In fact, hunting is not harmful, but rather very helpful to the wildlife and the environment. All animals have the basic necessities of food, water and shelter, and they get these from the land that they live on. There is not an endless supply of these resources and so the number of animals that can be supported on the land is in direct relation to how much of these resources are available. Every year as winter sets in, a number of deer will die over the winter. Food, hidden under the snow is in limited supply, and can only support so many.
Temperatures drop, and deer look for shelter.
In some cases this may also be in limited supply, and able to only shelter a certain number of deer. The condition and location of the land that the deer live on determines how many can survive. By hunting the deer and limiting them to a number the land can support, hunters save deer from a long drawn-out death by starvation or freezing to death. If no hunting was allowed, deer would still die, but those deer would have died through starvation and freezing, and the meat could not be used to feed people, nor the hides used for any purpose. The deer that did survive the winter would be left weaker and more malnourished than they would be if hunting were allowed, because they had to compete for food with the deer that ultimately died from the winter conditions.