Veun Sai–Siem Pang National Park: Cambodia's National Park and Protected Lowland Forest Landscape

The park is especially known for its remarkable primate populations, particularly the endangered Northern buffed-cheeked gibbon. Survey data indicates significant gibbon populations, with approximately 389 groups recorded in 2019 surveys. The park also supports healthy populations of red-shanked douc, Annamese silvered langur, and several macaque species. This concentration of threatened primates places Veun Sai, Siem Pang among the most important primate conservation areas in mainland Southeast Asia.

The area that became Veun Sai–Siem Pang National Park was originally managed as a conservation area by Cambodia's Ministry of Agriculture, Forestry and Fisheries, with technical support from Conservation International. During this earlier phase, the territory was expected to receive designation as a protected forest rather than national park status. On 9 May 2016, the area was officially designated as Veun Sai–Siem Pang National Park through Sub-decree No. 77, covering an initial area of 57,469 hectares across Ratanakiri and Stung Treng provinces. The park's history shifted dramatically in July 2023 when Sub-decree No. 183 expanded the boundaries to 280,359 hectares, a change implemented as part of a broader reclassification of biodiversity corridors as protected areas across Cambodia.

The park's landscape consists primarily of lowland terrain characteristic of northeastern Cambodia's interior, with elevations varying across gentle slopes and valleys. The forest cover is dominated by evergreen and semi-evergreen formations that remain verdant year-round in the tropical climate. The landscape provides a natural transition between the more mountainous areas of the Mekong corridor and the forested plains that stretch toward the Cambodian central lowlands.

The ecological character of Veun Sai–Siem Pang is defined by its extensive lowland forest ecosystems, which support exceptional biodiversity despite ongoing pressures. The forest type is classified as lowland evergreen and semi-evergreen, a habitat that has become increasingly rare across the Indochinese region due to agricultural expansion and logging. These forests maintain a complex vertical structure that provides shelter and resources for diverse species assemblages, from canopy-dwelling primates to forest-floor organisms.

The primate community within Veun Sai–Siem Pang represents one of the most significant wildlife features of the park. The endangered Northern buffed-cheeked gibbon populations have been the subject of systematic surveys, including auditory census methods that documented approximately 456 gibbon groups in 2010 and a more recent estimate of 389 groups in 2019. The park also supports the red-shanked douc, a strikingly colored colobine monkey, along with the Annamese silvered langur, northern pig-tailed macaque, long-tailed macaque, pygmy slow loris, and stump-tailed macaque. This diversity of primate species indicates a relatively intact forest ecosystem capable of supporting multiple arboreal mammal communities.

Veun Sai–Siem Pang holds significant conservation value as a protected area supporting endangered species and intact forest habitats in a region facing intense development pressure. The park's primate populations, particularly the Northern buffed-cheeked gibbon, represent conservation priorities at both national and regional levels. However, the park faces substantial challenges including illegal selective logging, agricultural expansion into forest areas, and hunting pressure on wildlife populations. Community-based conservation initiatives including joint patrols between community wardens and park rangers, along with ecotourism projects developed in partnership with Conservation International Cambodia and the TUI Care Foundation, represent efforts to address these pressures.

The park exists within a landscape inhabited by local communities who have historically utilized forest resources and continue to interact with the protected area. Villages surrounding the park boundary engage in traditional land use practices that sometimes overlap with forest areas. The relationship between local communities and the protected area represents an important dimension of the park's management, particularly as the 2023 boundary expansion brought additional agricultural land and community areas under formal protection.

The park's primate diversity stands as its most distinctive feature, with multiple species including the endangered Northern buffed-cheeked gibbon inhabiting the lowland forest canopy. The 2023 boundary expansion transformed the park from a medium-sized protected area into one of Cambodia's largest national parks, dramatically increasing its conservation significance. The forest ecosystem represents one of the last substantial lowland forest tracts in northeastern Cambodia, providing habitat for species assemblages that have been diminished across much of the Indochinese peninsula.

The optimal period to visit Veun Sai–Siem Pang corresponds to the dry season from November through April, when lower rainfall facilitates movement through the forest and wildlife viewing conditions improve. The wet season from May through October brings heavy precipitation that can restrict access and make field activities more challenging, though the landscape takes on a different character during this period. Temperature conditions remain consistently warm throughout the year, with average highs typically ranging from 31 to 36 degrees Celsius.