The Gulf of Thailand is teeming with seafood: mackerel, sardines, bream and squid. Snails and anchovies. Shiny green crabs and tiny pink shrimp.
"Every day, we are out catching fish and selling them," says Khiev Sat, the longtime leader of the coastal Cambodian village of Koh Kresna and the patriarch of a large family of people who have fished for generations. As he speaks, his sister arrives on a bicycle loaded with the morning's catch. "Our community fishery is strong," Khiev says, smiling.
But it hasn't always been this way. When Khiev was a young man, the waters near his home were largely empty. And around the world, other coastal fishing communities are still struggling with declining fish stocks, as climate change, environmental degradation and overfishing conspire to decimate marine populations, even as demand for seafood grows.
The key to Koh Kresna's bountiful, sustainable fishery has little to do with the fish themselves, and everything to do with one tree: the mangrove.
In many parts of the world, healthy fisheries rely on intact mangrove forests, says Radhika Bhargava Gajre, a coastal geographer and mangrove researcher at the National University of Singapore. "The majority of the fishes that we eat are supported by mangroves," she explains, because the submerged roots act as a nursery for baby fish.
And mangroves have other superpowers, some of which extend far beyond the tropical coastlines where they grow. What started as a local fishery solution in Cambodia is now a crucial part of the worldwide effort to slow global warming.
The tree that birthed a billion (or more) fish
In many ways, mangroves are a strange plant. They are semiaquatic, meaning they can grow in water and very wet soil. And they thrive in areas that most plants never could, where the water is salty.
There are dozens of types of mangroves, some that look more bushy and others that are full-blown trees. But all mangroves have elaborate root systems that hold the plants steady even when they're battered by waves and wind.
As a result, mangroves are a perfect place for aquatic animals to live, especially when they are young and vulnerable to predators. Mangrove roots act as a nursery, supporting 800 billion young fish, prawns and crustaceans each year, according to a 2024 analysis by a coalition of governments and international biodiversity organizations.
But about half of all mangrove ecosystems are at risk of collapse by 2050, the United Nations warns. The list of threats is long: Mangrove forests are cut down for aquaculture, logged for charcoal and destroyed to make room for coastal development.
Mangroves are also stressed by pollution and rising sea levels, Bhargava Gajre explains. "If mangroves are not intact, then a big cyclone can come," and kill the weakened plants, Bhargava Gajre says.
In Cambodia, political violence and mangrove destruction went hand in hand, Khiev says. In the late 1970s, the Khmer Rouge regime contributed to the deaths of an estimated 1.7 million people and forcibly moved millions more to brutal collective farms. When the regime fell in 1979, the country's economy was in tatters.
"People had nothing," Khiev says. "Many people cut the mangroves for charcoal. They had no other way to live."
But without the mangroves, there was no protection for young fish. The local fishery was decimated, Khiev says. "There was less and less to catch," he remembers. Some people left town to work in factories or emigrated out of Cambodia altogether to find work. Koh Kresna and other coastal villages shrank.
"That is when we started to educate ourselves, and educate each other," Khiev says. In the last three decades, scientists and international ecological protection organizations have led efforts to spread information about the importance of mangroves. That knowledge was immediately compelling to local fishermen in coastal Cambodia, Khiev says.
Since 2003, Koh Kresna and the neighboring village of Lok have collaborated to administer a community fishery organization, which manages the shallow nearby waters that are popular with fishermen and makes sure residents harvest seafood in sustainable ways. The fishery protects more than 145 acres of mangrove forest along its section of coastline.
They also plant new mangroves. In the last two years, fishery members and local residents planted more than 2,000 mangrove saplings with the support of multiple international organizations including the Red Cross and Landesa, a U.S.-based land rights organization.
"It is a lot of work. It takes a lot of cooperation between the fishery members, the government and nongovernmental organizations," says Rusrann Loeng, a fisheries expert who leads coastal projects in Cambodia for Landesa.
Cambodia's mangrove protection work is part of a bigger trend. Since 2000, global mangrove decline has slowed overall as restoration efforts have ramped up, according to the United Nations. Net loss of mangroves decreased by 44% in the period between 2010 and 2020, relative to the previous decade, a 2023 U.N. analysis found.
"When it comes to conservation stories, you don't come across lots of positive stories," says Bhargava Gajre. The falling rate of mangrove deforestation is a rare example, she says. "Credit [goes] to community stewards," she says. Stewards like the ones in Cambodia.
Mangrove tree: climate warrior
Mangrove restoration efforts have benefits far beyond fisheries.
Because of their intricate root systems, mangroves are uniquely resilient to the waves and wind from storms. The roots hold fast to mud and soil, reducing erosion and absorbing the power of storm surge to protect inland areas from flooding.
That protection can save lives. One study estimated that villages with more mangroves nearby had many fewer deaths from a major cyclone that hit India in 1999. Such protection is only growing in importance, as climate change makes powerful storms more likely.
Mangroves also help address climate change in a more direct way, by trapping planet-warming carbon. That's because dead mangrove leaves and branches fall into the water and are buried in the soil, where they decompose very slowly compared to other types of forests.
As a result, mangrove forests can store up to four times as much carbon as other types of forests, one study found.
In other words, mangrove forests punch way above their weight when it comes to trapping planet-warming gases before they can make it into the atmosphere. Just 0.2% of forests on Earth are mangroves, but the trees account for about 2% of all carbon removal, according to a recent analysis by the World Resources Institute.
Those benefits are not lost on people in Cambodia, many of whom have devoted their careers to protecting and restoring mangroves. "We know this helps with climate change," says 21-year-old Khiev Chien, a young member of the community fishery in Koh Kresna and the son of the town's leader. "We are helping the whole world."
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