The Western Ghats constitute a mountain range along the western side of India. It is a UNESCO World Heritage Site and is one of the eight hotspots of biological diversity in the world. This range runs north to south along the western edge of the Deccan Plateau, and separates the plateau from a narrow coastal plain along the Arabian Sea. These hills cover 160,000 km2 and form the catchment area for complex riverine drainage systems. The area has over 5,000 species of flowering plants, 139 mammal species, 508 bird species and 179 amphibian species; it is likely that many undiscovered species live in the Western Ghats. At least 325 globally threatened species are in the Western Ghats.