30th May 2022

The complex web of relationships in our ecosystems where each organism affects the others has not been fully recognized until comparatively recently.  One example of this is at Yellowstone Park.  Yellowstone Park was made a national park in 1872 but that did not protect the wolves who were all killed by the 1920’s to protect the ‘more valuable’ species.  They didn’t listen to the Scottish-American conservationist John Muir, the ‘Father of the National Parks’, who said “when we try to pick out anything by itself, we find it hitched to everything else.”

Wolves had been the top predator and without them the elk and deer numbers exploded.  This caused overgrazing of young willows, aspen trees and cottonwood plants, which in turn led to a decline in songbirds and beavers, the latter of whom rely on willows in winter. As beavers declined in numbers, the lack of damming and shade meant water temperatures rose, and certain cold-water fish could no longer survive in Yellowstone.

After much discussion and not a little opposition, wolves were reintroduced in 1995.  The impact on the biodiversity of Yellowstone National Park was seen within the decade – much quicker than those involved in the project had expected.  Willow stands had been in bad shape due to overgrazing , but with pressure from wolves keeping elks on the move, the grazing was not so intensive, and so willow stands became more robust – meaning they could again accommodate songbirds. Willows are still recovering, but strong willows also meant beavers had an abundant food source. When the wolf was reintroduced in 1995, there was only one beaver colony left in Yellowstone. There are now many. As beavers dammed and built ponds, the trees thrived, and cold, shaded water returned to accommodate fish.

In recent years, with a lack of snowy winters in Yellowstone, wolves have become the primary cause for elk mortality. Scavenger species that once relied on winter-killed elk are still able to thrive without the snow thanks to wolf-killed elk.  This is benefiting ravens, eagles, magpies, coyotes and bears. Wolves also kill coyotes, which increases the populations of rabbits and mice, and in turn provides a wider food source for hawks, weasels, foxes and badgers.

27 years on, the reintroduction of wolves to Yellowstone is considered one of the most successful examples of rewilding to take place. It is a remarkable example of the ripple effect that one animal can have on an entire ecosystem, and a lesson for us of the value of all the different species.


My fruit trees
have lichen on their branches,
crusted green-grey
and mustard yellow,
another crop
along with the apples and plums,
telling me
like grey hair
that they have been here
for a while
and are worthy
of my respect.