A balance lost and restored: a lesson in nature…
When Yellow Stone National Park came into being back in 1872, the Grey Wolf (canis lupus) was in decline across Montana, Wyoming and Idaho. The creation of the park did not protect wolves and other predators as control programmes in the early 1900s adversely persecuted them, and by 1926 Wolves were no longer living in the park. During the following years Yellow Stone fell victim to defoliation, erosion and an unbalanced ecosystem.
In 1995, a programme saw the reintroduction of 14 Grey Wolves into the park and what followed was incredible. They had an immediate impact on the habitat. They hunted the local deer population that had, despite human efforts, proliferated. Although they did not kill a huge number; they changed their behaviour. The deer moved from the low areas - the valleys and glades, to higher more remote areas where it was harder for the wolves to hunt them. Thanks to the absence of the deer, the areas they left regenerated: wildflowers and shrubs grew, and forests of Aspen, Willow and Cottonwood flourished, with some trees growing by five times in just six years.
And that’s when things really happened. With the trees and shrubs came more flowers, berries and insects. As soon as this happened the bird species moved back. Then, with the increasing tree population, the beavers, previously extinct in this area, returned. They selectively managed the trees and built dams, which led to new habitats that attracted muskrats, otters and reptiles, improving the balance of the waterways. With a greater range of foods and in particular berries, the bear population improved.
The wolves also killed coyotes, and this led to an increased population of rabbits and other small rodents. This led to an increase in the population of hawks, foxes, badgers and weasels: even bald eagles and raven populations grew - feeding from carrion left by the wolves.
Then something unexpected and miraculous happened: the impact of the wolves changed the physical geography of the park. The improved forests had stabilised the land, decreasing erosion. Riverbanks stabilised and channels narrowed: rivers stayed truer to their courses, and more ponds formed improving habitats for waterfowl.
The removal of the wolves in the early 20th century bought about a ‘trophic cascade’ - the wolves’ natural prey, the deer and elk multiplied unchecked and overgrazed the foliage causing the entire environment to deteriorate. It became unbalanced, leading to the decline in many species, both botanic and animal. When the wolves came back the phenomenon occurred in reverse, restoring the balance.
If minor changes can have such a major impact, it must give us hope that in doing so to our global environment will lead to a brighter future for our planet and its ecosystems.
Figure 2A return to balance - Yellow Stone