Subtropical Forests of Southern Bhutan

The subtropical forests of southern Bhutan form a belt of dense broadleaf vegetation across the country's southern foothills, at elevations below approximately 1,500 metres. These forests — ranging from tropical lowland jungle at around 200 metres along the Indian border to warm broadleaf forest higher up — are among the most biodiverse ecosystems in the Eastern Himalayas. They are the habitat of Bengal tigers, Asian elephants, golden langurs, gaur, and hundreds of bird and plant species. Protected within Royal Manas National Park, Phibsoo Wildlife Sanctuary, and other reserves, and connected by a network of biological corridors, these forests represent a critical component of Bhutan's conservation framework.

Geography and Forest Types

Bhutan's terrain rises from the Duars plains along the Indian border (roughly 200 metres elevation) to alpine peaks exceeding 7,000 metres, creating stacked vegetation zones within a horizontal distance of less than 150 kilometres. The subtropical belt — from the plains up to about 1,500 metres — encompasses several distinct forest types:

• Tropical lowland forest — riverine grasslands and semi-evergreen forest in the lowest valleys, particularly along the Manas, Sankosh, and Torsa river systems
• Sal forest — stands of Shorea robusta (sal), found principally within Phibsoo Wildlife Sanctuary, which protects Bhutan's only natural sal forest
• Warm broadleaf forest — mixed broadleaf canopy of chestnut, schima, alder, and laurel species, grading upward into the temperate zone

Bhutan maintains over 70 per cent forest cover nationally, with the constitution mandating a minimum of 60 per cent in perpetuity. The subtropical zone, though a relatively narrow band, contributes disproportionately to the country's biodiversity.

Biodiversity

The southern forests host an exceptionally dense concentration of species. Royal Manas National Park alone has recorded the highest tiger density in the world in some surveys — approximately one tiger per 25 square kilometres. Environmental DNA sampling in the park's waterways has identified 325 vertebrate species, including mammals, birds, fish, amphibians, and reptiles.^[1]

Notable fauna include:

• Bengal tiger — Bhutan forms part of the tiger's northern range; tigers move between Royal Manas and India's adjacent Manas National Park
• Asian elephant — herds migrate between Phibsoo and Royal Manas along forest corridors; human–elephant conflict is an ongoing issue in bordering farmland
• Golden langur (Trachypithecus geei) — a rare primate found only in a narrow range along the Bhutan–Assam border, first described to Western science in the 1950s
• Gaur (Indian bison), clouded leopard, Himalayan black bear, chital (spotted deer, present only in Phibsoo), and eight cat species
• Birds — rufous-necked hornbill, great Indian hornbill, white-bellied heron (one of the world's rarest), and hundreds of forest passerines

The flora includes tropical hardwoods, bamboo groves, tree ferns, orchids (Bhutan has over 600 orchid species, many concentrated in the subtropical zone), and medicinal herbs used in traditional Bhutanese medicine.

Protected Areas and Corridors

Bhutan's protected area system covers over 51 per cent of the country's land. The principal subtropical protected areas are:

• Royal Manas National Park — Bhutan's oldest national park (established 1966), covering 1,057 square kilometres in the south-central lowlands, contiguous with India's UNESCO-listed Manas National Park across the border
• Phibsoo Wildlife Sanctuary — 269 square kilometres in the south-west, protecting the only natural sal forest in Bhutan (designated a reserve forest in 1974, upgraded to wildlife sanctuary in 1993)

Nine biological corridors, established in 1999 and given formal protected status in 2017, link the country's parks and sanctuaries, enabling animal and plant movement across the landscape. These corridors are critical for maintaining gene flow among populations of wide-ranging species such as tigers and elephants.

Threats

Despite strong national conservation policies, the subtropical forests face pressures including illegal logging and poaching, agricultural encroachment along the southern border, human–wildlife conflict (particularly elephant crop-raiding), and the effects of climate change on species distribution and water availability. Road construction through forest corridors can fragment habitats. Bhutan's participation in the "Bhutan for Life" initiative — a project-finance mechanism supported by the WWF — aims to provide long-term funding for the protected area system.

See Also

• Royal Manas National Park
• Phibsoo Wildlife Sanctuary
• Wildlife Corridors of Bhutan
• Climate of Bhutan

References

1. Bhutan: Committed to Conservation — World Wildlife Fund
2. Biodiversity of Bhutan — National Biodiversity Centre
3. Bhutan for Life Landscape — Bhutan for Life
4. Phibsoo Wildlife Sanctuary — Wikipedia
5. Connectivity in National Policies: Bhutan — Conservation Corridor