The biological resources in the lowland areas (Terai and Siwalik Hills) are dominated by tropical evergreen forest and tropical deciduous riverine forest (see vegetation). These ecosystems are of international importance both in terms of the number of globally threatened plants and animals, as well as their diversity (NBS 2002). The Terai is also heavily populated with nearly half of the people of Nepal living there, and there are very high pressures on the forests and agricultural resources. Fortunately over 2700 km² of Terai and inner Terai is protected within National Parks and other protected areas. Royal Chitwan National Park has been designated as a natural World Heritage Site.