DEFINITION AND SIGNIFICANCE OF BIODIVERSITY(part 2)

DEFINITION AND SIGNIFICANCE OF BIODIVERSITY(part 2)

 THREATS TO BIODIVERSITY 

Important factors leading to extinction of species and consequent loss of biodiversity are: habitat loss and fragmentation, introduction of non-native species, overexploitation, soil, water and atmospheric pollution, and intensive agriculture and forestry.

Habitat Loss and Fragmentation 

The destruction of habitats is the primary reason for the loss of biodiversity. When people cut down trees, fill a wetland, plough a grassland or burn a forest, the natural habitat of a species is changed or destroyed. These changes can kill or force out many plants,animals, and microorganisms, as well as disrupt complex interactions among the species. A forest patch surrounded by croplands, orchards, plantations, or urban areas is an example of fragmented habitats. With the fragmentation of a large forest tract, species occupying deeper parts of forests are the first to disappear. Overexploitation of a particular species reduces the size of its population to an extent that it becomes vulnerable to extinction.

Disturbance and Pollution

Communities are affected by natural disturbances, such as fire, tree fall, and defoliation by insects. Man-made disturbances differ from natural disturbances in intensity, rate and spatial extent. For example, man by using fire more frequently may change species richness of a community. Then, some human impacts are new, never before faced by biota, e.g. the vast number of synthetic compounds, massive releases of radiation or spillover of oil in sea. These impacts lead to a change in the habitat quality. Pollution may reduce and eliminate populations of sensitive species. For example, pesticide linked decline of fish-eating birds and falcons. Lead poisoning is another major cause of mortality of many species, such as ducks, swans and cranes, as they ingest the spent shotgun pellets that fall into lakes and marshes. Eutrophication (nutrient enrichment) of water bodies drastically reduces species diversity.

Introduction of Exotic Species 

 New species entering a geographical region are called exotic or alien species. Introduction of such invasive species may cause disappearance of native species through changed biotic interactions. Invasive species are considered second only to habitat destruction as a major cause of extinction of species. Exotic species are having large impact especially in island ecosystems, which harbour much of the world’s threatened biodiversity. A few examples are:

(1) Nile perch, an exotic predatory fish introduced into Lake Victoria (South Africa) threatens the entire ecosystem of the lake by eliminating several native species of the small Cichlid fish species that were endemic to this freshwater aquatic system. 

(2) Water hyacinth clogs rivers and lakes and threatens the survival of many aquatic species in lakes and river flood plains in several tropical countries including India.

 (3) Lantana camara has invaded many forest lands in different parts of India, and strongly competes with the native species. 

Extinction of Species 

Extinction is a natural process. Species have disappeared and new ones have evolved to take their place over the long geological history of the earth. It is useful to distinguish three types of extinction processes.

Natural extinction:

With the change in environmental conditions, some species disappear and others, which are more adapted to changed conditions, take their place. This loss of species which occurred in the geological past at a very slow rate is called natural or background extinction.

Mass extinction: 

There have been several periods in the earth’s geological history when large number of species became extinct because of catastrophes. Mass extinctions occurred in millions of years.

 Anthropogenic extinction: 

An increasing number of species is disappearing from the face of the earth due to human activities. This man-made mass extinction represents a32 very severe depletion of biodiversity, particularly because it is occurring within a short period of time.

The World Conservation Monitoring Centre has recorded that 533 animal (mostly vertebrates) and 384 plant species (mostly flowering plants) have become extinct since the year 1600. More species have gone extinct from the islands than from the mainland or the oceans.

The current rate of extinction is 1000 to 10000 times higher than the background rate of extinction. Some interesting observations about the current loss of species are:

(1) From ten high-diversity localities in tropical forests covering 300,000 km2 , some 17,000 endemic plant species and 350,000 endemic animal species could be lost in near future.

(2) The tropical forests alone are losing roughly 14000-40000 species per year (or 2-5 species per hour). 

(3) The earth may lose up to 50% of the species by the end of the 21st century, if the current rate of loss continues. 

Susceptibility to extinction 

The characteristics of species particularly susceptible to extinction are: large body size (Bengal tiger, lion and elephant); small population size and low reproductive rate (Blue whale and Giant panda). Feeding at high trophic levels in the food chain (Bengal tiger and Bald eagle), fixed migratory routes and habit (Blue whale and Whooping crane) and localized and narrow range of distribution (woodland caribou; many island species) also make the species susceptible to extinction. 

The IUCN Red List Categories

The IUCN Red List is a catalogue of taxa that are facing the risk of extinction. It is important to understand that the Red List aims to impart information about the urgency and scale of conservation problems to the public and policy makers. The uses of the Red Lists are: 

 (1) Developing awareness about the importance of threatened biodiversity; 

 (2) identification and documentation of endangered species; 

 (3) providing a global index of the decline of biodiversity; 

 (4) defining conservation priorities at the local level and guiding conservation action. The World Conservation Union (formerly known as International Union for the Conservation of Nature and Natural Resources, IUCN) has recognized eight Red List Categories of species: Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Lower Risk, Data Deficient, and Not Evaluated. These categories are defined in Table 4.2. The species which are threatened with extinction are included in Vulnerable, Endangered, or Critically Endangered category.

Species with small world populations that are not at present endangered or vulnerable but are at risk are called rare. These species are usually localized within restricted geographical areas or habitats or are thinly scattered over a more extensive range.

The IUCN Red List System was initiated in 1963 and since then evaluation of the conservation status of species and subspecies is continuing on a global scale. The 2000 IUCN Red List is the most comprehensive inventory of the global conservation status of plant and animal species. It uses a set of criteria, relevant to all species and all regions of the world, to evaluate the extinction risk of species and subspecies. The 2000 Red List contains assessments of more than 18,000 species, 11,000 of which are threatened. The Red List also provides information to international agreements such as the Convention on Biological Diversity and the Convention on International Trade in Endangered Species of Wild Fauna and Flora.

STATUS OF THREATENED SPECIES 

There are 11,046 species (5,485 animals, and 5,611 plants) listed as threatened (Critically Endangered, Endangered, or Vulnerable) on the 2000 Red List. Of these, 1,939 are listed as Critically Endangered (925 animals, and 1,014 plants). The percentages of threatened species of Angiosperms and four vertebrate groups categorized as Critically Endangered, Endangered, Vulnerable and at Lower Risk are shown in Figure 4.5 Of the species evaluated for risk in these major groups, 17-22% are critically endangered, and 34-51% are vulnerable. According to the Red List, in India, 44 plant species are critically endangered, 113 endangered and 87 vulnerable. Amongst animals, 18 are critically endangered, 54 endangered and 143 vulnerable (Figure 4.6). Some examples of threatened species in India are given in Table 4.3. 

CONSERVATION OF BIODIVERSITY

We know that ecosystems are undergoing change due to pollution, invasive species, overexploitation by humans, and climate change. Most people are beginning to recognize that diversity at all levels - gene pool, species and biotic community is important and needs to be conserved. We should not deprive the future generations from the economic and aesthetic benefits that they can derive from biodiversity. The decisions we make now, as individuals and as a society, will determine the diversity of genes, species and ecosystems that remain in future. We may appreciate the fact that the most effective and efficient mechanism for conserving biodiversity is to prevent further destruction or degradation of habitats by us. We require more knowledge to conserve biodiversity in reduced space and under increased pressure of human activities. There are two basic strategies of biodiversity conservation, in situ (on site) and ex situ (off site)

In situ Conservation Strategies 

The in situ strategy emphasizes protection of total ecosystems. The in situ approach includes protection of a group of typical ecosystems through a network of protected areas.

Protected areas: 

These are areas of land and/or sea especially dedicated to the protection and maintenance of biological diversity, and of natural and associated cultural resources. These are managed through legal or other effective means. Examples of protected areas are National Parks, and Wildlife Sanctuaries. World Conservation Monitoring Centre has recognized 37000 protected areas around the world. As of September 2002, India has 581 protected areas (89 National Parks and 492 Wildlife Sanctuaries), covering 4.7% of the land surface as against 10% internationally suggested norm. The Jim Corbett National Park was the first National Park established in India.

Some of the main benefits of protected areas are:

 (1) maintaining viable populations of all native species and subspecies; 

 (2) maintaining the number and distribution of communities and habitats, and conserving the genetic diversity of all the present species;

 (3) preventing human-caused introductions of alien species; and 

 (4) making it possible for species/habitats to shift in response to environmental changes. 

Biosphere Reserves: 

Biosphere reserves are a special category of protected areas of land and/or coastal environments, wherein people are an integral component of the system. These are representative examples of natural biomes and contain unique biological communities. The concept of Biosphere Reserves was launched in 1975 as a part of the UNESCO’s Man and Biosphere Programme dealing with the conservation of ecosystems and the genetic resources contained therein. Till May 2002, there were 408 biosphere reserves located in 94 countries. There are 13 biosphere reserves in India . In India, Biosphere Reserves are also notified as National Parks.A Biosphere Reserve consists of core, buffer and transition zones. The natural or core zone comprises an undisturbed and legally protected ecosystem. The buffer zone surrounds the core area, and is managed to accommodate a greater variety of resource use strategies, and research and educational activities. The transition zone, the outermost part of the Biosphere Reserve, is an area of active cooperation between reserve management and the local people, wherein activities like settlements, cropping, forestry and recreation and other economic uses continue in harmony with conservation goals.

(1) Conservation: to ensure the conservation of landscapes, ecosystems, species and genetic resources. It also encourages traditional resource use. 

(2) Development: to promote economic development, which is culturally, socially and ecologically sustainable.

(3) Scientific research, monitoring and education: the aim is to provide support for research, monitoring, education and information exchange related to local, national and global issues of conservation and development. 

Sacred forests and sacred lakes:

A traditional strategy for the protection of biodiversity has been in practice in India and some other Asian countries in the form of sacred forests. These are forest patches of varying dimensions protected by tribal communities due to religious sanctity accorded to these forest patches. The sacred forests  represent islands of pristine forests (most undisturbed forests without any human impact) and have been free from all disturbances; though these are frequently surrounded by highly degraded landscapes. In India sacred forests are located in several parts, e.g. Karnataka, Maharashtra, Kerala, Meghalaya, etc., and are serving as refugia for a number of rare, endangered and endemic taxa. Similarly, several water bodies (e.g. Khecheopalri Lake in Sikkim) have been declared sacred by the people leading to protection of aquatic flora and fauna.

Ex-situ Conservation Strategies 

 The ex-situ conservation strategies include botanical gardens, zoos, conservation stands, and gene, pollen, seed, seedling, tissue culture and DNA banks. Seed gene banks are the easiest way to store germplasm of wild and cultivated plants at low temperature in cold rooms. Preservation of genetic resources is carried out in field gene banks under normal growing conditions. 

In vitro conservation, especially by cryopreservation in liquid nitrogen at a temperature of –196 oC, is particularly useful for conserving vegetatively propagated crops like potato. Cryopreservation is the storage of material at ultra-low temperature either by very rapid cooling (used for storing seeds) or by gradual cooling and simultaneous dehydration at low temperature (used for tissue culture). The material can be stored for a long period of time in compact, low maintenance refrigeration units.

Conservation of biological diversity in botanical gardens is already in practice. There are more than 1500 botanical gardens and arboreta (botanical gardens where specific tree and shrub species are cultivated) in the world containing more than 80,000 species. Many of these now have seed banks, tissue culture facilities and other ex situ technologies. Similarly there are more than 800 professionally managed zoos around the world with about 3000 species of mammals, birds, reptiles and amphibians. Many of these zoos have well-developed captive breeding programmes.

The conservation of wild relatives of crop plants and the off-site conservation of crop varieties or cultures of microorganisms provide breeders and genetic engineers with a ready source of genetic material. Plants and animals conserved in botanical gardens, arboreta, zoos and aquaria can be used to restore degraded land, reintroduce species into wild, and restock depleted populations.

International efforts for conserving biodiversity

The Earth Summit held in 1992 at Rio de Janeiro resulted into a Convention on Biodiversity, which came into force on 29 December 1993. The convention on Biodiversity has three key objectives:

(1) Conservation of biological diversity,

(2) Sustainable use of biodiversity, and 

(3) Fair and equitable sharing of benefits arising out of the utilization of genetic resources.

 The World Conservation Union and the World Wide Fund for Nature (WWF) support projects worldwide to promote conservation and appropriate development of Biosphere Reserves.

Biodiversity conservation in India 

Indian region has contributed significantly to the global biodiversity. India is a homeland of 167 cultivated species and 320 wild relatives of crop plants. It is the centre of diversity of animal species (zebu, mithun, chicken, water buffalo, camel); crop plants (rice, sugarcane, banana, tea, millet); fruit plants and vegetables ( mango, jackfruit,cucurbits), edible diascoreas, alocasia, colocasia; spices and condiments (cardamom, black pepper, ginger, turmeric); bamboos, brassicas, and tree cotton. India also represents a secondary centre of domestication for some animals (horse, goat, sheep, cattle, yak, and donkey) and plants (tobacco, potato and maize).

The Ministry of Environment and Forests is carrying out the in situ conservation of biodiversity through Biosphere Reserves, National Parks, Wildlife Sanctuaries and other protected areas. The joint forest management systems involve forest departments and local communities. This enables the tribal people and local communities to have access to non-wood forest products and at the same time protect the forest resources.

The National Bureau of Plant, Animal and Fish Genetic Resources has a number of programmes to collect and conserve the germplasm of plants and animals in seed gene banks, and field gene banks for in vitro conservation. Botanical and zoological gardens have large collections of plant and animal species in different climatic regions of India The land races and diverse food and medicinal plants are also being conserved successfully by the tribal people and women working individually or with various nongovernmental agencies. The women particularly have an important role in the conservation of agrobiodiversity. In India, a programme is underway to develop a system of community registers of local informal innovations related to the genetic resources as well as natural resource management in general.