Tropical Southeast Asia
The world region of Southeast Asia is separated from the rest of the continent by a vast area of high mountains near the border of India and China, but it is difficult to delineate its other physical boundaries. It, however, can be identified politically as the assemblage of the sovereign area of the countries Myanmar, Thailand, Malaysia, Singapore, Lao People's Democratic Republic, Cambodia, Vietnam, Indonesia, Timor Leste, Brunei Darussalam, and the Philippines. Southeast Asia is a complex mosaic of continental and maritime environments that include ancient stable landmasses, alluvial plains and deltas of large rivers, inland seas, and volcanic islands. The outer margin of Southeast Asia is marked by a number of islands and deep oceanic trenches with frequent earthquakes, volcanic eruptions, and tsunamis. A long human occupation has modified the landscape, converting alluvial valleys and deltas to agriculture, mostly rice. Closer to the present time, widespread deforestation, spread of plantation agriculture, agricultural expansion, and urbanization have further modified the physical landscape. The related degradation has been particularly severe on rainforests, peat swamps, mangroves, and coral reefs. The original widespread forest cover of Southeast Asia has been reduced to about half its original size. Both plate tectonics and people are thus important contributors to the state of the physical environment in Southeast Asia.