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It Might Be Impossible to Turn Back the Clock on Altered Ecosystems

“Rewilding” landscapes to return them to a natural state might sometimes be ineffective and even harmful

The tule elk has been reintroduced to its native range at Point Reyes National Seashore in California, but sometimes "rewilding" landscapes brings unintended effects. (Wikimedia Commons/Austlee)
smithsonian.com

While it's usually shrouded in fog, on a clear day two pictures emerge of Point Reyes National Seashore in California. 

In one landscape you’ll see an abundance of thigh-high coyote brush, purple bush lupine and hairy velvet grass waving with wind from the Pacific Ocean. The build-up of dead vegetation on the ground is thick enough that it has a trampoline-like feel when you walk on it, and though you may not be able to see them, deer mice, meadow voles and ground beetles are abundant in the understory.              

The second landscape is a little greener. More fresh seedlings sprout from the four-inch grass cover and less dead vegetation gathers on the ground. The rodents and ground beetles may not be as common in the large open spaces. Instead the compacted soil favors the carrion beetles, ants, spiders and pill bugs crawling about.

The difference? Tule elk, a species originally native to large parts of California, has been reintroduced to the second, greener area after being hunted to near extinction in the 19th century. Federal and state agencies collaborated to reintroduce the elk in the 1970s in an effort to "rewild" the seashore, or return it to its natural state.

Some people seem to think that ecosystems are fixed in time—with the ideal wildlife habitat dating to the pre-industrial age. To fix the problems we may have since caused via introducing invasive species or removing native wildlife, we just have to turn back the clock. But ecosystems aren't like that. Humans have been altering habitats for thousands of years. Now some experts are beginning to think that rewilding is not only impossible but possibly harmful if ecologists aren't able to untangle the many variables in these new, human-made landscapes.

Of the two areas in Point Reyes, “Is one better than the other? That’s a tough call,” says J. Hall Cushman, a professor of biology at Sonoma State University who has been tracking the ecosystem changes in Point Reyes due to elk reintroduction. He notes that there is a vast difference in reintroducing a species that has been absent for a few decades to a rewilding scheme in which a species that never lived in an area, or that has been gone for thousands of years, is reintroduced. 

He says that the elk have had a positive effect on the removal of invasive velvet grass. The lack of longer grass has also made it easier for land managers to conquer some invasive insects like Argentine ants and certain species of pill bugs. But then shorter plants, both invasive and native, thrive in the hoof-compacted earth. “In every single instance when you reintroduce a large animal that used to be in an area, it’s going to have a mixed bag of effects.”

The trouble is that the natural state of Point Reyes, whatever that was, was gone for good by the time the elk had been wiped out in the region.

“Grazers don’t deal with all plants equally. It could even exacerbate the increased dominance of some introduced plants in areas. That’s barely considered in any rewilding schemes,” says Daniel Simberloff, a professor of environmental science at the University of Tennessee, Knoxville. Simberloff recently co-authored a study in Current Biology questioning the idea of rewilding and restoration, and one of his principal messages was this: You may be able to take an animal back to the same place, but you can’t take it back to the same time. 

To some extent, Cushman and other researchers tracking the return of the tule elk agree.

“You can’t take a piece out and expect it to be the same way it was when you put it back in,” says Brent Johnson, a research coordinator with Pinnacles National Park who worked with Cushman on tracking the elk. “The same can be said for the removal of species.”

Even removing an invasive species can sometimes go wrong. Federal, state and local organizations coordinated in the Invasive Spartina Project to remove 92 percent of cordgrass, an invasive grass that alters the physical structure and biological makeup of the tidal marshes around San Francisco Bay. But the federally endangered California clapper rail, a chicken-sized shorebird, had taken to nesting in the invasive cordgrass.

“They couldn’t continue the eradication of the invasive,” says Adam Lampert, an assistant professor at Arizona State University who studied the situation. “The main message is, you cannot remove invasive species too rapidly. Once established in a sufficiently large area, the local population becomes dependent sometimes on the invasive species.”

Another study showed that veeries, small songbirds found across the northern U.S., find successful nesting opportunities in invasive and introduced shrubs like Japanese honeysuckle in New York state forests. In Hawaii, the wattle-necked turtle is wreaking havoc on freshwater lakes in Kauai, but hunters have brought the reptiles to the brink of extinction in their native range in China and Vietnam, creating a conundrum for conservationists.

Grad student Clark Richter and NPS Wildlife Biologist David Press investigate the dividing line between where tule elk are allowed to graze and where they are not, at Tomales Point at Point Reyes National Seashore. (Courtesy J. Hall Cushman)

The situation has some scientists questioning the concept of rewilding.

“Often you can’t even tell what’s being talked about or what the goal of a project is,” says Simberloff. “It’s sold as a conservation mechanism, and often it doesn’t conserve biodiversity.”

He points out a number of these schemes that have had unintended consequences: Wolves reintroduced to parts of the United States and Europe have lowered the number of grazers through predation, which results in more berries growing for grizzly bears. But they’ve also hybridized with dogs that are now ubiquitous in these areas, irrevocably changing the gene pool of some wolf populations. An extreme case in North Carolina has seen the fledgling experimental red wolf population hybridizing with coyotes, worrying since it’s the only population of wild red wolves in the world. If this continues in an extreme form, the species could be bred out of existence.

Simberloff stresses that his message isn’t that reintroduction or restoration is always bad, but that the whole cascade of possible effects to an ecosystem needs to be considered rather than looking at things one- or two-dimensionally.

“We’re not saying [rewilding] should never be done. We’re saying that it requires a lot more systematic and comprehensive thought than seems to have gone into it in many cases,” Simberloff says.

Often, the human footprint in a given area is so large that it’s impossible to restore the original ecosystem. Instead of rewilding, we may be better off focusing efforts on so-called novel ecosystems, Simberloff says. The latter include everything from the plants and animals living on or around old human buildings to the wildlife adapting to cities, farms or other factors of the Anthropocene. They could even be engineered to provide humans with desired services.

“Start with what we have, not what we had,” he says.

Cushman, the California biologist, continues with the experiment he’s running, with around 24 plots excluding or including elk, and researchers will keep tracking the results. He says that the answer is going to be complex in any situation, but he so far believes the elk have had a net positive effect on the Point Reyes ecosystem. Tall and lumbering, with horns both jagged and curvaceous, the tule elk can cut an epic silhouette on the horizon, particularly when the backdrop is the Pacific Ocean. And beyond aesthetics, the elk are steadily removing the invasive velvet grass.

“Elk are greatly decreasing the abundance and cover of this exotic grass," he says. "That’s a very positive effect of having elk in the system.”

About Joshua Rapp Learn
Joshua Rapp Learn

Joshua Rapp Learn is a D.C.-based journalist who writes about science, culture and the environment. He has crossed the Sahara Desert, floated down the Amazon River and explored in more than 50 countries.

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