Throughout the ages, the processes of evolution have driven innumerable species to extinction and, by mutations, have created new species better suited to the environment. In the debate about the world’s environmental problems, a recurrent theme is the conservation of non-renewable resources. A very special non-renewal resource is the biological diversity of all living species and the complex ecosystem. Biodiversity is defined as the variability among living organisms from all sources, including inter alia, terrestrial, marine, and other aquatic ecosystems, and the ecological complexes of which these are a part. The world’s biodiversity, the vast mosaic of living species, exists at three levels ~ diversity of species, genetic diversity within the species and diversity of ecosystems. In common parlance, this is called the diversity of species. Within the species there are different varieties known as genetic diversities. The increase in species richness and complexity act to buffer the community from the environmental stresses and disasters, rendering it more stable. The interactive relationships between population of different species form the interactive web of communities. Species and their genes once lost, are not retrievable.
Estimates about the number of species on our planet vary. The range of estimated numbers varies from 50 lakh to 300 lakh. The number of species identified so far (this was in 2003) is only 17.7 lakhs ~ 15 lakh animal species and 2.5 lakh plant species. India’s animal species account for 7.31 per cent of the faunal species in the world, and the flora accounts for 10.78 per cent of the world floral population. Most animals are insects. It has now been proved that other groups such as viruses, bacteria, and algae have been relatively unexplored, and their numbers probably exceed that of all other species combined. There are several geographical zones with great diversities in different parts, both on land and in water, of the world. Each geographical zone maintains its unique character in climate and the resultant biodiversity depending on the combing effect of distance from the equator, Polar Regions, oceans, altitude and topography. Our country is very rich in biodiversity. India is one of the twelve Mega Diversity countries in the world.
Biodiversity is declining rapidly due to factors such as land use change, climate change, invasive species, over-exploitation and pollution. Such natural or human-induced factors ~ referred to as drivers ~ tend to interact and amplify each other. The human impact on biodiversity ~ known as human footprint ~ is significant in all parts of the world except in some environments, notably the desert regions, some parts of the equatorial rain forests (though these are also under threat), and poleward (high-latitude) regions that are currently too cold for agriculture. The rest of the planet exhibits a heavy human footprint. The result is astonishing. Humanity is now taking as much as 40-50 per cent of the photosynthesis on the planet. It is like inviting a million guests (roughly 10 million species on the planet) to a banquet, and then announcing that half of the food supply will go to just one of the guests, Homo sapiens. The human-induced pressures are coming from all directions: changes in land use, depletion of water supplies, change in climate patterns, overharvesting (through fishing, logging, hunting and other extractive processes), urbanisation, and more. In the words of Joyce Msuya of UN Environment: “Nature makes human development possible but our relentless demand for earth’s resources is accelerating extinction rates and devastating the world’s ecosystem.”
Humans have been causing the extinction of plants and animals for thousands of years. Several large mammals disappeared from the Americas and Australia when humans first moved into these continents. Similarly, human colonization of the islands in the Pacific and Indian Oceans some 1000 to 2000 years ago may have led to the extinction of as many as one-fourth of the bird species. However, the exact rate of species extinction is difficult to assess because we do not know how many species there are. Estimates range from 5 to 30 per cent of species loss per decade. The International Union for Conservation of Nature (IUCN), the global scorekeeper for endangered species, predicts that the rate of extinction that we are currently witnessing is 100 to 1000 times the average rate measured in the fossil record.
The key determinant of the rate of species loss is the destruction of high-biodiversity habitats, which include rainforests and coral reefs. According to the Food and Agriculture Organization (FAO) of the UN, the Amazon, the world’s largest rainforest, holds over half of the terrestrial species of animals, plants and insects. But due to extreme weather events more than 2 lakh fire incidents were reported from January to mid-September 2019. It is also widely estimated that up to half of all species alive today could be extinct by the end of the century. Why is this accelerated loss of biodiversity a cause for concern? If only a small number of species die out, there can be a huge effect on the whole ecosystem, since there are often chain effects that affect many other species. However, the loss of a species is primarily a cost to society for three reasons:
Firstly, the species lost may have a direct value as a source of knowledge that can be used to locate the genetic material for food crops, or as a source of active chemical compounds for new medicines. For example, (i) Malaysia’s durian fruit crop shrunk markedly in the 1970s because of severe decline of the pollinating bat species, caused by destruction of mangrove foliage upon which the bats fed; causing certain crucial species to decline or out-migrate may also cause the ecosystem to lose vitality. (ii) If there is no genetic diversity in a species, all members of the species might belong to the same breed. Under such condition, the occurrence of a disease may lead to the probability of all members being wiped out. The situation is the same in case of pest infestation. Under the modern cultivation practices (monoculture), if high-yielding variety (HYV) of paddy/ wheat seeds are issued in a particular region or specified area of land, the entire cultivation will be lost in case of a pest attack or disease, if appropriate pesticides are not applied. In short, the capability of any new species is ensured by rich biodiversity. (iii) If Madagascar’s eastern rainforests are destroyed, about fifty species of wild coffee ~ many of them are caffeine-free ~ will be lost. (iv) Mangrove trees are critical to the functioning of coastal swamps. Loss of a species of mangrove, the primary producer in the ecosystem, would have a devastating effect on the local marine environment since there are no close substitutes for the species in its role of a primary producer capable of surviving in salt water and stabilizing the sediments in coastal swamps.
The most important contribution of biodiversity is in the health sector. Eighty per cent of the people in the developing countries depend on treatment provided by the traditional systems of plant-based medicines. In our country, Ayurvedic, Unani and Siddha Vaidyam systems of medicine play an important role and these systems of medicines use as many as 7,500 species of plants. In the former Soviet Union as well as in the traditional Chinese system of medicines, more than 2,500 and 5,000 species of plants are used respectively. Even in the USA around 25 per cent of the prescriptions by physicians contain one or other plant matters. About 3,000 varieties of antibiotics, including, penicillin and tetracycline, are obtained from microbes. Biodiversity is the lifeblood of any country. Secondly, species may play a critical role in maintaining ecosystems that surround us and providing humanity with a range of ‘life-support’ ecosystem services directly and indirectly, including water assimilation, water purification, and nutrient cycling. For instances, (i) a fall in earthworms, fungi or soil microbes limits the amount of recycled nutrients in the soil and the number of holes for rainwater to flow through, stunting crop growth and hindering humanity to feed itself. (ii) Trees in a rainforest act like a sponge and moderate the local water cycle by retaining water in the soil and transpiring rainfall, in a way, they reduce the frequency and intensity of floods. (iii) Coral reefs provide protection to coastal areas and protect delicate coastal wetlands and mangrove swamps from storms.
Scientific analysis establishes that reduced biodiversity affects ecosystems at levels compared to those of global warming and air pollution. Usually, greater species diversity leads to greater ecosystem stability. This is termed as the ‘diversity-stability hypothesis.’ But there are some exceptional cases. Certain biomes and ecosystems are less biodiverse and are still healthy. Across the globe, biodiversity tends to increase as we move towards the equator. This does not mean that ecosystems away from the equator are not healthy. However, scientists are studying ecosystem and diversity, and there is much to be learned.
a species may have aesthetic and non-use benefits: for instance, large mammals, birds and brightly colored flowing plants tend to be valued more highly than insects, fungi, amphibians and grass species, even though these species may be essential to the functioning of an ecosystem. People also like to see ‘charismatic’ species such as birds and butterflies in the wild and place a value on knowing that a valued ecosystem is functioning and protected. The Economics of Ecosystems and Biodiversity (TEEB) project recently highlighted the potential economic consequences of the current rates of loss in biodiversity.
Conservation of biodiversity is essential for the very existence of mankind. Its conservation has three main objectives: (1) To preserve the diversity of species. (2) Sustainable utilization of species and ecosystem. (3) To maintain life-supporting systems and essential ecological processes. If the policies and strategies adopted for such conservation are to succeed, awareness about their utility has to inculcated in all sections of the society. The focus of development efforts should be on the protection of ecosystem and natural resources.