is the national sport in Nauru.[450] It has a large following in Papua New Guinea, where it is the second most popular sport after Rugby League.[451][452][453] Additionally, it attracts significant attention across New Zealand and the Pacific Islands. The highest level of the sport is the Australian Football League (AFL), which was the fourth best attended sporting league in the world during the 2010s.[454]
Vanuatu is the only country in Oceania to call association football its national sport. However, it is also the most popular sport in Kiribati, Solomon Islands and Tuvalu, and has a significant (and growing) popularity in Australia. In 2006 Australia left the Oceania Football Confederation (OFC) for the Asian Football Confederation (AFC), and their men’s team the Socceroos have qualified for every subsequent FIFA World Cup as an Asian entrant.[455] The sole Micronesian country with membership in the OFC is Kiribati, although they are not recognised by FIFA like the other OFC members. Federated States of Micronesia, Marshall Islands, Nauru and Palau all have no presence, primarily due to lack of infrastructure and logistical difficulties related to Micronesia’s remoteness.[456][457][458] Like Australia, the Micronesian dependent territories of Guam and Northern Mariana Islands currently compete in the AFC instead of the OFC.[459] The OFC was dominated by Australia for many years, and became known for one-sided results.[460]
Australians view sport as an important part of their cultural identity, and the country performs well on the international stage, despite having a relatively small population.[461] They have hosted two Summer Olympics: Melbourne 1956 and Sydney 2000, and the city of Brisbane is also set to host the 2032 edition.[462] Australia has hosted five editions of the Commonwealth Games and New Zealand three times. The Pacific Games (formerly known as the South Pacific Games) is a multi-sport event, much like the Olympics on a much smaller scale, with participation exclusively from countries around the Pacific; Australia and New Zealand competed in the games for the first time in 2015.[463]
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