By Wild Origins Australia
For decades, conservation biology has been guided by a powerful assumption: native species are inherently good for ecosystems, while non-native species are disruptive invaders. This belief has shaped policy, justified eradication campaigns, and influenced public perception. But what if this foundational idea is flawed—or even harmful?
In a groundbreaking study published in Science, Dr. Erick J. Lundgren and colleagues challenge the ecological and ethical validity of this assumption. Their research, which analyzes nearly 4,000 plot-scale plant responses across 221 studies, reveals a striking conclusion: the ecological impact of large mammalian herbivores is not determined by whether they are native or non- native, but by their functional traits—such as body size, feeding behavior, and diet selectivity.
This finding has profound implications for conservation practice. It suggests that decisions based on nativeness may be misguided, and that the real drivers of ecological change lie in how animals interact with their environments—not where they come from.
The researchers set out to test a widely held belief: that introduced large herbivores have stronger and more negative effects on plant communities than native ones. To do this, they conducted a meta-analysis of thousands of plant abundance and diversity responses from ecosystems around the world. They examined whether factors like nativeness, “invasiveness,” “feralness,” coevolutionary history, or functional novelty influenced herbivore impacts. The results were clear. There was no evidence that megafauna impacts were shaped by nativeness. Nor was there evidence that introduced megafauna facilitated introduced plants more than native megafauna.
Instead, the strongest predictors of ecological impact were functional traits. Large-bodied herbivores tended to promote plant diversity. Bulk feeders—those with broad, non-selective diets—had more positive effects on vegetation. In contrast, selective grazers, such as grass specialists, were more likely to reduce graminoid diversity. In short, what an animal does matters more than where it came from.
The paper highlights the ecological nuance often overlooked in wildlife management. Take wild horses in arid landscapes, for example. Often labeled as invasive, they are accused of degrading rangelands. Yet their bulk-feeding behavior and seed dispersal functions can mimic extinct megafauna, contributing to ecosystem heterogeneity. Their impact depends on population density and landscape context—not their non-native status.
In African savannas, elephants and feral livestock exert similar pressures on vegetation. Yet elephants are celebrated as keystone species, while livestock are vilified. The ecological outcomes may be comparable, but the moral framing differs sharply. Meanwhile, in Europe, domestic cattle are being reintroduced to mimic extinct aurochs. Though technically non-native in their modern form, they fulfill ecological roles that restore plant diversity and structure. Their utility is recognized, but their “nativeness” is often debated.
These examples underscore the authors’ central point: management decisions should be based on ecological function, not origin stories. Yet conservation has long operated under a moral double standard. Native species are presumed to be ecologically beneficial, even when they cause harm. Non-native species are presumed harmful, even when they provide ecological services.
This bias is not supported by empirical evidence. The study found no consistent pattern of introduced herbivores causing more damage than natives. In fact, some introduced species enhanced plant diversity and ecosystem resilience. The authors warn that this bias leads to unjustified eradication campaigns, often causing suffering and ecological disruption. It also obscures the real drivers of change—such as land use, climate shifts, and human activity.
This brings us to the central ethical question: should non-native wildlife be eradicated simply because people think they are bad? Lundgren and his colleagues suggest that such decisions are rarely based on ecological evidence. Instead, they reflect human values—aesthetic preferences, cultural narratives, and utility judgments. Feral pigs may be killed for damaging crops, not for being non-native. Wild horses may be removed to protect grazing rights, not biodiversity. Deer may be tolerated despite over browsing, because they are native and charismatic.
The authors draw on a wide array of case studies to demonstrate that the ecological impacts of large mammalian herbivores are shaped by their functional traits—not by whether they are native or non-native. Here are five specific examples referenced in the paper that illustrate how non- native species compare to native ones:
Wild Horses (Equus ferus caballus) in Arid Ecosystems
Wild horses, often considered non-native in North America and Australia, were shown to have ecological effects comparable to native herbivores. Their bulk-feeding behavior promotes plant heterogeneity and seed dispersal, similar to extinct megafauna. Despite being labeled invasive, their functional traits align with those of native species that once occupied similar niches.
Feral Donkeys (Equus asinus) and Native Kangaroos in Australia
The study cites research comparing feral donkeys and native kangaroos, showing that both species exert similar grazing pressures and influence on vegetation structure. Donkeys, though non-native, do not necessarily cause more ecological harm than kangaroos, challenging assumptions that nativeness equates to ecological compatibility.
Introduced Deer Species in Europe and Native Ungulates
In European landscapes, introduced deer species such as fallow deer (Dama dama) were found to have comparable impacts on plant communities as native red deer (Cervus elaphus). Their effects on understory vegetation and tree regeneration were more closely tied to population density and feeding behavior than to origin.
Domestic Cattle in Rewilding Projects vs. Extinct Aurochs
Modern domestic cattle, used in rewilding efforts to mimic the extinct native aurochs (Bos primigenius), fulfill similar ecological roles. Though genetically and historically distinct, their grazing patterns and ecosystem functions support plant diversity and landscape heterogeneity, demonstrating that functional traits can substitute for nativeness in restoration contexts.
Feral Pigs (Sus scrofa) vs. Native Herbivores in Tropical Forests
Feral pigs, widely considered invasive, were compared to native herbivores in tropical forests. The study notes that their rooting behavior can increase plant diversity and nutrient cycling in some contexts, effects that mirror those of native species with similar foraging traits. Their ecological role is complex and not uniformly negative.
The authors highlight the immense financial burden of global eradication efforts targeting non- native large herbivores. They cite that such programs have cost billions of dollars worldwide, often with limited ecological justification. For example, they reference that Australia alone has spent over AUD $50 million on feral horse management, and New Zealand has invested more than NZD $100 million in goat and deer eradication campaigns. These figures underscore the scale of investment driven by assumptions about nativeness rather than clear evidence of ecological harm.
The authors argue that these expenditures are frequently justified by the perceived non-native status of the animals, rather than by rigorous assessments of their functional roles in ecosystems. They caution that such campaigns can divert resources from more effective conservation strategies and may cause unnecessary suffering to animals that, in many cases, are ecologically integrated.
The authors call for honesty in wildlife management. If animals are being removed for economic or social reasons, those reasons should be stated openly—not disguised as ecological necessity. So how should wildlife management be reconciled with these findings? The authors propose a new framework that shifts the focus from origin to function.
Management should prioritize species’ ecological roles—how they feed, move, and interact with ecosystems—rather than their origin. This allows for more accurate predictions and more effective interventions. Conservation is not value-free. Decisions are shaped by cultural, economic, and ethical considerations. Recognizing this allows for more transparent and inclusive policymaking. Eradication campaigns should be scrutinized for their ethical implications. The welfare of individual animals matters and killing should not be the default response to perceived invasiveness. Ecosystems are dynamic. Species move, adapt, and evolve. Trying to freeze ecological baselines based on colonial-era definitions of nativeness is both unrealistic and ethically fraught.
Perhaps the most powerful message in the paper is this: nativeness is not a reliable guide for conservation. It is a historical label, often rooted in colonial timelines and arbitrary baselines. Using it to justify killing is scientifically weak and ethically questionable. As the authors write,
“Trait-based ecology provides better insight into interactions between megafauna and plants than do concepts of nativeness.” This is a call for conceptual reform. Conservation must move beyond purity-based thinking and embrace a more nuanced, evidence-based, and ethically grounded approach.
Lundgren et al.’s study is more than a scientific analysis—it’s a philosophical challenge to the field of conservation. It asks us to confront our biases, question our assumptions, and rethink our moral frameworks. The eradication of non-native wildlife should not be based on fear, aesthetics, or outdated notions of ecological purity. Instead, we must ask: what are the actual ecological impacts? What values are driving our decisions? Are we being honest about our motivations? Can we manage ecosystems with compassion and transparency?
By shifting the focus from nativeness to functional traits, and by acknowledging the human values embedded in wildlife management, we can build a more ethical, effective, and inclusive conservation practice.
This study examined how herbivores affect plant diversity. Non-native predators may create additional challenges for wildlife management. This research indicates that deer impact vegetation more through population density and feeding habits than origin. Managing wildlife density within the land’s carrying capacity is a practical and widely accepted way to conserve plant biodiversity. Hunting and utilizing both native and non-native wildlife as resources can benefit people, communities and the environment.
Reference:
Lundgren, E. J., Ramp, D., Carroll, S. P., Wallach, A. D., & Davis, M. (2023). Functional traits—not nativeness—shape the effects of large mammalian herbivores on plant communities. Science, 380(6643), 144–148. https://doi.org/10.1126/science.adh2616