Bhutan is situated in the eastern Himalayas. The country is almost entirely mountainous with nearly 95 percent of the country being above 600 meters. The terrain is rugged and steep. The country can be divided into three broad physiographic zones:
- The southern belt made up of the Himalayan foothills along the Indian border with altitude ranging from 200 m to about 2,000 m.
- The inner Himalayas encompassing the main river valleys and steep mountains with altitude ranging from about 2,000 m to 4,000 m and
- The great Himalayas in the north along the Tibetan border that encompass snow-capped peaks and alpine meadows above 4,000 m.
Bhutan can also be divided into 5 major ecological zones:
- Alpine Zone : This zone lies between 3,600 – 4,600 m, and is characterized by alpine meadows. This zone is too high to cultivate any food crops. Nomadic yak-herding communities use this alpine meadows as summer pasture grounds for their yaks.
- Cool Temperate Zone: This zone covers cultivated areas between 2,600 – 3,600 m. Precipitation is low. Livestock farming is a predominant feature.
- Warm Temperate Zone: This zone is between 1,800 – 2,500 m. Precipitation is still low but the temperature is mildly warm, except during winter. Farming activities are an integral part in here.
- Dry Subtropical Zone: This zone occurs between 1,200 – 1,800 m. Precipitation is moderate here. Rice and maize are major crops grown in this zone.
- Wet Subtropical Zone : This zone receives very high rainfall ranging between 2,500 – 5,500 mm annually. Cattle rearing are common. Rice, wheat, millet, mustard and oranges are common crops grown in this zone.
Bhutan has an impressive list of wild plant species. The Royal Botanic Garden of Edinburgh, which published the Flora of Bhutan, has recorded 5,603 species of angiosperms and gymnosperms. This includes 369 species of orchids and 46 species of rhododendrons. Of the recorded plant species, 105 are endemic to Bhutan.
Bhutan also boasts 90 species of mushrooms. Bhutan is also expected to be rich in insect-fungi due to its wide-ranging geo-climatic conditions. Chinese caterpillar fungus (Cordyceps sinensis), locally known as Yartsa Guenbub which roughly translates as ‘Grass in summer and caterpillar in winter’ found in alpine meadows of the country, is highly valued for it medicinal properties and as an aphrodisiac and cure for lung and kidney ailments.
Bhutan, although one of the smallest nations in Asia, has close to 200 species of mammals. These mammal species include the globally endangered bengal tiger, snow leopard, clouded leopard, red panda, bhutan takin, golden langur, capped langur, asian elephant, and the himalayan musk deer. In total, there are 27 globally threatened mammal species in the country.
Bhutan also has an outstanding birdlife. 678 species have been recorded so far. Bhutan is part of the Sino-Himalayan mountain forests; Indo-Burmese forests; Indo-Gangetic grasslands; South Asian arid habitats; and Tibetan Plateau wetlands – which are all categorized as globally important bird regions by Birdlife International. There are 14 globally threatened bird species and 10 restricted bird species in the country. Of the 14 globally threatened, the white-bellied heron is considered critically endangered. Bhutan also has around 800-900 species of butterfly. The Ludlow’s Swallowtail butterfly, which is found only in Bhutan, has recently been named the national butterfly of Bhutan.