In the first, large-scale comparative study of the role of a predator in a terrestrial ecosystem, Canadian researchers discovered evidence of the visibly large impact on nature when the wolf population is eliminated.
During the 1960s hunters eliminated most of the wolf population around Banff in the Canadian Rockies. By the 1980s, wolves had reappeared in some areas, but not others, the researchers noted, giving them a natural laboratory to study the different impacts.
"We were able to compare two areas at the same time right beside each other: one with wolves, one that did not have wolves," said Mark Hebblewhite, author of the study.
"In that respect it is a really powerful study," said Hebblewhite.
The researchers found that the absence of wolves permitted a rise in the number of elk, a large North American deer also known as wapiti that is the preferred prey for the wolves.
That was good for the elk, but not for other parts of the forest flora and fauna, as the comparison with areas with wolf populations showed.
The rise in elk numbers resulted in the decline of willow trees, and then of woodpeckers, who live high in the trees.
With less willows to use for erecting their dwellings, the beaver population also suffered.
"You don't need an ecologist to see this. Anybody who comes to Banff can drive a five kilometer- (three mile-) line from Banff out towards where there are lots of wolves' activities and you can see these changes occurring," said Hebblewhite, a doctorate candidate in biology at the University of Alberta.
The impact of humans in the area exacerbate the ecological imbalance. Humans have cut into the large amount of land and forest the wolves need for hunting.
The whole complex chain of forest life creates a headache for the authorities of the Banff National Park, a favorite of tourists who come for the sprawling views of the pristine Rockies.
Visitors are attracted by a "healthy ecosystem," said Marjorie Huculak, spokeswoman for the Banff park.
"We have to find a delicate balance," she said.