New plant survey finds unique flora in karst hills of southeast Cambodia

In June, a team led by American botanist Andrew McDonald set out into the karst hills of southeast Cambodia to survey the rare and endemic plants that grow in this unique environment. The team has already identified at least one plant species previously unknown to science belonging to the Amorphophallus family known for their large phallic-shaped flower. 

Karst hills in Kampot Province are home to a unique flora © Steven Bernacki, IUCN

This discovery illustrates why IUCN chose to prioritize this botanical survey: the karst landscapes of Cambodia are a largely unstudied ecosystem characterized by the survival of highly specialized life forms that don't exist anywhere else on the planet.

The plants and animals on these hills have to cope with extreme conditions: very thin or no top soil, substrate that is rich in calcium and iron but with very low general fertility, very little standing or running water, and often low shade on the karst surface. In shallow depressions, conditions may be more favorable, but in deep crevices and inside caves, low light levels and extreme scarcity of food are determinants for survival and adaptation.

Given the geographic isolation of the karst hills, which are located hundreds of kilometers from the karst landscapes in Laos and Vietnam, it is only a matter of time and natural selection that drives the evolution of new species. Team member Nguyen Quoc Dat from the Southern Institute of Ecology in HCMC, who specializes in the karst flora of Southeast Asia, noted that he saw many similarities between the flora on these hills and those in neighboring Kien Giang Province in Vietnam but that there were also differences. 

(L) Nguyen Quoc Dat and Chhum Moeun. (R) A rare species of Amorphophallus is found on the hill © Steven Bernacki, IUCN

“After no more than a few days of collection, it is likely that we have encountered more than a handful of plant species unknown to science, and this is rare, even for a seasoned collector,” said Dr. McDonald, making clear that there is much more to be found in these mountains.

These initial impressions will need to be confirmed over the next few months as botanists in the US and Vietnam pour over the specimens to determine exactly how many of these species are endemic to the Kampot karst hills. 

Around these hills is a patchwork of rice fields dotted with sugar palms and coconut trees. Som Art, the local guide who knows the area like the back of his hand, said that these fields used to be forest once. The only forest that survives now resides on the inaccessible slopes of the karst hills.

There is a pressing need for better scientific understanding because these hills and under imminent threat from quarrying to produce cement. Rapid economic growth has created a high demand for cement and these hills form some of Cambodia's few limestone resources. Several of the largest hills are already being quarried. 

Members of the survey team pass bags of cement, produced from the limestones in the hills © Steven Bernacki, IUCN

Despite their biological importance and threat level, karst rarely features in discussions about biodiversity conservation in Cambodia. Dr. McDonald sees an immediate need to protect of this small but important piece of Cambodian natural history: “Cambodia has never included a karst formation in its conservation, and that needs to change - it’s that simple".

The survey was funded by the Manna Foundation.

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