Environmental Studies

Module 4. Biodiversity and its conservation

Lesson 14
BIODIVERSITY AT GLOBAL, NATIONAL AND LOCAL LEVELS: INIDA AS A MEGA-DIVERSITY NATION

14.1 The Global Patterns in Biodiversity

The present geological era is perhaps the richest in biological diversity. About 2.1 million species have been identified till date, while many more species are believed to exist. According to UNEP (1993-94) (UN convention on environment protection) estimate, the total number of species that might exist on Earth range between 9.0 – 52 million (Table 14.1).

Invertebrate animals and plants make-up most of the species. About 70% of all known species are invertebrates (animals without backbones such as insects, sponges, worms, etc.); while, about 15% are plants. Mammals, the animal group to which man belong, comprise a comparatively small number of species. Of all the world’s species, only 10 to 15% live in North America and Europe. By contrast, the centers of greatest biodiversity tend to be in the tropics. The twenty countries most rich in biodiversity are listed in Table 14.1

Table 14.1 The world biota

Table 14.2 The twenty countries most rich in biodiversity

14.2 Patterns in Biodiversity

Species are not uniformly distributed over the Earth; diversity varies greatly from place to place. In terms of the number of basic kinds of organism and number of species of each kind, biodiversity has varied markedly through geological time; and, in terms of present day species richness, biodiversity varies greatly between one part of the earth and another. The present global patterns in biodiversity indicate that the species richness tends to vary geographically according to a series of fairly well defined rules. For example, in case of terrestrial environments:

• Warmer areas hold more species than the colder areas;
• Wetter areas hold more species than the drier ones;
• Larger areas hold more species than the smaller areas;
• Areas of varied climate and topography hold more species than the areas of uniform climate and topography;
• Areas at lower altitude (elevation) hold more species than the high altitude areas; and
• Less seasonal areas hold more species than the highly seasonal areas.

Similarly, in case of pelagic marine species, there tends to be more species in warmer and less seasonal waters, i.e. at lower latitudes.

In a much more simplified way, it can be said that there are much more species, both per unit area and overall, in the tropics than in temperate regions and for more in the latter (temperate regions) than in Polar Regions. The moist tropical forests, in general, are the most species rich areas or environments on earth. Though they cover just about 7% of the world’s surface; but it is estimated that they may hold more than 90% of the world’s species, if the yet unknown tropical forest micro fauna (mainly insects) are accepted. If small tropical forest insects are discounted, then the areas that may be similarly rich in species are:

• Coral reefs; and
• Areas of Mediterranean climate in South Africa and Western Australia. These areas are rich in species, especially for flowering plants (angiosperms).

14.3 The Reasons for Greater Biodiversity in the Tropics

The centers of greatest biodiversity tend to be in the tropics. The reasons for greater biodiversity in the tropics are as under:

1. Tropical areas receive more solar energy over the year. Therefore, tropical communities are more productive resulting in a greater resource base that can support a wider range of species.
2. Warm temperatures and high humidity of tropical areas provide favourable environmental conditions for many species that are unable to survive in the temperate areas.
3. Over geological times, the tropics have had a more stable climate than the temperate areas. In tropics, therefore, local species continued to thrive and live there itself; whereas, in temperate zones, they tend to disperse to other areas.
4. There has been more time for tropical communities to evolve as they are older than temperate ones. This could have allowed tropical communities greater degree of specialization and local adaptation to occur.
5. In tropics, the greater pressure from pests, parasites and diseases does not allow any single species to dominate. Thus, there is opportunity for many species to coexist. In temperate areas, on the other hand, there is reduced pressure from pests, parasites and diseases due to cold, and there is one or a few dominating species that exclude many other species.
6. In tropics, higher rates of out crossing among plants may lead to higher levels of genetic variability.

14.4 India as Mega-Diverse Biodiversity

Biodiversity has three aspects, viz. genetics, species and ecosystem. India is recognized to be uniquely rich in all these three aspects. The country has a rich heritage of biodiversity, encompassing a wide spectrum of habitats from tropical rainforests to alpine vegetation, and from temperate forests to coastal wetlands. Almost all the biogeographical regions of the world are represented here in India. With a mere 2.4% of the total land area of the world, the known biodiversity of India contributes 8.22% of the known global biodiversity. India is one of the twelve mega-diversity nations of the world accounting for 7.31% of the global faunal and 10.88% of the global floral total species. Currently available data place India in the tenth position in the world and fourth in the Asia in plant diversity. In terms of number of mammalian species, the country ranks tenth in the world; and in terms of endemic species of higher vertebrates, it ranks eleventh. In terms of number of species contributed to agriculture and animal husbandry, it ranks seventh in the world.
Some of the salient features of India’s biodiversity are as under:

• India has two major realms called the Palaearctic and the Indo Malayan; and three biomes, namely the tropical humid forests, the tropical dry deciduous forests and the warm desert/ semi-deserts.
• India has ten biogeographic regions, namely the Trans-Himalayan, the Himalayan, the Indian desert, the semi-arid zone, the Western Ghats, the Deccan Peninsula, the Genetic plain, North-East India, the Islands, and the coasts.
• India is one of the 12 mega-diversity nations of the world.
• India is one of the 12 centres of origin of cultivated plants.
• There are two hotspots that extend into India. There are the Western Ghats/ Sri Lanka and the Indo-Burma region (covering the Eastern Himalayas). Further these hotspots are included amongst the top eight most important or hottest hotspots.
• India has 26 recognised endemic centres that are home to nearly a third of all the flowering plants (angiosperms) identified and described to date.
• India has six Ramsar Wetlands. They are –
• Chilika Lake, Harike Lake, Loktak Lake, Keoladeo National Park, Wular Lake and Sambhar Lake.
• India has 5 world heritage sites namely, Kaziranga National Park, Keolades Ghana National Park, Manas Wildlife Sanctuary, Nanda Devi National Park and Sundarban National Park.
• India has twelve biosphere reserves, namely Nilgiri, Nanda Devi, Nokrerk, Manas, Sunderbans, Gulf or Mannar, Great Nicobar, Similpal, Dibru-Saikhowa, Dehang Debang, Pachmarchi and Kanchanjanga.
• Further, amongst the protected areas, there are 88 national parks and 490 sanctuaries in India covering an area of 1.53 lakh sq.km.

Based on a survey of about two-third of the geographical area of the country, the Ministry of Forests and Environment (MOEF) reports that India has at present 89,317 species of fauna and 45,364 species of flora representing about 7.31% of the world fauna and 10.88% the world flora described so far.

In plants, the species richness is high in angiosperms, bryophyta and petridophyta, and in the family orchidaceae. In animals, arthropoda (insects) are predominant.

India is also rich in agro-biodiversity. There are 167 crop species and wild relatives. Further, India is considered to be the centre of origin of 30,000 to 50,000 varieties of rice, pigeon-pea, mango, turmeric, ginger, sugarcane, gooseberries, etc. and ranks seventh in terms of contribution to world agriculture.

India also boasts of rich marine biodiversity, along the coastline of 7516.5 km with exclusive economic zone of 202 million sq.km, supporting the most productive ecosystems such as mangrooves, estivaries, lagoons and coral reefs. The number of zooplankton recorded is about 16,000 species. The benthic fauna largely consists of polychaeta (62%), crustacean (20%) and molluscs (18%) with the biomass of about 12 gm per sq.metre. Over 30 species of marine algae and 14 species of seagrass have been reported. There are over 45 species of mangrove plants. Over 342 species of corals belonging to 76 genera have been reported and about 50% of the world’s reef building corals are found in India.