1.2 Causes of Depletion of wildlife resources

a. Destruction of habitat: The natural habitat may be destroyed by man for his settlement, grazing grounds, agriculture, mining, industries, highway construction, drainage, dam building etc. as a consequence of this the species must either adapt to the changes, move elsewhere or may succumb to predation, starvation or disease and eventually die.
Construction of Dams: In India due to the construction of 1877 large and small scale dams all over india between 1980 and 2000 resulted in the submerging of 4.5 million hectors. No reforestation attempts were successful so far. The narmada vally project resulted in the submerging of 40000 hectors of forests in Madhyapradesh. A study done on the Indira Sagar Project of MP on the effects on wildlife showed that nearly 30% of the wildlife vanished due to project flooding.
Construction of dam on a river can block or delay upstream fish migrations and thus contribute to the decline or even the extcition of species. Construction of Hydroelectric Dam in Nepal cuts off local fish species eg. Tor and bangarius bagarius from their valuable spawining grounds upstream which resulted in decreasing of their numbers drastically.

b. Hunting for commercial products/trophies the wild animals are killed for their products such as hides and skin, tusks, fur meat, pharmaceuticals, perfumes, cosmetics and decoration purposes.
For example. In Africa, inrecent years 95% of the black rhino populations have exterminated by poachers for their horn. Today rhino hrn fetches upto 25000 dollars in pharmaceutical markets. In the last 10 years over one third of Africa’s elephants have been wiped out for some 3000 tonnes of ivory. In the international market the cost of ivory is 1000 dollars per kg. The major buyers are japan, honkong followed by US, Germany and UK. Indian government banned African Ivory in 1992
The scarlet macaw once common throughout south america has been eliminated from most of its range in central america. Several species of spotted cats as the ocelot and jaguar have been declining in numbers for the demand for their fur
In 1962, nearly 70000 whales were slaughtered. However international trade in whale products is banned now.
In india Rhino is hunted for its horns and musk deer for musk, elephant for ivory, Gharial and crocodile for their skin and jackal for fur. CITES lists nine indian animal species whiche have been depleted due to international trade. They are Fin Whale (Balenoptera physalus), Himalayan musk deer (Moschus moschiferus), Green turtle (Chelonia mydas), Desert Monitor Lizard (Varanus griseus), Yellow monitor lizar (Veranus flavescens) and Bengal monitor Lizard (Veranus bengalensis

c. Over Exploitation Excessive harvesting of marine organisms such as fishes, molluscs, sea cows and sea turtles has resulted in extinction of these animals
D. Collection for Zoo and research: animals and plants are collected throughout the world for zoos and biological laboratories for study and research in science and medicine. For example primates such as monkeys and chimpanzees are used for research as they have anatomical, genetic and physiological similarities to human beings.
E. Introduction of exotic species: Native species are subjected to competetion for food and space due to introduction of exotic species. For example, introduction of goats into galapogas islands in 20th century, resulted in destruction of habitats of several plants, birds and reptiles.
F. Control of pests and predators: predator and pest control measures, generally kill predators that are a component of balanced ecosystem and may also indiscriminately poison non target species.
G. Pollution/poisoning: Pollution alters the natural habitat. Water pollution especially injurious to the biotic components of estuary and coastal ecosystems. Toxic wastes entering the water bodies disturb the food chain and so that the aquatic ecosystems, insecticides and pesticides too affect adversely the plant and animal species.
h. hunting for food and fun: Hunting of wild animals takes place for the purpose of food because they form rich source of protein. Shikars are organized to kill wild animals for just fun and sport. Such activities decrease the number of wild life.
Other factors that contribute to the depletion of wild life are as follows
a. Distribution Range: the smaller the range of distribution the treater the threat of extinction
b. Degree of specialization: the more specialised an organism is the more vulnerable it is to extinction
c. Position of the organisms in the food chain: the higher the organisms is in the food chain, the more suceptible it becomes extict
d. Reproductive rate: large organisms tend to produce fewwer offsprings a widely spaced intervels