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Dr. Bill Ripple, Oregon State University – Large Predators and Ecological Health

In today’s Academic Minute, Dr. Bill Ripple of Oregon State University explains the important role large predators play in the health of any ecosystem.

Bill Ripple is Director of the Trophic Cascades Program at Oregon State University where his research specialties include wildlife habitat analysis and landscape ecology. His recent work has focused on the connection between wolf populations and aspen ecological health. His research can be found in a number of peer-reviewed journals and he holds a Ph.D. from Oregon State University.

About Dr. Ripple

Dr. Bill Ripple – Large Predators and Ecological Health

Many large predators are declining around the world, and scientists want to understand the role these carnivores play in nature. Much of our research has focused on Yellowstone, the world’s first national park. In Yellowstone, aspen trees were declining for most of the 20th century, but the reason for this decline was a mystery.  We conducted tree ring studies on the aspen there, and were able to determine their ages. What we found was amazing. The aspen trees began to decline right after wolves were eliminated from the park in the 1920s.

When wolves were present 100 years ago, they preyed on elk and limited their population. But when the wolves were gone, more elk browsed on the aspen sprouts and killed them. What’s really interesting is that this began to change after wolves returned to the park in the 1990s. Both the elk numbers and their browsing of young aspen sprouts declined, giving the trees a better chance to survive. The aspen began to recover.

Other species were also affected. Cottonwood and willow grew taller along some streams, providing improved habitat for beaver and fish. A greater diversity and abundance of songbirds soon followed. This was a re-birth of the ecosystem—similar to the way it used to be.

We replicated our findings in other parks in western North America and found the same cascading forces at work –predators affecting prey and prey affecting plants. This research shows how wolves can have profound effects on the health of entire ecosystems. When we make land and wildlife management decisions, it’s important to consider the role that all species play – especially the large predators.

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