Date released
31 May 2018

Supporting Vietnam's Mekong Delta farmers to meet sea-level challenges has given rise to new climate policy, new rice varieties, new technologies and new students.

The Mekong Delta in southwestern Vietnam is the country’s main rice growing region, comprising over four million hectares of flood plains and hills, two-thirds of which are used for agriculture. The region produces over 23 million tonnes, or more than 50%, of Vietnam’s rice. Over 6 million tonnes of rice are exported annually, bringing more than US$2 billion to Vietnam’s economy.

With over 25 years in Vietnam and recently signing up for another 10 years, ACIAR’s commitment to agricultural research in the Mekong Delta is deep and welcomed in this globally important region.

Agro-hydrological changes are threatening farming and social systems in the region and consequently food security across Southeast Asia. Coastal flood plains in the Mekong region are susceptible to rising sea levels that may be associated with climate change. These areas are especially vulnerable to changing environmental conditions and altered hydrology that affects rice growing.

While Vietnamese farmers are constantly adapting to these changing conditions, recent and predicted significant agro-hydrological events are forcing a broad re-evaluation of farming practices. Key challenges to this include availability of suitable cultivars, soil nutrient management options, the lack of knowledge of the potential threats from acid sulfate soil, and planning tools.

Dr Reiner Wassmann, coordinator of climate change research for the International Rice Research Institute (IRRI), is acutely aware of the impacts of climate change in the Mekong Delta region. Leading the ACIAR-funded $3.8m project, ‘Climate change affecting land use in the Mekong Delta’ (CLUES project), his team set out to improve the adaptive capacity of rice-based farming systems for effectivelymanaging impacts associated with climate change.

The scope of the project was based on six themes: environmental impact and vulnerability assessment, specifically using spatial data to assess flooding and salinity risks; improving locally adapted and elite lines of rice varieties against salinity and prolonged submergence; refining the options to manage rice cropping systems using decision support tools to better understand the responses of cropping systems to altered hydrology; examining farmers’ decision making capacity and ability to adapt to climate change through their actions; measuring greenhouse gas emissions in rice systems; and a land use planning case study in the coastal Bac Lieu Province using geographic information systems.

Four provinces in the Mekong Delta region—An Giang, Can Tho, Hau Giang, and Bac Lieu—benefited from the project.

Rising Tide

Rising sea levels have caused salt-water intrusion further up-river and into rice paddies, hurting the rice industry. Using spatial data, the project maps the risks of sea-level rise to predict future flooding. The project is also working on salt-tolerant and high-yielding rice varieties through the marker-assisted backcrossing plant breeding technique.

A total of 300 traditional and improved rice varieties were screened for survival and recovery potential, and new breeding lines were developed. Four rice lines were submitted for varietal release across the four target provinces in 2014. These included varieties for short growth duration, submergence and salinity-tolerance, and high yield. A total of five tonnes of seed of improved breeding varieties, comprising either four or eight varieties for each province, was distributed to the four provinces. Reduced phosphorus requirements for all varieties without affecting yield have also enabled farmers to increase their net incomes. In addition to breeding work, climate-smart agricultural practices and technologies, such as alternate wetting and drying to reduce greenhouse gas emissions, were implemented and are now influencing new climate change policies.

An inexpensive alternate wetting and drying technique was assessed by 100 farmers in Bac Lieu province. The ‘drain and re-flood’, or alternate wetting and drying approach reduces water use by 30 to 50% and reduces methane emissions from rice paddies by up to 50% compared to conventional continuous flooding. In all, 1,418 farmers were trained in the technique across 30 hectares of demonstration sites.

The CLUES project also trained 3,960 farmers (3,260 men and 700 women) on participatory rice varietal selection, and raised awareness of climate change for 2,979 local farmers and local government staff (including 862 females) through participatory discussions.

‘The interdisciplinary approach adopted by the CLUES project—encompassing hydrology, plant breeding, crop management and socio-economic approaches—yielded a range of tangible results on future risks stemming from sea level rise as well as possible response strategies in terms of adaptation and mitigation in rice-based systems of the delta,’ says Dr Wassmann.

The CLUES project has yielded useful results to benefit farmers in the Mekong Delta region and other coastal areas to improve rice production. Vietnam’s ‘white gold’ industry now has a stronger chance of improving even when faced with climate change.