The amazing variety of life on Earth is called biodiversity. Biodiversity is the degree of variation of life forms within a given species, ecosystem, biome, or an entire planet. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas Polar Regions support fewer species. Rapid environmental changes typically cause mass extinctions. One estimate is that less than 1% of the species that have existed on Earth are extant. The period since the emergence of humans has displayed an ongoing biodiversity reduction and an accompanying loss of genetic diversity. Named the Holocene extinction, the reduction is caused primarily by human impacts, particularly habitat destruction. Conversely, biodiversity impacts human health in a number of ways, both positively and negatively.
The following human activities can be enumerated as the principal threats to conservation of biodiversity in the country:
Tropical hardwood has dominated the trade based on natural resources in Nepal for more than a century. However, this trend has very recently declined because of the depletion of timber reserves from the natural forest through logging and conversion of forest land to other uses. Over 87 per cent of the nation's energy requirement is met by forest products and each person consumes one cubic meter of wood per year for this purpose (Upreti, 1985).
Population pressure and the so-called developmental activities are causing a rapid depletion of forests in every part of the country. As a result, countless plant species are facing considerable danger of extinction.
2. Forest fires
Occasionally, forests are intentionally set to fire to kill trees to obtain fuel wood and construction materials, and also to extend the area of the adjoining agricultural lands. Forest fires, especially those in the high-altitude pine (Pinuswallichiana A.B. Jacks.) forests are set to enhance the growth and yield of the high-priced morel mushrooms (Morchellaconica L., M. esculenta L., etc.). The pastures are regularly subjected to fire to produce tender grasses. Consequently, many valuable herbs flourishing in those habitats are heavily affected. Organic matter in the upper layer of the soil is usually destroyed resulting in the disappearance of many valuable biological species from the area.
3. Shifting cultivation
The shifting cultivation, called 'khoreaphandne', is another form of destruction of habitat. A patch of the climax forest is cleared, burnt and used for farming for some years after which it is abandoned and the farmers shift to another forest area, clearing another patch of the climax vegetation. This practice results in the destruction of a large number of biological species.
The shortage of fodder and other feeding materials has resulted in overgrazing in the pastures and over lopping of fodder trees in the forests. Fodder for the estimated 15 million cattle in the country, which includes important non-timber forest products used by the villagers, is estimated at 5.6 million tons of fodder per year (Upreti, 1985). About three-quarters of the fodder comes from the forest and grassland, thus posing pressing threat to the country's biodiversity (Sigdyal, 1984).
5. Over exploitation
In Nepal, there are traditional extraction systems in which very little processing of the products occurs in the area in which they are found. The general pattern is to gather, dry, pack and transport out of the region of origin. A major proportion of the non-wood forest products, especially the medicinal and aromatic herbs collected from the wild, is meant for export. Hence, the quantities of different forest products collected are mostly determined by the demand from abroad. At the same time, the local collectors, mostly belonging to the poorer classes of the community, are being attracted by the market prices for some items that have gone through the roof. As a consequence, raw materials are overharvested by the removal, for example, of immature plants, roots, tubers and rhizomes, or by over pruning. As an outside interest dictates the price and quantity of raw materials extracted, a major part of local ecosystem has suffered irreversible harm.
6. Medicinal plants in trade and industry
The list of Nepalese medicinal plants contains well over 700 species comprising about 10% of the known vascular plant species of the country (Malla and Shakya, 1984). Every year, thousands of tons of medicinal herbs are collected from the forests and pastures, and traded to foreign countries. The trade in medicinal herbs is an important source of revenue for the government and a major source of income for the rural people. About 100 species of medicinal herbs are currently exploited for commercial and industrial purposes (Mallaet al., 1995). The uncontrolled commercial extraction has significantly eroded the country's medicinal plant resources, and particular species have gradually become more difficult to find in a given locality where they once flourished. In addition to direct export of herbs, many entrepreneurs are taking an interest in processing for industrial uses such as the production of essential oils and ayurvedic medicines involving thousands of tons of crude herbs collected locally. Collection and trade of medicinal herbs and other non-wood forest products provide up to 50 percent of a family's income in certain areas of the country.
7. Wild plant resources in the livelihood of the rural people
Apart from commercial and industrial uses, the majority of the lay population use wild plants in a variety of ways, the additional uses being for food, folk medicine, fodder, fuel, and a variety of domestic articles. They are also used as sources of dyes, tannins, fibres, gums and resins, for producing agricultural and hunting tools and weapons, and in witchcraft and magic. Some species are also used in worships and religious rituals.
8. Reasons for the excessive extraction of wild plant resources
The improper and excessive exploitation of biological resources leading to habitat destruction and placing threat on biodiversity is largely due to illiteracy, poverty and the shortage of off-farm employment opportunities for the rural population. Non-timber forest products, especially medicinal and aromatic plants, are regarded as a free commodity to be collected from nature. Consequently, the raw materials are mostly being overharvested. Illiteracy and poverty have forced the rural Nepalese people to continue activities which help them survive in the present but which will cause more severe problems in the future.