Although tropical forests cover only about 7% of the Earth’s dry land, they probably harbor about half of all species on Earth. Therefore, the destruction of the world's tropical forests at the alarming rate of 13 million hectares each year poses a huge threat to biodiversity.
Oil palm plantation in Kalimantan - Source
Tropical deforestation
The 2005 FAO report on the status world's forest resources concludes that, although net deforestation rates have fallen since the 1990-2000 period, some 13 million hectares of the world's forests are still lost each year, including 6 million hectares of primary forests (forests with no visible signs of past or present human activities), which are considered the most biologically diverse ecosystems on the planet.
South America (where large tracts of the Amazon rainforest are being cleared for cattle ranches and soybean plantations) and Africa suffered the largest net loss of forests between 2000 and 2005, while Asia reported a net gain of 1 million hectares per year, primarily as a result of large-scale afforestation reported by China.
However, the regions with the highest tropical deforestation rate were Central America (1.3% or 285,000 hectares) and tropical Asia, which lost about 1% of its forests each year. From 2000 to 2005, the Asia Pacific region lost more than six million hectares of natural forests. With a rate of 3.8 ha (5 football fields) a minute, Indonesia is the second country after Brazil with the largest net forest loss. Without preservation actions, tropical rainforests in Indonesia would be logged out in 2022.
Source
FAO defines deforestation as "the conversion of forest to another land use or
the long-term reduction of the tree canopy cover below the minimum 10 percent threshold."
Monoculture and biodiversity
The Asian region makes up about one-quarter of Earth's land area, but holds almost 60% of the world's population. Tremendous population pressures throughout the region have contributed to the region's substantial forest loss. Additionally, many Asian-countries have entered a period of sustained spectacular economic growth in the past few years, resulting in the increased consumption of forest resources.
In Southeast Asia and the Pacific, especially in Malaysia, Indonesia, and Papua New Guinea, one of the major cause o
f tropical forest loss is the conversion to palm oil plantations. Globally, palm oil production has increased by more than 50% since 1990. In 2006, Indonesia and Malaysia accounted together for 84% of total world production and 88% of global exports of palm oil, with export trends expected to double by the year 2020.
Source: mongabay.com
Oil palm plantations support significantly lower levels of biodiversity than even logged rainforests. It has been demonstrated that conversion of old-growth forest to oil palm plantations leads to a 77% decline in forest bird species, to a 83% loss of butterfly species and to 80 to 100% decline in mammals and reptiles. By comparison, secondary forest 30 years after logging retained roughly 80% of the original forest species.
Many tropical forests species are very vulnerable to extinction owing to the fact that they are specialized to microhabitats within the forest. In addition to the species lost when an area is totally deforested, the plants and animals in the fragments of forest that remain also become increasingly vulnerable, sometimes even committed, to extinction.
The edges of the fragments dry out and are buffeted by hot winds; mature rainforest trees often die standing at the margins. Cascading changes in the types of trees, plants, and insects that can survive in the fragments rapidly reduces biodiversity in the forest that remains.
Oriental Pied-hornbill (Anthracoceros albirostris) - Source: Wikimedia
Moreover, where natural ecosystems have been converted to other land uses, conflicts arise between humans and wildlife, resulting in wildlife being killed, and poached for trade. This includes tigers, rhinoceros, elephants and orangutans, the only great apes found in Asia, in the forests of Sumatra and Kalimantan (Borneo).
In the past twenty years 80% of orangutan habitat has been lost. The orangutans are particularly vulnerable because of their extremely long inter-birth interval, typically eight years, making them the slowest breeding primates on Earth. Today, orangutans are threatened by extinction in the wild.
Source: UNEP World Conservation Monitoring Centre
Sources
The state of the forest - Indonesia
Global Forest Resources assessment 2005 - FAO
Tropical Deforestation - Earth Observatory
World deforestation rates and forest cover statistics, 2000-2005 & Tropical deforestation tables
A World Imperiled: Forces behind forest loss
Better management practices human-orangutan conflict - WWF
Link
Climate change and biodiversity (11 Jan 2010) - Published by the European Environment Agency in the framework of the International Year of Biodiversity.
This page was written in 2009, as additional information to the poster series "10 years of Imaging the Earth"