VIDEO: 'Animal armageddon' hits Southeast Asian rainforest due to human development

Species living in rainforest fragmented by human development face "animal armageddon" according to a researcher involved in a two decade study in southern Thailand. A multinational team of scientists witnessed the near-complete extinction of native small mammals on forest islands created by a large hydroelectric reservoir which, they say, caused a drastic change in the ecological system.
 

The forests surrounding Chiew Larn Reservoir are alive with sound of gibbons and other wildlife. But on the hundreds of islands created when the area was flooded 28 years ago, it's a different story.

A team of scientists led by Luke Gibson from National University of Singapore (NUS), says the islands are almost devoid of the native species that thrived in the forest before it was flooded for hydro-electric power.

Chiew Larn Reservoir was developed in 1986. An intact forest valley of 165-sq kilometers was flooded, creating islands that had previously been hilltops in the valley. The reservoir covers parts of

of the Khlong Saeng Wildlife Sanctuary and Khao Sok National Park in the Thai southern province of Surat Thani. Gibson says the resulting forest fragmentation has driven wildlife extinction to a drastic decline. He says an ecological wipeout is just a matter of time.

A survey conducted by a multinational team of scientists, including Gibson, over two decades concludes that forest fragmentation produced by the flooding isolated native populations to the point where they were unsustainable over the long term. Those populations were also left to compete with the Malayan field rat, an invasive species that has thrived on the islands.

"And that species is Rattus tiomanicus', said Gibson. 'It's actually not native to these undisturbed forests. It came in from surrounding agricultural areas and it has displaced virtually all native species such as today, we only find a handful of native species on the islands. Everything else has disappeared," he said.

In just a few years, the invading rat grew so abundant on the islands that it virtually displaced all native small mammals. The researchers say they saw native small mammals vanish with alarming speed, with just a handful remaining - on average, less than one individual per island - after 25 years.

The research team has now set up more than 100 camera traps to monitor the movements of medium-sized and large native wildlife species in the remaining forest areas. Gibson says he hopes the resulting data will support new rules and regulations governing future development of forest lands. But he worries it may take too long and come too late for many species.

"With forest fragmentation, the effects are not immediate. So right after you chop a forest into a small piece, much of the biodiversity will still remain but a lot of it may disappear over some period of time," he said.

The Chiew Larn Reservoir was designed to produce clean, inexpensive elecricity for communities in southern Thailand. Gibson says the consequences have been dire but hopes the study will have an impact of future development decisions. The survey was motivated by a desire to understand how long species can live in forest fragments. If they persist for many decades, this gives conservationists a window of time to create wildlife corridors or restore surrounding forests to reduce the harmful effects of forest isolation.

"I would hope that this research will really highlight the value of large expanses of forest and also, will highlight one of the costs of these hydro-electric reservoirs," he said. — Reuters