Since the beginning of life ninety five percent of different species of animals and plants have gone extinct till date during the evolutionary process, most of them during early stage when Earth experienced frequent and drastic environmental changes.
Ever since the life originated on Earth in the form of unicellular organisms, the gradual process of evolution has continued giving rise to different forms of life. As a result we have millions of species ranging from unicellular bacteria to giant and highly complex life forms like blue whale. During this natural process of evolution, species have evolved, proliferated and have become extinct. Extinction of species is a part of the natural process of evolution.
Natural extinction is not the cause of great worry as it is inevitable, but extinction due to reasons other than natural, particularly human-induced factors, are definitely a cause of worry. Once the process of environmental alterations stabilised on Earth, the rate of extinction due to natural factors slowed down drastically and most of the species could manage to survive for long after their evolution. The rate of extinction has accelerated in recent past, particularly during previous two-three centuries, largely as a result of human activities. The speed of exploitation of natural resources necessitated by the exponentially rising human numbers is the root cause of extinction of several species. For obtaining short term benefits we are rapidly destroying the wealth of life which has taken billions of years to reach the present state.
The major causes of extinction are:
Hunting: This is an age old activity. Initially hunting was aimed at obtaining food but later it turned out to be a hobby for many. Hunting is also carried out for some commercial purpose as a part of wildlife trade described later.
Habitat Loss: Most human activities have resulted in loss of habitat for several species. Deforestation for obtaining wood (for paper and furniture) and rarely available herbal products has destroyed thick forest habitats. Development of tourism involving forests and mountains as places of interest has also forced us to destroy natural habitat by construction of roads and resorts. Moreover, some parts of the forests have been converted into residences for humans, the rising population being the main reason.
Wildlife Trade: Wildlife trade involves activities like trading of skins of wild animals, extraction of some medicinally important compounds from the bodies of some mammals and fish (codliver oil, for example), Extracts obtained from some herbal plants, organs of these animals as well as smuggling of rare species of animals to different parts of the world. Wildlife trade is highly profitable and many are involved in it. Unlike hunting transfer of an animal does not involve spot killing but the place of their captivity where they are transferred does not replicate their natural habitat and in the absence of natural environment they lose their reproductive potential or their progeny, if any, cannot survive long. Most of the smuggled animals are killed later after removing important organs from their body. Their population (in their natural habitat), in the long run, goes on diminishing and ultimately they become extinct.