After a drought of new aspen growth in Yellowstone's northern range, wolves appear to have flipped the script for these iconic trees, ushering in the first new generation of aspen to reach the forest canopy in 80 years. Gray wolves vanished from the park in 1930, with hunting and eradication programs blamed for their disappearance. In their absence, elk populations exploded, reaching up to 18,000 and putting aspen saplings on the menu—so much so that by the 1990s, new aspen were nearly nonexistent, per Live Science. That began to change in 1995, when wolves were reintroduced to Yellowstone. As the wolf packs multiplied, elk numbers plummeted to about 2,000, easing the munching pressure on young aspens.
A new study led by Oregon State University ecologist Luke Painter, published Tuesday in Forest Ecology and Management, revisited sites first surveyed in 2012. The results: about a third of aspen stands are now filled with tall, healthy saplings—some with trunks thicker than two inches at chest height, a size not seen since Franklin D. Roosevelt's presidency—and another third have tall saplings in patches, per the BBC. Painter notes these young trees are "old enough to spread themselves," either by root or seed, and their growing size makes them tougher to kill. Still, the aspen comeback isn't uniform. Bison populations—less vulnerable to wolf predation—are rising in some pockets, presenting a new challenge for the trees.
The resurgence of aspen is more than just a win for the trees. Their return supports everything from berry shrubs and birds to beavers, who find food and building material among their branches. The study underscores what can happen when a top predator is restored, with cascading benefits for the entire ecosystem—a point echoed by other scientists. As Painter tells Live Science, "Aspen are a key species for biodiversity. The canopy is more open than it is with conifers and you get filtering light that creates a habitat that supports a lot of diversity of plants."
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