The Philippines-based institution is devoting fresh efforts to mitigating the coming threat, but senior climate scientist Reiner Wassman said adequate funding had yet to materialise.

"Some of Asia's most important rice-growing areas are located in low-lying deltas, which play a vital role in regional food security and supplying export markets," Wassman told the IRRI magazine Rice Today.

"With Vietnam so dependent on rice grown in and around low-lying river deltas, the implications of a sea-level rise are ominous indeed."

Rice is the staple cereal of nearly half the world's 6.6 billion people.

Wassman said the impact of global warming on the key cereal would depend on the patterns of change in rice-growing regions.

But he warned a threatened rise of between 10 and 85 centimetres (four to 34 inches) in sea levels over the next century could have "enormous" impacts on some countries, including key rice exporter Vietnam.

IRRI is cooperating with Hanoi to assess the impact of sea-level rise scenarios in the Mekong delta, he said.

The organisation this year launched a project to assess the possible impact of climate change on rice output and find ways of adapting rice-growing to the new realities of global warming.

He said higher temperatures could decrease rice yields, and that the organisation would initially focus on improving the resilience of rice to heat through research on plant physiology.

Aside from the sea-level rise threat to areas such as the Mekong delta, Wassman said more frequent or more intense droughts, cyclones and heat waves posed "incalculable threats to agricultural production."

But he said the IRRI was optimistic it would be able to develop new varieties that could cope with higher temperatures.

Scientists are also confident that the resilience of rice production systems to climate extremes, such as floods and droughts, can be improved, he said.

However, he warned it was unclear to what extent the impact of higher sea levels could be compensated for, and what the costs and socioeconomic consequences of any such changes would be.

The magazine said an increase in carbon dioxide concentration could actually improve rice yields.

However, funding constraints have prevented scientists from studying the issue under realistic conditions even though the technology is now available, it said.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.