The Return of the Wolves

In 1995, 41 Gray wolves were reintroduced into the first national park in the US-Yellowstone. The impact was mind-blowing.

In the 1900s, wolves were considered a risk to people and livestock, and hence they were exterminated from the park. The last wolf pack in Yellowstone was killed in 1926.

This move led to the collapse of the park's ecosystem. Wolves were the main predators of elks in the park. After the wolves disappeared from the scene, the elk population almost doubled over a couple of years. The elks feed on grasses, shrubs and trees. With reduced predation, they overgrazed the entire park, upsetting the ecosystem's natural balance.

Small mammals like mice and rabbits suffered as there were fewer plants for them to hide from predators. The Grizzly bear populations declined as the elks ate up all the berries required to build up fat before hibernation. Pollinators like bees and hummingbirds had fewer flowers to feed on, and as for the songbirds, there were fewer trees to build nests on.

But the biggest problem that the elks caused was not any of these. The elks were vulnerable to the wolves at the river bank. So they spent as little time as possible near the river. But after the elimination of the wolves, they gathered at the riverbank in large herds. The elk's hooves eroded the soil on the river bank and caused the river and the streams to be clouded with mud. This harmed the fish populations that inhabited the river. With fewer trees and no clean water, beavers could not make dams on the streams, which negatively affected the fishes, amphibians, otters, etc. These issues came up just because wolves were driven out of the ecosystem.

When the wolves were brought back in 1995, it had a spectacular impact on the landscape. The elk population came down from 17,000 in 1995 to 4000. Only the fittest ones in the herd survived when the wolves started to hunt down the elks, leading to a more robust elk population. More elk carcasses meant more food for scavengers like coyotes, ravens and eagles. The Grizzly bear population started to increase as they benefited from the carcasses that the wolves left and from more berries available.

When the elks stopped gathering at the riverbank, the riverside trees grew five times their original size. As the number of trees increased, the root structure developed, leading to less erosion. As the water in the river became cleaner, the beavers built more dams creating new habitats for fish and amphibians.

Even scientists were amazed by the numerous consequences of wolf reintroduction. Upon analysing the trophic cascade of events it caused, they slowly realised the role of wolves in the food web as a keystone species.