“The reason why the park put that alternative (of wolf reintroduction) on there is because science has unequivocally shown in Yellowstone and recently Banff (in Canada) that wolves help keep ecosystems healthy,” says Gary Wockner, a wildlife ecologist at Colorado State University. In those parks, the predators’ return means that elk no longer loiter along rivers and streams, where ambushes are more likely. This helps native vegetation recover and with it, species such as beavers and songbirds.

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