The flooded forest is the Tonlé Sap's most important habitat and its least photogenic. The trees are short, tangled, and unremarkable to look at in the dry season, which is precisely why so much of it has been cut. What they do is structural. Their trunks and roots slow the incoming flood, dropping sediment and organic matter into a shallow, warm, oxygen-rich soup. Fish move in behind the water to spawn among the submerged branches, and their fry stay there through the high months, feeding and hidden. Nearly everything the lake produces — and it produces enough fish to supply most of the animal protein in the Cambodian diet — begins in drowned undergrowth like this. Boeng Chhmar's flooded forest is among the best-preserved stretches left.

The colonies are the other reason this place is protected. Painted storks nest here in numbers, their pink-flushed wings unmistakable when a flock lifts off a shoal. Spot-billed pelicans work the shallows in ragged lines. Oriental darters — the snakebird, which swims with only its neck above water — hang in the trees with wings spread to dry. Indian cormorants, black-necked storks and brahminy kites all breed or forage in the area. Most striking are the adjutants: the lesser adjutant is threatened across its range, and the greater adjutant, a huge, bare-necked, faintly disreputable-looking stork, is one of the rarest in the world, clinging on in only a handful of places, of which Cambodia is one.

Boeng Chhmar was designated a Wetland of International Importance under the Ramsar Convention on 23 June 1999, registered as site number 997 — one of Cambodia's first. That same year it was gazetted domestically as a multiple use management area of 145.6 square kilometres. It also serves as one of the core zones of the Tonlé Sap Biosphere Reserve, which UNESCO had established two years earlier in 1997. Three overlapping designations is a lot of paper for a place most Cambodians have never visited, and the layering reflects genuine difficulty: this is not a wilderness to be fenced off. People live inside it, and the water it protects belongs to a river system governed by six countries.

The protected area sits within Peam Bang commune, in Stoung district of Kampong Thom province, and the commune holds five floating villages — Pov Veuy, Pechakrei, Peam Bang, Ba Lat and Doun Sdaeng. Their houses are built on rafts or on stilts tall enough to clear a ten-metre rise, and some of them shift position with the shoreline as it advances and retreats each year. School, clinic, shop and monastery all float. The people here fish the same forest the designation exists to protect, which puts them permanently on the wrong side of enforcement conversations they rarely get to shape. Conservation on the Tonlé Sap has a long record of treating residents as the problem. The households in these five villages have a considerably longer record of living off a flood without exhausting it.

Everything about Boeng Chhmar depends on a pulse arriving on schedule and reaching a particular height. Dams upstream on the Mekong and its tributaries have begun flattening that pulse, holding water back through the wet season and releasing it in the dry, and in July 2020 the lake's level hit a sixty-year low for that point in the year. A smaller flood means less forest submerged, fewer spawning grounds, fewer fry, fewer fish. Meanwhile the forest itself keeps being cleared for farmland and fuelwood, with net losses recorded inside Tonlé Sap protected areas between 1992 and 2019. A wetland can be listed under an international convention, mapped, zoned and patrolled, and still fail — because the thing that made it is 500 kilometres upstream and answers to somebody else.