Sea Level Rise Threatens Mekong Rice


By Marwaan Macan-Markar

With Vietnam’s fertile Mekong delta threatened by rising sea levels and salt water ingress, the country’s future as a major rice exporter depends critically on research underway in the Philippines.

Scientists at the International Rice Research Institute (IRRI) are working with Vietnamese counterparts in the town of Los Baños, 63 km southeast of Manila, to develop a new strain of rice that can withstand submergence for over two weeks and also resist salinity.

A flood-tolerant variety, dubbed “scuba rice”, which has the submergence (SUB 1) rice gene, already offers half the solution.

“IRRI is experimenting to find a rice variety to deal with both problems,” says Bjorn Ole Sander, a scientist at the world’s leading non-governmental research center on rice. “Even if we have rice crops that are tolerant to floods they can die because of salinity.”

The search for this new grain had its roots in the Indian state of Orissa, home to the flood-resistant rice variety that resumes growth after being underwater for even 14 days – unlike other rice varieties that die if submerged for just over a week.

“This has been achieved without genetic manipulation, by breeding the SUB 1 variety,” Sander told Tierramérica. “It can be submerged for 17 days.”

Rice was domesticated roughly 12,000 years ago. It is the main staple food for a large part of the world’s human population, especially in Asia, and is the grain with the third-highest worldwide production, after maize (corn) and wheat.

Throughout its long history, it has been adapted to different climate conditions and agricultural practices. In Asia it is commonly grown in flooded parcels of land known as paddy fields, both on flatlands and on terraces built into hillsides. Today it is the only grain crop that can withstand submersion.

But a controlled aquatic environment between five and 15 centimeters deep is one thing, and flooding caused by rising sea levels is quite another.

The quest for a salinity-tolerant variety that could be blended with scuba rice is more daunting.

“It will take at least four years to find a rice variety that will be tolerant to both salinity and flooding,” said Sander. “That would be the answer to the problems faced in the Mekong Delta from flooding and salinity from the rising sea tides,” he added.

The Mekong River begins its 4,880-km route in the Tibetan plateau and flows through southern China, touches Myanmar and Thailand, and winds its way through Laos, Cambodia and Vietnam before flowing out into the South China Sea.

The mouth of the Mekong, a vast delta stretching 39,000 sq km in southwestern Vietnam, is known as the country’s “rice belt”.

Salt water from the South China Sea now spreads 40 km into the delta, unlike the 10-km inland reach of the sea 30 years ago.

“The future of the delta is at stake. That is why we are working with IRRI to develop a rice variety to deal with floods and salinity,” says Nguyen Van Bo, president of the Vietnam Academy of Agricultural Science, a government-backed entity in Hanoi.

“Seven percent of the paddy fields in the delta are affected by rising sea levels,” he noted. Already farmers have begun to change occupations, many going from rice farming to shrimp farming, he told Tierramérica.

“There is a very noticeable shift from the previous times when growing rice and shrimp farming were seasonal,” he added.

And Vietnam’s fate – particularly on the delta – is going to worsen, warned Asian agriculture scientists and climate change specialists at a meeting in Bangkok on Apr. 11-12.

This would add to existing woes from erratic weather patterns that have hit the region’s other major rice producers like Thailand, they added.

The delta accounts for nearly half of the 42 million tons of unmilled rice produced in Vietnam – the world’s second largest rice exporter after Thailand – with three annual harvests.

In 2011, Vietnam exported a record seven million tons of rice, mainly to the Philippines and other Asian markets.

For over 17 million of Vietnam’s 87 million people, who call the flat, humid delta their home, the network of waterways has been pivotal to rice production.

Four dams built by China on the Mekong were the first to impact the delta’s rice farmers.

As the usual water flow ebbed, salt water raced inland and the alluvial soil dumped on the delta by the river during the annual monsoon floods also dropped, reducing the natural fertility.

But the dams provided clues to the possible impact of climate change. Almost one third of the delta could be submerged by salt water if there is a one-meter rise in the sea levels, a report by the country’s National Institute for Hydrometeorology and Environmental Science warned in 2009.

World Bank studies rank Mekong delta communities among the most threatened by sea level rise in 87 developing countries surveyed.

Warnings that 21 percent of Asia’s crops will be affected by climate change by 2050 have yet to push government leaders from the 190 countries who gather at the annual United Nations climate change summit to include agriculture in the negotiations.

“Agriculture and food production are mentioned in the UNFCCC (United Nations Framework Convention on Climate Change) but they have not been translated into language that will initiate a specific work program on agriculture in relation to climate change,” says Bruce Campbell at the Consultative Group on International Agricultural Research (CGIAR).

“There isn’t a common voice on agriculture at the UNFCCC negotiations,” said Campbell, a director at CGIAR, which is sponsored by a number of United Nations agencies and the World Bank.

“Climate change is impacting farming systems and it is endangering crops,” Campbell told Tierramérica.

“Agriculture systems have to be transformed to make agriculture climate resilient,” he added.


Tierramérica is a joint project of the United Nations Environment Programme (UNEP), the United Nations Development Programme (UNDP) and The World Bank (WB), with IPS serving as the executive agency.

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