Nearly 250,000 hectares of flooded forests around the Tonle Sap lake – about a third of the total – have been consumed by fire since January, according to estimates by Conservation International (CI).

CI Cambodia director Bunra Seng described the situation as a “disaster”.

“Based on data from NASA’s MODIS satellite we found 230,100 hectares burned in Zone 3,” Seng said, referring to the administrative designation for the 640,000 hectares of forest, wetlands and grasslands that surround the Tonle Sap.

While negligence and land grabbing (which often involves conversion of forests into rice fields by burning) are suspected to be the immediate causes of the fires, experts say a combination of man-made and environmental factors are at play.

Climate change and a strong El Niño-induced drought, deforestation and upstream hydropower and irrigation projects all factor into the extremely dry conditions that allowed the wetland forests to burn.

Some 20 per cent of water flowing into the Tonle Sap comes from the Cardamon Mountains, while a similar portion flows from forested areas north of the lake, said Seng.

Wildlife Conservation Society (WCS) director Ross Sinclair said the degradation of these “water catchments” from large-scale deforestation had contributed substantially to the lack of water.

“They are part of the resilience of the system,” he said, an assessment Seng agreed with.

Seng and Sinclair also pointed to hydropower and irrigation projects upstream being contributing factors to changes in the flood cycle.

“It’s a concern,” Seng said, adding that this year Tonle Sap and Mekong water levels were the lowest since CI began keeping records in 2007.

Simon Mahood, senior technical adviser for WCS, on the phone from the Prek Toal bird sanctuary where fires have consumed over a quarter of the forests over the past months, said that by his organisation’s measurements at the ranger station “the highest water level recorded this year was 3 metres below the next lowest from the past five years”. He said the gauge was “now out of the water”.

Tonle Sap’s fisheries are also threatened by the burning of the forests, which are the breeding grounds for fish during the wet season, a concern shared by CI and WCS.

What’s more, unusually low water levels typically spell a lower fish catch, according to Harvard hydrologist Mauricio Arias whose doctoral research focused on the Tonle Sap.

“It will probably have huge implications for fisheries,” he wrote in an email yesterday.

Meanwhile, continued efforts by rangers and several days of rain this week has, for the time being, significantly helped control the fire, according to Mahood.

“All it takes is a few days of dry conditions and strong winds for the fire to pick up again.”

Spokesmen for the Ministry of Agriculture, Forests and Fisheries and for the Ministry of Environment could not be reached yesterday.