Mekong megadrought erodes food security

The worst drought ever recorded in Vietnam is stoking fears of a food security crisis. In a meeting with government officials next week, researchers with the International Center for Tropical Agriculture (CIAT)’s Asia regional office in Hanoi will unveil maps showing how water scarcity and climate change may imperil key crops—rice, cassava, maize, coffee, and cashew nuts—across the country. 

Drought is hammering Vietnam's agriculture, including crops like rambutan seen here being transported in the Mekong delta.
 

"The severity of this year's drought will have a profound impact on Mekong delta agricultural production,” says Brian Eyler, deputy director of the Southeast Asia Program at the Stimson Center in Washington, D.C.

As of mid-March, nearly a million people in central and southern Vietnam lack access to fresh drinking water, according to a recent United Nations report. And supplies of rice, the main staple crop, are in jeopardy. Saltwater intrusion in the Mekong delta has destroyed at least 159,000 hectares of paddy rice so far, with a further 500,000 hectares at risk before the onset of the summer monsoon. The Vietnam government has approved $23.3 million in emergency funds to compensate hard-hit farmers and provide water tanks and other critical provisions. Meanwhile, the Vietnam Red Cross Society has been mobilized to provide assistance in provinces where local health clinics are struggling to deliver essential services due to insufficient freshwater.

Concern is focused on the Mekong River, Southeast Asia’s longest waterway and the lifeblood of the region. The river originates on the Tibetan Plateau and flows south through China’s western Yunnan province, Myanmar, Laos, Thailand, Cambodia, and Vietnam before spilling into the South China Sea. According to the U.N. report issued last month, “Since the end of 2015, water levels in the lower Mekong River have been at their lowest level since records began nearly 100 years ago.” The United Nations estimates that the water level flowing through the Mekong and its lower tributaries last month was down 30% to 50% compared with average March levels.

Water levels customarily drop during the dry season, resulting in saltwater intrusion from the South China Sea. But last year, because of unusually sparse rainfall, the saltwater intrusion began 2 months early—tainting groundwater and rice paddies as far as 90 kilometers inland, according to the United Nations. Most rice growers in the region get at least two yields annually out of the delta’s fertile soil, Eyler says. “Typically this time of the year, farmers there will have planted the first crop,” he says. “But currently most fields are dry and the earth cracked.”

Several factors reduced the Mekong to a trickle this year, says Leocadio Sebastian, regional program leader for the International Rice Research Institute’s office in Hanoi. “El Niño contributed to the drought by reducing rains, and this may be exacerbated by climate change,” he says. Upstream dams, a perennial concern in Southeast Asia, have also constricted flow. Under normal flow conditions, Sebastian says, “the river’s fresh water drives more saline water back to the sea.” China, which has often come under criticism from environmentalists for building and financing dams on the Mekong, is now attempting to ameliorate conditions: It is currently releasing water from a major Mekong dam in Yunnan, the Jinghong hydropower station, to alleviate shortages downstream, the state news agency Xinhua reports.

On 12 April, a CIAT research team assembling maps will brief Vietnamese officials on projected vulnerabilities from climate change. The bottom line, says CIAT’s Clément Bourgoin, is that “the coastal Mekong region may become less suitable for some agriculture,” especially rice, because of warmer summer temperatures and saltwater intrusion from rising sea levels.

Rice varieties with enhanced tolerance to salt and drought may rescue some farmers, but the use of modified seeds “must be matched” with good climate modeling, Sebastian says. “Even ‘drought tolerant’ rice doesn’t tolerate the worst possible droughts.”

Khoa Le

Source: Science Mag