Growing pressures from increasing human populations and the consequent greater need for agricultural land tend to reduce the areas of land available for wildlife. Once land is taken over for agricultural and pastoral practices, its wildlife will be largely exterminated and its natural vegetation disturbed, if not completely destroyed.
Since the area of land which can be set aside for nature reserves is limited, ecological influences on animal populations and their distribution are distorted. Natural fluctuations in animal numbers cannot be absorbed in a limited habitat. The danger of destruction of the habitat by population explosions within the reserves (often a result of the imbalance produced by restraining man from his traditional hunting activities) cannot be prevented by the overspill or dispersion of the surplus population into the neighbouring areas, which would occur in a completely natural state. The human need for farm activities, which are pressing ever more closely upon the borders of reserved areas, takes priority over the needs for unlimited space of uncontrolled game herds, and domestic herds need to be kept within tolerable limits.