Return of wolves to Yellowstone has led to a surge in aspen trees

Summary

Yellowstone's wolves are helping a new generation of young aspen trees to grow tall and join the forest canopy — the first new generation of such trees in Yellowstone's northern range in 80 years.Gray wolves (Canis lupus) had disappeared from Yellowstone National Park by 1930 following extensive habitat loss, human hunting and government eradication programs. Without these top predators, populations of elk (Cervus canadensis) grew unfettered. At their peak population, an estimated 18,000 elk ranged across the park, chomping on grasses and shrubs as well as the leaves, twigs and bark of trees like quaking aspen (Populus tremuloides). This stopped saplings from establishing themselves, and surveys in the 1990s found no aspen saplings."You had older trees, and then nothing underneath," Luke Painter, an ecologist at Oregon State University and lead author of the new study, told Live Science.But when wolves were reintroduced in 1995, the picture began to change. As wolf numbers rose, the elk population in the park dropped sharply, and it is now down to about 2,000.In the new study, published Tuesday (July 22) in the journal Forest Ecology and Management, Painter and his colleagues surveyed aspen stands — specific areas of the forest where these trees grow.Related: Reintroducing wolves to Yellowstone helped entire ecosystem thrive, 20-year study findsThe team returned to three areas surveyed in 2012 to examine changes to aspen sapling numbers. Of the 87 aspen stands studied, a third had a large number of tall aspen saplings throughout, indicating the trees are healthy and growing. Another third of the stands had patches of tall saplings.Get the world’s most fascinating discoveries delivered straight to your inbox."We're seeing significant new growth of young aspen and this is the first time that we've found it in our plots," Painter said. These are young aspen with a trunk greater than 2 inches (5 centimetres) in diameter at chest height — which haven't been seen there si...