Killing in conservation: Lethal control

Animals are often deliberately killed with the aim of conserving threatened species, habitats and ecosystems. It is usually assumed that the ends justify the means and that the costs to life are outweighed by the benefits. Although lethal control measures are common practice in conservation, the ethical issues involved are not often explicitly discussed. This is not to say that these decisions are not based on ethical values, they certainly are, but these decisions are frequently made using implied ethics rather than rigorously examining the ethical issues. This post aims to identify the ethical issues involved in justifying lethal control for conservation purposes. This post is not covering  lethal control for financial gain or other non-conservation motivations (e.g. badger culls or illegal killing of birds of prey by gamekeepers), killing wild animals for conservation research (this will be a future post) or solidly suggesting where lines should be drawn, only identifying the issues which should be considered in lethal control decisions in conservation.

Equal consideration of interests versus effective conservation

The essence of this decision is the balance between the interests of individuals of the “problem species” and the conservation benefit resulting from their removal. The interests of the problem species must be given full and equal consideration and are more straightforward to determine, assuming there is no question of a threat to their conservation. This is an important assumption; the decision is much more complex if there is a possibility that the problem species is also under threat of extinction or could become threatened as a result of control measures. However, as many problem species are detrimental to other species, habitats or ecosystems as a result of their abundance, this is usually a safe assumption. Another assumption is that the problem species is not necessary for the conservation of another species, habitat or ecosystem in the proposed control area. The interests of the problem species are balanced against conservation values – the continued survival of ecosystems and the prevention of biodiversity loss. The value of an ecosystem or habitat is not the same type of value given to the interests of individuals of the problem species and so they can be difficult to weigh against each other – comparing apples and oranges. Even when the conservation interest under threat is a sole species, it is not usually correct to simply compare the interests of individuals of the threatened species with those of individuals of the problem species as the threatened species presumably has an additional conservation value.

Lethal control is not the only option to deal with a conservation threat, many other methods exist, but limited resources for conservation frequently lead to the decision that lethal control is the most efficient and effective option. Once the decision has been made that action must be taken to protect a threatened species, habitat or ecosystem, these financial considerations come into the decision to use lethal control but are not the only factors; several other issues affect the decision on whether lethal control is the most ethical solution.

Factors affecting the weight given to the interests of problem species

Intelligence and awareness

The interests of individuals of problem species largely depend on their level of sentience. This is sometimes considered in generalised terms by considering taxa, but this does not fully represent the ethical issues as species within a taxon may have a wide range of sentience levels. The issues involved in determining the weight given to the interests of a problem species include self-awareness, intelligence, rationality and the ability to view itself as a being existing through time. This topic is discussed by Peter Singer in terms of the ethics of killing animals for any reason, in a chapter entitled “Taking life: Animals” in Practical Ethics (3^rd ed., 2011) and many of the discussions can be applied to lethal control. The key issue is whether or not an animal has an interest in continuing to live. If so, this interest must be considered. All animals have evolved defensive and protective responses to certain threats to their lives but this does not necessarily mean that they view themselves as beings existing through time which wish to continue living. However, studies of several species, including primates, pigs and birds, have found that some species do have the ability to understand themselves as beings which exist over time and so potentially have an interest in continuing to live which will be violated by lethal control. This does not necessarily mean that lethal control cannot be justified but this information affects the weight given to the interests of individuals of the problem species.

 

Native or non-native

Non-native species cause many threats to conservation as they often outcompete or predate native species which have not evolved in their presence and so are unprepared to cope with this sudden new pressure. However, it should be the problem caused rather than the non-native species status alone which contributes to justifying lethal control. But does the native or non-native status of the problem species affect the weight given to the interests of individuals of this species? That is, if a similar problem is caused by a native species and a non-native species, is there more justification for controlling the non-native species than the native species? This justification may take the form of an argument for conserving an ecosystem “as it should be”, as it would have been without this non-native species. Yet ecosystems have been modified to such a degree by humans (the source of the vast majority, if not all, species introductions) that removing a non-native problem species will not result in a return to this utopian, perfect ecosystem, weakening the argument for aiming for this “natural ecosystem”. Also, if a non-native species is beneficial to conservation, such as non-native sycamores in the UK providing good habitats for native birds and invertebrates, the non-native status of the species seems little justification for removing it. Perhaps aiming for new, sustainable ecosystems with the aim of maximising global biodiversity regardless of the geographic origin of species would be a better solution – though this will often, but not necessarily, mean the removal of non-native species. So although non-native species are often problematic, there appears to be little justification for using this status as a factor justifying lethal control – though it is frequently vaguely mentioned as a factor.

 

Source of problem

The previous section mentions that humans are the source of most, if not all, problematic species introductions. Humans are also the cause of many other problems in conservation which may lead to the possibility of using lethal control. Examples include hunting natural predators to extinction or low levels (e.g. unsustainable deer populations resulting from wolves being hunted to extinction in the UK) or destroying habitats such that species, habitats or ecosystems are now threatened with extinction due to factors which were previously not a problem (e.g. the impact of predation on breeding wading birds is now possibly unsustainably high after wader populations have been reduced following massive habitat loss). As humans are the source of these problems, it may be that we have an ethical obligation to resolve them which could reduce the weight given to the interests of individuals of the problem species. (In the case of humans causing the extinction of natural predators, it could be argued that lethal control of the now problematic prey species is justified as humans are theoretically taking the place of the predators. However, the effects of killing by humans are likely to be very different to the effects of killing by natural predators unless efforts are made to kill the individuals which would be most likely to be taken by natural predators, e.g. the slowest and weakest animals. When the species being controlled is also considered to be a game animal, for example deer in the UK and the “Big Five game” in Africa, the issues are also clouded by financial and political motivations.)

Factors affecting the weight given to the threatened conservation interest

Species, habitats and ecosystems can be considered to have a variable conservation value which is given a variable weight – with the product of these two factors to be compared with the considerations of the problem species discussed above. What determines the value of a species, habitat or ecosystem and what determines the weight given to this value? 

Certain elements concerning the value of a species, habitat or ecosystem are constant across all conservation interests. These include existence value - the idea that a species should be allowed to continue to exist and evolve without being destroyed by humans (discussed in my previous post) - and heritage value – that species, habitats and ecosystems should be conserved for future generations. These values are particularly subjective. In addition to these values, other elements concerning the value of a species can be variable and generally concern their ecology. One such element is the contribution of a species to ecosystem functioning (an ecosystem function is a useful process carried out by biota, such as nutrient cycling), e.g. a keystone species, vital for the maintenance of ecosystem functioning, may be assigned a greater value than a species considered redundant as it only contributes an ecosystem function also performed by many other species. Other elements adding variable values could include spiritual and aesthetic values and ecosystem services (ecosystem functions which benefit humans, such as crop pollination) – though while these are not strictly conservation values as they are for human benefit, they are factors which are considered.

Let us assume that biodiversity has a very high value and the extinction of any species is a great evil to be avoided. The next stage is considering how great a weight to assign this value. The level of extinction risk is the main factor influencing the weight given to these conservation interests when making a decision regarding lethal control – simply that the greater the risk of extinction, the greater the weight given to the conservation value of this species. When considering the conservation value and weight given to a habitat or ecosystem, the combined conservation values of and extinction risks posed by the loss of the habitat or ecosystem to multiple species can be used. The other important factor in assigning a weight to conservation value is the size of the expected benefit – if only a small advance against extinction risk is made then the weight given to the conservation interest is reduced and vice versa. (The level of certainty that lethal control will result in this benefit is discussed below.)

Factors affecting the decision to use lethal control

If it is decided that the benefit to conservation outweighs the interests of the problem species, what affects the decision to use lethal control over non-lethal methods? (Financial considerations are one factor, but the ethics of conservation funding is outwith the scope of this post.)

 

Imbalance between interests of problem species and conservation interest

If the degree of difference between the interests of the problem species and the conservation interest is very slight, then this difference does not seem to be enough to violate the interests of the problem species. How great does the difference need to be in order to justify lethal control? If these competing interests were quantifiable, perhaps if the conservation interest were at least double that of the interests of the problem species, and so the harm of violating the interests of the problem species was made up for by the benefit of the conservation interest, then lethal control could be ethically justified. But these values are not quantifiable and are interests with very different qualities and so are difficult to compare. This does not mean that it is impossible to consider the imbalance between interests when making decisions about lethal control; this is a very important factor to consider and this difficultly means that very careful thought must be put into the weights given to both the interests of individuals of the problems species and the conservation interest.

 

Effectiveness of control measures

The level of certainty about the benefit to the conservation interest as a result of control measures is another vital factor in decisions about lethal control. It is important that the proposed measures have been thoroughly researched (this may in fact involve a lethal control trial, the ethics of which will be discussed in a future post) and that the level of certainty (highly unlikely to be 100%) that the required benefit will occur as a result is taken into account in the decision.

Alternative measures

Lethal control is considered by some to be a last resort and by others as the go-to solution. Either way, full investigation and consideration of alternative measures are sometimes not carried out. Non-lethal control measures exist which can be highly effective, ineffective, cheap, costly, understudied and/or dependent on the conditions of individual sites. Non-lethal methods must be fully considered and if a similarly effective non-lethal method can be carried out then best efforts should be made to use this method, as to use lethal control in this case would be to violate the interests of individuals of the problem species without sufficient justification. (This is the point in the decision-making process when funding considerations may become particularly influential.)

Method of control

The method of lethal control is another factor to be considered when making a decision about the use of lethal control in conservation. The main considerations are the potential of the problem species to experience pain, suffering and anxiety. The level of development of the nervous system of the problem species is an important factor for control measures with the potential to cause pain and suffering, for example using a toxic chemical which slowly kills an animal may be more justifiable when used on an animal with a very basic nervous system and limited capacity to feel pain (e.g. bivalves such as oysters or mussels) compared with animals which have a more developed nervous system (e.g. vertebrates). The additional ability of “higher” animals to feel anxiety and fear, for example when captured, contained or handled before control takes place, is also a factor for similar reasons. Efforts must be made to reduce such suffering and if some suffering is still likely to occur then this must be taken into account when making the decision about using a method of lethal control.

Conclusions

Lethal control is widely used in conservation and in many cases may be ethically justifiable, though the ethical implications are sometimes implicitly rather than explicitly explored. This may be due in part to a lack of time and resources, interest in or understanding of the ethical issues involved or not considering lethal control to be an ethical problem. The key issue is addressing the difference between the interests of individuals of the problem species and the conservation interest of the threatened species, habitat or ecosystem, followed by a decision on whether the difference between the costs and benefits justifies the use of lethal control. It is important to consider these issues to ensure that conservation is carried out in the most effective and ethical way.