JACKSON, Wyo. — A recent article by Erin Blakemore in the Washington Post delves into the relationship between aspen trees and wolves in Yellowstone National Park (YNP), spotlighting a scientific paper that suggests increased elk predation allows for healthier vegetation growth.
The study, published in journal Forest Ecology and Management, analyzed data after 1995, when wolves were reintroduced to the park, Blakemore wrote. During most of the 20th century, there were no apex predators in YNP aside from bears and cougars, resulting in elk herds increasing to “record numbers.” Without predation, grazing species like elk increase until limited by starvation, causing vegetation degradation and negative impacts to other species down the food chain.
According to Live Science, prior to wolf recovery, an estimated 18,000 elk foraged on grasses, shrubs, leaves, twigs and the bark of trees, including quaking aspen, within the park’s boundaries. The Washington Post reported that elk had kept young aspen to 1 meter (3.28 feet) or less in height, preventing the trees from growing to their natural height of up to 40 feet.
Luke Painter, who teaches ecology and conservation at the Oregon State University College of Agricultural Sciences, stated in the study that increased elk predation has allowed aspen stands to grow, with young trees reaching more than 5 centimeters in diameter for the first time in more than 80 years. According to the Washington Post, researchers found a 152-fold increase in sapling and young-tree density, with 38% of aspen stands still suppressed by grazing elk and bison and 32% showing only patchy growth.
Researchers wrote in the study that the park now contains “historically and ecologically significant” amounts of growing aspen saplings. Aspens help to support a healthy ecosystem by providing a variety of grasses and forbs for a number of species, per the study.
