Cambodia is recognized globally for its high biological diversity, supported by a geography shaped by the massive Mekong River system and extensive mountain ranges. The country retains a high percentage of its land area under forest cover, estimated at nearly 47 percent, a figure many neighbors do not match. This extensive coverage acts as a refuge for numerous species, many of which are endangered or endemic. The nation’s unique environment is defined by the seasonal dynamics of its waterways and the structure of its terrestrial forests.
The Seasonal Pulse of the Tonle Sap and Mekong
Cambodia’s ecology is governed by the annual flood pulse created by the Mekong River and its connection to the Tonle Sap, or Great Lake. During the rainy season, the enormous volume of water flowing down the Mekong causes the Tonle Sap River to reverse its direction of flow. This phenomenon is the largest natural freshwater flow reversal system in the world. This massive influx of water dramatically increases the lake’s surface area from approximately 2,500 square kilometers in the dry season to as much as 15,000 square kilometers during the peak flood.
The water also inundates the surrounding low-lying forest for up to six months, creating vast flooded forests and wetlands. This seasonal expansion is fundamental to the ecosystem’s productivity, transporting nutrient-rich sediment and fish larvae into the lake’s nursery grounds. The flooded forest acts as a feeding and spawning habitat, supporting what is considered the world’s most productive inland fishery.
Terrestrial Habitats and Rare Land Mammals
Beyond the great lake, Cambodia’s terrestrial environments, particularly the Cardamom Mountains, are major centers for biodiversity. These mountains are dominated by dry evergreen forests that provide refuge for numerous large mammals and rare species. The Cardamom Mountains act as a vital habitat corridor, preserving one of the country’s least deforested areas.
The forests shelter the Indochinese leopard and other elusive wild cats, such as the Clouded leopard and the Asiatic golden cat. The Endangered Asian elephant maintains a presence in this landscape, with fewer than 100 individuals estimated to survive in the Cardamom Mountains. The canopy of these forests is home to several primate species, including the Endangered Pileated gibbon, a highly specialized arboreal ape.
The forests also protect the Critically Endangered Sunda pangolin, an armored, nocturnal mammal. Another globally threatened primate, the Yellow-cheeked Crested Gibbon, is found in the semi-evergreen forests of northeastern Cambodia. These gibbons are known for their loud, duetting calls that echo through the canopy, establishing territory in the tall trees where they spend their entire lives.
Aquatic and Wetland Biodiversity
The Mekong River and the Tonle Sap Great Lake system are home to an aquatic fauna unique to this pulsing wetland environment. The Mekong River’s deep pools are the last refuge for the Irrawaddy River Dolphin, a freshwater cetacean that lives in a small, isolated population. The river system also supports the Mekong Giant Catfish, one of the world’s largest freshwater fish species, which can reach weights of up to 300 kilograms.
The Tonle Sap’s flooded forests are important for numerous waterbird species that rely on the seasonal abundance of fish and amphibians. Among the most globally significant are large colonial waterbirds that breed in the lake’s flooded shrublands and trees. These include the Spot-billed Pelican and the Greater Adjutant, which utilize the temporary flooded habitats to raise their young. The ecosystem also provides habitat for the Milky Stork and the Painted Stork, birds that feed on the rich fish stocks generated by the annual flood pulse.
Critical Conservation Landscapes
Safeguarding Cambodia’s unique wildlife relies on the protection of specific geographical areas that function as ecological strongholds. The Cardamom Mountains National Park is the largest protected area, dedicated to preserving the terrestrial rainforests and the animals that require vast, uninterrupted habitats. This landscape protects the remaining populations of species like the Asian elephant, dhole, and various wild cats by maintaining forest connectivity. Its dense forest structure also provides watershed services, feeding the Tonle Sap Lake downstream.
The Prek Toal Core Bird Reserve, located within the Tonle Sap Biosphere Reserve, represents an aquatic conservation priority. This reserve is recognized as the largest breeding colony of large waterbirds in Southeast Asia. Its designation is aimed at protecting the nesting sites of species like the Spot-billed Pelican, Greater Adjutant, and Milky Stork. The reserve’s flooded forest and shrub habitats are managed to ensure minimal disturbance to the birds during their breeding season.