Geography of Arunachal Pradesh

Relief range varies between plains that are a few hundred meters in height and mountains above 7,000 metres (23,000 ft).[5] The elevation of the towns of Naharlagun, Pasighat and Tezu in the south are 290 m, 155 m and 210 m respectively,[7] while Kangto, Nyegi Kangsang and the Gorichen group of mountains are some of the highest peaks in this region of the Himalayas.[15] The southern borders of Arunachal Pradesh are encompassed by the Shivalik ranges which merge into plains.[5] The hills and mountains have associated features such as valleys and intermontane plateaus, that is plateaus between mountains.[5]

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Passes and mountains in Arunachal, or on or close to its borders.[16][17][18][19]

Legend：
1: Gori Chen 2: Kangto 3: Bum La Pass 4: Yonggyap La 5: Nyegyi Kansang 6: Diphu Pass 7: Sela Pass 8: Dzo La 9: Chubumbu La 10: Gyoa La 11: Lo La 12: Shagam La 13: Tama La 14: Tapgyu La 15: Chupung La 16: Kashong La 17: Andra La 18: Zhabu La 19: Kaya La 20: Pangsau Pass 21: Kumjawng Pass 22: Chaukan Pass 23: Hpungan Pass 24: Dafla Range High Point 25: Dapha Bum 26: Pakhain Range High Point 27: Tulung La 28: Chumo 29: Lusha Pass 30: Kangri Karpo La 31: Adjamkho La 32: Tsang Khang La 33: Glei Dakhru 34: Mayodia Pass 35: Kepang La 36: Siang Pass 37: Aguia La 38: Hadigra Dakhru 39: Milakatong La 40: Chera La 41: Tse La 42: Poshing La 43: Shoka La 44: Tunga La 45: Vorjing Peak 46: Lamdo La

47: Tsangdhar

Gorichen group

Sangestar Tso

Parts of the Lohit district, Changlang district and Tirap district are covered by the Patkai hills. The hills extend towards Nagaland, and form a natural boundary between India and Burma.[27][28]

Namcha Barwa Himal range extends into India up to Siyom River.[29]

Major hills found in this region include:[30]

• Aka Hills
• Daphla Hills
• Miri Hills
• Abor Hills
• Mishmi Hills
• Patkai Hills

Water/wetland cover is 154,609 hectares (1,546.09 km²) or 1.91% of the total area.[4] Out of this, 86% of wetlands are rivers.[4] Lohit district and Dibang Valley district have the highest number of wetlands in the state.[4]

Lohit River

Nuranang Falls

The major river systems are (from west to east clockwise):[33][34]

• Kameng
• Subansiri
• Siang
• Dibang
• Lohit

All of these are fed by snow from the Himalayas and numerous rivers and rivulets and eventually flow into Siang/Brahmaputra. Abrasion by the rivers which flow through the mountains has created a broad valley, which is a major feature of the geography of the state.

River Siyom

Other rivers include Tawang Chu, Dikrong, Ranga, Kamala/Kamla, Kamplang, Siyum, Dihing/ Noadihing and Tirap.[35]

Major rivers in Arunachal and their basins

• Four major river basins of the state
• 
  Kameng River Basin
• 
  Subansiri River basin
• 
  Dibang River basin
• 
  Lohit River basin

Arunachal consists of a number of eco-regions. At the lowest elevations, at Arunachal Pradesh's border with Assam, are the Brahmaputra Valley semi-evergreen forests. Much of the state, including the Himalayan foothills and the Patkai hills, are home to Eastern Himalayan broadleaf forests. Towards the northern border with Tibet, with increasing elevation, come a mixture of Eastern and Northeastern Himalayan subalpine conifer forests followed by Eastern Himalayan alpine shrub and meadows.

• Ecoregions
• 
  Eastern Himalayan broadleaf forests
• 
  Eastern Himalayan subalpine conifer forests
• 
  Northeastern Himalayan subalpine conifer forests
• 
  Brahmaputra Valley semi-evergreen forests
• 
  Eastern Himalayan alpine shrub and meadows

Climatically, the forests can be categorised as Tropical forests, subtropical forests, temperate forest, subalpine coniferous forest, alpine and secondary forests.[36][37] At the lowest elevations, densely forested areas are seen with the trees ranging from seasonal tropical forest to broadleaf and semi-alpine coniferous forests. Alpine shrubs and meadows follow, ultimately leading to ice-clad peaks.

Evergreen forest of Pakke, Aurnachal Pradesh.

The Forest Research Institute of India's India State of Forest Report 2019 lists area under different forest types in the state.[38] The major forest types as a percentage of the forest cover area are:

• East Himalayan Sub-Tropical Wet Hill Forest = 24.35%[38]
• East Himalayan Wet Temperate Forest = 22.92%[38]
• East Himalayan Sub-Alpine Birch/Fir Forest = 13.46%[38]
• Alpine Pastures = 6.73%[38]
• Sub-Himalayan Light Alluvial Semi-Evergreen Forest = 6.60%[38]
• Others = Remaining[38]

Forest cover varies from 54% in Tawang district to 92% in Papum Pare district.[39] There are 110 species of trees.[38]

Protected areas include the Dihang-Dibang Biosphere Reserve, Namdapha National Park, Mouling National Park, and 11 wildlife sanctuaries and reserves including elephant reserves, tiger reserves and an orchid sanctuary,[lower-alpha 1] covering about 12% of the geographical area of the state.[40]

Flora and fauna in the state includes over 4000 species of flowering plants,[41] 600 bird species, 200 fish species,[42] 42 amphibian species, 85 terrestrial mammals and a wide number of insects, butterflies and reptiles.[36][43] Orchids, fern, bamboo, cane, rhododendrons, oak, hedychiums, and various medicinal plants form a diverse range of the state's green cover. Among the crops grown here are rice, maize, millet, wheat, pulses, sugarcane, ginger, and oilseeds. Arunachal is also ideal for horticulture and fruit orchards. Its major industries are rice mills, fruit preservation and processing units, and handloom handicrafts Apart from them, the forests of Arunachal are also home to a large number of people belonging to the different tribes. These tribal people, aloof from urbanization, dwell in these forests where the various forest-based products form a part of their livelihood.

• 
  The Strobilanthus flower at the Namdapha National Park
• 
  Hornbills at the Namdapha National Park
• 
  Male azure sapphire
• 
  Renanthera imschootiana
• 
  View of Eaglenest forest canopy