Restoration ecology is the practice of fixing the ecosystems that we broke. Often in restoration ecology, you can pick up all the pieces and try to put the ecosystem back together again like a puzzle. But sometimes, the puzzle is missing very important pieces. Recently, the concept of “rewilding” has been proposed as a possible solution for the missing puzzle pieces. Rewilding is the idea that we can allow nature to recover by simply removing humans from the picture and life will find a way. This act of passive restoration is not without its controversies. But in a world plagued by environmental destruction, scientists are doing whatever they can to restore degraded ecosystems during the United Nations Decade on Ecological Restoration from 2021 to 2030.
One of the most damaged and degraded ecosystems in the world is also the site of the largest and longest unintentional rewilding experiments to date – Chernobyl.
In 1986, a nuclear power plant had a meltdown and authorities formed the Belarusian Chernobyl Exclusion Zone (CEZ) to prevent people from returning to their homes and being exposed to life-threatening radiation. As a result, human activities in the 47000 km^2 CEZ were basically nonexistent. Since the nuclear meltdown, scientists have been studying the impact of the radiation on wildlife and plants in the CEZ since they were only able to exclude people, not the other organisms in the area. However, from a restoration perspective, the CEZ also provides a unique opportunity to explore rewilding.
Since humans left the area megafauna like wolves, elk, Przewalski’s horse, and bison have returned to the CEZ . However, there has been little scientific study about how land-abandonment by humans have impacted wildlife. Recently a group of scientists from Belarus and the United Kingdom published their results from a 22-year study measuring the changes in raptor populations within the CEZ.
Between 1998 and 2019, the researchers identified every bird of prey within their 147km^2 sampling area and made notes about their abundance and their behavior. In total, they identified thirteen species of raptors and found that some species declined during the 22 years while others increased. Most of the species that declined, like the Lesser Spotted Eagles and the European Honey Buzzard are commonly found in dry forests. They compared the species abundance within the CEZ with the national average and of the nine species that declined, 3 declined then stabilized to match the national average. The Lesser Spotted Eagle declined from 13 pairs in 1998 to just four in 2019 and at the end of sampling, there was only one pair of Short-Toed Snake Eagle.
However, four species increased within the CEZ: the Marsh Harrier, Greater Spotted Eagle, White-Tailed Eagle, and Eurasian Hobby. The latter three were surprisingly more abundant in the CEZ compared to the national average. This was especially surprising because the Greater Spotted Eagle was locally extinct in the area until it showed up in the CEZ in the year 2000.
One of the explanations for the difference in recovery between the species is that each species depends on a unique habitat type to find food, shelter, and mates. Because habitat is so important, the researchers also looked at how the landscape changed during the study. Initially, before the Chernobyl disaster, the landscape was scattered with farmlands and towns. But, without humans there to farm and upkeep the town, the landscape slowly began to change. Between 1999 and 2017, the researchers observed a 680% increase in wetlands and a decrease of open fields by 14%. Unsurprisingly, the raptor species that recovered within the CEZ are often found in wetlands across Belarus while farmland species, those using the open fields, declined.
This human exclusion zone is similar to nature reserves where human activity is minimized and although it was created for a very different reason, the CEZ provides a refuge for species at risk in humanized landscapes. This is true for at least one of the species in this study, the Greater Spotted Eagle. The Greater Spotted Eagle is endangered in Europe but it is thriving in the CEZ where there are abundant wetlands for it to hunt. The recovery of the Greater Spotted Eagle may be enough to classify this unintentional rewilding experiment as a success. This eagle can be used as an indicator of conservation success because where the eagles are abundant the wetlands are healthier and other species of conservation concern are also thriving.
This study makes the most out of a grave disaster that took a tremendous toll on both the ecosystem and human life. The silver lining is that nature does seem to recover from ecological disasters with minimal human intervention, given enough time. But, as the researchers point out, there are “winners” and “losers” in the rewilding game. Top predators and wetland specialists did well while middle-level predators, farmland specialists, and dry forest specialists continue to decline.
So is rewilding a good method for restoration? Like most things in ecology, it is complicated. But in the CEZ, a thirty-year break from human intervention was enough to change the landscape and passively restore lost raptor communities.
Source: Dombrovski, V.C., Zhurauliou, D.V., and Ashton-Butt, A. Long-term Effects of Rewilding on Species Composition: 22-years of Raptor Monitoring in the Chernobyl Exclusion Zone. 2022. Restoration Ecology.