What is biological diversity?
Biological diversity or biodiversity refers to the variety of life forms: the different plants, animals and microorganisms, the genes they contain, and the ecosystems they form. Biological diversity is usually considered at three different levels: a) genetic diversity, b) species diversity, and c) ecosystem diversity.
Genetic diversity refers to the variety of genetic information contained in all of the individual plants, animals and micro-organisms. Genetic diversity occurs within and between populations of species as well as between species. The pool of genetic variation present in an inter- breeding population is shaped by selection. Selection leads to certain genetic attributes being preferred and results in changes to the frequency of genes within this pool. India has high genetic diversity and is regarded as a Vavilov centre of high crop genetic diversity - so named after the Russian agro-botanist NI Vavilov who identified eight such centres around the world in the 1950s.
Species diversity refers to the variety of species within a geographical area. Aspects of species diversity can be measured in terms of :
a) species richness - the number of species in a defined area.
b) Species abundance - relative numbers among species.
c) taxonomic or phylogenetic diversity - genetic relationships between different groups of species.
At the global level, an estimated 1.7 million species have been described to date; current estimates for the total number of species vary from five million to nearly 100 million. On a broad scale species diversity is not evenly distributed across the globe. The overall species richness is concentrated in equatorial regions and tends to decrease as one moves from equatorial to polar regions. In general, there are more species per unit area in the tropics than in temperate regions and far more species in temperate regions than there are in polar regions. In addition, diversity in land ecosystems generally decreases with increasing altitude. Other factors which are believed to influence diversity on land are rainfall patterns and nutrient levels. In marine ecosystems, species richness tends to be concentrated on continental shelves, though deep sea communities are also significant.
Lying at the junction of Afro-tropical, Eurasian and the Indo-Malayan biogeographic realms, India is a country of vast diversity (Table 1). It is among the 12 megadiversity countries in the world. In recent years, biodiversity conservation has become a thrust area in Indian scientific and political agenda.
Table 1a. India s floristic diversity.
---------------------------------------------- Groups No. of species ---------------------------------------------- Angiosperms 15,000 Gymnosperms 64 Pteridophytes 1,022 Bryophytes 2,584 Lichens 1,600 Fungi 23,000 Algae 2,500 ----------------------------------------------
Table 1b. India s faunistic diversity.
---------------------------------------------- Groups No. of species ---------------------------------------------- Mammals 372 Birds 1,175 Reptiles 399 Amphibians 181 Fish 1,693 Insects 60,000 Molluscs 5,000 ----------------------------------------------
Ecosystem diversity encompasses the broad differences between ecosystem types, and the diversity of habitats and ecological processes occurring within each ecosystem type. Since the ecosystem concept is dynamic and thus variable, it can be applied at different scales, though for management purposes it is generally used to group broadly similar assemblages of communities, such as rainforests, wetlands or coral reefs. India has very diverse terrestrial and aquatic ecosystems, from the ice-capped Himalayas to deserts, arid grasslands and wetlands, and tropical rainforests , from coral reefs to the deep sea. Each of these comprises a great variety of habitats and interactions between and within biotic and abiotic components.
Why is biological diversity important?
In the evolutionary history, human beings are always dependent for their sustenance, health, well-being and enjoyment of life on fundamental biological systems and processes. Humanity derives all of its food and many medicines and industrial products from the wild and domesticated components of biological diversity. Biotic resources also serve recreation and tourism, and underpin the ecosystems which provide many services. While the benefits of such resources are considerable, the value of biological diversity is not restricted to these. The enormous diversity of life in itself is of crucial value, probably giving greater resilience to ecosystems and organisms. Biodiversity also has important social and cultural values.
The value of biological diversity
Generally, benefits arising from the conservation of components of biological diversity can be considered in three groups: a) ecosystem services, b) biological resources, and c) social benefits.
Protection of water resources
Natural vegetation cover in water catchments helps to maintain hydrological cycles, regulating and stabilising water runoff, and acting as a buffer against extreme events such as floods and droughts. Vegetation removal results in siltation of catchment waterways, loss of water yield and quality, and degradation of aquatic habitat. Vegetation also helps to regulate underground water tables, preventing dryland salinity. Wetlands and forests act as water purifying systems, while mangroves trap silt, reducing impacts on marine ecosystems.
Soil formation and protection
Biological diversity helps in the formation and maintenance of soil structure and the retention of moisture and nutrient levels. The loss of biological diversity through clearing of vegetation has contributed to the salinisation of soils, leaching of nutrients, laterisation of minerals accelerated erosion of topsoil, reducing the land s productivity. Soil protection by maintenance of biological diversity can preserve the productive capacity of soil, prevent landslides, safeguard coastlines and riverbanks, and prevent the degradation of wetlands and coral reefs. Trees and other vegetation also assist in soil formation by the introduction of organic matter through litter formation and the decay and regeneration of fibrous roots, both of which facilitate microbial activity. Another contribution is through the effects of roots systems which break up soil and rock leading to penetration of water. Root systems also bring mineral nutrients to the surface through root uptake. Organic matter formed by the decay of tiny fibrous roots can also bind with minerals, such as iron and aluminium, which can reduce the potential deleterious effects of these minerals on other vegetation.
Nutrient storage and cycling
Ecosystems perform the vital function of recycling nutrients. These nutrients include the elements of the atmosphere as well as those found in the soil, which are necessary for the elements of the atmosphere as well as those found in the soil, which are necessary for the maintenance of life. Biological diversity is essential in this process. Plants are able to take up nutrients from the soil as well as from the air, and these nutrients can then form the basis of food chains, to be used by a wide range of other life forms. The soil s nutrient status, in turn, is replenished by dead or waste matter which is transformed by micro organisms; this may then feed other species such as earthworms which also mix and aerate the soil and make nutrients more readily available.
Pollution breakdown and absorption
Ecosystems and ecological processes play an important role in the breakdown and absorption of many pollutants. These include wastes such as sewage, garbage and oil spills. Components of ecosystems, from bacteria to higher life forms are involved in these breakdown and assimilative processes. Excessive quantities of pollutants, however, can be detrimental to the integrity of ecosystems and their biota. Some ecosystems, especially wetlands, have qualities that are particularly well suited to breaking down and absorbing pollutants. Natural and artificial wetlands are being used to filter effluents to remove nutrients, heavy metals and suspended solids, reduce the biochemical oxygen demand and destroy potentially harmful micro organisms.
Contribution to climate stability
Vegetation influences climate at the macro and micro levels. Growing evidence suggests that undisturbed forests help to maintain the rainfall in their immediate vicinity by recycling water vapour at a steady rate back into the atmosphere and through the canopy s effect in promoting atmospheric turbulence. At smaller scales, vegetation has a moderating influence on local climates and may create quite specific micro-climates. Some organisms are dependent on such micro-climates for their existence.
Maintenance of ecosystems
Ecosystem relationships resemble a web of connections from one living thing to many other living and non- living things. They not only allow survival, but also maintain a balance between living things and the resources they need to survive on. Vegetation is integral to the maintenance of water and humidity levels and is essential for the maintenance of the oxygen/carbon dioxide balance of the atmosphere. Due to the complex nature of ecosystem relationships, the removal or disturbance of one part of the ecosystem could affect the functioning of many other components of the ecosystem. Maintaining natural habitats helps ecosystem function over a wider area. Natural habitats afford sanctuary to breeding populations of birds and other predators which help control insect pests, thus reducing the need or, and cost of artificial control measures. Birds and nectar-loving insects which roost and breed in natural habitats may range some distance and pollinate crops and native flora in surrounding areas.
Recovery from unpredictable events
Maintaining healthy ecosystems improves the chances of recovery of plant and animal populations from unpredictable natural catastrophic events such as fire, flood and cyclones and from disasters caused by humans. Inadequately conserved and isolated populations, and ecosystems which are degraded, are less likely to recover or to recover as quickly, to their former state. Populations of biota may end up with small, possibly non-viable, genetic bases, which can lead to extinction.
Food, fibre, medicine, fuel wood and ornamental plants
Human existence and that of most other organisms is dependent on what biologists call primary producers, mainly plants. Five thousand plant species have been used as food by humans, but less than 20 now feed the majority of the world s population and just three or four carbohydrate crops are staples for the vast majority. One of the important benefits of conservation of biodiversity is the wild plant gene pool which is available to augment the narrow genetic base of these established food crops, providing disease resistance, improved productivity and different environmental tolerances. The short and long-term values of these genetic resources are enormous and most improvements in agriculture and silviculture depend on their preservation. Moreover, the gene pool value of natural habitats will increase as remaining natural habitats become more scarce. These areas are therefore of great value as in situ gene banks, and need to be effectively managed.
India has a very long history of using medicinal plants. The traditional system of medicine in India prescribing plant extracts in therapy dates back to the early age of Rig Veda (4500-1600 BC). The therapeutic efficacies of herbal medicines led to the evolution of Ayurveda which literally means Science of Life . The World Health Organisation has estimated that 80 per cent of the world s population will depend primarily on medicinal plants for their health requirements. In India about 7,500 species of plants have been recorded to have medicinal value out of which 1,200 are found in South India. The World Conservation Monitoring Centre lists 41 Indian medicinal plants species as threatened due to over exploitation.
Wood is a basic commodity used worldwide, and is still largely harvested from the wild. It is a primary source of fuel in Third World countries, is used in construction, and forms the basis for paper production. Apart from producing fibres for our day to day use many plant species are increasingly being used for ornamental and horticultural purposes, with new hybrids and strains being developed.
Breeding stocks, population reservoirs
Natural areas provide support systems or commercially valuable environmental benefits and resources. Some habitats protect crucial life stages or elements of wildlife populations such as spawning areas in mangroves and wetlands. For example, when mangrove areas are cleared for urban development, populations of commercial fish species which rely on mangroves for breeding habitats also diminish. Some of these crucial habitats have been declared protected areas, as their importance for maintaining stocks of fish, crustaceans such as prawns and mud-crabs, and other aquatic fauna has been recognised. Other habitats act as genetic reservoirs from which seed and other material can be assessed for enhancement of harvested species.
There is a clear relationship between the conservation of biological diversity and the discovery of new biological resources. The relatively few developed plant species currently cultivated have had a large amount of research and selective breeding applied to them. Many presently under-utilised food crops have the potential to become important in the future. The documentation of local peoples use of plants is often the source for ideas on developing plant species for wider use and/or economic benefits. Potential products which may be derived from biological resources include sunscreens from corals, light and high tensile fibres from silk worms, and instant adhesives from velvet worms or barnacles. Micro organisms are important in the production of extensive ranges of agrochemicals, proteins for animal feed, enzymes and biopolymers. The conservation of diversity is also essential for finding effective biological control organisms and for breeding disease resistant species.
Biological diversity is an intrinsic part of many areas valued for tourism and recreational purposes. The aesthetic qualities of such areas are often strikingly different, in large part due to the range of biological diversity to be found on this continent. People value such areas for a variety of recreational pursuits: films, photographs or literature based on or using wildlife, natural habitats and natural features; birdwatching; and ecological field study and other scientific pursuits.
The relationships of local people to the land and sea, and its animals and plants are complex with the deep spiritual, economic, social, protective and recreational significance. By hunting and gathering, local people are not only supplementing their diet with food very high in nutritional value; they are also confirming their self- sufficiency and, more importantly, educating their children in relationships to the land and to other aspects of their culture. Biological diversity conservation can contribute to the conservation of local cultural identity. The cultural value of biological diversity conservation for present and future generations is an important reason for conserving it today. Human cultures co-evolve with their environment, and the conservation of biological diversity can be important for cultural identity. The natural environment provides for many of the inspirational, aesthetic, spiritual and educational needs of people, of all cultures, now and in the future. The aesthetic values of our natural ecosystems and landscapes contribute to the emotional and spiritual well-being of a highly urbanised population. The conservation of biological diversity also has ethical benefits. The presence of a wide range of living organisms reminds people that they are but one interdependent part of Earth.
Research, education and monitoring
There is still much to learn on how to get better use from biological resources, how to maintain the genetic base of harvested biological resources, and how to rehabilitate degraded ecosystems. Natural areas provide excellent living laboratories for such studies, for comparison with other areas under different systems of use, and for valuable research into ecology and evolution. Unaltered habitats are often essential for certain research approaches, providing controls against which the changes brought about by different management regimes may be measured and assessed.
The Ministry of Environment & Forests, Government of India, has established five advance level research centres viz, the Wildlife Institute of India (WII), the Indian Council of Forestry Research and Education (ICFRE), GB Pant Institute of Himalayan Ecology, Indian Institute of Forest Management and Salim Ali Centre for Ornithology and Natural History Society, for the conservation management of India s diverse biological diversity. Apart from these, the traditional institutions such as Botanical and Zoological Survey of India are also documenting India s biodiversity.
There is no single particular argument which on its own provides sufficient grounds for attempting to maintain all existing biological diversity. A more general and pragmatic approach, however, recognises that different but equally valid arguments - resource values, precautionary values, ethics and aesthetics, and simple self-interest - apply in different cases, and between them provide an overwhelmingly powerful and convincing case for the conservation of biological diversity.
The many values of biological diversity and its importance for development indicate why biological diversity conservation differs from traditional nature conservation. Biological diversity conservation entails a shift from a reactive posture - protecting nature from the impacts of development - to a proactive effort seeking to meet people s needs from biological resources while ensuring the long-term ecological sustainability of Earth s biotic wealth. On a global level, it thus involves not only the protection of wild species and their habitats but also the safeguarding of the genetic diversity of cultivated and domesticated species and their wild relatives.
The conservation of biological diversity seeks to maintain the life-support system provided by nature in all its variety, and the living resources essential for ecologically sustainable development.