By Joe Glentworth, Emma Cary, Anna Gilchrist & Ian Thornhill, 16th September 2025
Species reintroductions—the human-mediated return of wild species to areas where they occurred in the past but have been extirpated—may seem like a modern phase in nature recovery, yet this type of conservation intervention is rooted in a long and radical history. In 1922, a government-sanctioned project translocated Eurasian beavers from Norway, transporting them by horse-drawn sleigh, train, boat and even seaplane to a remote forest in Sweden. Other bold returns soon followed. In 1948, wildlife rangers in Idaho parachuted beavers in wooden crates to Chamberlain Basin to help restore and enhance wetland ecosystems—the origins of the ‘beaver bombing’ movement. Despite the last wild European bison being shot in 1927, careful breeding and international cooperation reestablished these ungulates in the wild, from only 12 individuals that had clung on in zoos. Now, approximately 10,000 of the shaggy beasts roam across landscapes in Europe, reinstating natural processes such as grazing, disturbance of the soil, browsing and seed dispersal. By the 1990s, reintroduction projects had gained global media attention, headlined by the return of grey wolves to Yellowstone National Park. This joint effort between the U.S. Fish & Wildlife Service, the National Park Service, and state wildlife agencies demonstrated the significant benefits that could be realised from reinstating large carnivores after decades of absence. Meanwhile, on the steppe grasslands of Mongolia, the Przewalski’s horse was brought back from the brink of extinction through captive breeding, with the first animals released in 1992.
Beavers being parachuted into Chamberlain Basin in Central Idaho. Photo: Idaho Department of Fish and Game (IDFG), Idaho State Historical Archives, and the Pittman Robertson Trout Fund (now known as the Wildlife Restoration Act) curtesy of Sharon Clark.
Early beaver reintroduction into Chamberlain Basin in Central Idaho. Photo: Idaho Department of Fish and Game (IDFG), Idaho State Historical Archives, and the Pittman Robertson Trout Fund (now known as the Wildlife Restoration Act) curtesy of Sharon Clark.
Yet despite these radical successes, the UK has been slow to fully embrace large-scale, legally sanctioned species reintroductions. The process remains lengthy, tightly regulated and vulnerable to political uncertainties. Meanwhile, nature in Britain continues to decline, leaving the UK among the most nature-depleted countries in the world.
Goshawk Astur gentilis. Photo: thomas871014 via Pixabay.
Alongside this slow progress and perceived inactivity of the authorities responsible for nature recovery, a controversial counterculture has emerged. For decades, individuals and informal groups have taken it upon themselves to return species to the British countryside without formal approval. While the scale of this activity has, for a long time, largely flown under the radar, its ecological impacts are visible within the country’s wildlife. Goshawks, for example, were reintroduced covertly by falconers in the 20th century. Butterflies such as the large copper—extinct since the mid-19th century in the UK—have reappeared in places where there are no records of official releases. Beavers were living wild in Britain before any licensed projects began, and wild boar have established self-sustaining populations following both accidental escapes and deliberate releases. Most recently, lynx releases have captured the media’s attention, highlighting the uneasy relationship between public enthusiasm for rewilding and the pace of official decision-making.
Wild boar Sus scrofa. Photo: Paul_Henri via Pixabay.
These secretive reintroductions raise important and difficult questions. Ethically, is it ever justifiable for individuals to take conservation into their own hands, outside the framework of law, consultation and science? To what extent is the welfare of reintroduced individuals monitored or even considered? Ecologically, what risks do such releases carry for interactions between species in degraded ecosystems, the genetic diversity of reintroduced species or disease management? Politically, what does the rise of guerrilla rewilding tell us about the accessibility, responsiveness and legitimacy of formal conservation strategies? Are these unofficial acts a symptom of a deeper disconnect between public conservation values and regulatory processes?
In our new paper, published in Oryx, we explore these questions and offer one of the first dedicated accounts of guerrilla rewilding in the UK that traces a diverse range of covert reintroductions. Using case studies from some of the key species involved, we outline the history of this movement and reflect on how these acts, whether celebrated or condemned, are reshaping landscapes and challenging conservation and rewilding norms. We are not aiming to provide simple answers, but to open a wider conversation about how conservation is governed, the ecological risks involved, and the role of communities in shaping these decisions.
One of the lynx reintroduced to the Cairngorms, Scotland, which was subsequently recaptured and quarantined at Edinburgh Zoo. Photo used with permission from the Royal Zoological Society of Scotland (RZSS).
We welcome responses to our forum discussion, whether by offering perspectives on the ethical, ecological or political issues raised, or by sharing accounts of guerrilla rewilding, either from the UK or from elsewhere in the world. Much of this activity remains undocumented, but we believe a clearer understanding of its scope, motivations and impacts is urgently needed. We have already heard accounts of other guerrilla rewilding examples from across Europe and beyond. For example, the case of Olivier Rubbers in 1998 who, frustrated by the absence of beavers in Belgium, borrowed his father’s car and released nearly 100 German beavers into Belgian rivers. In other cases, official reintroductions, such as those of the lynx to the Jura Mountains, appear to have been preceded or quietly supported by unlicensed releases.
Beaver at Mill dam in Dunkeld. Photo: Danny Thomas.
By bringing these stories into the open, we can better inform the future of nature recovery and species reintroductions in a time of ecological uncertainty and a growing public appetite for a wilder nature in the UK and beyond.
The article ‘Can we learn from the UK’s guerrilla rewilding movement?‘ is available open access in Oryx—The International Journal of Conservation.
We welcome responses to this forum article. Responses should be submitted using this template via the ScholarOne website.
