A continental crossroads
The Tenasserim Range creates a long mountainous spine separating Myanmar from Thailand. For millennia, this barrier has shaped the distribution of life in Southeast Asia. The Kawkareik Pass is the lowest gap in this wall, a funnel for animal movement and a distinct meeting point for separate biogeographical zones. The pass lies within the broader Dawna-Tenasserim Landscape, which marks the transition between the Indochinese zoogeographic subregion to the north and the Sundaic subregion to the south.
This location is a complex intersection of four different biogeographic zones: the Indo-Burmese, Indo-Chinese, Sundaic, and Sino-Himalayan. This overlap contributes to an high species diversity. The western slopes on the Myanmar side receive significantly more rainfall from the Bay of Bengal than the drier eastern slopes in Thailand, creating different forest types. The Myanmar side supports vast tracts of lowland evergreen forest, while Thailand's side is a mosaic of evergreen and deciduous forests. This environmental gradient across the pass further drives the variety of species found here. Genetic studies on various animals, including felids and bulbuls, confirm a deep evolutionary divergence between Indochinese and Sundaic populations, making this transitional zone an area of scientific interest.