Nepal comprises only 0.09% of land area on a global scale, but it possesses a disproportionately rich diversity of flora and fauna at genetic, species and ecosystem levels. These species are found in the dense tropical monsoon forests of the Terai, in the deciduous and coniferous forests of the subtropical and temperate regions, and in the sub-alpine and alpine pastures and snow-covered Himalayan peaks. Nepal falls within two biogeographical realms - the Indo-Malayan and the Palaearctic realms – which adds to the high biodiversity level. A comprehensive summary of species diversity is given in Table 2.23.
18.104.22.168 Diversity of flora
There has been comparatively much work carried out on the higher groups of plants (angiosperms and gymnosperms), but research on the lower groups has not been extensive or systematic. Collection of Nepalese specimens began in 1802 by Buchanan Hamilton and was continued by N. Wallich during 1820-21. Since then, many parts of Nepal have been well explored. Major herbaria that house Nepalese specimens are found in the National Herbarium and Plant Laboratories, Kathmandu, the British Museum, London, the Royal Botanic Garden, Kew, the University of Tokyo, Japan, the Smithsonian Institution, Washington, D.C., the University of Grenoble, France, and the Royal Botanic Garden, Edinburg. It is estimated that the British Museum has over 40,000 specimens, the University of Tokyo about 100,000 specimens, and the National Herbarium and Plant Laboratories of Kathmandu, 150,000 specimens. Additionally, approximately 10,000 specimens are housed in different institutions of Tribhuvan University.
The compilation of a comprehensive list of the flora of Nepal is a very important task. However, despite the occasional efforts made by various institutions, such a work has not been finalised. The Flora of Nepal programme was initiated by the National Herbarium and Plant Laboratories of Godavari under the Department of Plant Resources, established during 1960-61 (DPR-MFSC 1997). The Department of Plant Resources has established seven district offices for the development of plant resources activities at district-level. The MFSC, Tribhuvan University, and the Royal Nepal Academy of Science and Technology have signed an agreement to produce a comprehensive list of the flora of Nepal.
The Department of Plant Resources has published 32 books and booklets about local and regional flora, and Tribhuvan University has published several papers on the subject. There are several M.Sc. dissertations from Tribhuvan University dealing with local flora, ecology, and biological diversity. Foreign institutions actively involved in the Flora of Nepal programme include the British Museum in London, Tokyo University, and the Royal Botanic Garden of Edinburgh.
Bacteria The number of bacteria species described in the world is between 3,000-4,000, but enormous numbers of uncultured bacteria are yet to be identified from soils, deep sea sediments and the digestive tracts and pockets of a wide variety of animals and insects (WCMC 1992). This important group of organisms has not received adequate attention in Nepal and the study of bacteria in different habitats is much needed.
Lichens During the International Workshop on Lichen Taxonomy, held in Kathmandu in 1994, lichenologists estimated that there are about 2,000 lichen species in Nepal. Lichens are found in all climatic zones. Forty-eight species of lichens are reported to be endemic to Nepal. Sharma (1995) identified 465 species from 79 genera and 30 families. Studies on lichens have been carried out mainly in eastern and central Nepal. Lichens from the lowland Terai and Siwalik Hills are much less known, and the lichens of western Nepal remain largely unexplored.
Fungi Adhikari (1999) listed 1,822 species of fungi belonging to 585 genera and 80 families. However, studies on fungi have been mainly focused in the Mid-hills and high altitudes and in the Kathmandu Valley, and exploration in the lowlands has been inadequate. Little is known about the distribution of fungi in Nepal.
Algae Baral (1995) identified 687 species of algae belonging to 150 genera and 50 families in Nepal, with 12 species presumed to be endemic. Most work has been concentrated in the high mountain and Mid-hills regions. The Terai belt, which supports luxuriant growths of algae owing to its hot and humid climate, has not been extensively investigated.
Bryophytes A total of 853 species of bryophytes (mosses and liverworts) have been recorded (Kattel & Adhikari 1992). 627 species are found in eastern Nepal and 283 species are found in central Nepal (BPP 1995h). The largest number of bryophyte species (493) have been recorded in the Mid-hills (subtropical and temperate zones), 347 in the high mountains (alpine and sub-alpine zones) and 61 in the Siwalik Hills and Terai (tropical zone). The bryophytes of eastern and central Nepal have been reasonably well studied, but work is still required on the bryophytes of western Nepal.
Pteridophytes An enumeration of pteridophytes (ferns and fern allies) has been compiled by Iwatsuki (1988). Iwatsuki recorded a total of 380 species, with 258 distributed in the eastern region and 97 in the central region of Nepal, but no collections have been made from western Nepal. The greatest number of pteridophyte species has been recorded in the Mid-hills (272 species, subtropical and temperate zones). The Siwalik Hills and the Terai (tropical zones) have 81 species, the high mountains (alpine and sub-alpine zones) 78 species, and the high Himalaya (nival zone) one species.
Gymnosperms Gymnosperms have been the best studied amongst the vascular plants of Nepal. Altogether, 27 species of gymnosperms have been listed (Koba et al. 1994). These include 20 indigenous species belonging to 13 genera and 10 families (Shrestha 1984-85).
Angiosperms The angiosperm flora of Nepal is impressively high on a global scale considering the area of the country. Koba et al. (1994) extended the list of flowering plant species prepared by Hara and Williams (1979), Hara et al. (1978), and Hara et al. (1982), and enumerated 5,806 species belonging to 203 families. To this number, a list of 50 species has been added by Akiyama et al. (1998), making the total number of angiosperm species in Nepal 5,856. However, Hara et al. (1978) and the World Conservation Monitoring Centre (Caldecot et al. 1994) estimated that number to be 6,500 species. The Biodiversity Profiles Project (1995h) ranked Nepal as having the tenth richest flowering plant diversity in Asia. On a world scale Nepal is placed 31st (Caldecot et al. 1994). It is noteworthy to mention that out of about 410 angiosperm families in the world, 203 (almost 50%) are represented in Nepal. Families with large numbers of species are the daisies (Asteraceae or Compositae, about 400 species), grasses (Poaceae or Gramineae, over 350 species), orchid (Orchidaceae, over 300 species), peas (Fabaceae or Leguminosae, 300 species), rose (Rosaceae, 180 species), sedge (Cyperacace, over 170 species), crowfoot or buttercup (Ranunculaceae, 150 species), mustard (Cruciferae, 90 species), and pink or carnation (Caryophyllaceae, 80 species).
Some families are represented by a single species, such as Dipterocarpaceae (Shorea robusta), Teteracentraceae (Teteracentron sinense), Bombacaceae (Silk tree, Bombax ceiba), Ochnaceae (Ochnea obtusata), Burseraceae (Garuga pinnata), Hippocastanaceae (Horse-Chestnut, Aesculus indica), Hamamelidaceae (Witch Hazel, Exbucklandia populnea), Toricelliaceae (Toricellia tiliifolia), Saururaceae (Hottuynia cordata), Myricaceae (Myrica esculenta), and Daphniphyllaceae (Daphniphyllum himalense).
Genera in Nepal represented by more than 25 species are Saxifraga (89), Primula (77), Pedicularis (74), Carex (70), Gentiana (51), Ficus (47), Berberis (46), Persicaria (45), Rhododendron (43), Impatiens (42), Rubus (41), Saussurea (38), Potentilla (37), Salix (37), Corydalis (36), Aconitum (35), Cotoneaster (35), Poa (33), Desmodium (32), Juncus (32), Swertia (32), Astragalus (31), Stellaria (30), Silene (29), Lonicera (28), Ranunculus (28), Senecio (28), Cyperus (27), Kobresia (27), Dendrobium (26) and Epilobium (26) (Koba et al. 1994).
In general, eastern (Sino-Japanese) elements dominate throughout the country, but these become less dominant as one proceeds towards the west of Nepal where Mediterranean elements become more dominant. The Terai possesses widespread North Indian elements, while in the northern Trans-Himalayan arid zone, the vegetation is similar to that of Tibet. The country can therefore be regarded as an area of transition, or merging of flora. As suggested by Stearn (1960) and later by other botanists and phytogeographers, the latitude 83o E can be taken as the delimiting boundary between the western and eastern Himalayan floral provinces.