Islands

An island is a landmass that is completely surrounded by water and is smaller than a continent. Islands occur in oceans, seas, rivers, and lakes, ranging from tiny islets to vast landmasses such as Greenland. The largest island in the world by conventional definition is Greenland; Australia is considered a continent, not an island.

Islands form through several processes. Oceanic islands typically originate from volcanic activity on the seafloor or from coral growth that builds up above sea level. Continental islands are pieces of continental crust that became separated from larger landmasses by rising seas or tectonic movement; they may preserve plant and animal lineages connected to larger continents.

Ecology and biogeography: Isolation leads to distinctive ecosystems and often high levels of endemic species. Island biogeography explains patterns of species richness in terms of island size and distance from the mainland, with larger and closer islands tending to host more species. Human activity has also shaped islands through habitat modification, introduction of nonnative species, and archipelagic connectivity.

Human use and significance: Islands host diverse cultures, languages, and economies. Many islands rely on fishing, tourism, agriculture, or resource extraction. Territorial and political status can be complex, especially for small or disputed islands.

Threats and conservation: Islands are particularly vulnerable to invasive species, habitat loss, and climate change, including sea-level rise and coral bleaching. Conservation efforts include habitat protection, invasive species management, and marine protected areas.