Biodiversity : An Overview
Biodiversity : An Overview
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PREFACE Biodiversity at global scale is a balance between the rate of speciation and the rate of extinction. At a regional level it is a balance between the rate of immigration invasion and that of local regional extinction. These rates determine the persistence of the communities. It can be assessed at genetic, population, species, ecosystem and landscape levels, at three spatial scales, viz., local, regional and global. While for assessment at genetic level, molecular techniques are most profitably used, assessment at other levels depends upon field samplings. Depending upon the objectives, the inventory could focus on single species or multiple taxa. For single species inventories, the focus could be on high impact, indicator, umbrella, flagship, threatened or economically important species. Biodiversity provides to the humankind enormous benefits in the form of food, medicines and industrial products, and has the potential for offering many more yet unknown benefits. It also provides an array of essential services through natural ecosystems. These include maintenance of the gaseous composition of the atmosphere, shaping the climate and producing the soil. It is essential for the ecosystem function and stability. There are several hypotheses being tested for relationship between biodiversity and ecosystem function. Biodiversity is not uniformly distributed on the earth. There are broad patterns, such as increasing variations in plants and animals from poles to the equator. It is more concentrated in the tropics because of conditions which permit higher rates of speciation and lower rates of extinction. About 44 of vascular plants and 35 of vertebrates are concentrated as endemic species in 25 hotspots, which account for only 1.4 of the local land area. The pool of living diversity is dynamic, it increases when new gene variation is produced, a new species is created or a novel ecosystem formed and it decreases when the genetic variation within the species decreases, a species becomes extinct or an ecosystem complex is lost. Today, as ever, human-beings are dependent on their sustenance, health, well-being and enjoyment of life on fundamental biological systems and processes. Humanity derives all of its food, many medicines and industrial products from wild or domesticated components of biological diversity. Biotic reservoirs are source of recreation, and tourism and underpin the ecosystem which provides us with many services. The Indian region represents an immense variety of climatic and altitudinal zones and is floristically rich. The ecological habitats vary from humid tropical Western Ghats to the hot deserts of Rajasthan and ice-capped mountains of the Himalaya to warm coasts of Peninsular India. These habitats favor a wide variety of plants and animals as well. It is estimated that over 45,000 species of plants are accounted for in India which represent 11 of the known
x Preface Contents plant species of the world. These are distributed in varied groups, viz., Angiosperms-16657 spp., Gymnosperms-64 spp., Pteridophytes-1022 spp., Bryophytes-2584 spp., Lichens-1600 spp., Fungi-23000 spp., Algae-2500 spp., and Bacteria-850 spp. The flowering plants of India comprise about 6 of the world s known flowering plants. About 315 families of a total of 400 now defined and 2250 genera of flowering plants are known to occur in India in different ecosystems. The loss of biodiversity is a global crisis. There is hardly any reason on the earth that is not facing ecological catastrophes. Biological extinction has been a natural phenomenon in geological history. However, man s intervention has speeded up extinction rates all the more. The destruction of the world s tropical forests, which are disappearing at an alarming rate, is one of today s urgent global environmental issues. The loss of plant animal diversity has immediate and long-term effects on human survival. The plant genetic resources are being depleted at an alarming pace throughout the world. Current rates of extinction demand immediate concerted efforts for conservation of biodiversity.