The Age of Extinction

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The Age of Extinction

By Ravi Chellam on The Hindu Folio
April 2010

By the time you finish reading this issue of Folio, perhaps one more plant or animal species somewhere in the world would have disappeared. Gone forever, never to come back.

Extinction is forever. What is the significance of this pithy little phrase, oft used in conservation circles? Why should it concern us as humans? Anyway, is extinction not part of nature?

Extinction by definition means that no live individual of a particular species exists anywhere in the world, either in its natural habitat (in situ), or in captivity (ex situ). Dinosaurs today exist only in reconstructed models and on film screens. But conservationists do not easily accept the fact that a species has gone extinct. By the strictest definitions for officially recognising that a species has gone extinct, it takes numerous intensive surveys spread over many years, before one can come to this conclusion. In some cases species believed to be extinct will "reappear" after decades . . . remnant populations that no one had earlier chanced upon. On the other hand, new species can be described and added to our knowledge much more easily and in much shorter periods of time.

It is natural for species to go extinct. Life evolved on earth more than 600 million years ago. Many species have evolved and many others gone extinct over these long millennia, a fact revealed to us through fossils. This fossil record enables us to reconstruct the manner in which species have evolved, and to fix time scales over which certain forms of life were dominant on earth. These have also enabled us to detect that there is a cycle of mass extinctions that takes place periodically in the evolutionary history of the earth. Mass extinctions are defined as episodes when an exceptional global decline in biodiversity takes place, one which affects a broad range of life forms over a short period of time. For example, there could be forest dwelling insects, land dwelling dinosaurs and ocean-bottom dwelling molluscs, all disappearing at the same time. This time scale could be over a few thousand to hundred thousand or million years, which will seem very long in the normal human perception, but is a very short period in the earth's evolutionary history.

Five mass extinctions in the earth's history have been identified: during the Ordovician Era (450 million years ago), Late Devonian (350 million years ago), Late Permian (275 million years ago), Late Triassic (190 million years ago) and Late Cretaceous (65 million years ago). Various explanations have been given for these extinctions, the ones with greatest credibility being the effects of glaciation and the impact of an extra-terrestrial object collision with the earth. Both of these would have had widespread and drastic impacts on the prevailing climate. The sea would have retreated from many areas, the sun would have been obscured for many weeks if not months, by massive clouds of dust, and in general the flow of energy would have been drastically disrupted resulting in the extinction of many forms of life.

Yet the evolution of new species exists side by side with such extinction. It is important to note that a much reduced number of life forms would have survived these difficult times of mass extinctions, adapting to the gross environmental changes and over a period of time evolving into many more forms or species.

This process of continuous extinction and evolution characterises the history of life on earth. A good example is the information we have on birds. Currently, about 9,000 species of birds survive worldwide. The fossil history indicates that over the last 150 million years, some 1,50,000 species of birds have evolved and become extinct. Yet, it appears that we are today in the midst of the greatest ever diversity of species to have existed at any one given moment.

But not for long. We are again today living in an age of mass extinction. So what? Should we be concerned, given that biodiversity has sprung back from five previous mass extinctions?

The present episode of mass extinction has important differences from previous ones. These extinctions are largely caused by the impacts of one species - human beings. They are taking place over extremely short periods of time, maybe just a few decades or centuries. Human actions have resulted in the widespread loss of natural habitats, fragmentation of the remaining habitats, poisoning of many areas, displacement of uniquely adapted species by exotics, and in general the gross disruption of the numerous intricate natural processes which govern the evolution of species.

The result is that human-induced extinction rates not only far outstrip natural extinction rates but also disrupt normal evolutionary processes. Contemporary species extinction rates are estimated to be 1,000 to 10,000 times higher than the normal background extinction rates expected in the absence of human influences.

The result is that in a short period of time there has been a drastic and irreversible decline in the biodiversity of the earth. This is not an alarmist's reaction but a realistic assessment based on data collected over the past few decades from all over the world.

The most quoted example of how dramatic human-caused extinctions can be, is the case of passenger pigeons in the U.S.. In the 19th Century, there are estimated to have been an astounding 2,000 million individuals of this species. When some of the huge flocks flew across the skies, they used to obscure the sun for many hours. Due to hunting and habitat destruction, the population was reduced to 2,50,000 by 1896, and by 1914 the species became extinct with the death of the last bird in captivity. If this is the rapidity and scale of human destruction, we can well imagine what awaits the hundreds of endangered species all over the world. The Asiatic lion population is estimated to be only around 320 in only one protected area, Gir National Park in Gujarat. India's tiger population is estimated to be about 5,000 and that of the one horned rhino about 1,500. Despite heroic conservation efforts, unless some very drastic changes are made immediately by the human race as a whole, there is no escaping the fact that most practitioners in the field of conservation will only go down in history as chroniclers of extinctions!

Extinctions are probably happening on a daily basis in India, especially amongst some of the smaller and lesser known organisms like insects and fungi. The better known examples of recorded extinctions in India are the pink-headed duck, mountain quail and the cheetah. In fact, extinction of mammal or bird species is more likely to be recognised than for example, plant or amphibian species.

Estimates of global species richness range from a minimum of 10 million to 30 and maybe even 50 million. Much of this richness is found in tropical countries like India. Only a fraction of the estimated number of species has been described, about 1.2 million. In India, about 1,36,000 species have been listed (see Table), but there are probably at least 3 to 4 times that many that are not yet recorded. With the rampant destruction of habitats all over the country, especially of the species-rich tropical forests and coral reefs, we are losing numerous species, many of which might still be undescribed and unknown to us. Some scientists estimate that at current rates of habitat destruction, we may lose upto one-third of the total wild species in the country within the next few decades . . . that is, an astounding 45,000 known species, and probably many more unrecorded ones.

Extinctions are not restricted to wild species alone. Numerous varieties of crops and breeds of livestock have become extinct in India due to the over-reliance on a handful of high-yielding and hybrid varieties. The genetic erosion this represents is extremely serious and threatens the long-term viability of our agriculture and animal husbandry systems.

Of the many initiatives taken to conserve what remains of our biodiversity, the ones that merit mention are the continuation of traditional conservation practices amongst many village communities, the creation of legally protected areas by State governments and the ban on hunting of, and trade in, several species of wildlife. While in themselves commendable, they have been woefully inadequate in halting the decline of biodiversity. A much greater national effort is needed, especially to resolve the basic conflicts between the development aspirations of an industrialising country, and the need to conserve the natural habitats and biodiversity that co-exist with us.

A new national process promises to point towards such a resolution, and help us take a small step towards securing the country's biodiversity. This is the National Biodiversity Strategy and Action Plan (NBSAP), being formulated by the Ministry of Environment and Forests with execution by hundreds of NGOs, official agencies, community groups, and others (see Introductory piece). As part of this, specialist Working Groups on Wild Plants, Wild Animals, Micro-organisms, Natural Terrestrial Ecosystems, Natural Aquatic Ecosystems, and Domesticated Biodiversity, are collating existing information on the status of biodiversity, the major threats to its continuation, and the gaps in coverage of conservation initiatives. From this will emerge a picture of what habitats and species need to focused on for urgent conservation intervention, and what concrete steps would be needed to achieve this.

It is important for us to immediately realise that there are no technological solutions for the human-induced crisis of extinction. If we do not reform our ways, the extinction of life itself on earth may well become a reality . . . and when millions of species go, can we be far behind?

So what if there is mass extinction?

Ashish Kothari

Smug as we are in our technological cocoons and monetary illusions, we may think that mass extinction of plants and animals, is of little consequence. We couldn't be farther from the truth. Note the following from R. Prasanna Venkatesh/Wilderfile:

More important than all the above is the great ethical tragedy of mass extinction: whatever gave us, just one out of 50 million species, the right to snatch life away from any other species? Surely is the ultimate act of ingratitude, to destroy the very natural conditions that gave rise to us?

But even if we are not moved by moral arguments, it should not take a genius to realise that tampering with the earth's fragile web of life is to invite trouble onto ourselves . . . yet our species, considering itself to be the most intelligent, continues to do precisely that!