Geography here is a story about a wall. The Cardamom and Elephant ranges stand across the path of the southwest monsoon, wringing it out on their seaward flanks and leaving the country behind them comparatively parched. The consequences show up in the map of neighbouring ecoregions: the Central Indochina dry forests begin immediately east and north, sitting in the rain shadow, while the Chao Phraya lowland moist deciduous forests take over to the northwest. To the southwest lies the Gulf of Thailand, its shoreline fringed by the Indochina mangroves. The one part of the system that has largely gone is the strip that was easiest to reach - the lowland evergreen forest of the narrow coastal plain, cleared over generations, is now mostly a memory.

Above roughly 700 metres the montane forest takes over, and it is dominated by a family most people associate with temperate woodland. Beeches and oaks - Fagaceae - form the bulk of the canopy: Lithocarpus cambodiensis, Lithocarpus guinieri, Lithocarpus farinulentus, Lithocarpus harmandii, and Castanopsis cambodiana. Alongside them grow laurels in the genera Cinnamomum and Litsea, and myrtles including Syzygium and Tristaniopsis. The canopy closes at around thirty metres. Beneath it, palms and shrubs crowd the understorey, tree ferns unroll in the gaps, and epiphytes load every horizontal branch - orchids especially, in a diversity nobody has fully catalogued. Because the range is remote, thinly populated and genuinely hard to walk, most of these forests remain among the least botanically explored in the region.

Species found nowhere else carry the mountains in their names. The Cardamom Mountains wolf snake, Lycodon cardamomensis, and the Cardamom Mountains bent-toed gecko, Cyrtodactylus cardamomensis, are endemic reptiles. Among more than 450 recorded bird species, the chestnut-headed partridge, Arborophila cambodiana, is confined to Cambodian highland forest; it was described in 1928 by Jean Theodore Delacour and Pierre Jabouille from a bird collected near Bokor, and the IUCN lists it as Near Threatened. Its close relative the Siamese partridge is treated by some taxonomists as a full species, Arborophila diversa, and by others as one of its subspecies - an argument that will probably outlast several field seasons. The large mammals are the ones people come for: Asian elephant, gaur, banteng, Sumatran serow, dhole, clouded leopard, and the pileated gibbon, whose bubbling territorial song is the signature sound of a Cardamom dawn.

The tiger is the ghost in this inventory. Older accounts list it among the ecoregion's fauna; in truth no wild tiger has been confirmed in Cambodia since 2007, and the species is now considered gone from the country. Reintroducing it was one of the stated ambitions behind the designation of Southern Cardamom National Park on 9 May 2016, a 4,104-square-kilometre addition that brought nearly the whole range under formal protection alongside a string of Thai national parks and wildlife sanctuaries. Formal protection is not the same as protection. Mining, plantation clearance, sand pumping, road and dam construction, illegal logging and organised poaching all continue. And protection can carry its own costs: Human Rights Watch has documented Chong communities displaced from ancestral land in Southern Cardamom by a REDD+ carbon-offset scheme between 2018 and 2023, prompting an investigation by the certifier Verra. The Chong were living in these forests long before anyone assigned them an ecoregion code - the WWF's designation for this one is IM0106 - and whether the last intact rainforest in Southeast Asia can be kept without pushing them out of it remains the open question here.