फ़रवरी 08, 2016
Vietnamese scientists say climate change will probably exacerbate existing ecological problems in the Mekong delta, such as water pollution, salinity intrusion, loss of aquatic biodiversity and rising susceptibility to flooding.
Their concerns echo a 2006 warning by the Intergovernmental Panel on Climate Change (IPCC) that the Mekong River Delta and two others — the Ganga and the Nile — are particularly susceptible to rising sea levels.
The delta region – a low-lying area in southern Vietnam dotted with paddy fields and shrimp farms – is home to an estimated 17 million Vietnamese, yielding not only rice but also a third of the country’s GDP.
It is also among Vietnam’s poorest areas, and environmental restoration projects in the region are often a low priority for officials busy trying to kickstart a slumping economy.
“They’ve made some progress, but because of the economic crisis, investment capital is a serious problem,” said Tran Minh Khoi, director of the Center for Water Quality and Environment, a government institute in Ho Chi Minh City that monitors water quality in the Mekong Delta.
Large-scale rice production causes soil pollution
The problems are rooted in the large-scale expansion of rice production in the Mekong Delta, which now produces roughly half of the country’s rice.
In the 1990s, the Vietnamese government began the widespread construction of sluice gates, high dikes and other irrigation measures that were designed to control the Mekong River’s natural flood pulses for the sake of boosting rice cultivation. While the measures have helped Vietnam become one of the world’s top three rice exporters, they have also altered the Mekong’s alluvial flood pulse and changed its ecological balance.
For example, rice farming in the upstream regions of the delta discharges effluents that cause eutrophication of freshwater systems and damages fish populations, according to a recent study by a team of scientists from Can Tho University. And because so many of the delta’s soils are naturally acidic, converting them to rice fields has increased the mobility of heavy metals like arsenic and cadmium.
Le Anh Tuan, a professor at the university’s college of environment and natural resources, said the overuse of fertilisers and pesticides by many Mekong Delta farmers only exacerbates those problems.
“Native fish species will be lost, and biodiversity will be degraded,” he said. “And the consequences may be worse with climate change.”
The construction of high dikes in the delta’s upper reaches has also correlated directly with an increased risk of flooding in Can Tho, one of the delta’s largest cities, according to research by Hideto Fujii, a researcher at the Japan International Research Center for Agricultural Sciences.
According to Fujii, upstream dikes store a large amount of water that can be dangerous when dikes break. That was evident in 2011 when heavy floods in the delta province of An Giang broke through dikes and caused damage in downstream areas, he said.
And when seasonal floods subside, fresh danger surfaces in the form of saline intrusion.
Because the Mekong is a tidal river, it has a flood pulse in which saline water from the South China Sea travels up its tributaries during the February-to-April dry season. But the construction of so much irrigation infrastructure, coupled with heavy water use in upstream provinces, has in many cases reduced seaward flows of freshwater — and allowed more saline water to travel in the other direction.
A slew of controversial hydropower dams proposed for stretches of the Mekong River in China, Laos and Cambodia would only heighten the risk of more saline intrusion in the delta, according to Dao Trong Tu, senior advisor to the Vietnam Rivers Network, a Vietnamese NGO.
“In the Mekong Delta we have very dense canal system, so if water intrudes it impacts agricultural production very much,” he said. “It’s a big impact.”
International funds pour in to tackle climate change
Several governments and international donors have recently identified climate change as a central priority in Vietnam, and there are several ongoing projects aimed at mapping the extent of the delta’s environmental problems and devise solutions.
The German and Australian governments, for instance, are promoting climate-adaptation measures in the Mekong Delta, and the Dutch government has partnered with local researchers to develop a 100-year plan for sustainable growth in the region. The first version of the plan, released in 2012, suggests closing off branches of the Mekong River in the dry season to prevent further saline intrusion.
On a recent trip to the Mekong region in December ,US Secretary of State John Kerry said that the US will give US$17 million for a new American-led project to help Vietnamese communities adapt to climate change and “reverse” environmental problems. He said the project will be administered by the US Agency for International Development.
“Vietnam is one of the most vulnerable countries in the world when it comes to climate change,” Kerry said. “And we will see very serious impacts if we don’t change course today.”
But there are considerable obstacles. Here’s one challenge — though demand for freshwater is increasing across the Mekong Delta, the Ministry of Agriculture and Rural Development has largely resisted calls from Vietnamese scientists to alter its ambitious agricultural production targets, which scientists say are ecologically unsustainable and sorely outdated.
According to Tung Phung Duc, director the Mekong Development Research Institute in Hanoi, a central problem is that state-owned enterprises (SOEs) exert significant control over Vietnam’s nearly US$4 billion rice-export industry and are resistant to reforms that would cut into their profits.
“We don’t have a problem with food security,” he said. “There are a lot of SOEs in the agriculture sector, and I think it’s better (for the government) to sell them.”
Shrimp industry causes fresh conflict
And in the southern reaches of the Mekong Delta, the creation in recent years of coastal shrimp farms has led to “severe losses” of mangrove forests, according to a January study by a team of German and Vietnamese scientists. Shrimp exports from Vietnam are now worth US$2.8 billion per year, according to the state-controlled media, but scientists say the loss of mangroves is problematic because the trees have historically been a natural defense against storms along the delta’s 600 kilometre coastline
And as the shrimp industry grows, conflicts are deepening between shrimp and rice farmers, according to Tran Minh Khoi. He said shrimp farming uses a mix of fresh and brackish water, and the conflicts typically arise when the practice prevents rice farmers from getting the freshwater they require.
The conflicts, Khoi added, are likely to worsen as sea levels rise and demand for freshwater increases.