"I have lived to see state after state extirpate its wolves. I have seen every edible bush and seedling browsed, first to anemic desuetude, and then to death."
-- Aldo Leopold

Randall comments on a press release regarding a new paper from the OSU College of Forestry which notes further confirmation of the benefit of top predators in healthy ecologies.

The wolves are back, and for the first time in more than 50 years, young aspen trees are growing again in the northern range of Yellowstone National Park.

The findings of a new study, just published in Biological Conservation, show that a process called “the ecology of fear” is at work, a balance has been restored to an important natural ecosystem, and aspen trees are surviving elk browsing for the first time in decades. . .

“We’ve seen some recovery of willows and cottonwood, but this is the first time we can document significant aspen growth, a tree species in decline all over the West. We’ve waited a long time to see this, but now we’re optimistic that things may be on the right track.” . . .

Aspen, a beautiful hardwood tree with golden fall color, a key to ecosystem biodiversity and a hallmark feature of mountain areas across the West, has been the focus of concern. Unlike willows, aspen are more easily killed or suppressed by browsing and have been the slowest to show any recovery. In some areas of the West, up to 90 percent of the aspen have disappeared.

“When I first looked at these degraded ecosystems in the mid-1990s in Yellowstone, I had doubts we would ever be able to bring the aspen back,” said Robert Beschta, a professor emeritus of forestry at OSU and co-author on the study. “There were so many elk, and the stream ecosystems were in such poor shape. The level of recovery we’re seeing is very encouraging.”

The OSU research comes from their Trophic Cascades Program.

Trophic Cascades in Terrestrial Ecosystems is a research and educational program with the purpose of investigating the role of predators in structuring ecological communities. This program puts special emphasis on the role of potential keystone species in top-down community regulation, with linkages to biodiversity via trophic cascades.

Wolves aren't the only predator and Yellowstone is not the only park being studied. For example, they also have a cougar program in Zion National Park.

I've been paying attention to such research for some time now. See Lagomorpha Fear, which in turn points to an old Crumb Trail post, The Ecology of Fear. It's an old idea that has been argued by naturalists for many decades, though the notions are far older.

Humans can have a major role in food web dynamics by displacing or extirpating top predators. Over a half century ago, the iconoclast Aldo Leopold was among the first to argue that elimination of large mammalian predators had strong topdown influences on ecosystems (Leopold et al., 1947). Based on widespread empirical observations in the early to mid- 20th century, when large carnivores were being extirpated from significant portions of the United States, Leopold and colleagues suggested that the loss of these carnivores set the stage for ungulate irruptions and ecosystem damage. . .

A trophic cascade occurs when the presence of a top predator significantly affects consumers and this interaction alters or influences species composition, age structure, or spatial distribution of producers (plants).

It isn't just carnivorous top predators that balance systems. Consider that the elk from the Yellowstone study are predators too, but they prey on plants. The principles generalize. Even insects are predators in this sense in that they consume plants and/or other insects. Elimination of any one of them will have cascade effects, though perhaps not as obvious and dramatic as the case with top carnivores. See Habitat Management for a discussion of the effects of elimination of plant predators from a system, as well as some of the finer points of intentional management of relative pressures of predation to achieve desired ends.

If you are fascinated by this type of thinking about natural systems you might enjoy following a couple of related threads. See How humans affected the climate system for 8000 years for a perspective on the largely unremarked effects of humans and agriculture over deep time, and see Enhancing ecosystem services in agricultural lands for an attitude adjustment.

if one accepts that virtually all of nature is now domesticated, the key scientific and social questions concern future options for the type of domesticated nature humans impose upon the world

We broke it, we bought it. It's time to pay up.