The sprawling range of eastern Himalayas comprises of the Darjeeling hills (i.e. north Bengal), Bhutan, Sikkim and north east states of India including Assam, Arunachal Pradesh, Manipur, Meghalaya, Nagaland, Mizoram and Tripura. Majority of the Eastern Himalayas region is drained by the Brahmaputra River and its tributaries. For instance, the Teesta River drains the Darjeeling and Sikkim region. The Manas drains part of Arunachal Pradesh and Bhutan. The important rivers that drain the regions of Eastern Himalayas are Kameng and the Subansiri.
The climate of Eastern Himalayas is characterized by climate ranging between arctic, subarctic, temperate, subtropical, and warm tropical. The dense, moist, temperate, evergreen and semi-evergreen forests are known to contain within themselves some of the unique species of flora and fauna. It is home to several varieties of birds and animals including one horn rhinoceros, tiger, the golden langur, clouded leopard, the Indian civet and the golden cat. Even, there are several wildlife sanctuaries and biosphere reserves too, which are located here to protect the rare and endangered species.
- Jaldapara, located in the Bhutan foothills of Bengal, is famous for hog deer, one-horned rhinoceros, and tiger floricans.
- Buxa Sanctuary located at the junction of northern West Bengal, Assam, and Bhutan is a renowned tiger reserve serving as a vital passage for the migrating elephants between the forests of Assam and Bhutan.
- The Kangchendzonga national park located in Sikkim is habitat of several high-altitude birds and mammals such as the red panda, clouded leopard, snow cock, musk deer and pheasants. The coniferous and Alpine scrub is the principal forest types found here.
- The Manas sanctuary lying on the either side of the Manas River in Bhutan and Assam has dense semi-evergreen and deciduous forests, swamps, and marshes. Besides, the only habitat of the golden languor, other animals present here includes sambar, barking deer, and golden cat. It is also a famous tiger reserve under the Project Tiger.
- The Namdapa national reserve located in Arunachal Pradesh is the only protected area in the whole Himalayas containing the leopard, tiger, clouded leopard, and the snow leopard. It is also characterized with a rich flora and fauna.
- Located in Lohit and Tirap districts in southeastern Arunachal Pradesh, The Namdapa biosphere reserve is considered as one of the richest biotic areas in India. It is partly drained by the Brahmaputra river system and is characterized by typical to subtropical monsoon climate. It also receives very heavy rainfall.