Bangkok- With 80 per cent of South-east Asia's 563 million people living within 100 kilometres of the coastline, the region is among the "most vulnerable" to climate change, the Asian Development Bank (ADB) warned Monday. South-East Asia, responsible for about 12 per cent of the global greenhouse gas emissions, can expect to see an average temperature rise by 4.8 degrees Celsius and a 70-centimetre increase in sea levels by the year 2100 if no serious measures aretaken to halt global warming, a regional survey on the economic effects of climate change, released in Bangkok, said.

The report, which took 15 months to compile, provides a detailed forecast on the negative economic and social impact of climate change on Indonesia, the Philippines, Singapore, Thailand and Vietnam over the coming decades if the world community fails to act on greenhouse gas emissions.

Climate change is already evident in the region, where the average temperature rose 0.1 to 0.3 degrees Celsius between 1951 to 2000, the sea level is rising 1-3 millimetres a year and in the frequency of extreme weather events witnessed in recent decades, the report noted.

The worst is yet to come.

"If the world continues 'business as usual' by 2100 the cost of preventing the problems we are looking at will be equivalent of 6.7 per cent of combined gross domestic product, more than twice the global average loss," ADB assistant chief economist Juzhong Zhuang said.

South-East Asia is deemed particularly vulnerable to climate change because of its long coastlines and high reliance on the agricultural sector which still employs 43 per cent of the labour force.

While climate change is expected to result in declining rainfall in Indonesia, Thailand and Vietnam over the next three decades, the Philippines will see increased precipitation throughout the century, the ADB report said.

Rice production in the region could decline 50 per cent by 2100, unless adaptation measures are implemented such as switching to drought- and flood-resistant strains of rice, it warned.

"The rice yield decline would range from 34 per cent in Indonesia to 75 per cent in the Philippines, with the decline projected to start in 2020 for most countries," it said.

"South-East Asian governments need to invest now in adaptation measures such as coastal zones, sea wall and in the agricultural sector in drought and flood resistant crops," ADB vice president Ursula Shaeffer-Preuss said.

Besides investing in adaptation measures, the region also needs to get serious about reducing it own emissions of greenhouse gases.

In 2000, South-East Asia accounted for 5,187 million tons of carbon dioxide equivalent, or 9.3 tons per annum per capita, compared with the world average of 6.1 tons.

Of that, 75 per cent was accounted for by "land use change and forestry," a category that covers the mass destruction of forest lands in Indonesian and Malaysia to plant palm oil plantations over the past two decades as the world demand for palm oil has soared.

Indonesia in 2000 accounted for 59 per cent of the region's greenhouse gas emissions, Thailand 6 per cent, Philippines 4 per cent, Vietnam 2 per cent, Singapore 1 per cent and the rest of South-East Asia 28 per cent.

Malaysia's data was not included in the ADB report.

Indonesia's former environmental minister, Emil Salim, a leading economist who helped compile the ADB report, said it will require political will and persuasiveness to alter the region's past practices.

"You mist hit hard and say if we don't do anything on this then you and I will all suffer," Salim advised his government. "Common language is crucial, not this language we use in this report," he told a press conference.

Salim advised regional governments to make climate change part of this fiscal stimulus packages being introduced this year to counter the global recession.

"Climate change can be coped with through mitigation and adaptation if we put our political will into it," Salim said. "That's the message."(dpa)