The report, released Monday in Bangkok, found that the total cost of lost agricultural production and other negative impacts from climate change would be equivalent to as much as 6.7% of gross domestic product in major Southeast Asian countries by the end of this century, more than double the 2.6% loss estimated for the world as a whole.
It also found that rice yields would decline by as much as 34% in Indonesia and 75% in the Philippines, while Thailand and Vietnam, among the world's biggest exporters of the food, would also experience declines.
Southeast Asia 'will have to do something' to offset those losses, including making new investments to maintain agricultural production, says Juzhong Zhuang, an economist at the ADB.
The vulnerability of Southeast Asia stems largely from its geography, which includes the vast archipelago of Indonesia and other low-lying nations such as Thailand and Vietnam with long coastlines. Some 80% of the region's population and much of its economic activity are within 100 kilometers of the coast, the ADB said. Southeast Asia's economy also relies heavily on agriculture and forestry, both of which may be affected significantly by changing weather patterns.
Economists and scientists are still debating how emissions will affect climate in Asia, though generally they agree that weather patterns should become more volatile. The ADB, for its part, said it believes Thailand, Vietnam and Indonesia will experience drier weather over the next several decades, with that pattern possibly reversing later in the century.
Annual mean temperatures in those countries and the Philippines could rise by as much as 4.8 degrees Celsius by 2100 compared with 1990 levels, while sea levels could increase by 70 centimeters.
Those changes, especially the higher temperatures and a rising incidence of storms, could combine to cut rice yields and otherwise damage crops, the ADB said.
In debates on global climate change, Southeast Asia has traditionally received less scrutiny than other areas because it remains a relatively small contributor to greenhouse-gas emissions, accounting for about 12% of the world's total. But the region's role as a key supplier of rice and other agricultural commodities means any negative impact on farming could have big ripple effects, driving food prices higher.