Pulitzer Center
There was a traffic jam on the main canal of Kampong Luong, a village that begins on the shore of Cambodia’s Lake Tonle Sap and sprawls out onto the water. My sampan slowed, then stopped, the roar of its outboard softening to a growl that let in the clamor of a working waterfront. People called out from fishing boats laden with nets and yellow, plastic fuel jugs. They haggled at floating shops buoyed by empty steel barrels and bamboo rafts, piled high with sacks of rice, bottled water, beer, eggs, fish paste, and cooking pots. Up ahead, a convoy of longboats eased a wood-plank house with a thatch roof into deeper water.
Moving is a way of life here. On a map, Lake Tonle Sap looks like a tipped-over violin, with its neck, the Tonle Sap River, stretching southeast to join the Mekong River at Phnom Penh. Every year, monsoon rains force so much water down the Mekong that the Tonle Sap River changes direction and flows back into the lake, swelling the violin into a cello roughly five times its dry-season size. When the rains abate, the river flows south again, draining back into the Mekong.
This “flood pulse” mixes aquatic and terrestrial habitats and causes a churning of phosphorous, nitrogen, and carbon that makes the Tonle Sap incredibly fertile and rich in biodiversity. Every year, the lake yields about 300,000 tons of fish, the primary protein source for Cambodians. As the lake recedes, it deposits sediment across a vast floodplain for rice and other crops and sends a glut of fish downstream toward Phnom Penh. The river’s return to a southerly flow is a national holiday called Bonn Om Touk—three days of music, fireworks, and river races between pirogues powered by dozens of rowers. They celebrate the end of the rains and the coming of the fish, which will pour out of the lake for the next five months, feeding Cambodians as it has done for centuries.
But the Tonle Sap is in danger. Overfishing, deforestation, and a hydropower boom on the Mekong threaten to choke off the lake’s vital flood pulse and the migration of fish that follow it. A changing climate, meanwhile, promises longer, hotter dry seasons and shorter, more intense monsoon floods. When I visited the lake in late January 2014, three months into the dry season, the waters were already receding. Plastic bags, bottles, and paper trash clung like ornaments to the prickly mimosa brush all along the shore. Fish heads and coconut husks lay rotting in red mud. Blankets of water hyacinth and morning glory floated in the shallows.