Oceaniais a region of the South Pacific Ocean that consists of many different island groups. It covers an area of more than 3.3 million square miles (8.5 million sq km). The island groups within Oceania are both countries and dependencies or territories of other foreign nations. There are 14 countries within Oceania, and they range in size from the very large, such as Australia (which is both a continent and a country), to the very small, like Nauru. But like any landmass on earth, these islands are changing constantly, with the tiniest at risk of disappearing entirely due to rising waters.

The following is a list of Oceania's 14 different countries arranged by land area from the largest to the smallest. All information in the list was obtained from theCIA World Factbook.

Area: 2,988,901 square miles (7,741,220 sq km)

Population: 23,232,413Capital: Canberra

Even though the continent ofAustraliahas the most species of marsupials, they originated in South America, back when the continents were the landmass of Gondwana.

Area: 178,703 square miles (462,840 sq km)Population: 6,909,701Capital: Port Moresby

Ulawun, one of Papua New Guinea's volcanoes, has been deemed a Decade Volcano by the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI). Decade volcanoes are those that are historically destructiveand close to populated areas, so they merit intensive study, according to the IAVCEI.

Although the whole world is feeling the effects of climate change, the people dwelling on the small islands of Oceania do have something serious and imminent to worry about: the complete loss of their homes. Eventually, entire islands could be consumed by the expanding sea. What sounds like tiny changes in the sea level, often talked about in inches or millimeters, is very real to these islands and the people who live there (as well as the U.S. military installations there) because the warmer, expanding oceans have more devastating storms and storm surges, more flooding, and more erosion.

It's not just that the water comes a few inches higher on the beach. Higher tides and more flooding can mean more saltwater in freshwater aquifers, more homes destroyed, and more saltwater reaching agricultural areas, with the potential to ruin the soil for growing crops.

Some of the smallest Oceania islands, such as Kiribati (mean elevation, 6.5 feet), Tuvalu (highest point, 16.4 feet), and the Marshall Islands (highest point, 46 feet)], are not that many feet above sea level, so even a small rise can have dramatic effects.

Five small, low-lying Solomon Islands have already been submerged, and six more have had entire villages swept out to sea or lost habitable land. The largest countries may not see the devastation on such a scale as quickly as the smallest, but all of the Oceania countries have a considerable amount of coastline to consider.

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Discover Oceania's 14 Countries by Area - thoughtco.com