Forgotten predators: Ecological understanding is often marred by the exclusion of extirpated species

New research published in the journal BioScience describes how the removal large predators is often unrecognized in ecological scholarship, creating an issue of "shifting baselines," with profound implications for restoration efforts.

A team led by researchers from Oregon State University, including co-lead authors William J. Ripple and Christopher Wolf, reviewed 96 published studies from 1955 to 2021 that were conducted in 11 national parks where gray wolves had been extirpated. Their analysis found that only 39 of these studies discussed the historical presence of wolves or other large carnivores. By failing to account for the loss of these apex predators, say the authors, approximately 59% of the studies may have overlooked fundamental changes to ecosystems in the region.

This lack of historical context could have serious impacts on present-day conservation, say the authors, who argue that "studying an altered ecosystem without recognizing how or why the system has changed over time because of the absence of a large predator could have serious implications for wildlife management, biodiversity conservation, and ecosystem restoration, like diagnosing a sick patient without a baseline health exam."

In the case of gray wolves, the researchers highlight that the species' removal allowed elk populations to overshoot historical numbers, damaging plant communities through overgrazing. Wolf extirpation also enabled a rise of mesopredators, such as coyotes, that can threaten smaller animal populations and further upend ecosystem dynamics.

"Various national parks in the western United States, which are considered the crown jewels of American wilderness, lack their apex predators, resulting in them being shadows of their supposed ecological integrity," say the authors. Compounding the problem, they argue, is the fact that "restoration decisions made without consideration of past conditions may themselves continue to alter ecosystems in novel ways."

To avoid such pitfalls, the authors urge researchers to investigate the potential effects of historic predator extirpations when studying areas currently lacking apex carnivores. They also recommend exploring archival data to better understand historical ecosystems. Although the present research is focused on the northwestern United States, the issue of shifting baselines is global, say the authors, as "the same issues likely apply to research conducted in other portions of the United States, as well as in many areas globally, given the widespread and long-term impacts of the decline of large predators and the release of herbivore prey."

The research has significant implications for the long-term conservation of wolves and other large predators, potentially impacting current gray wolf management and legal actions in the West. "We hope our study will assist both conservation organizations and government agencies in setting wolf management goals," added Ripple.