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K.S.Sivanesan Loss of Biodiversity The Global Convention on Biological Diversity, signed in 1992 at the Earth Summit, describes biodiversity as the "variability among all living organisms from all sources, including terrestrial, marine and other aquatic ecosystems and ecological complexes of which they are part, this includes diversity within species, between species and of ecosystems." refers to the range of variation or differences among some set of entities; biological diversity thus refers to variety within the living world. This very broad usage, embracing many different parameters, is essentially a synonym of 'Life on Earth'.Among the policy fields, Loss of Biodiversity is probably the most controversial one. The diversity of nature is the result of an evolutionary process that started about two billion years ago. When looking, for example, at the destruction of rain forests over the last twenty years, it becomes obvious that mankind is destroying this heritage at an incredible speed. Management requires measurement, and measures of diversity only become possible when a quantitative value can be ascribed to them and these values can be compared. It is thus necessary to try and disentangle some of the separate elements of which biodiversity is composed. It has become a widespread practice to define biodiversity in terms of genes, species and ecosystems, corresponding to three fundamental and hierarchically-related levels of biological organization. Following key indicators are important to the long term survival of the species ,there are Species richness, Species composition, Species interactions, Ecosystem stability. The loss of biodiversity has many consequences that we understand, and many that we do not. It is apparent that mankind is willing to sustain a great deal of biodiversity loss if there are concomitant benefits to society; we hope they are net benefits. In many cases, the benefits seem to accrue to a few individuals only, with net societal loss. According to pollen data and information gathered from fossil bones, few modern ecosystems are the same as they were 10,000 years ago. They originate bit by bit as the environment changes, and as species become extinct or shift their geographical range or their anatomy or behavior.As we continue to lose species at a rapid rate, we must discover which losses will have the most deleterious consequences on ecosystems. At present, we know little, and what we do have is information on short-term, small-scale experimental plots. We need to know more, much more. It is vital to realize, then, that biodiversity does not mean simply the number and kinds of living organisms present. Biodiversity depends upon the habitats and ecosystems which support them. As John Muir said, “When we try to pick out anything by itself, we find it hitched to everything else in the universe.” Among the threats that human activities pose to landscapes, ecosystems and species, it is possible to identify the following causes reflect loss of bio diversity. Overexploitation   harvesting species from the wild at rates faster than natural populations can recover. Overfishing and overhunting are both types of overexploitation. Currently, about a third of the world's endangered vertebrates are threatened by overexploitation. Two birds that were victims of overhunting are passenger pigeons and great auks. Both were hunted to extinction. Freshwater ecosystems are severely affected by fragmentation and floodplain ecosystems Overexploitation Overexploitation of wild species to meet consumer demand threatens biodiversity, with unregulated overconsumption contributing to declines in terrestrial, marine and freshwater ecosystems. Although overexploitation is often difficult to quantify in terrestrial systems, major exploited groups include plants for timber, food and medicine; mammals for wild meat and recreational hunting; birds for food and the pet trade; and amphibians for traditional medicine and food. The threat to vertebrates from overexploitation is particularly severe, driven, in particular, by demand for wildlife and wildlife products from East Asia. Globally, utilized vertebrate populations have declined by 15 per cent since 1970 as indicated by the Living Planet Index. Similarly, the extinction risk of utilized bird species increased during 1988–2008, driven in part by overexploitation. In the marine realm, capture fisheries more than quadrupled their catch from the early 1950s to the mid-1990s. The proportion of marine fish stocks that are overexploited, depleted or recovering from depletion rose from 10 per cent in 1974 to 32 per cent in 2008. Of the 133 local, regional and global extinctions of marine species documented worldwide over the last 200 years, 55 per cent were caused by overexploitation, Such practices can ultimately lead to major shifts in community composition. For example, coral communities have been transformed into algal-dominated systems because of overfishing of herbivores .The use of destructive fishing practices further amplifies the impacts of unsustainable fishing on marine biodiversity and habitats (FAO and UNEP). Technology can enhance the intensity and range of human impacts on marine biodiversity although it can also play a significant role in making fishing practices less destructive. Moreover, abandoned and lost fishing gear is having negative ecological consequences on marine biodiversity (also known as ghost fishing). Recreational fishery practices such as stocking and selective take can also have important evolutionary impacts on freshwater fish stocks. By-catch from fisheries can be a major threat to groups such as sharks, turtles and albatrosses. Alien species are organisms that have been transported by human and other activities into regions where they have not historically been found. Introduction may be accidental for example when organisms are carried from one port to another on ships, Introduced species are responsible for many recorded   species etinction Climate change is an increasingly important threat to species and natural habitats. There is widespread evidence that changes in phenology, including the timing of reproduction and migration, physiology, behavior, morphology, population density and distributions of many different types of species are driven by climate change. For example, trends in European bird populations since 1990 show a growing impact: populations are increasing among the species projected to benefit from climate change while population decline is documented for those projected to undergo range contraction. In the Arctic, tundra habitats are shrinking owing to tree-line advance. In the marine realm, climate change is causing widespread die-off of coral reefs through rising temperatures and ocean acidification. The Arctic ice cap is also shrinking rapidly, with likely impacts on ice-dependent species, as well as shifts in phenology and distribution of marine species. Recent studies have also projected distribution shifts of 1 066 marine fish and invertebrate species polewards at an average rate of 40 km per decade, leading to likely disruption of community composition and local extinctions. For many wetlands, changes in rainfall and evaporation are expected to have major impacts on water regimes, affecting both migratory and residential species, while changes in flow in both the short and long term will impact many aquatic species. Climate change will also act synergistically with other threats, such as the spread of diseases and invasive alien species. However, in many instances it may be difficult to differentiate the effects of these different threats, as has been outlined for wetlands and rivers in Australia. Habitat loss in the terrestrial domain has been caused largely by the expansion of agriculture: more than 30 percent of land has been converted for agricultural production. Large-scale commercial agriculture has adversely affected biodiversity, particularly agro-biodiversity. Moreover, the growing demand for biofuels has taken a toll, with expanses of forests and natural lands in South East Asia being converted into mono-crop plantations .Direct habitat loss is a major threat to coastal ecosystems through aquaculture. Wetlands in particular have faced a 50 per cent loss in the 20th century. Invasive alien species threaten to native biodiversity and are spreading through both deliberate and unintentional introductions as a consequence of increasing levels of global travel and trade. Poorly planned economic introductions, air transport, hull-fouling and ballast water from ships, as well as trade in pets, garden plants and aquarium species, are significant pathways for the dispersal of invasive species. Invasive alien species affect native species principally through predation, competition and habitat modification. They are found in nearly all countries and habitats, including marine ecosystems – for example the red lionfish Pterois volitansaffects coral reef fish in the Caribbean and freshwater. Natural hazards are generally unavoidable and potentially very destructive. eg. Hurricanes, Flooding, Drought, Volcanic activity. Pollutants such as pesticide and fertilizer effluents from agriculture and forestry, industry including mining and oil or gas extraction, sewage plants, run-off from urban and suburban areas, and oil spills, harm biodiversity directly through mortality and reduced reproductive success, and also indirectly through habitat degradation. Inland wetlands and coastal marine habitats face a major threat from waterborne pollutants. Meanwhile, atmospheric pollution in terrestrial systems, particularly the deposition of eutrophying and acidifying compounds such as nitrogen and sulphur also important. Rates of nitrogen deposition increased sharply after 1940 but have leveled out since 1990, probably owing to an overall decrease in biomass burning, though there is regional variation. Nevertheless, nitrogen deposition continues to be a significant threat to biodiversity, especially for species that have adapted to low-nitrogen habitats. Pollution (land and marine) are long known to have negative impacts on wildlife and the environment. From industrial and agricultural run-offs to household waste and more can end up far from the source, causing problems for people and the environment, even as far as the arctic, as the video from WWF notes.The WWF also says over 80% of marine pollution comes from land-based activities and that “a staggering amount of waste, much of which has only existed for the past 50 years or so, enters the oceans each year.” Examples of waste produced on land ending up in the oceans that the WWF lists include:Oil, Fertilizer, Solid garbage, Sewage disposal, Toxic man-made chemicals. The WWF also notes that more oil pollution comes from land than from oil spills, while fertilizer runoff contributes to various oceanic dead zones around the world. The solid garbage includes plastic bags, bottles, packaging, etc. Sewage disposal is often untreated and toxic chemicals contaminate almost every marine organism, from the tiniest to the largest. Inter Press Service adds that military debris also threaten coral ecosystems, reefs, fish and marine wildlife. Additional threats to biodiversity include changes in fire regimes, spreading disease ,Problematic native  species  and negative  Influences from human activities that may be harmful to biodiversity include artificial illumination,                                                                                                           The IUCN notes in a video that many species are threatened with extinction. In addition, At threat of extinction are •	1 out of 8 birds •	1 out of 4 mammals •	1 out of 4 conifers •	1 out of 3 amphibians •	6 out of 7 marine turtles 75% of genetic diversity of agricultural crops has been lost 75% of the world’s fisheries are fully or over exploited Up to 70% of the world’s known species risk extinction if the global temperatures rise by more than 3.5°C 1/3rd of reef-building corals around the world are threatened with extinction Over 350 million people suffer from severe water scarcity The loss of biodiversity is due to an array of social, economic and political factors at various levels .while any of the individual factors alone are sufficient to cause biodiversity loss ,in reality, multiple factors are acting simultaneously to drive such loss. loss of biodiversity be halted by following practices, Finding alternatives to land-use change and habitat destruction: For instance, we must find alternatives to fulfill the needs met by slash-and-burn agriculture, which is highly destructive of primary forest, and for other activities which degrade forests. Identification of “biodiversity hotspots,” which have very high concentrations of endemic species, and which are rapidly losing habitat and species, as primary targets for conservation. Habitat and ecosystem restoration: Partially-logged areas can be allowed to reforest, and abandoned farms and pastures may be revegetated  in some cases where damage to the soil is not too great and there is some natural habitat in the vicinity. In addition to restoring ecosystems, revegetation can also aid in carbon sequestration since growing plants absorb large quantities of carbon dioxide. Careful planning of land-use changes and consideration of the consequences of biodiversity change during this planning, setting aside various kinds of habitats as conservation reserves, parks, and wildlife refuges. Utilization of managed forests: It is becoming obvious, however, that reserves alone cannot conserve all biodiversity approaching conservation comprehensively: This means that conservation must be done with a view to higher levels of organization (such as ecosystems), not on a piecemeal basis, or species by species making the public, government policymakers and land managers aware of the global and local consequences of biodiversity changes, both social and environmental collaboration of scientists with governments to determine policies that will reduce biodiversity loss and environmental deterioration. Establishment of international agreements which would act to reduce the activities relevant to the decline in biodiversity – land-use changes.Integrated conservation and development projects. Reference… •	Shahid Naeem 2002. Ecosystem Consequences Of Biodiversity loss: The Evoluation of a Paradigm Ecology. •	James P. Gibbs, Conservation Biology(2000) •	Sharon L. Spray, Karen Leah McGlothli, Loss of Biodiversity •	Schulze, E. D. & Mooney, H. A. Biodiversity and Ecosystem Function (Springer,1993). •	http://biodiversitygroup.org •	http://www.eea.europa.eu •	http://www.wwf.org.au