Biodiversity encompasses all biological entities occurring as an interacting system in a habitat or ecosystem and plants constitute a very important segment of such biological systems. Biodiversity of plants collectively known as 'plant genetic resources' is a key component of any agricultural production system - indeed, of any ecosystem, without which, natural evolutionary adjustment of the system to the changing environmental and biotic conditions would be impossible. Plant biodiversity is an irreplaceable resource, providing raw materials for introduction, domestication as well as improvement programmes in agriculture and forestry. Conservation and use of genetic diversity for sustainable ecosystem or agro ecosystem should be continuous to meet food, clothing, shelter and health requirements of India's growing population.
India is a treasure chest of biodiversity which hosts a large variety of plants and has been identified as one of the eight important 'Vavilorian' centres of origin and crop diversity. Although its total land area is only 2.4% of the total geographical area of the world, the country accounts for 8% of the total global biodiversity with an estimated 49,000 species of plants of which 4,900 are endemic (Kumar and Asija 2000). The ecosystems of the Himalayas, the Khasi and Mizo hills of northeastern India, the Vindhya and Satpura ranges of northern peninsular India, and the Western Ghats contain nearly 90% of the country's higher plant species and are therefore of special importance to traditional medicine. Although, a good proportion of species of Medicinal Plants (MP) do occur throughout the country, peninsular Indian forests and the Western Ghats are highly significant with respect to varietal richness (Parrota 2001).
Peninsular India extending downwards from Gujarath, Madhya pradesh and Southern Bihar was once dominated by a continuum of tropical forests namely; thorn forests, dry deciduous forests, moist deciduous forests, dry evergreen forests, wet evergreen forests and semi evergreen forests. The complexity with respect to soils, topography and climate, have created an exceptional variety of bio mass and specialized habitats within this region. The ecosystems of southern peninsular India including the southern Western Ghats contain more than 6000 species of higher plants including an estimated 2000 endemic species. Of these, 2500 species representing over 1000 genera and 250 families have been used in Indian systems of medicine (Jain 1991).
Medicinal plants which constitute a segment of the flora provide raw material for use in all the indigenous systems of medicine in India namely Ayurveda, Unani, Siddha and Tibetan Medicine. According to the World Health Organization (WHO), 80% of the population in developing countries relies on traditional medicine, mostly in the form of plant drugs for their health care needs. Additionally, modern medicines contain plant derivatives to the extent of about 25%.
On account of the fact that the derivatives of medicinal plants are non-narcotic having no side effects, the demand for these plants is on the increase in both developing and developed countries. There are estimated to be around 25000 effective plant based formulations available in Indian medicine. Over 1.5m practitioners of the Indian system of medicine in the oral and codified streams use medicinal plants in preventive, promotional and curative applications. It is estimated that there are over 7800 medicinal drug manufacturing units in India, which consume about 2000 tonnes of herbs annually (Singh 2001). According to Exim Bank, the international market for medicinal plant related trade is to the tune of US$ 60 billion having a growth rate of 7% per annum. The annual export of medicinal plants from India is valued at Rs.1200 million.
Currently more than 75% of the herbal requirement is met through wild collections. While the demand for medicinal plants is increasing, their survival in their natural habitat is under growing threat. Species likeRauvolfia serpentina, Terminalia chebula, Sapindus laurifolius, Jatropha curcasare becoming uncommon in the Western Ghat forests (Anonymous, 2001). Collection of herbs from the wild by destructive harvesting followed by unscientific handling have resulted in poor quality products.
Cultivation of medicinal plants in a grower's field is a recent phenomenon. Industry prefers raw material from cultivated source because of authentication, reliability and continuity. Non availability of quality planting material coupled with poor development and extension support in the cultivation and processing and also unorganized markets are the major constraints coming in the way of commercialisation of cultivation. Therefore, concentrated efforts are required, both in collection and cultivation of medicinal plants, in order to ensure sustainability of the Industry.
To elicit the impact of cultivation and gathering on the biodiversity of medicinal plants, two case studies, one at Maradavally Forest Range in the semi evergreen forest of Western Ghats and the other at Devarayanadurga state forest in the dry deciduous forest of Deccan Plateau were conducted.