SE Asia faces 'catastrophic' extinction rate

Posted: 29 July 2003

The rate of extinction threatening south-east Asia this century could be a "catastrophic" 20 per cent, scientists say in the journal Nature.

Reporting their findings for BBC Online, environment correspondent Alex Kirby says their warning is based on the example of Singapore, where key habitats have shrunk by 95 per cent since 1819. South-east Asia is one of the Earth's most important biodiversity "hotspots".

The scientists, from Singapore, Japan and Australia, say they found "substantial rates of documented and inferred extinctions, especially for forest species", with butterflies, fish, birds and mammals all affected.

"Observed extinctions were generally fewer, but inferred losses often higher, in vascular plants, phasmids (stick and leaf insects), decapods (crustaceans), amphibians and reptiles, the authors say.

Global impact

"Forest reserves comprising only 0.25 per cent of Singapore's area now harbour over 50 per cent of the residual native biodiversity."

They think the rate at which habitats are disappearing is so great that south-east Asia will lose up to two-fifths of all its species over this century, at least half of them endemic species found nowhere else on Earth.

Since the British arrived in Singapore in 1819, they say,mmore than 95 per cent of the estimated 540 square kilometres of original vegetation has been entirely cleared. Less than 10 per cent of the remaining 24 sq km of forest is primary growth.

The authors also used checklists from nearby peninsular Malaysia to deduce the possible species composition of Singapore in 1819, compensating for probably incomplete extinction records.

The overall loss of biodiversity, they calculated, was at least 28 per cent - 881 of 3,196 recorded species.

Butterflies, freshwater fish, birds and mammals lost 34-43 per cent of all species. About a quarter of all vascular plants, freshwater decapods and phasmids have disappeared.

'Living dead'

But there seem to have been comparatively fewer extinctions of amphibians and reptiles. Total local extinction rates, the authors say, could be as high as 73 per cent.

They say their lists of surviving species include several long-lived ones whose populations are too small to survive in the long term, like the white-bellied woodpecker, the banded leaf monkey and the cream-coloured giant squirrel.

They say: "These 'living dead' taxa will almost certainly become extinct in the coming decades."

Forest birds have fared worse than open-habitat species: since 1923, 61 of the 91 known forest-dependent birds have disappeared.

The authors say rapid and large-scale habitat destruction was undoubtedly the predominant cause of Singapore's extinctions.

But hunting may also have been important: Singapore's last tiger was shot in 1930.

They describe the prospects for its surviving species as "bleak", with 77 per cent classified as threatened by IUCN-The World Conservation Union.

Small reserves

With the few remaining protected nature reserves occupying only 0.25 per cent of the island's total land area, they worry at how much biodiversity is packed into so small a space.

On Singapore's lessons for south-east Asia, they note a projected overall deforestation rate of 74 per cent for the region by 2100.

They conclude: "We predict the overall loss of 13-42 per cent of regional populations due to the effects of deforestation in south-east Asia by the end of the present century, at least half of which are likely to represent global species extinctions."

Caroline Pollock, of IUCN's Red List programme, told BBC News Online: "The projected loss for south-east Asia is very high, but it's not really a surprise.

"We're finding increasing numbers of species are being assessed as threatened, and we expect more and more species will go downhill."