Causes of Extinction

There are many reasons for the extinction of species leading to the biodiversity loss. They are biological, environmental and human activities. Out of these, the human activities deserve serious consideration as the extinction caused by the first two factors is less severe.

(1) Random Variation in Population: If a species has low abundance, the variations in its (low) birth and death rates can lead to its extinction. This is called population risk.

(2) Environmental Factors: The variation in physical or biological environments and changes in predator, prey, competitor or symbiotic species may lead to extinction especially if the species are rare and isolated.

(3) Natural Catastrophe: A sudden change in environment such as earthquake, flood, fire or storm can greatly affect the survival of biodiversity of the area.

(4) Genetic Risk: The small populations of a species have less genetic variability. Such a population is more vulnerable to various factors (environmental as well) causing extinction as compared to large populations which have enough genetic variability to withstand such risks.

(5) Human Activities: Although human beings have affected the extinction of species since ancient times by clearing of forests and land for settlement, the rate of extinction has increased tremendously in the recent past.

According to IUCN estimates, humans have caused 75% of the extinctions ofbirds and mammal since 1600. Hunting is responsible for the extinction of 42% of the birds and 33% of the mammals.

Introduction of exotic species (species introduced into a new geographic area) can cause both positive and negative effects. Some inadvertentely introduced species have caused spread of diseases or have become pests or parasites to the existing ones. In nineteenth century, introduction of cats, rats, goats, dogs, insects etc.

Many species face additional risk of extinction because they are killed for their fur, skin, horns, ivory and other products. The illegal trade in horns of the rhinoceros which are in the list of endangered species, puts them at risk in spite of the legal restrictions in such trade.

Human activities cause alteration and destruction of habitats of species by changes in land use patterns i.e., deforestation, clearing of land for agriculture and urbanization, industrial activities. With increasing pressure of population and its requirements, the plants and animals are being over harvested.

The recent origin Ofbiotechnological techniques has led to many Genetically Modified Organisms (GMOs). The impacts of such proliferation are yet to be observed but they would definitely affect the biodiversity since introduction of GMOs would have serious effects on existing species and other varieties with which they may have to compete for their existence.

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