Tigers occupy the pinnacle of the food chain and a healthy tiger population is an indicator of the well being of the whole forest. Throughout evolution, predators have had a regulatory influence on the population sizes of other species; it is thanks to carnivores, such as tigers, that the number of herbivores is kept in check. In turn, the populations can therefore only fluctuate between certain limits because of this "feedback mechanism".
With the number of herbivores under control, but not depleted, the forest vegetation is likely to thrive provided humans do not over exploit it. Seeds will be dispersed by new growth will not be prevented by excessive grazing pressure. Healthy vegetation protects the rainwater and safeguards the water table. Many forest are important catchments areas for rivers, upon which many species, including human beings, depend.
Species at the top of the food chain are generally larger and require more space than other animals, particularly if they are territorial . Conserving such species in the wild protects the habitat of many other animals, as well as safeguarding the essential ecological processes such as water and nutrient cycling. Thus the tiger is the guardian of many other creatures.