There are different names for Assam Himalayas. In the east, the Himalayan mountain block drained by the Dibang is called the Mishmi Hills. To the west of these hills are the Abor Hills which lie within Siang district. The Brahmaputra called the Dihang (or Siang) passes through these hills.
The Great Himalaya Range in the north is snow-bound and can be crossed through passes. The Bum La in the west is an important pass across the great Himalayan Range. The Tse La (4740 metres) is an important pass in Kameng district.
There is the rainfall of 250 cm in southern part of mountain. Pasighat receives 450.9 cm. of rainfall a year. The western and northern parts of this Himalayan belt receive less rainfall. Because of heavy rainfall the southern part of this mountain belt is heavily forested at most of the places.
There is dense evergreen forest of different species of trees. These forests are rich in wild life such as wild buffaloes and goats, elephants (generally in low damp valleys), monkeys, tigers and a variety of deer and snakes.
There is sparse population in Arunachal Pradesh. Only 1,382,611 persons inhabited it in 2011. The density of population (17 persons per square km. in 2011) is even less than that of the Rajasthan Desert. Only 22.67 percent of the population is urbanized. Four districts Tawang, East Kameng, Upper Subansiri and Changland have urban population.
There is less space for raising agriculture. Of the reporting area in 2011, 61.551 percent of Arunachal Pradesh is under forest and 3.73% percent is classed as net sown area. Agriculture is, however, the main occupation of the people and they produce a few crops on low, wet tropical and subtropical slopes.
There is high-grade coal in the Namchik-Namphuk coal-field in the Tirap district. Kharsang oil-field produces crude oil and natural gas. There are also large deposits of dolomite in West Kameng and Lohit districts. Graphite and ores of copper and iron also occur at some places in this region.
Industries include plywood factories, a fruit processing plant at Nigmoi and a roofing sheet factory at Pasighat. Cottage industries such as spinning, weaving and dyeing of cotton and wool are common among many tribes of this region.