Biological Corridor 6

Biological Corridor 6 is a designated wildlife connectivity zone in Bhutan's Trashigang district in the eastern Himalayan region. As one of Bhutan's network of nine biological corridors, it serves as a critical linkage between larger protected areas, allowing wildlife to move freely across the landscape without fragmentation. The corridor runs through a mosaic of forests, farmland, and community-managed lands, integrating human-inhabited areas into the broader conservation network. Bhutan's biological corridors are nationally recognized under the country's protected area system and form an essential part of the kingdom's commitment to maintaining at least 60 percent of its land under forest cover as mandated by its constitution. Trashigang district, where this corridor is situated, lies in the far east of Bhutan and is characterized by deep river valleys, subtropical foothills, and montane forests spanning a wide elevational range.

The corridor supports a range of wildlife species that depend on landscape connectivity to meet their seasonal movement and breeding needs. Large mammals such as tigers, leopards, and Asian elephants are known to use eastern Bhutan's forest corridors as movement pathways between core protected areas. The diverse terrain of Trashigang, from subtropical valleys to temperate ridges, accommodates species adapted to multiple ecological zones. Ungulates including sambar and barking deer are common, providing prey for large predators. The corridor's function is not simply as a wildlife haven in itself but as a passageway that sustains viable populations across a wider geographic area. Bird diversity is high in eastern Bhutan, with numerous forest-dependent species benefiting from the unbroken forest canopy maintained through the corridor designation. Maintaining this connectivity is considered vital for the long-term genetic health of wildlife populations throughout Bhutan.

Biological Corridor 6 encompasses vegetation types ranging from subtropical broadleaf forests at lower elevations to cool temperate forests at higher altitudes, reflecting the dramatic elevation gradient of Trashigang district. Subtropical zones support dense stands of evergreen trees, bamboo thickets, and a rich understory of ferns and shrubs. As elevation increases, subtropical species give way to oak and rhododendron forests characteristic of eastern Himalayan montane zones. Chir pine and other conifers appear on drier slopes and ridgelines. The corridor includes community forests and private lands where traditional land-use practices such as agroforestry help maintain tree cover and reduce the sharpness of boundaries between natural and agricultural habitats. Rhododendrons, which are among Bhutan's most iconic plant groups, bloom across the corridor's mid-elevation bands in spring, supporting insect and bird pollinators.

The corridor traverses the geologically complex eastern Himalayan zone of Bhutan, where ancient metamorphic and sedimentary rock formations have been uplifted and folded by the ongoing collision between the Indian and Eurasian tectonic plates. Trashigang district is cut through by deep river valleys incised into the landscape over millions of years, most notably the Gamri River drainage system. The valley walls expose layered rock sequences that record phases of tectonic activity and uplift. Soils derived from these parent materials vary considerably with elevation and aspect, influencing vegetation patterns across the corridor. The region is part of the broader Himalayan arc, one of the most geologically active zones on Earth, and experiences regular seismic activity as a result. Landslides and slope instability are natural features of the terrain, periodically reshaping forest habitats and stream channels throughout the corridor.

The climate of Biological Corridor 6 is governed by its position in eastern Bhutan and the strong influence of the South Asian monsoon system. Summers are warm and humid, with heavy rainfall arriving from June through September driven by the monsoon. Annual precipitation in much of Trashigang district exceeds 1,000 millimetres (39 inches), with the heaviest totals falling at lower elevations facing moisture-laden winds from the south. Winters are dry and cool at lower elevations, with snowfall at higher altitudes within the corridor's range. Spring and autumn are transitional seasons with moderate temperatures and lower rainfall, representing the most comfortable periods for travel in the region. The pronounced seasonal cycle is critical for forest regeneration, river hydrology, and the annual rhythms of wildlife movement. Climate change is increasingly affecting precipitation patterns and snowmelt timing across the eastern Himalayas.

Trashigang district has been inhabited for centuries and is one of the most culturally rich regions of Bhutan, known historically as the gateway to eastern Bhutan and neighboring regions of India and Tibet. The district's settlements have long maintained traditional subsistence farming practices, growing crops such as maize, buckwheat, and cardamom in terraced fields along valley slopes. Buddhist culture deeply permeates the landscape, with dzongs, monasteries, and chortens marking important sites throughout the area. Communities living within and adjacent to the corridor have traditionally depended on surrounding forests for firewood, timber, fodder, and non-timber forest products. The establishment of the biological corridor framework formalized what in many areas had already been practiced informally: maintaining forest connectivity as both a cultural value and a livelihood necessity. Local communities are formally involved in corridor management through Bhutan's community forestry programs.

Bhutan's network of biological corridors, including Corridor 6 in Trashigang, was formally established as part of the country's comprehensive protected area strategy developed in the 1990s and refined in subsequent decades. The corridor system was designed to link Bhutan's five national parks and four wildlife sanctuaries into a functionally connected landscape covering roughly half of the country's total area. Conservation biologists recognized that isolated reserves, however well managed, could not sustain viable populations of wide-ranging species such as tigers and elephants without connectivity across the landscape. The corridors were therefore designated to fill the gaps between core protected areas, ensuring gene flow and seasonal movement remained possible. Corridor 6 connects areas of eastern Bhutan into the national network. Management responsibility falls under the Department of Forests and Park Services in coordination with local government and communities.

Biological Corridor 6 in Trashigang is not a conventional visitor destination with developed tourist infrastructure, but the surrounding district offers significant cultural and natural attractions that draw visitors to the region. Trashigang Dzong, perched dramatically above the Gamri River, is one of Bhutan's most impressive fortress-monasteries and serves as the cultural centerpiece of the district. Traditional villages in the corridor's vicinity offer insight into eastern Bhutanese architecture, textiles, and customs that differ distinctly from western Bhutan. Forest trails used by local communities pass through sections of the corridor, providing opportunities for birdwatching and nature observation in relatively undisturbed habitat. The rugged terrain offers trekking possibilities for experienced hikers, though formal trekking routes in the region are less developed than in other parts of Bhutan. The Merak-Sakteng area in broader eastern Bhutan, home to the semi-nomadic Brokpa people, lies in this region.

Bhutan requires all foreign visitors to enter on a government-regulated tourism package, which includes a daily fee covering accommodation, meals, transport, and a licensed guide. Trashigang town, the administrative center of the district, offers guesthouses and basic facilities. Access to the corridor area is primarily by road, with a highway connecting eastern Bhutan to the capital Thimphu via a multi-day journey, or by domestic flight to Yonphula airport near Trashigang when conditions permit. The corridor itself has no visitor facilities, entrance gates, or marked trails designated for tourism. Travel in the eastern districts requires additional permits available through licensed tour operators. Visitors to the region are advised to travel in the dry seasons of autumn and spring when road conditions are most reliable and weather is favorable. Eastern Bhutan receives far fewer tourists than the western regions, preserving a more remote and authentic experience.

Biological Corridor 6 plays an essential role in Bhutan's broader conservation strategy, which aims to maintain landscape-scale connectivity across the entire country. The corridor helps sustain populations of globally threatened species including tigers and clouded leopards by enabling movement between core protected areas. Bhutan is one of the few countries in the world where tiger populations are increasing, a success attributed in part to the effectiveness of its protected area network and corridor system. Threats to the corridor's integrity include agricultural encroachment, infrastructure development such as road expansion, and retaliatory killing of wildlife that preys on livestock. Human-wildlife conflict is an ongoing challenge in corridor areas where wildlife and farming communities share space. Conservation programs promote coexistence through compensation schemes for livestock losses, community patrols, and environmental education. Bhutan's constitutional mandate to maintain 60 percent forest cover provides strong legal backing for corridor protection.