How The Removal Of A 'Nuisance' Predator Wreaked Havoc On Yellowstone National Park's Ecosystem

In the 1800's the Rocky Mountain West area of the USA that now includes Yellowstone National Park, was teeming with gray wolves. However they were considered nuisance predators who killed livestock and therefore, actively hunted down. By the time the National Park was established in 1827, the number of gray wolves had diminished substantially, a trend that continued thanks to a government predator control program that ensured that by 1926, there were none left.

Nobody missed them until 1929, when environmentalists began noticing that the park's ecosystem was starting to change. Once densely populated with cottonwood and aspen, it had begun to appear dry and barren. Turns out that without the wolves to control them, the elk population in the park had not only ballooned in numbers, but also, become fearless. This meant that they consumed everything in sight, including the all important willows that grew close to the streams.

But park rangers were reluctant to bring the predators back. Instead they decided to control the number of elk by capturing and moving or killing them. Though the park's flora and fauna never returned to its original state, reducing the number of grazers did help conditions from deteriorating any further.

Then came another setback. In the late 1960's, hunters began to complain that there were not enough elk. As a result, some US congressmen threatened to cut the National Park's funding, if the population control program was not stopped. Not surprisingly, as soon as the number of elk increased, park conditions began to worsen as the animals grazed through everything in sight.

The destruction of flora also led to other unforeseen casualties, among the biggest of which was the loss of beavers. Turns out that the willows that grew by the stream had a positive symbiotic relationship with the animals. The deep-rooted trees supplied the beavers with food and materials and also helped slow down the water flows so that the industrious animals could build dams. In return, the beaver dams provided the willows the sediment upon which to take root. As the willows started to get eaten by the elk, the beavers lost their food and raw material supplies. Additionally, the streams became too fast for their liking, resulting in a drastic reduction in population. This made conditions even worse for the willows!

In 1995, environmentalists were finally able to convince officials to re-introduce gray wolves to the park. As soon as the elk numbers started to come down, little tufts of aspen and willow began to reappear in the once barren areas and slowly but surely, things began to improve.

While some attribute the restoration solely to the gray wolves, others are not so sure. Arthur Middleton of the Yale School of Forestry and Environmental Studies, says that the elk population which has gone from a high of 14,000 to about 6,000, has also been impacted by human hunters, bears and a recent drought. Lisa Baril, a wildlife biologist at Yellowstone agrees and attributes some of the revival to climate change which she says has resulted in a better snow pack and helped the recovery.

No matter what the reason, the good news is that though Yellowstone National Park will probably never return to its former glory, we have managed to repair some of the damage. More importantly, it has taught environmentalists an extremely important lesson about the disastrous impact of destroying an element of a thriving ecosystem just because it appears to be a 'nuisance' to us!

Resources:pbs.org,nsf.gov,popsci.org, wikipedia.org