Seawater dents rice production

Urgent action is needed to prevent salt intrusion causing severe damage to rice production and loss of drinking water in Bangladesh and Vietnam, according to reports by the World Bank and the Norwegian Institute of Bioeconomy Research (NIBIO).

The reports say sea level rise, combined with floods and waterlogging caused by cyclones and typhoons, is threatening large areas of land that is currently highly productive.

Unless counter measures are taken to stop the levels of salt rising and to develop more salt-resistant strains of rice, both the nations will increasingly struggle to feed their rising populations, say the World Bank and the NIBIO.

Their reports also say there will be mass migration away from the affected areas, according to information received here from London.

Dr Udaya Sekhar Nagothu, international coordinator for the ClimaViet project, says, “Saline levels in soils and irrigation waters in coastal areas are steadily increasing, it is vital that something is done about it before the situation gets out of hand.”Bangladesh and Vietnam are already being affected by the sea level rise, and NIBIO is working with local governments in the Vietnamese delta regions to reduce the impacts, according to Climate News Network.

One of the most helpful solutions would be to develop more salt-resistant varieties of rice.

According to the World Bank, salinity issues in Bangladesh will most probably lead to significant shortages of water for drinking and irrigation by 2050.

It is estimated that increased soil salinity may cause decline in rice production by 15.6 percent in the next 30 years, resulting in significant reduction in income of the affected farmers.

“Due to their extensive coastline and many river deltas, countries like Bangladesh and Vietnam are hotspots for climate change impacts such as sea-level rise and salt water intrusion,” says Dr Nagothu, who is based at NIBIO.

“High levels of salt in agricultural soil or irrigation water make it difficult for salt-sensitive rice plants and other crops to absorb water and necessary nutrients. As a result, plant growth is suppressed and crop yields are significantly reduced.”

In some regions in Vietnam's Red River and Mekong deltas, rice production has now been abandoned in favour of shrimp cultivation in ponds, as brackish water shrimp varieties tolerate higher salt levels than most rice varieties.

In the Red River delta, salt water can intrude 30-40 km inland, followed by high water levels in the riverbeds and increased sedimentation in canals and flooded plains.

During the dry season, seawater moves even further inland because of the lack of fresh water in the canals.

The situation in southern Bangladesh, where various measures to meet these issues have been tested, is similar.

“In Bangladesh, one successful measure has been an aquifer recharge that collects fresh water during the rainy season for use in the dry season,” Dr Nagothu says. “This, in combination with improved soil management, can greatly benefit agricultural land vulnerable to salt water intrusion.”

However, he insists that the development of salt-tolerant varieties of rice and other crops accessible to small-scale farmers is vital.

SALT-TOLERANT VARIETIES

“The salt-tolerant rice varieties developed so far are not good enough to survive the high salinity levels. They are also expensive, and thus unavailable to most small-scale farmers.”

According to Dr Nagothu, there is a need for several improvements, including advancement in science developing new rice varieties; alternative cropping systems; physical infrastructure to withstand sea-level rise; and ways of increasing production for a growing population.

A more hands-on approach from local policymakers is also necessary, he says. Although they acknowledge the issues at hand, adequate funding is rarely provided for research on the development and extension of salinity management measures.