Terai-Duar savanna and grasslands

Terai-Duar savanna and grasslands is a distinctive ecoregion spanning the base of the Himalayas across parts of South Asia. This narrow belt of alluvial grasslands and savannas forms a vital transition between the lowland Indo-Gangetic Plain and the forested Sivalik Hills. It is recognized as one of the world's most biologically significant grasslands, hosting an exceptional concentration of megafauna and serving as a crucial corridor for wildlife movement.

Geography and location

The ecoregion stretches approximately 800 kilometers from the Yamuna River in the Indian state of Uttarakhand eastward through Uttar Pradesh, Bihar, and the Siliguri Corridor into Nepal and southern Bhutan. It occupies the Terai plains and the Dooars region, a name derived from the word for 'doors' or gateways into the Himalayas. The landscape is primarily composed of recent alluvial deposits from rivers like the Karnali River, Koshi River, and Manas River, which descend from the high mountains. This physiography creates a mosaic of riverine grasslands, sal forests, and chure formations, acting as a critical buffer zone between the agricultural plains and the protected areas of the Sivalik Range.

Climate and ecology

The region experiences a monsoon-influenced humid subtropical climate with high annual rainfall, often exceeding 2,000 millimeters, primarily during the summer months influenced by the Bay of Bengal. This abundant precipitation, combined with seasonal flooding from Himalayan rivers, creates highly productive, nutrient-rich soils that support rapid grass growth. The ecology is defined by a dynamic disturbance regime of fire and flood, which maintains the grassland habitat by preventing forest encroachment. This disturbance-based system fosters a unique assemblage of species adapted to these conditions, making it distinct from the surrounding Himalayan subtropical pine forests and Eastern Himalayan broadleaf forests.

Flora and fauna

The dominant vegetation consists of tall, coarse grasses such as kans grass (Saccharum spontaneum), narenga (Narenga porphyrocoma), and reed (Phragmites karka), which can grow over five meters tall. Scattered stands of sal (Shorea robusta) trees dot the landscape. The fauna is exceptionally rich, supporting the highest densities of Bengal tiger, Indian rhinoceros, and Asian elephant found anywhere on Earth. Other notable species include the gaur, wild water buffalo, hispid hare, and the endangered Bengal florican. The region is a critical stronghold for the greater one-horned rhinoceros, with major populations in Kaziranga National Park, Chitwan National Park, and Bardiya National Park.

Conservation and threats

Significant portions of the ecoregion are protected within a network of national parks and wildlife sanctuaries, including Jim Corbett National Park, Dudhwa National Park, and Manas National Park, a UNESCO World Heritage Site. However, it faces severe threats from habitat fragmentation due to agricultural expansion, human settlement, and infrastructure projects like highways. Poaching for the illegal wildlife trade, particularly targeting rhinoceros for their horns, remains a persistent problem. Invasive species such as Mikania micrantha and altered hydrological regimes from upstream dams also degrade the grassland ecosystem. International conservation efforts involve organizations like the World Wide Fund for Nature and the International Union for Conservation of Nature.

Human use and cultural significance

The fertile soils and abundant water have long supported agriculture, with the region being a major producer of crops like rice, jute, and sugarcane. Indigenous communities, including the Tharu people of Nepal and India, have developed unique cultural adaptations to the environment, such as building elevated houses to avoid floods. The area holds historical significance as part of ancient trade routes and was the site of pivotal events during the rise of Buddhism in regions like Lumbini. Traditional practices such as controlled grassland burning for pasture management are part of the local ecological knowledge, though these now often conflict with modern conservation policies.

Category:Ecoregions of Asia Category:Grasslands of India Category:Grasslands of Nepal Category:Grasslands of Bhutan