The moral debate surrounding the lethal control of invasive alien species

Historically, humans have been translocating animal and plant species from one region to the planet to another, from seeds and exotic birds from the new world to rice and spices from Asian regions. Some of these translocations are well documented, like the introduction of rabbits (Oryctolagus cuniculus) from the Iberian Peninsula into the rest of Europe by the Romans during the second Punic wars (201-219 B.C), or the deliberate introduction of pigs (Sus scrofa domesticus) into Mauritius island in 1606 (Hume, 2006). Humans have globalized the movement of biodiversity and, with this globalization, we have introduced drastic changes in the composition of communities and ecosystems (Figure 1). The introduction of “new” species in areas outside their natural range can cause massive damage to the native flora and fauna (Spatz et al., 2017). When a species, with the assistance of humans, “invades” a new area and creates problems to the native biodiversity, or the ecosystem, we call it an invasive alien species.

Figure 1. This 1601, Johann Theodor de Bry, copper engraving shows the new Dutch settlers’ activities during the early exploration of Mauritius island, 1598, during the voyage of Admiral Jacob van Neck. The first depiction of a Dodo (2) can be seen in the background, along with drawings of giant tortoises (1). The arrival of humans to this island meant a great impact for the native and naïve fauna that was easily hunted and largely appreciated by sailors. Along with humans, other species were, deliberately and accidentally, introduced into Mauritius, spreading rapidly and causing negative impacts to the native biota. The Dodo would become extinct soon after, presumably due to the combined effects of black rats and wild pigs (Hume 2006).

Methods to prevent the spread of invasive species include lethal control techniques such as hunting with firearms, live-trapping and posterior euthanizing or poisoning (B. Phillips et al., 2005; CAMPBELL & DONLAN, 2005). The increase of public awareness around animal rights and the resurge of ecologist and pro-animal life movements have reopened the debate surrounding the use of such techniques for the control and eradication of invasive alien species. In some cases, creating a division between scientist, politicians, public and stakeholders.

What are alien invasive species?

The International Union for Conservation of Nature (IUCN) describes invasive species as “animals, plants or other organism introduced by man into places out of their natural range of distribution, where they become established and disperse, generating a negative impact on the local ecosystem and species” (Luque et al., 2014). Not all the exotic species can be classified as invasive though: to be considered as such, those species must be able to establish into the new habitat, disperse and cause disruption to the native species or the ecosystem. Therefore, not all exotic species are invasive, but all invasive species are exotic.

Alien invasive species are one of the most frequent threats to biodiversity across the globe, with more than 4.500 species classified under the IUCN endangered categories being currently threatened by invasive species (Figure 2) (IUCN, 2020). Amongst these species, we can find microorganisms such as Plasmodium relictum (that causes avian malaria), insects like the crazy ant (Anoplolepis gracilipes), mammal species like black-rats (Rattus rattus), goats (Capra hircus), ornamental plants like the Jamaica mountain sage (Lantana camara) and even fungi species such as the frog chytrid fungus (Batrachochytrium dendrobatidis).  In some cases, a single species in the wrong place can cause the extinction of several species, as in the case of the brown tree snake (Boiga irregularis). This snake, native of Australia, Papua New Guinea and the Solomon Islands, was introduced into Guam island sometime between the late 1940s and early 1970s. The lack of natural predators and the inexperience of the native fauna allowed this species to exterminate almost all of Guam’s native forest bird species (Bates, Mächler, Bolker, & Walker, 2015).

Figure 2. The IUCN Red List of Threatened Species is a critical indicator of the health of the world´s biodiversity. More than 100.000 species have been evaluated and classified into seven main categories that reflect the risk of extinction of these species. Over 27% of species classified into any of the three threat categories (CR, Critically Endangered; EN, Endangered and; VU, Vulnerable). Between the 10 more frequent threats for these species, we find the introduction of invasive species (code 8.1) with more than 25% of the Critically endangered species being affected, 15.53 % and 11,54% of Endangered and Vulnerable species impacted by this threat.

Lethal control: visions and conflicts

Lethal control of invasive species is a widespread method of population management and eradication (Martin & Richardson, 2019; Russell et al., 2016). Many successful conservation projects that include habitat restoration and invasive alien species control rely on lethal control methods for conservation. From a practical point of view, these methods are fast, cheap and, if they are applied adequately, permanent. Most successful lethal control campaigns have taken place on islands and have proven essential for the recovery of native biodiversity (B. Phillips et al., 2005; Campbell & Donlan, 2005; Jones, 2010). Recently, South Georgia Island eradication project, the largest project of this type to date, has been declared successful. Rats and mice have been completely eradicated from South Georgia Island, where these species were threatening and preventing the settlement of native seabird populations (Martin & Richardson, 2019).

From a conservation point of view, the need to apply these methods is a failure by itself. The first principle for the control of invasive species is to prevent the human translocation of species out of their natural ranges. Prevention is the most important factor to control invasive species (IUCN, 2000). The introduction of these species is a human mistake driven by ignorance or lack of control, in some cases, and by irresponsibility, in many others. By the time the situation reaches the point at which we need to take drastic actions, we have already failed. Many conservations scientists state that this failure is accompanied by the moral commitment to taking action and solve these human-driven environmental problems (Russell et al., 2016), even if the solutions involve culling or lethal control of invasive animal/plant species.

From a sociological point of view, things get more complex. Morally, all species have the right to exist, native or non-native, and it is not up to humans to decide which species are worth preserving. Therefore, the lethal control of non-native species collides with this principle. Some social sectors, such as animal rights activists and many ecologist movements, follow this principle and state that, since the introduction of these species is a human mistake, we must make the effort to find humane solutions to its environmental consequences (Wallach, Bekoff, Nelson, & Ramp, 2015). In other words, that it is the moral obligation of scientist and conservationist to resolve the problem in a way that native and non-native species rights are respected. In many occasions, these moral grounds are also reinforced by cultural factors such as human interaction with the non-native species, aesthetic values of the invasive species (e.g. ornamental plants), or commercial value.

With these different points of view, it is normal that conflict arises between conservation scientists and certain social movements. In some occasions, these differences have caused delays in the application of conservation projects, social rejection towards scientists and conservationists, and even long-term failure of conservation initiatives altogether. In 2016, a feral goat eradication project in Gran Canaria (Canary Islands), had to be interrupted due to the sabotage and heavy media campaign of animal rights activists and hunting associations. As a result, the local government withdrew from the eradication project in favour of non-lethal strategies, of more difficult application in the challenging landscapes of the island. Similar disputes have arisen in the United Kingdom relative to the eradication and control of parakeet (Myiopsitta monachus) populations (Crowley, Hinchliffe, & McDonald, 2019), in Italy with attempts to eradicate grey squirrel (Scirus carolinensis) populations (Genovesi & Bertolino, 2001) and in Scotland with hedgehogs (Erinaceous europaeus) eradication attempts from some islands (Crowley, Hinchliffe, & McDonald, 2017). This type of conflicts can lead to fierce opposition to the lethal control of non-native species as well as an increase in the distrust on scientist and administration from the general public.

These incidents are a symptom of the lack of attention that scientists have given to the social relevance of invasive species and their management (Crowley et al., 2017, 2019). A better understanding of the public’s perceptions of invasive species, their impacts on the native ecosystems and the available management options to face these problems are needed. The construction of values towards native species, against non-native invasive species, implies greater efforts in outreach and public engagement (Schüttler, Rozzi, & Jax, 2011). The cultural links or human perception towards emblematic non-native species cannot work as a justification for not acting when native species or ecosystems are threatened (Russell et al., 2016). At the same time, scientists need to consider public perceptions and opinion on the management of alien species (Sharp, Larson, & Green, 2011). After all, social support is fundamental for biodiversity conservation.

Killing for conservation has monopolized management of invasive non-native species. With the increase of public awareness, social media and the overall higher visibility of conservation projects, more ethic and socially approved methods are needed. It is therefore important that management planning includes spaces and opportunities for open, inclusive exploration of the possibilities and limitations of different management alternatives, including their variable social, legal, financial, and technical feasibility. Previous experiences have demonstrated that misinformation, lack of transparency or communication between conservationists, managers and social agents can severely damage the trust and support of the society to conservation projects.

As conservation scientists, we must make the effort to communicate, as equals, with the communities that are going to be affected by our decisions. Without the trust and support of local stakeholders, social structures and the general public, conservation is simply not possible.


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