Alongside social inequality, the economy and political instability, climate change now routinely makes its way into people’s lists of their biggest fears for the future. Although the existential threat posed by climate change has become deeply ingrained into public consciousness, the twinned crisis of biodiversity loss has received a fraction of the attention.

Last year, the 16th meeting of the Conference of the Parties (COP16) to the Convention on Biological Diversity went some way to redressing the balance by highlighting the urgent need for action on biodiversity. For plant diversity conservation, the outlook is sobering. Kew’s most recent State of the World’s Plants and Fungi report revealed that 45% of documented flowering species are at risk of extinction. This figure rises to 75% for the estimated 100,000 undescribed vascular plants1. As land-use change, pollution and climate change continue to drive this unprecedented loss in diversity, increasingly complex and interventionist conservation measures are being implemented to halt this decline, which raises questions as to what degree of human modification is deemed ‘acceptable’ in the conservation of natural ecosystems.

In the early 20th century, the North American population of American chestnut (Castanea dentata) was decimated by blight, which rendered this keystone species functionally extinct. Over the past few decades, efforts to revive the chestnut have centred on the development of a genetically modified blight-resistant variety. In 2020, the transgenic line Darling-58 was submitted for approval to US regulatory bodies. Containing the wheat-derived enzyme oxalic oxalate, which reduces fungal pathogenicity by inactivating oxalic acid, Darling-58 showed promising signs of resistance despite variable field performance. Although revelations of a laboratory labelling error looked set to unravel much of the progress made, Darling-58 is still being considered for approval and — if successful — it would be the first genetically modified organism (GMO) released for the purposes of ecological restoration2.

Plant scientists have long been familiar with the divisive discussions around GMOs. Although cultivation of genetically modified crops is still banned in most countries, the advent of gene-editing technologies, which expedite the selection processes in traditional crop breeding, has prompted a turn of the tide in public perception. Even the European Union (which for decades has been staunchly against the cultivation of GMOs) has loosened regulations on gene-edited crops, with the recognition that these varieties can advance sustainable agricultural practices in line with the values of conservation3.

For American chestnut, some of the arguments against the release of Darling-58 will sound familiar to plant scientists: fears that cross-pollination of poorly performing transgenic individuals with the few unblighted mature trees will reduce the fitness of the remnant wild population, migration of transgenic species across borders and opposition from Indigenous groups concerned about the effect on their sovereignty. But there are distinct elements to the debate around GMOs for ecological restoration. Rather than the moral imperative of food security, arguments both for and against the release of genetically modified plants for the purposes of conservation are underpinned by the desire to protect natural ecosystems. For some, the release of GMOs into the wild — even to save an iconic species from extinction — is an intervention too far.

Similarly, another argument has been brewing in the forest ecology community for several decades: the role of assisted migration in forest conservation. This is the practice of artificially moving tree populations outside of their native ranges to areas that will become more suitable under climate change; proponents argue that, given the limited migration capacity of trees, this is a necessary tool that will prevent the extinction of many species. A 2024 study published in Nature Climate Change reported that assisted migration can increase forest resilience and preserve the European forest carbon sink under climate change, even increasing storage capacity by 48–60 Tg of carbon per year4.

Opponents, however, raise concerns over the unintended consequences of assisted migration on recipient ecosystems. Much of this centres on the potential for translocated species to either become invasive or to inadvertently bring in novel pests for which receiver forests are unprepared5. Broadly, this debate boils down to weighing up the cost of action versus inaction for biodiversity conservation and whether human interventions can ever be as effective as natural ecosystem responses to disturbance. As ever, more research is needed — particularly into tree reproductive biology — to ensure that the practice of assisted migration is implemented as robustly as possible.

Several high-profile projects, such as the Knepp Estate in England, have launched the ecological concept of trophic rewilding into the public eye. There are two core tenets of trophic rewilding. Firstly, that the reintroduction of megafauna can restore top-down trophic interactions to promote a self-regulating ecosystem. Secondly, that after reintroduction, management of the landscape should be passive, with limited human interference: nature should be allowed to take its course6. Although evidence for how rewilding will influence long-term ecological trajectories is lacking, a growing evidence base now demonstrates the critical role that large animals have in ecosystem functioning. Several meta-analyses have revealed that herbivorous megafauna introduce spatial heterogeneity to open vegetation structure7, which is an important driver of biodiversity, and are also positively related to native plant richness, which promotes resistance against alien plant dominance8.

The reintroduction of large fauna to mimic pre-human levels is an attractive concept that allows for the hope that we can reverse millennia of damage inflicted upon the planet. The mode of this recovery, however, is not without its critics. Rewilded landscapes are untamed, messy and often at odds with manicured visions of scenic beauty. Research published in People and Nature explored how the visual aesthetics of rewilding have become politicized and positioned as being at odds with the traditional conservative ideals of orderliness and tidiness9. Resistance has also come from farmers who are concerned about the risk of livestock predation from reintroduced carnivores, and from fears for public safety. For trophic rewilding to be successful, the engagement of local communities is critical.

The goal of ecosystem restoration to a natural state, free from human modification, may suggest that we view ourselves as apart from nature. This rhetoric — that we are somehow exempt from or above the natural world — has far-reaching consequences that influence how we interact with and study nature, as well as the methods through which we protect it.

Debates around these conservation measures are complex, but for too long they have neglected Indigenous knowledge systems in favour of Western perspectives. A tension that runs through these debates is that although ecosystems are in desperate need of protection, the human fingerprint these measures leave behind may itself be an ‘unnatural’ disturbance. Although the degree to which this is viewed is acceptable will vary, the framing of humans as distinct from nature may limit action at a time when it is needed most.