Bhutan straddle two major bio-geographic realms, the Indo-Malayan realm consisting of the lowland rain forests of South and Southeast Asia and the Pale-arctic realm consisting of conifer forests and alpine meadows of northern Asia and Europe.
Ecosystem Diversity
Bhutan ranks among the most bio-diverse country in the world and has an incredible range of habitat type due to her location. The warm southern part of Bhutan supports wildlife that is usually associated with a tropical-jungle climate. As one progresses north, the wildlife changes accordingly as the elevation increases. Bhutan falls under one of the ten global biodiversity ‘hotspots’ with many animal and plant species. Considering her size, Bhutan has the most diverse ecosystem in Asia.
Forest Ecosystems:
Forests are Bhutan’s largest renewable resource and the most dominant land cover measuring 72.5 percent of Bhutan’s total landmass. Bhutan’s forests can be classified into three broad and distinct eco-floristic zones comprising of alpine forests (above 4000 meters above sea level (masl)), temperate forests (2000-4000 masl) and sub-tropical forests (150-2000 masl). Several forest types occur corresponding to variations in altitude and climatic conditions as below:
| Forest Type | Area (Sq Km) | Percentage of Total Landmass | Common Species |
| Broadleaf | 13260 | 34.5% | |
| Mixed Conifer | 4523 | 11.8% | Spruce, hemlock, larch |
| Fir | 3132 | 8.2% | Fir, hemlock, birch, juniper, rhododendron |
| Broadleaf and conifer | 1598 | 4.2% | |
| Blue Pine | 1199 | 3.1% | Blue pine, oak species |
| Chirpine | 1006 | 2.6% | Chirpine |
| Scrub forests | 3457 | 9.0% | Shrubs and alpine meadow grasses |
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Aquatic Ecosystem:
Bhutan has a large number of inland water resources comprising a network of freshwater rivers, wetlands, glaciers, lakes and underground water.
Rivers:
Bhutan has four major river systems: Drangme Chhu; Puna Tsang Chhu, Wang Chhu; and Amo Chhu. Each flows swiftly out of the Himalayas, southerly through the plans to join the Brahmaputra River in India. These rivers are fed by many tributaries.
The largest river system, the Drangme Chhu, flows southwesterly from India’s state of Arunachal Pradesh and has three major branches: the Drangme Chhu, Mangde Chhu, and Chamkhar Chhu. These branches form the Drangme Chhu basin, which spreads over most of eastern Bhutan and drains the Tongsa and Bumthang valleys. In the plans, where eight tributaries join it, the Drangme Chhu is called the Manas Chhu.
The 320-kilometer-long Puna Tsang Chhu rises in northwestern Bhutan as the Mo Chhu and Pho Chhu which are fed by the snows from the Great Himalayan Range. They flow southerly to Punakha, where they join to form the Puna Tsang Chhu, which flows southerly into India’s state of West Bengal.
The tributaries of the 370-kilometer-long Wang Chhu rise in Tibet. The Wang Chhu itself flows southeasterly through west-central Bhutan, drains the Ha, Paro, and Thimphu valleys, and continues into the plains and enters West Bengal.
The smallest river system is the Amo Chhu. The Amo Chhu in its northern reaches flows out of Tibet into the Chumbi Valley and swiftly through western Bhutan before broadening near Phuntsholing and then flowing into India.
Lakes and Marshes:
Lakes and marshes form important part of the wetland ecosystem although they are not well documented in Bhutan. However, there is a complete inventory of Bhutan’s 677 glaciers containing 2,674 glacial lakes which are also sources to some of the largest river basins in the country. Phobjikha valley by far is known to be the largest high altitude wetland in the country and is the wintering habitat of vulnerable Black-necked cranes.
| Wetland Type | # Lake | Area Subtotal (Sqm) | Average Area (Sqm) | Largest Lake (Sqm) | Smallest Lake (Sqm) |
| Supra-snow lake | 110 | 52327.0 | 475.7 | 4758.8 | 36.2 |
| Supraglacial lake | 495 | 28554801.3 | 57686.5 | 1517436.4 | 133.6 |
| Glacial lake | 637 | 23230604.6 | 36468.8 | 878311.5 | 114.7 |
| Lake | 1722 | 49973272.8 | 29020.5 | 868048.9 | 34.6 |
| Marsh | 63 | 497334.4 | 7894.2 | 63811.1 | 126.1 |
Source: Inventory of High Altitude Wetland in Bhutan
Hotsprings:
Ten hot springs (Tshachu) have been officially recorded including gNyes and Yonten Kuenjong Tshachu in Lhuentshe, Dur Tshachu in Bumthang, Gaylegphu Tshachu in Sarpang, Dungmang Tshachu in Zhemgang, Koma and Chu Phug Tshachu in Punakha and Laya, Wachi and Gasa Tshachu in Gasa(Source: BAP III)
Flora and Fauna:
Owing to the various climatic types, Bhutan supports a diversity of flora and fauna representing both the Indo-Malayan and Pale-arctic biodiversity.
Flora:
The Flora of Bhutan series has a record of 5603 species of angiosperm and gymnosperms including 579 wild orchids, 46 rhododendrons, and over 300 medicinal plants. At least 30 bamboo species have been recorded in Bhutan till date including ‘Ringshoo’ (Neomicrocalamus andropogonifolius), a species used extensively in the fine art of ‘Tsazo’ or bamboo weaving.
Fauna:
Bhutan creates a heaven for wide range of animals. Close to 200 species of mammals have been recorded in Bhutan including some of the globally significant Royal Bengal Tiger (Panthera tigris), Snow Leopard (Unicia uncia), Red Panda (Ailurus fulgens), Takin, (Budorcas taxicolor), Golden Langur (Trachypithecus geei), Asiatic Elephant (Elephus maximus), and the Himalayan Musk Deer (Moschus chrysogaster leucogaster). The Royal Bengal Tiger living at 4000 meters above sea level in Bhutan is an extraordinary finding and has been recently documented on film by the BBC.
Birds:
Bhutan is considered a birding paradise with 678 recorded species. At least 14 species are globally threatened and ten fall within the restricted range. The white-bellied heron (Ardea Insignis) is considered critically endangered by the IUCN because of its low population status and loss of habitat.
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