Carrying capacity refers to the maximum amount of organisms within a particular species that an area can support indefinitely. This is directly affected by space, food, water, light and other limiting factors. These factors control an organism's growth and the growth of the species. For example, due to the lack of wolves in the natural environment as they were wiped out of most of the United States in the past, the deer populations soared. The wolves which were limiting factors on the deer population because of predation, were no longer available to keep the deer population in check. This caused an increase in deer which in turn, ate most of the vegetation and they then experienced starvation as competition between deer increased. Humans use hunting laws to control carrying capacity by having a hunting season. Special licenses are granted for hunters to take a certain amount of male game each season and doe permits allow a number of females to be hunted also. The introduction of hunters replaces the limiting factor of predatory wolves and affects carrying capacity by keeping the deer population from experiencing exponential growth, which can never be sustained in the long run.