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When Hai Thach weighed his rice harvest last week it was half as much as it should have been. But it was still better than 2013, the year he lost everything.

For Thach and millions of other poor farmers in Vietnam's Mekong Delta, earning an income off the land is getting harder. Prolonged dry seasons and sea-level rise, brought about by climate change, is pushing saltwater from the South China Sea deeper inland, compromising farmers' irrigation channels.

"The water is salty every year," Thach, 64, told VICE News, "but it's been worse in the last three years. I'm scared because I cannot live without rice."

Pointing next door to an empty rice field that is now caked earth with a thin white layer of salt on top, Thach said his neighbors quit farming last year. "They're trying to sell their land and open a business in the city," Thach told VICE News. "They are wealthier than me. That's not something I can afford to do."

More than 17 million people live within the Mekong Delta. Farmers and fishermen have been intensively working the tributaries and fertile fields for only about 150 years. Agricultural success there has made Vietnam the world's third largest rice exporter. But a changing climate now threatens food security and livelihoods.

Hai Thach, 64, stands over his empty rice field. He lost half of his rice crop this season to saline intrusion.

Hai Thach's neighbor walks across an abandoned rice field.

Vietnam is one of the countries most vulnerable to rising seas. And its low-lying Mekong Delta is expected to be hit hardest. The region is, on average, just over a meter above sea level.

According to Andrew Wyatt of the International Union for the Conservation of Nature, a worst-case scenario would be something on the order of one meter of sea level rise by 2100. That could leave 40 percent of the delta flooded, potentially leading to a mass internal migration of almost 10 million people and devastating economic losses estimated at $17 billion. That's in an area that produced almost half of Vietnam's 45 million tons of rice in 2014. In a country of 90 million, that would be a major blow to national income and food security.

"Saline intrusion has always been a natural, seasonal process," Wyatt told VICE News. "But with sea level rise projections, saltwater will go further inland. Much of what the local communities are reporting is in line with our climate projections."

Saltwater intrusion comes during the Mekong Delta's dry season, which usually lasts from November to April. Lack of rainwater allows saltwater to flow farther upstream into the Mekong River's tributaries, the main irrigation source. In the past, Farmers adapted to this cycle by planting a single rice crop during the wet season. Following war with the United States in the 1970s, farmers started a second crop, and then a third in an attempt to increase meager incomes. That's becoming increasingly difficult now that the dry is lasting longer.

And this past season was extraordinary. The dry season came a month early and precipitation has yet to return despite the onset of delta's wet season.

"There's usually enough freshwater to use, but the rainy season has come late," Thach said. "The rain has not diluted the salty water enough to grow rice."

Salt water intrusion in Bac Lieu Province has turned this rice crop yellow.

Ngo Van Dong's family have been rice farmers for generations. He recently converted his family's rice fields to shrimp ponds.

Saline intrusion has reached up to 35 miles inland this year, according to Vietnam's Southern Hydrometeorology Station. In Bac Lieu Province, a coastal floodplain one hundred miles southwest of Ho Chi Minh City**, **salinity is twice the level it was last year. That's not so much a problem anymore for Bac Lieu, as most of the rice fields have been converted to shrimp ponds. Rather than struggling to find more freshwater for a third crop, many farmers took advantage of increased salinization and switched to intensive shrimp cultivation, which thrives in brackish water.

"Ten years ago this area was all rice fields," Ngo Van Dong, 56, told VICE News. "We can make more money this way." Ngo cleared five acres of rice fields to make seven shrimp ponds. "I'm trying to buy more land to expand, but no one is selling."

Bac Lieu has prospered from shrimp farming, but for aquaculturists along the coastline this livelihood is much more precarious. Do Thi Dieu started shrimp farming 15 years ago. She says the water in her shrimp ponds is becoming too salty. "Before, even in the dry season, there was some rain, but now there is none. It's lasting longer than it used to," Dieu said. "In the dry season, the salt content is sometimes too high for shrimp to develop well."

Shrimp cultivation is expensive and is usually only an option for wealthier farmers who can afford the high cost of dredging land and buying equipment. Shrimp farming also comes with its share of ecological problems. The land closer to the sea in Bac Lieu used to be mangrove forests, but it was cleared to make way for the shrimp farms.

Do Thi Dieu, 35, worries climate change will force her to abandon shrimp farming.

"Vietnam had about 60 percent mangrove forest loss during the last 70 years," said Le Anh Tuan, Deputy Director of the Research Institute for Climate Change. "Vietnam's mangrove forest areas have fell from 408,500 hectares in 1943 to 189,200 hectares in 2000, and just 168,688 hectares in 2013."

Mangroves are important habitats for a vast array of plant and animal species. They also absorb carbon dioxide, helping to regulate the amount of the greenhouse gas in the atmosphere. And they provide crucial barriers against coastal erosion, storm surges, and sea level rise.

"Mangrove forests are buffer belts that reduce the magnitude of sea tides to the delta floodplains." Tuan said. "Thick mangrove forests can also effectively reduce sea winds that push saltwater inland."

In efforts to keep the sea back, the Vietnamese government has continued to construct coastal infrastructure, but it needs to reinforce and expand the existing 5,000 miles of dikes and canals, according to the United Nations. They've also attempted to reforest large areas of mangroves, but the results have been mixed.

Vietnam is going to need all the coastal protection it can get. The country experiences six to eight typhoons annually, and they could become more extreme as the impacts of climate change intensify over the coming decades.

In 2012, floods swept away all the shrimp in Do Thi Dieu's ponds. "In the last three years the water levels have risen and it's breaking our dykes and flooding our houses and shrimp ponds," Dieu told VICE News.

"If climate change is to affect us, we will leave."

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