Sharing the blame

The discovery of the role played by pre-historic people in the extinction of several species of animals and birds gives the subject of biodiversity depletion and conservation strategies a new twist

Last Updated: Saturday 04 July 2015

The major island groups in the (Credit: SHRI KRISHAN)the extinction of wildlife due to the harm caused by human activities in the modern world is well-documented and widely-known. For the more conspicuous groups of birds and mammals, rates of extinction have been estimated at about one species per year. Since the total number of species of living organisms is 2,000 times the number of birds and mammals, the overall rates of extinction may even exceed five species per day. With the continued destruction of tropical rainforests around the world and the higher susceptibility of lower forms of life to extinction, global extinction rates are expected to reach 100 species per day by the end of the 20th century.

However, it is now coming to light that the issue of extinction of species is not merely a product of the present-day human's prerogative. The world's pre-historic people appear to have contributed their own bit to species extinction. The presence of bones of birds that are known to be extinct, at archeological sites in Pacific islands show that the human-made biodiversity crisis began thousands of years ago.

The colonisation of Melanesia, Micronesia and Polynesia appears to have begun about 30,000 years ago and was virtually complete nearly 1,000 years ago. The clearing of forests, cultivation of crops, rearing of domestic animals and hunting of wildlife are some of the activities carried out by both pre-historic and present-day humans which can seriously impact the populations of certain species and lead to a reduction in their populations. The introduction of new predators and especially new pathogens -- that inevitably occurs after human colonisation -- are other important factors that affect the well-being of species. These factors can induce either the local or global extinction of species.

David W Steadman of the New York State Museum has estimated that an average of 10 species or populations have been lost on each of the approximately 800 islands in the Pacific ocean due to human activity during pre-historic times. This amounts to a total loss of 8,000 species. At least 2,000 of these appear to represent the global extinction of the entire species, a figure which accounts for the disappearance of about 20 per cent of the world's bird species. On five of the largest Hawaiian islands, 31 to 65 per cent of the birds have been driven to extinction since pre-historic human settlements were established. Flightless birds such as rails seem to be the most vulnerable to the impact of human settlement. This means that in addition to the reduction in species diversity the very nature of bird fauna has undergone qualitative changes.

The implications of so significant a finding are many. From the point of view of analysing the biogeography and evolution of birds, these findings raise serious problems for any study that may be based solely on present-day or merely historical records of the distribution of birds. The repercussions of the discovery on conservation programmes would be even more serious. What is true of birds could largely hold good for other groups too and may be even more serious in the case of lower organisms.

In addition, there is also the danger of people becoming complacent about their lifestyles once they get the feeling that their activities alone are not responsible for the extinction of other organisms. There is the risk of people justifying human activities that endanger wildlife and biodiversity and thus making efforts at conservation much more difficult to pursue.

On the other hand, these findings could help us put things in correct perspective specially since education on nature conservation is currently based too heavily on creating the impression that it is the ecologically-unfriendly lifestyle which is responsible for the biodiversity crisis and that if we lived in harmony with nature, as pre-20th century people supposedly did, we would solve many problems. It may now be possible to plan conservation strategies that are more realistic. A reorientation of public education on the causes of species extinction and the ways to mitigate the impact of human activities is urgently called for.

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