Cambodia's mangroves under threat

The remains of a mangrove forest in Peam Krasop Wildlife Sanctuary in Koh Kong province. Sand dredging, rising sea levels and storms have taken a toll. Photograph: Sun Kong

Cambodia's vital southern mangrove systems are choking as rising sea levels, agitated by climate change, inundate them with sand, while sand dredging sucks them dry of sediment, a study by the International Union for the Conservation of Nature (IUCN) has found.

Stressed by a host of escalating environmental pressures, mangroves in Koh Kong and Kampot provinces, including the largest in all of Southeast Asia, are struggling, the IUCN study reports.

Researchers focused on the 23,750-hectare Peam Krasop Wildlife Sanctuary in Koh Kong province, where the mangrove plays a “vital” role in stabalising coastlines and protecting coral reefs and sea grass meadows, while trapping sediment that nourishes sea life crucial to livelihoods.

Brian Kastl, an international consultant for IUCN, which conducted the study, said that costal beach barriers protecting the mangrove and others throughout Southeast Asia had undergone unprecedented rates of landward migration. 

“Beaches are fed by sediment sourced [in the] upstream river, but there have been developments such as sand dredging, dam constructions and river banks collapsing,” he said.

Therefore, they will experience sediment shortages, erosion in beach height and length and also beaches disappear in places.”

In the past few years, the Post has repeatedly documented large-scale industrial dredging operations in mangrove areas of Koh Kong and Kampot province, including ships that were tracked into Peam Krasop Wildlife Sanctuary.

Kastl said that since 1973, the beach barrier in Peam Krasop had receded an enormous 390 metres, resulting in the total loss of 0.60 square kilometres of mangrove forest.

The rate of beach migration was also accelerating and had claimed as many as 90 metres between 2010 and 2011, Kastl added.

Forests could not survive the increasing quantity of sand that was dumped on them through rising sea levels, while increasing numbers of storms and rates of costal erosion had left mangroves exposed to greater wave energy, causing further landward beach migration.

Mom Phalla, acting administrator of the Koh Kong Environment Department, said the mangrove forest feeds aquaculture, which was “the life” of fishing communities in Koh Kong.

“The impacts of climate changes such as changes in rainfall and an increase of storms and the changes to the level of the tide have caused the fishery products and fields stocking shrimp to decline year-on-year,” he said.

Sediment shortages and sand erosion had killed swaths of mangroves in the Peam Krasop and Bang Kachang forests, Phalla said.

Rampant sand dredging was conducted by ruling party Senator Ly Yong Phat in the Tatai river, which flows straight past Peam Krasop, though he wound up the operation after several years in October last year.

Simon Wilkinson, a manager at the Rainbow Lodge eco-resort on the Tatai river, said yesterday that small-scale dredging boats crewed by two to four men continued to operate in the area.

“They do have dredgers down here. I don’t think they’re the super industrial dredgers. They seem to be small boats. The noise is still a problem but it’s not really as bad as before,” he said.

IUCN Southeast Asia director Robert Mather told the Post that sea levels had risen three millimetres a year on average globally in the past decade and five millimetres in the South China Sea, though the rise had not been so bad in Indochina, only slightly effecting countries in the region.

“Within the sea level rise, we will face the problems of erosion, bigger storms and changes in rainfalls,” he said.

“In Cambodia, it is not the case yet, but in some places, mangrove forests are degraded and shifting to the shores. Not only have the mangrove forests shifted, but the island people also moved to the shores, too.”

The Ben Tre and Soc Trang mangroves, located in the Mekong Delta in Vietnam, were two areas that scientists predict would be most affected by rising sea levels, he added.

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