Wolf pack brings park back to life

It’s easy to imagine how predators take things out of an ecosystem by killing and eating their prey, however researchers studying the return of wolves to parts of the US were amazed at what they add.

When a wolf pack re-entered Yellowstone Park after a 70-year absence it set off a chain of events that has cast light on the surprising ways ecosystems are connected.

The first effect of the wolves returning was that deer – which had bred unchecked in their absence – started avoiding places where they could be easily caught. These areas, which had until then been grazed bare, suddenly saw entire new forests regrow.

The young forests supported huge numbers of birds, plus bears, which were attracted by the new supply of berries. Beavers were also attracted to the new trees – and the dams they made provided homes for more otters, fish, frogs and muskrats.

Meanwhile, the wolves also supressed coyotes, which in turn boosted rabbit and mouse numbers – and that attracted a wider range of predators including hawks, foxes, weasels and badgers.

Within a few years the wolves had enriched the whole system. Perhaps most surprising, however, was the effect they had on the rivers: the new forests stabilised the valleys, preventing landslips and reducing the amount of soil washed into the rivers below, ultimately creating faster, healthier waterways and altering the geography of the entire park.

See George Monbiot TED talk to learn more.