Rising sea level and salt water intrusion threaten Mekong Delta agriculture
By Marwaan Macan-Markar
19 April 2012
BANGKOK – 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 Banos, southeast of Manila, to develop a strain of rice that can withstand submergence for over two weeks and resistant 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 centre on rice. “Even if we have rice crops that are tolerant to floods they can die because of salinity.” Four dams built by China on the Mekong have already had an impact on the delta’s rice farms. 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 have provided clues to the possible impact of climate change. Almost one-third of the delta, where nearly half of Vietnam’s rice is grown, 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. The search for this grain has its roots in the Indian state of Orissa, home to a 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 said in an interview. “It can be submerged for 17 days.” But 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,” he said. “That would be the answer to the problems faced in the Mekong Delta from flooding and salinity from the rising sea tides.” Salt water from the South China Sea now spreads 40 kilometers into the delta, unlike the 10 kilometer 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.” Already farmers have begun to change occupations, many going from rice farming to shrimp farming, he told IPS. “There is a very noticeable shift from the previous times when growing rice and shrimp farming were seasonal.” […]
Thứ ba, ngày 22 tháng 02 năm 2011 cập nhật lúc 16:08 Residents in the Mekong delta are in despair at the speedy salinity of the river bed. This year has seen the salinity to reach high levels and earlier than expected. The area has seen tens of hectares of paddy fields and hundreds of hectares of vegetables destroyed and fresh water supply for human consumption has dried up. Most of the winter-spring rice crop in district Tra Cu and Cau Ngang in the Mekong delta province of Tra Vinh has turned yellow, although farmers have not yet harvested the crop. Mr. Kim Ngoc Leng in district Tra Cu is in despair as 1.7 hectares of his paddy has turned yellow. At first he thought that the crop has been plagued with insects but later he discovered that it was the excessive salt in the water which had caused the crops to turn yellow. According to the initial statistics from the Department of Agriculture and Rural Development in the province, more than 1,700 hectares of rice in two districts has been destroyed due to salinity. Farmers in two Mekong delta provinces of Soc Trang and Bac Lieu are also in despair because water in their rice fields has dried and the canal water is too salty to use. Nearly 9,000 hectares of high quality winter-spring crops in district Nga Nam in Soc Trang are facing destruction. The Hau River has a high salinity penetration two weeks earlier than at the same period last year, according to Eng. Ngo Thi Duc Hanh of the Center for Hydro-meteorological Forecasting in the province. The salinity level measured was up to 6.3 grams in the rivulet mouth of Dai Ngai in the Hau River, as compared to only 3 grams during the same period last year. Residents in the coastal Mekong delta provinces faced an additional problem of shortage of fresh water. People in coastal regions like Binh Dai, Ba Tri in Ben Tre province and Duyen Hai in Tra Vinh had to buy fresh water. Le Van Tot, chief of Ca Thu hamlet in district Tan Phu Dong in Tien Giang province, said residents felt helpless and depressed as salinity has come too early. Some people in these areas have to filter alum water from nearby canals or ponds for daily household chores of cooking and cleaning. Many others have had to purchase fresh water at VND2, 000 per a 20 liter can.
