Nepal is a landlocked country in South Asia. It is mainly situated in the Himalayas, but also includes parts of the Indo-Gangetic Plain, bordering Tibet of China to the north, and India in the south, east, and west, while it is narrowly separated from Bangladesh by the Siliguri Corridor, and from Bhutan by the Indian state of Sikkim. Nepal has a diverse geography, including fertile plains, subalpine forested hills, and eight of the world's ten tallest mountains, including Mount Everest, the highest point on Earth.
Nepal contains a disproportionately large diversity of plants and animals, relative to its size. Nepal, in its entirety, forms the western portion of the eastern Himalayan biodiversity hotspot, with notable biocultural diversity. The dramatic differences in elevation found in Nepal result in a variety of biomes. The Eastern half of Nepal is richer in biodiversity as it receives more rain, compared to western parts, where arctic desert-type conditions are more common at higher elevations. Nepal is a habitat for 4.0% of all mammal species, 8.9% of bird species, 1.0% of reptile species, 2.5% of amphibian species, 1.9% of fish species, 3.7% of butterfly species, 0.5% of moth species and 0.4% of spider species. In its 35 forest-types and 118 ecosystems, Nepal harbours 2% of the flowering plant species, 3% of pteridophytes and 6% of bryophytes.
Nepal's forest cover is 59,624 km2, 40.36% of the country's total land area, with an additional 4.38% of scrubland, for a total forested area of 44.74%, an increase of 5% since the turn of the millennium. The country had a 2019 Forest Landscape Integrity Index mean score of 7.23/10, ranking it 45th globally out of 172 countries. In the southern plains, Terai–Duar savanna and grasslands ecoregion contains some of the world's tallest grasses as well as Sal forests, tropical evergreen forests and tropical riverine deciduous forests. In the lower hills, subtropical and temperate deciduous mixed forests containing mostly Sal, Chilaune and Katus, as well as subtropical pine forest dominated by chir pine are common. The middle hills are dominated by oak and rhododendron. Subalpine coniferous forests cover the 3,000 m to 3,500 m range, dominated by oak, Eastern Himalayan fir, Himalayan pine and Himalayan hemlock; rhododendron is common as well. Above 3,500 m in the west and 4,000 m in the east, coniferous trees give way to rhododendron-dominated alpine shrubs and meadows.
Among the notable trees, are the astringent Azadirachta indica, or neem, which is widely used in traditional herbal medicine, and the luxuriant Ficus religiosa, or peepal, which is displayed on the ancient seals of Mohenjo-daro, and under which Gautam Buddha is recorded in the Pali canon to have sought enlightenment.
Most of the subtropical evergreen broad-leaved forest of the lower Himalayan region is descended from the Tethyan Tertiary flora. As the Indian Plate collided with Eurasia forming and raising the Himalayas, the arid and semi-arid Mediterranean flora was pushed up and adapted to the more alpine climate over the next 40–50 million years. The Himalayan biodiversity hotspot was the site of mass exchange and intermingling of the Indian and Eurasian species in the neogene. One mammal species, two each of bird and reptile species, nine amphibia, eight fish and 29 butterfly species are endemic to Nepal.
Nepal contains 107 IUCN-designated threatened species, 88 of them animal species, 18 plant species and one species of 'fungi or protist' group. These include the endangered Bengal tiger, the red panda, the Asiatic elephant, the Himalayan musk deer, the wild water buffalo and the South Asian river dolphin, as well as the critically endangered gharial, the Bengal florican, and the white-rumped vulture, which has become nearly extinct by having ingested the carrion of diclofenac-treated cattle. The pervasive and ecologically devastating human encroachment of recent decades has critically endangered Nepali wildlife. In response, the system of national parks and protected areas was substantially expanded. Vulture restaurants coupled with a ban on veterinary usage of diclofenac has seen a rise in the number of white-rumped vultures. The community forestry programme which has seen a third of the country's population directly participate in managing a quarter of the total forested area has helped the local economies while reducing human-wildlife conflict. The breeding programmes coupled with community-assisted military patrols, and a crackdown on poaching and smuggling, has seen poaching of critically endangered tigers and elephants as well as vulnerable rhinos, among others, go down to effectively zero, and their numbers have steadily increased. Nepal has ten national parks, three wildlife reserves, one hunting reserve, three Conservation Areas and eleven buffer zones, covering a total area of 28,959.67 km2, or 19.67% of the total land area, while ten wetlands are registered under the Ramsar Convention.