Koshi Tappu Wildlife Reserve occupies 17,500 ha of the Sapta Koshi River floodplain at the most northeasterly extension of the Gangetic Plain. It ranges in altitude from 75-81 m (Green 1993). The reserve is located between two flood control embankments and is subject to annual flooding. Approximately 70% of the reserve's land area is covered in grasslands (Heinen 1993), although during high flood years a large area of grassland is destroyed and replaced by new alluvial deposits. Typha and Saccharum are major grassland types found here, although patches of Imperata and Phragmites are often seen (Peet et al. 1999a). Medium size phantas interspersed with young Acacia trees are found in sandy islands. Riverine vegetation with Acacia catechu/Dalbergia sissoo forest dominates on the islands and edges of the reserve. Mostly young trees grow inside and on the edges of the reserve within embankments, the old mature trees being swept away by annual floods.
South of Koshi Tappu Wildlife Reserve lies the Koshi Barrage area. The area is 7 km from north to south and nearly 5 km from east to west. More than 50% of the land area at the barrage is covered by water, and the remaining land area is subject to intensive agriculture. The barrage gates are regulated by the Indian Government according to a 99-year lease agreement between Nepal and India.
The large number of 486 bird species has been recorded in the Koshi Tappu and Barrage area (Baral 2000c, Giri and Choudhary 2000ab, 2001ab, 2002abc, 2003ab, 2004ab, in prep., Tebb et al. 2004). Koshi is by far the most important wetland staging post for migrating waders and waterfowl in Nepal (Inskipp and Inskipp 1991) and was considered one of the most important in Asia (Scott 1989). Koshi Tappu also has the largest heronry in Nepal (Baral 1993), where as many as 25,730 nests belonging to 12 species of medium to large waders were reported in 1996 (Choudhary 1996b).
As many as 20 globally threatened bird species have been recorded in the Koshi Tappu and Koshi Barrage area and eleven of these occur regularly. This IBA is especially important for some wetland and grassland species, notably Swamp Francolin Francolinus gularis, Baer’s Pochard Aythya baeri, Pallas’s Fish Eagle Haliaeetus leucoryphus, Greater Spotted Eagle, Imperial Eagle Aquila heliaca, Lesser Adjutant, Spot-billed Pelican and Bristled Grassbird Chaetornis striatus. It holds the largest population of the globally threatened Swamp Francolin in Nepal (Baral 1998a), and also supports a good population of the Bristled Grassbird (Baral in prep.). The site is also important for Nepal's near-threatened birds; 13 of the country’s total of 23 occur and eight of these are wetland birds. Only two restricted-range species have been recorded and both are rare visitors.
A marked decline in wintering and passage migrant waterbird has been noted since 1990 and has been highlighted by the Annual Waterfowl Counts. In February 2003 a total of nearly 9,800 birds was counted at the site in one day, a very low number compared to twenty years ago when more than 50,000 birds were estimated (Choudhary 2003).
Non-bird biodiversity: The reserve contains Nepal's last population of Asian Buffalo Bubalus bubalis, a globally threatened species (Hilton-Taylor 2000). Other globally threatened species include Ganges River Dolphin Platanista gangetica, Nilgai Boselaphus tragocamelus, Smooth-coated Otter Lutrogale perspicillata, Gharial Gavialis gangeticus and Mugger Crocodile Crocodylus palustris (Hilton-Taylor 2000).
Conservation responses/actions for key biodiversity
Koshi Tappu is protected as a Ramsar Site for its importance for migrating wildfowl, the first Ramsar Site established in Nepal (Green 1993). In spite of this, the reserve faces severe problems. Koshi’s wetland habitats are threatened by the large population of subsistence farmers and fishermen living in close proximity to the reserve. Illegal grazing by domestic animals, fodder collection, hunting, illegal fishing, disturbance of nesting and feeding areas, poisoning that not only kills fish, but also birds that feed on fish and aquatic insects, have together resulted in the deterioration and loss of suitable habitats for birds and other wildlife (Anon 1992, Petersson 1998, Giri 1997, 2002). Removal of dead logs and debris deposited in the river from the Reserve is rampant and has a direct effect on fish population. Significant populations of feral cattle and buffalo that are now very wary are adding to the problem of illegal grazing. Heinen (1993) found that the main reason local people disliked the reserve was the frequent damage to crops caused by the Asian Buffalo.
A study carried out in 1986-1988 found that people in the area are dependent on the reserve for the collection of grasses that are used in building. The reserve also provides fish that are sold cheaply in local markets. Other products such as fuelwood, edible and medicinal plants, and seeds are occasionally collected illegally (Heinen 1993). A recent IUCN Nepal study estimated the annual value of biodiversity, wetland products and services and community dependence at the site as over US$ 9 million (Anon 2003b). Despite these measurable benefits, conservation awareness amongst local people is low. There have been a few environmental education initiatives mainly carried out to date by the United Nations Development (UNDP) funded Participatory Conservation Programme and Bird Conservation Nepal.
The Koshi Barrage area is unprotected. Hunting, overfishing, disturbance and drainage of wetlands for agriculture are major threats. The globally threatened Ganges River Dolphin, which is protected by Nepal’s National Parks and Wildlife Conservation Act-1973, is occasionally hunted here.
Many fish-eating bird species, for instance Black-bellied Tern and Indian Skimmer, have shown precipitous declines in the Koshi area during the last ten years and are probably suffering from prey shortage due to overfishing (Baral and Inskipp 2004).
Two invasive alien plants are both widespread at Koshi and are causing major problems. Water hyacinth Eichhornia crassipes can rapidly cover and choke water surfaces. The climber Mikania micantha can cover trees, shrubs and the entire forest floor (Baral 2002a).
BirdLife International (2019) Important Bird Areas factsheet: Koshi Tappu Wildlife Reserve and Koshi Barrage. Downloaded from
http://www.birdlife.org on 10/12/2019.