The loss of these biodiversity hot spots, much of it driven by the illegal timber trade and the growth of oil palm, biofuel and rubber plantations, is worsening global warming, species loss and poverty, they said.

Globally, tropical forest destruction "is a super crisis we are facing, it's an appalling crisis," said Oxford University's Professor Norman Myers, keynote speaker at the Asia-Pacific Forestry Week conference in Hanoi.

"It's one of the worst crises since we came out of our caves 10,000 years ago," Myers said at the five-day meeting of 500 foresters, researchers, state officials and activists held last week in the Vietnamese capital.

Over-logging in Southeast Asia caused 19 percent of global rainforest loss in 2005, Myers said, compared to cattle ranching -- once a leading cause, mainly in South America -- which now caused five percent of world losses.

The rapid growth of palm oil and other plantations accounted for 22 percent, and slash-and-burn farming, unsustainable as more poor people exploit fast-shrinking forests, caused 54 percent of rainforest destruction, he said.

Asia's forest cover, including tree plantations, in fact grew by three million hectares from 2000 to 2005 -- largely because of China's 1998 logging ban and afforestation -- said the UN Food and Agriculture Organisation (FAO).

"In contrast, forest loss persists at a very high rate in several countries," said an FAO report. "Indonesia, Cambodia, Myanmar, Australia and Papua New Guinea and a number of other countries have seen significant losses."

Ecologists stress that new forests in China, India and Vietnam are man-made plantations lacking high varieties of plant and animal species.

"Many plantations, in terms of biodiversity, are green concrete," said Peter Walpole, head of the non-profit Asia Forest Network.

Yet what environmentalists call "tree farms" are set to grow at the expense of natural forests, especially palm plantations, which produce oil used in products such as soap, chocolate and cosmetics as well as biodiesel.

Commercial crops "will be the most important factor contributing to deforestation in Asia-Pacific countries," said the FAO report, citing record prices for food grains, energy and commodities.

Demand for forest products is also surging in Asia's boom economies.

Imports to China, now the world's top furniture exporter, increased more than tenfold from 53 billion dollars in 1990 to 561 billion dollars in 2004.

India's imports of wood products, including paper, grew from about 750 million dollars in 1990 to 3.1 billion dollars in 2005, the FAO said.

-- Forests' environmental services not factored into timber prices --

Asia's boom economies are now importing timber from as far as Central Africa and South America, said FAO forestry economist C.T.S. Nair.

"In a way, they are exporting the problem to other countries, especially those where policies and institutions are extremely weak," he said.

The illegal timber trade, fuelled by poverty and corruption, is rife in much of Asia, where 78 percent of forests are state-owned and often managed by the armed forces, not the people who live in or near them, experts said.

"The history of logging in Southeast Asia has been under the auspices of the military and of political families," Walpole said. "If you look at how Cambodia has been logged, this cannot happen without military acknowledgement.

"Burma has been logged by Thai generals. And if you look at the corruption of forestry in the Philippines, it's tied in many areas during the Marcos years to military presence and control. It's still in many military families."

Precise data is rare in the world timber trade, but spot checks by environmental monitoring groups have revealed disturbing trends.

Vietnam was named as a major hub for illegally-logged timber from neighbouring Laos in a recent report by Britain's Environmental Investigation Agency and Indonesian group Telapak -- a claim Hanoi has strenuously denied.

"Indonesia has had an export ban on sawn timber since 2004, and yet countries are still accepting sawn timber from Indonesia," said Chen Hin Keong of TRAFFIC, which monitors the illegal trade in endangered flora and fauna.

"Malaysia, Singapore, China, Taiwan, Korea, Japan, the UK, Germany, France, Italy, the US -- in big or small volumes, they are all accepting that."

Tropical timber is relatively cheap because key functions of forests -- clean air and water, and biodiversity -- are not factored into market prices, said Dr Daniel Murdiyarso of the Center for International Forestry Research.

"These services are underpriced or unpriced. It's a market failure."

Solutions are being debated -- including a universal timber certification system to rein in the illegal trade, and carbon credit schemes that would reward countries for preserving forests and offsetting pollution elsewhere.

But for now these are ideas, not realities, and the FAO report called support for forestry carbon offset schemes "disappointing" so far.

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