As per 2001 census tribes constitute 84.4 million people which account around 8.2 per cent of India′s population. The concentration of tribal population is seen in states like Jammu and Kashmir, Himachal Pradesh, Uttar Pradesh, Assam, Meghalaya, Tripura, Mizoram, Arunachal Pradesh, Manipur, Nagaland, Madhya Pradesh, Bihar and Orissa and to a lesser extent in Andhra Pradesh which is bounded by river Narmada in the north and river Godavari in the South east. The tribal people generally occupy the slopes of the mountains. The tribals also inhabit the tract extending from the western coast of Gujarat and Maharastra passing through central India up to the north–eastern region. Scheduled Tribes (ST) have been enumerated in 25 out of the 30 States and Union Territories (UTs). The sharpest decline in tribal population is noticed in Arunachal Pradesh where the proportion has declined from 69.82 per cent in 1981 to 63 per cent in 1991. Out of the 12 States and UTs, in Manipur, Meghalaya, Mizoram, Nagaland and Tripura, the proportion of ST population has increased by more than one percentage. In the remaining states and Union Territories the proportion of ST population increased marginally during 1981–1991. Almost a similar trend has been found in the 1991–2001 period. Lakshadweep has an increase in ST population. In India there are six tribal zones where tribals are highly concentrated. The first tribal zone is the North–Western Tribal Region which comprises of mainly the central Himalayan and western Himalayan regions, including sub–Himalayan areas stretching from the foot of the Aiwalik hills to Dehra Dun district of Utharanchal to the northern bordering traits of Lahul–Spiti in Himachal Pradesh and Ladaakh in Jammu and Kashmir. There are eight hill districts in Uttaranchal, namely, Chamoli, Uttarkashi, Tehri, Puri and Dehra Dun of Garhwal division and Pittorgarh, Almora, Nainital of Kumaon division. Some regions remain snow–clad for four to five months in a year. The second tribal zone is the Western Tribal Region, which comprises of some parts of Rajasthan, Gujarat, Maharashtra, Dadra and Nagar Haveli, Goa, Daman and Diu. Some portions of this region are arid and semi arid while some are in high rain fall zones of western India. The third and important tribal region is the Southern Region which comprises of Karnataka, Kerala, and Tamil Nadu. The region in general is of high rainfall and a series of undulations covered with dense forests where we find Dravidian–speaking tribal communities. The fourth tribal concentrated zone is the Central Tribal Region, stretching between the plateau and hilly belt of Andhra Pradesh, Madhya Pradesh, Orissa, Bihar and parts of West–Bengal. The fifth tribal zone is the North–Eastern Tribal Region, which includes states of northeastern India. The region is hilly but some portions are dotted with dense forest.