Phnom is Khmer for hill, and the sanctuary carries the names of two of them across roughly 421 square kilometres of country that had until then been quietly available to anyone with a chainsaw or a length of wire. Cambodia's protected-area system now runs to more than seventy designated sites, and designation is the easy part. The sub-decree handed the Ministry of Environment jurisdiction over ground it has never had the staff to walk. What the paperwork actually accomplished was to make the forest legible. Land that is merely forest gets cleared first and registered afterwards, a sequence repeated across Southeast Asia for decades. Land inside a wildlife sanctuary cannot follow that path lawfully, and in the years since, that distinction has been the difference between an argument the conservationists can win and one they cannot.

More than seventy species have been recorded here, and a handful of them are the reason any of this happened. Pileated gibbons sing at dawn, mated pairs duetting to advertise a patch of canopy as theirs; the males are black, the females a pale buff with dark caps and bellies, both sexes fringed by a shaggy ring of white around the face. Banteng move through the understorey, wild cattle with a bright white patch on the rump, reduced worldwide to a few thousand animals. Green peafowl, listed as endangered since 2009 and now scattered in isolated pockets across Southeast Asia, call at dusk with a repeated ki-wao. Add Indochinese silvered langurs, dhole, and the elongated tortoise, and the list stops reading like an inventory and starts reading like a set of survivors.

The official record names the threats without ornament: hunting, especially snaring; logging; and illegal land clearance for agriculture and speculation. Snaring is the quiet one. A loop of bicycle brake cable costs almost nothing, takes minutes to set, and does not care what walks into it — gibbon, banteng, peafowl, or somebody's dog. A single hunter can leave hundreds across a hillside and never come back for most of them. Against that arithmetic the sanctuary fields a community-based patrol team, working alongside rangers supplied by Wildlife Alliance, walking the same ground repeatedly and pulling wire out of the grass. It is unglamorous work with no natural end point, which is precisely why it has to be somebody's job rather than somebody's project.

The conservation programme grew out of BeTreed Adventures, an ecotourism enterprise that put visitors in the forest and then put their money back into it. More than seventeen thousand US dollars raised through guests has gone to roads, tree planting, patrolling, and the purchase of resin trees — the tall dipterocarps that families in northern Cambodia tap for resin, and that are worth more standing to a tapper than felled to a trader. In November 2019 the work was formally registered with Cambodia's Ministry of Interior as Our Future Organization, founded by Chris, John, Ben, Sharyn, Pich Piseth, Kheng Maly and Soeur Sodany. Alongside the sanctuary it runs a village school programme some fifty kilometres east of the forest station: English classes, computer classes, a library, a vegetable garden. Conservation here is not separable from the question of what the children nearby will do for a living.