Return to IntroductionHabitat degradation, destruction and fragmentation have taken a great toll on tiger populations. Much of the habitat loss can be attributed to a marked increase in forestry, mining, and road construction (Hornocker, 1997). These, like decreased on ground enforcement, are brought about, in part, by increasing poverty in many nations and the willingness of the rest of the world to exploit the land. Destruction and degradation have obvious impacts on various species; if the habitat is not there anymore then you cannot use it.
We destroy habitats in order to, in industrial countries, maintain our standards of living. In "underdeveloped" nations the habitat destruction is to support an increasing population or to try and become more successful financially. It is the need and desire to survive and thrive that often allows for environmental concerns to take a backseat in the decision making process. In tropical Asia 65% of wildlife habitat has been lost (Primack, 1993).
Habitat which has not had its structure changed may still be degraded by anthropogenic activities. Water pollution can, and does, affect many levels of the food chain both through direct consumption and through bioamplification. Even increasing levels of required nutrients can have disastrous consequences.
As with water, air pollution can impact populations far from the source. Greenhouse gasses are causing a change in the climactic structure of the world, thus altering the regions in which various species can survive (Primack, 1993). Another activity with a large impact on the tigers is habitat fragmentation.
Habitat fragmentation is a product of habitat destruction but it may be dangerous since it does leave some habitat intact and this is used as justification. As destruction continues the fragments becomes increasingly isolated, and therefore the populations. As the overall population declines so does the number of breeding individuals and therefore the effective population size (Ne).
With little immigration or emigration due to isolation and with a reduced effective population size there follows an inevitable decline in genetic diversity. Isolation is partly a factor of the hostility of the intervening habitat. Fragmentation has had dramatic effects on tiger populations. Some subspecies have overall populations of approximately 100 individuals, not all of which are in the same fragment. Even assuming a high percentage of the population are breeding individuals (it has been estimated at 40%) there is still a greatly reduced chance of maintaining genetic diversity. These small, fragmented populations are very vulnerable to stochastic events which can lead to bottlenecks and random genetic drift as well as to the eventual inevitability of inbreeding.