The Nilgiri Biosphere Reserve is an International Biosphere Reserve in the Western Ghats, Nilgiri Hills range of South India. The Western Ghats, Nilgiri Sub-Cluster (6,000+ km²), conjoining the Nilgiri Biosphere Reserve, is under consideration by the UNESCO World Heritage Committee for selection as a World Heritage Site.
The Nilgiris Biosphere Reserve was constituted by UNESCO in September 1986.
The reserve encompasses 5,520 km² in the states of Tamil Nadu (2537.6 km²), Karnataka (1527.4 km²) and Kerala (1455.4 km²). It forms an almost complete ring around the Nilgiri Plateau. The biosphere lies Between 10°50′N and 12°16′N latitude and 76°00′E to 77°15′E longitude. Central location: 11°33′00″N 76°37′30″E / 11.55000°N 76.62500°E.
The reserve extends from the tropical and subtropical moist broadleaf forests, tropical moist forests of the western slopes of the Ghats to the tropical and subtropical dry broadleaf forests tropical dry forests on the east slopes. Rainfall ranges from 500mm to 7000mm per year. The reserve encompasses three ecoregions, the South Western Ghats moist deciduous forests, South Western Ghats montane rain forests, and South Deccan Plateau dry deciduous forests. The habitat types include montane rain forest, semi-evergreen moist forest, thorn forest and scrub, montane grassland, and high-elevation, Shola forests.
Fauna includes over 100 species of mammals, 350 species of birds, 80 species of reptiles, about 39 species of fish, 31 amphibians, 316 species of butterflies. It includes the tiger, Asian elephant, and Nilgiri tahr.
The Nilgiri Biosphere Reserve is very rich in plant diversity. About 3,300 species of flowering plants can be seen here. Of the 3,300 species 132 are endemic to the reserve. The genus Baeolepis is exclusively endemic to the Nilgiris. Some of the plants entirely restricted to the Nilgiri Biosphere Reserve include species of Adenoon, Calacanthus, Baeolepis, Frerea, Jarodina, Wagatea, Poeciloneuron, etc.
Of the 175 species of orchids found in the Nilgiri Biosphere Reserve, eight are endemic. These include endemic and endangered species of Vanda, Liparis, Bulbophyllum, Spiranthes and Thrixspermum. The sholas of the reserve are a treasure house of rare plant species.