Tuesday, November 22, 2011

A Brief History of the Southeast Asian Rainforest

Since the Pleistocene Epoch (dating 70 million years back on the earth's geologic time scale),the Southeast Asian rainforests existed on Earth.Over millions of years, however, the tropical rainforests of Southeast Asia have undergone a multitude of changes. Nearly 8000 years ago, almost the entire region of Southeast Asia was covered by forestry. Currently, only about one half of the initial forest-covered land remains, and most of the countries in this region are experiencing rapid deforestation. Southeast Asia contains the world's third largest concentration of tropical forests, and it is experiencing deforestation at a rate higher than almost anywhere else on Earth. It estimated that by 2100, this region will lose up to three quarters of its initial forest coverage and up to 42% of its current biodiversity.(Trends in Ecology 2004)

The rainforests of Southeast Asia attest to an incredibly high level of biodiversity. The reason for this is because millions of years ago, while the rest of the world's climate underwent extreme cooling and warming cycles, the climate of Southeast Asia remained relatively stable because of the ecosystem's proximity to the equator and water. The water from the surrounding oceans provided the rainforests with plenty of moisture in the form of rain. The increased levels of precipitation (as well as periods of warming and cooling) caused the sea levels to fluctuate and subsequently episodically mold mountains into geographically isolated islands; these set of conditions turned out to be ideal for speciation. During the Pleistocene glacial episodes, unique wildlife reservoirs, known as "forest refugia", survived in small patches of forest. Additionally, during the last Ice Age, Malaysia and the islands of Borneo, Sumatra and Java all belonged to the same singular landmass. Once the glaciers melted and the sea levels rose, however, these "wildlife reservoirs" were isolated and cut off from each other, subsequently forcing species to develop their own evolutionary paths in response to their local environment. The isolation of the islands enabled the extreme diversification of species by driving the animals to adapt to their varying locales. The unique geological history of Southeast Asia, places the rainforests of this region at the top of world's list of the most biologically diverse ecosystems (in terms of species richness and endemism). (Trends in Ecology 2004)

Source: jeep56.edu.glogster.com

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