According to definition ‘Biodiversity’ is the degree of variation of life”. This can refer to genetic variation, species variation, or ecosystem variationwithin an area, a biome or a planet. Biodiversity is a result of around 3.5 billion years of evolution of life. All the life present on the planet until 600 million years ago consisted of single-celled organisms. The history of biodiversity during the Phanerozoic Eon (during the last 540 million years), started with rapid growth during the Cambrian explosion – a period during which nearly every phylum of multi cellular organisms first appeared. Over the next 400 million years or so, the invertebrate diversity exhibited little progress while the vertebrate diversity displayed an overall exponentially increasing trend.

Biodiversity generally tends to cluster in hotspots, and has been increasing through timebut will be likely to slow in the future. Estimates of the present global macroscopic species diversity vary from 2 million to 100 million, with a best estimate of somewhere near 9 million, the vast majority arthropods.

Since life began on Earth, five major mass extinctions and several minor events have led to large and sudden drops in biodiversity. The most recent, the Cretaceous–Paleogene extinction event, occurred 65 million years ago and has often attracted more attention than others because it resulted in the extinction of the dinosaurs.During each extinction event, between 50 and 95 percent of the planet’s life was lost, thereby resulting in dramatically changed biotic characteristics. Generally, ten million years pass before biodiversity reaches pre-event levels.

Contemporarily, a large number of scientists agree on the assumption that we are currently on the verge of the outbreak of the next Mass Extinction event. The Holocene extinction sometimes called the Sixth Extinction is a name proposed to describe the extinction event of species that has occurred during the present Holocene epoch .The Sixth extinction however, may be the most catastrophic in history. It is estimated that half of all plants, animals and birds on the planet will die off before 2100.

The report, Global Biodiversity Outlook 2 from the secretariat of the UN Convention on Biological Diversity, says:

Humans have provoked the worst spate of extinctions since the dinosaurs were wiped out 65m years ago. The report paints a grim picture of life on earth, with declining numbers of plants, animals, insects and birds across the globe, and warns that the current extinction rate is up to 1,000 times faster than in the past.

“In effect, we are currently responsible for the sixth major extinction event in the history of earth.” A rising human population of around 7 billion is wrecking the environment for thousands of other species, it adds, and undermining efforts to slow the rate of decline. The global demand for biological resources now exceeds the planet’s capacity to renew them by 20%.

“The direct causes of biodiversity loss – habitat change, over-exploitation, the introduction of invasive alien species, nutrient loading and climate change – show no sign of abating.”

The report concludes: “Biodiversity is in decline at all levels and geographical scales,” and international travel, trade and tourism are expected to introduce more alien species to fragile ecosystems.

According to the species-area theory and based on upper-bound estimating, the present rate of extinction may be up to 140,000 species per year. Also, some scientists estimate that between 150 – 200 species become extinct every 24 hours.

For the IUCN Red List system, scientific criteria are used to classify species into one of eight categories: Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Lower Risk, Data Deficient and Not Evaluated. A species is classed as threatened if it falls in the Critically Endangered, Endangered or Vulnerable categories

There has been a new recognition of the importance of protecting marine and aquatic biodiversity. The first quantitative estimates of species losses due to growing coral reef destruction predict that almost 200,000 species, or one in five presently contributing to coral reef biodiversity, could die out in the next 40 years if human pressures on reefs continue to increase (Reaka-Kudla, 1996).

Recognition by countries

Since Rio, many countries have improved their understanding of the status and importance of their biodiversity, particularly through biodiversity country studies such as those prepared under the auspices of UNEP/GEF. The United Kingdom identified 1250 species needing monitoring, of which 400 require action plans to ensure their survival (Bendall, 1996). Protective measures for biodiversity, such as legislation to protect species, can prove effective. In the USA, almost 40 percent of the plants and animals protected under the Endangered Species Act are now stable or improving as a direct result of recovery efforts (USFWS, 1994). Some African countries have joined efforts to protect threatened species through the 1994 Lusaka Agreement, and more highly migratory species are being protected by specialized cooperative agreements among range states under the Bonn Convention.

Works being done

On the positive side, the number and size of protected areas is increasing, though most types of natural environment fall short of the target to protect 10%. About 12% of the land surface is protected, against 0.6% of the oceans.

There is an emerging realization that a major part of conservation of biological diversity must take place outside of protected areas and involve local communities. The extensive agricultural areas occupied by small farmers contain much biodiversity that is important for sustainable food production. Indigenous agricultural practices have been and continue to be important elements in the maintenance of biodiversity, but these are being displaced and lost. There is a new focus on the interrelationship between agro diversity conservation and sustainable use and development practices in smallholder agriculture, with emphasis on use of farmers’ knowledge and skills as a source of information for sustainable farming (Global Environmental Change: Human and Policy Implications, 1995Uitto and Ono, 1996).

There are many contributing factors to the Sixth Great Extinction; today, destruction of habitat, introduction of alien species and pollution claim the most species. Extinctions are also caused by overexploitation of species for consumption, collection and trade, agricultural monoculture, human-induced climate change, nitrogen loss in soil and oceanic acidification as a result of a warming climate, and urbanization leading to sedimentation and soil erosion. Growing human populations have led to increased demand for natural resources, and with a current world population of more than seven billion people, our demands, many of which require environmentally damaging practices to fulfill, will continue to grow.

Biodiversity provides climate stability, nutritiously varied and abundant foods, medicines, clean water and pollination of crops, disease-control, cultural diversity, environmental knowledge, food-chain stability, and oxygen.

The world’s leading scientists suggest that conservation measures, sustainable development, stabilization of the human population and the support of environmentally responsible economic development will be essential in halting the extinction crisis.






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