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Singapore Extinctions Spell Doom For Asia? |
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John Pickrell in England for National Geographic News |
| July 23, 2003 |
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Singapore has lost up to 73 percent of its plants and animals over the last two centuries, new data reveals. According to one of the most robust studies of tropical extinctions yet attempted, more than one- fifth of Southeast Asia's total species could follow suit by the end of the century, if land degradation continues unabated. "In a worst-case scenario Singapore is a microcosm of what may happen in Southeast Asia as urban pockets increasingly expand," warned ecologist Barry Brook of the Northern Territory University in Darwin, Australia. To further conservationists' woes, prospects for the remaining species are bleak. World Conservation Union (IUCN) figures estimate that 77 percent of the island's remaining butterflies, fish, birds, mammals, and other species are threatened. Deforestation for agriculture, rapid urban development, over-hunting, and even the shelling of nature reserves during World War II are all to blame, says a letter detailing the findings in the 24 July edition of the journal Nature. Colonial Rule Tropical forests harbor the majority of terrestrial life on earth, yet they are being destroyed or degraded at unprecedented rates by fragmentation, exploitation, and the introduction of non-native species. Though extinction rates are well documented in temperate regions, home to most developed nations, tropical data is rarer. Most reports are anecdotal or based on loose predictions of how many species can remain in shrinking forest patches. To fill that knowledge gap, Brook along with biologists Navjot Sodhi and Peter Ng of the National University of Singapore's Raffles Museum of Biodiversity decided to study Singapore: a perfect example of urban development, blessed with detailed historical lists of species recorded by British and Singaporean naturalists. The British commandeered the island in 1819 as an oriental colonial outpost. Previously the island was home to no more than a few small fishing settlements. "To have data on species going back two centuries for tropical forest is very unusual," commented ecologist Daniel Simberloff at the University of Tennessee in Knoxville. Most tropical regions are lucky to have species lists going back 30 years, he said. To estimate extinctions, Brooks' team used both modern species lists and historical ones going back to the 1870s for plants, crustaceans, butterflies, fish, amphibians, reptiles, birds, mammals, and other groups. As less data was available for earlier colonial times, the researchers also inferred the presence of species found on checklists for very similar habitats in Malaysia's adjacent peninsula. Huge Losses of Species The analysis that species that may have been lost include as many as 4,866 plants, 627 butterflies, 234 fish, 111 reptiles, and 91 mammals. Since 1923 alone, 61 of the 91 known forest-bird species have died out. As much as 73 percent of the island's original biota (flora and fauna) has been extirpated. Even measuring recorded losses for Singapore alone, and not adding the data from Malaysian lists, a minimum of 28 percent of species have been lost in the last 183 years. One well-documented loss is the tiger, the last of which was shot in the 1930s. Other species are "living dead"—reduced to impossibly small numbers and very unlikely to bounce back. The white-bellied woodpecker, banded leaf monkey, cream-colored giant squirrel, and many tree species are all represented by just a handful of individuals. More than 95 percent of Singapore's original 540 square kilometers (208 square miles) of tropical forest have been felled: first for agricultural crops such as black pepper, and later for urban development in the burgeoning city state. Less than one tenth of the remaining 24 square kilometers (9 square miles) of forest is old-growth vegetation and much of it has been re-established on abandoned farmland. In addition, 50 percent of remaining species are squeezed into tiny reserves covering no more than 1,547 hectares (3,800 acres). One quarter of the remaining freshwater fish species are found in just a single five-hectare (12-acre) patch of one reserve. Biodiversity in Crisis The figures reported for Singapore have wider implications, said Brook. "In most respects a local extinction is like a global extinction," he said. When all the local populations of a species have been extirpated, it becomes globally extinct. The scientists used the data to estimate how Southeast Asia's entire tropical diversity might fare if current rates of deforestation continue. Satellite images show that around 0.7 percent of the forests are currently lost annually. Extrapolating this loss into the future they predict that 74 percent of the region's original vegetation will disappear by the turn of the next century. Almost half the forests found prior to human alteration of the environment have already gone, said Brook. Following the Singaporean example, the researchers estimate that up to 42 percent of local plant and animal populations will have died out by the year 2100. "More than half of those will be global species extinctions," said Brook. That's one fifth of Southeast Asian species. "This is a very interesting and depressing analysis," commented the University of Tennessee's Simberloff, adding that the actual and inferred species losses for Singapore were almost certainly correct. "There's certainly nothing outrageous about the extrapolations either," he said. It's plausible and worrying that Asia could lose so many species in the next century, he added. However, " we hope that measures will be taken to minimize extinctions by preserving habitats very rich in species." There are steps that can be taken to mitigate species losses even with such "horrendous" rates of deforestation, he said. 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