Sikkim is one of just three ecoregions in India located in an ecological hotspot in the lower Himalayas. The state's wooded areas are home to a rich array of animals and vegetation. Because of its altitudinal gradation, the state boasts diverse plants, ranging from tropical to temperate, alpine, and tundra species. It is one of the few destinations in the world to have such diversity in such a small space. Sikkim's forest department is responsible for over 81 percent of the state's land.
Around 5,000 blooming plant species, 515 unique orchids, 60 primula species, 36 rhododendron species, 11 oak kinds, 23 bamboo variants, 16 conifer species, 362 ferns and fern allies, 8 tree ferns, and over 900 medicinal plants may be found in Sikkim. A Poinsettia cousin called "Christmas Flower" may be found in profusion in the mountainous state. Pine, juniper, firs, cypresses, and rhododendrons from the Eastern Himalayan subalpine conifer forests can be found at lower elevations. In addition, Eastern Himalayan alpine shrub and meadows and high-altitude wetlands provide a diverse range of rhododendrons and wildflowers.
Snow leopards, musk deer, Himalayan tahr, red pandas, Himalayan marmots, Himalayan serows, Himalayan gorals, muntjacs, common langurs, Asian black bears, clouded leopards, marbled cats, leopard cats, dholes, Tibetan wolves, hog badgers, binturongs, and Himalayan jungle cats are among Sikkim's biodiversity. Yaks are one of the more frequent animals found in the alpine zone, and they are primarily raised for milk, meat, and as a beast of burden.
The impeyan pheasant, snow partridge, crimson horned pheasant, bearded vulture, Tibetan snowcock, and griffon vulture are among Sikkim's avifauna, which also includes golden eagles, quails, plovers, woodcocks, sandpipers, pigeons, Old World flycatchers, babblers, and robin Sikkim is home to around 550 bird species, some of which have been designated as endangered.
Sikkim is also home to a diverse range of arthropods, many of which have yet to be researched. Sikkimese arthropods, particularly butterflies, are among the most understudied species. Sikkim is home to 695 of the approximately 1,438 butterfly species found in the Indian subcontinent. The endangered Kaiser-i-hind, the Bhutan Glory and the Yellow Gorgon are among them.