In nature, taking away one detail from the natural ecology of an area can shift the balance of the whole ecosystem. This is what happened when the wolves that naturally roam the Yellowstone National Park in Wyoming United States, were taken out. However, when the wolves were re-introduced after 70 years of absence, the ecology in Yellowstone dramatically changed.
Since the wolves were not around, the population of deer began to grow out of control. Although human intervention was already used to regulate the deer population, it still wasn’t enough. They had grazed a huge amount of the park’s vegetation. In 1995, wolves were taken to the park and this changed the behaviors of the deer. They then started to avoid certain areas in the park like valleys and gorges which in turn, helped the vegetation to re-grow. In a span of less than a decade, the trees became taller, bare spots of lands became forest of willow, aspen and cottonwood which attracted other animals.
The regrowth of the vegetation triggered other species to come back and repopulate faster such as beavers and wild birds. Population of other animals in the park like bears started to become larger, mainly because of the availability of food.
This amazing effect is called the trophic cascade. This is an ecological process that begins on the top of the food chain and affects everything below it. Re-introducing the wolves gave the park a chance to regenerate and give life and homes to hundreds of species of animals and plants.