Research interests

As an academic, my role is to understand and explain the complexity of the world. More specifically, my research interests focus on the conservation of threatened species and biodiversity. I conduct research to understand and explain why species disappear. However, because conservation is also a normative scholarly discipline – whereby the destruction of nature is a moral wrong, I also expect that my work somewhat contributes to nature conservation. As such, I view my role as being also one of a public intellectual engaging into contemporary political debates relevant to nature conservation. In that context, I have three separate and articulated research topics: the conservation of large carnivores, legal conservation and population modelling.

Conservation of large carnivores

Most large carnivores are globally experiencing a dramatic decline in their populations and ranges but although some species are recovering in Europe (e.g. all mainland European countries now have wolf presence) and some parts of the USA. Securing these contemporary recoveries while halting and preventing further declines is one of the most difficult global conservation challenges. Conserving large carnivores is unique compared to other species because large carnivores 

display particular ecological characteristics such as low densities, large spatial requirements or limited reproductive potential. Last and certainly not least, the conservation of large carnivores can be contentious and politically conflictive as it often implies an adjustment of human activities. The conservation of large carnivores may indeed be a preview of what nature conservation and more broadly sustainability will imply in our increasingly crowded world.

From persecution to coexistence

After a long history of persecution, large carnivores became restricted to remote wilderness and protected areas with few human activities. As a consequence, they have now become emblematic of such areas and large carnivores are nowadays considered as species of wilderness value. However, evidence points out that large carnivores are not wilderness dependent and that a coexistence approach to their conservation can be successful.
We have defined coexistence as the continuing persistence of self-sustaining large carnivore populations in landscapes with a high human activity. Our research has shown that a coexistence approach can be very successful: Europe hosts twice as many wolves (>11,000) as the contiguous United States (~5500 wolves), despite being half the size (4.3 million km2 versus 8 million km2) and more than twice as densely populated (97 inhabitants/km2 versus 40 inhabitants/km2).

Figure: Conceptual model of large carnivore population trajectories. The history of large carnivores shows massive decline due to persecution and deliberate eradication policies that goes back to the earliest expansion of livestock farming. Only during the past five decades have human societies shifted from persecuting large carnivores toward preserving and restoring them. The enactment of conservation measures and political commitment has prevented the extinction of many populations from the 1970s onward. But the recovery of large carnivores may be limited by a land-sparing paradigm (separation). Adopting a land-sharing view (sharing) allows for larger, viable and possibly functional populations.

López-Bao, J.V., Bruskotter, J. & Chapron, G. (2017). Finding space for large carnivores. Nature Ecology and Evolution 1(5): 0140.

Developing a theory of coexistence

We can theorize the conservation of endangered species as securing the maintenance of a community of species with one of them being hyper-predatory humans. The resource these species mainly compete for is space.
Ecologists have shown that communities of competing species will converge to single species communities when one species displays strong competitive abilities and has a limited niche differentiation with others. In contrast, species can coexist when they show moderate competitive abilities and large niche differentiation.
The question of how to conserve species in the Anthropocene therefore requires understanding how a hyper-predator –humans– may avoid displacing other competing species by deliberately developing i) a higher niche differentiation and ii) a lesser competitive ability.

Figure: Conceptual framework and theoretical examples on how coexistence between large carnivores and people emerges from differences in competitive abilities and ecological niches.
A) Extinction: unregulated killing increases human competitive abilities and inadequate human practices maintain strong niche overlap. 
B) Weak conservation: lack of effective protection maintains high human competitive abilities, but protected areas increase niche differentiation. 
C) Weak conservation: high tolerance to predators reduces human competitive abilities but inadequate human practices maintain strong niche overlap.
D) Strong conservation: environmental rule of law reduces human competitive abilities and protected areas increase niche differentiation.

Chapron, G. & López-Bao, J.V. (2016). Coexistence with Large Carnivores Informed by Community Ecology. Trends in Ecology and Evolution 31(8): 578-580.

Predator recovery in Europe

We report a conservation success for an unexpected taxa in an unexpected region of the world: Europe's large carnivores are making a comeback. Using an exhaustive data set on the past and current status of brown bears, Eurasian lynx, gray wolves, and wolverines in European countries, we show that roughly one-third of mainland Europe hosts at least one large carnivore species, with stable or increasing abundance in most cases in 21st-century records. The reasons for this overall conservation success include protective legislation, supportive public opinion, and a variety of practices making coexistence between large carnivores and people possible.

Chapron et al. (2014). Recovery of large carnivores in Europe’s modern human-dominated landscapes. Science 346(6216): 1517-1519.

Download the paper shape files of current and historical distribution maps of large carnivore species in Europe from

Decline of African lions

Is the lion still the flagship species of the once vast natural ecosystems across the African continent? We answer this question by compiling all credible repeated lion surveys and present time series data for 47 lion populations and analysed them with population models We found a striking geographical pattern: African lion populations are declining everywhere, except in four southern countries (Botswana, Namibia, South Africa, and Zimbabwe). Population models indicate a 67% chance that lions in West and Central Africa decline by one-half, while estimating a 37% chance that lions in East Africa also decline by one-half over two decades. Our findings support listing lions in the IUCN Red List as regionally endangered in Central and East Africa and least concern in southern Africa.

Bauer et al. (2015). Lion (Panthera leo) populations are declining rapidly across Africa, except in intensively managed areas. Proceedings of the National Academy of Sciences of the United States of America 112(48): 14894-14899.

Understanding illegal killing

People and large carnivores are parts of social–ecological systems (SESs), in which human and biophysical subsystems mutually influence one another. Illegal killing of carnivores is an especially challenging issue for SESs because in many contexts there are strong incentives to hide illegal killing and thus its social–ecological causes and consequences are not completely understood. We propose a SES framework that reveals key linkages among people, carnivores, and the broader contexts in which they live. Our framework underscores how conservation interventions are more likely to be effective when both proximal and distal social–ecological causes and consequences of human–wildlife interactions are accounted for.

Carter et al. (2017). A conceptual framework for understanding illegal killing of large carnivores. Ambio 46(3): 251-264.

Towards evidence-based conservation

Carnivore predation on livestock often leads people to retaliate and persecution by humans has contributed strongly to global endangerment of carnivores. It is likely that preventing livestock losses would help to achieve three goals common to many human societies: preserve nature, protect animal welfare, and safeguard human livelihoods. Between 2016 and 2018, four independent reviews (including ours) evaluated >40 years of research on lethal and nonlethal interventions for reducing predation on livestock. When pooling these 114 studies reviewed, we found a striking conclusion: scarce quantitative comparisons of interventions and scarce comparisons against experimental controls preclude strong inference about the effectiveness of methods.
Immense resources are spent globally each year to protect livestock from carnivores, but too often without science-based evidence that the methods work. Evidence of the effectiveness of a deterrent should be a mandatory prerequisite to large-scale funding, policy-making and implementation. An appropriate evidence base is needed, and we recommend a coalition of scientists and managers be formed to establish and encourage use of consistent standards in future experimental evaluations.

Figure: Percent of studies that measured interventions as “Effective,” “Ineffective,” or “Counter-productive” in reducing livestock loss to large carnivores, as measured by four independent reviews in 2016–2018. The sample sizes inside disks represent the number of studies or tests, as some studies reported more than one test of the same or different interventions. Darker colors represent reviews that included experimental or quasiexperimental controls; lighter colors represent reviews that also included comparative or correlative studies. “Deterrents” include nonlethal interventions such as audio or visual deterrents, fladry, and livestock protection collars. “Enclosure/barrier” includes electrified and nonelectrified fencing and corralling. “Guarding” includes human shepherding and livestock guardian animals. “Lethal removal” includes hunting, poison baiting, and other lethal methods. “Non-lethal removal” refers to translocation of carnivores. “Other” includes carnivore sterilization and diversionary feeding.

van Eeden, L.M., Eklund, A., Miller, J.R.B., López-Bao, J.V., Chapron, G., Cejtin, M.R., Crowther, M.S., Dickman, C.R., Frank, J., Krofel, M., Macdonald, D.W., McManus, J., Meyer, T.K., Middleton, A.D., Newsome, T.M., Ripple, W.J., Ritchie, E.G., Schmitz, O.J., Stoner, K.J., Tourani, M. & Treves, A. (2018). Carnivore conservation needs evidence-based livestock protection. PLOS Biology 16(9): e2005577.

Just over three decades ago, the scientific community created a new discipline – conservation biology – to address the loss of biodiversity. That discipline has since succeeded in delivering answers to many ecological questions to stop the loss of biodiversity. However, I believe today that further contributions from this discipline alone may somewhat be limited, with additional ecological knowledge likely to bring only marginal gains for conserving biodiversity. More substantial gains can certainly be gained through interdisciplinary research. One discipline with an untapped potential is law. However, conservation scholars appear in general to be ignorant of nature protection laws. This absence of a legal perspective in conservation is a critical omission because ecology alone is unlikely to halt species extinctions.

Indeed, the science of conservation biology could end today, biodiversity would likely not notice. However, it is not unreasonable to believe that if nature protection laws would expire today, biodiversity would immediately notice –and collapse. By grounding law in ecological knowledge and more systematically using law to steer conservation policies, the impact of legal instruments for biodiversity conservation may be strengthened and leveraged. Considering the unprecendeted scale of the biodiversity crisis, the time has come to break walls between these two disciplines – scientifically distinct but nevertheless interacting on a daily basis– and to develop legal conservation scholarship.

The role of law in species conservation

Legislation functions to designate and protect sites, ensure strict protection of vulnerable species and populations from a range of threats, and regulate the sustainable use of more robust populations. Following the rise of environmental movements in the 1970s, environmental laws are credited today with numerous successes. For biodiversity conservation in Europe, the Directive 2009/147/EC on the conservation of wild birds and the Directive 92/43/EEC on the conservation of natural habitats and of wild fauna and flora have had a positive impact on species conservation status. In the USA, the Endangered Species Act (ESA) of 1973 is similarly credited with having been instrumental in the recovery process of many listed species.

My research, in collaboration with lawyers and other ecologists, aims to better quantify the conservation effectiveness of laws and understand how it can be improved. We will use diverse approaches such as jurimetrics, the logocratic method and legal AI. Our website Claws & Laws gives a detailed presentation of what our interdisciplinary research initiative has achieved.

Favorable Conservation Status

One of the most important concept used in the EU Habitats Directive is the one of favorable conservation status (FCS). There are however many contested aspects when interpreting FCS that have not yet been conclusively settled. In a paper published in Conservation Letters, we have provided legal-ecological clarifications of the most contested aspects: at what level should FCS be measured, what it means for a species to be a “viable component of its natural habitat”, what is a “long‐term basis”, what does it mean for a species to “maintain itself”, whether FCS should be measured from extinction or carrying capacity and whether FCS requires that a population approaches historical levels. Our paper was featured in the European Commission newsletter Science for Environment Policy.

Epstein, Y., López-Bao, J.V. & Chapron, G. (2016). A Legal-Ecological Understanding of Favorable Conservation Status for Species in Europe. Conservation Letters 9(2): 81-88.

Derogations to strict protection

Whether or under what circumstances the hunting of species listed as strictly protected in the Habitats Directive's Annex IV can be allowed has been the subject of extensive controversy and litigation in several EU Member States. In fall 2017, Finland has asked the Court of Justice of the European Union for a preliminary ruling on several related questions, which we have addressed in a paper published in European Energy and Environmental Law Review. Specifically, we focus on the permissibility of the management hunting of strictly protected species, the permissibility of allowing hunting with the goal of preventing poaching, and at what scale the ``favourable conservation status'' of species populations should be considered.

Epstein, Y. & Chapron, G. (2018). The Hunting of Strictly Protected Species: The Tapiola Case and the Limits of Derogation under Article 16 of the Habitats Directive. European Energy and Environmental Law Review 27(3): 78-87.

Obligations to reintroduce

The obligations of Member States when a population of species protected in the Habitats Directive has almost gone extinct also remain unclear. In a paper published in Biological Conservation, we use the case of the quasi-extinct wolf population in the Sierra Morena region in Spain to provide legal-ecological clarifications on the obligations by Member States. We show that Articles 6 and 12 of the Directive require Member States to restore populations, and the complete extinction of the species does not exonerate Member States from their obligations regarding the conservation of the species in Natura 2000 sites.

López-Bao, J.V., Fleurke, F., Chapron, G. & Trouwborst, A. (2018). Legal obligations regarding populations on the verge of extinction in Europe: Conservation, Restoration, Recolonization, Reintroduction. Biological Conservation 227: 319-325.

When is hunting legal?

The European Union (EU) bans the killing of strictly protected animals through the Habitats Directive. This law allows exceptions in special circumstances when doing so would not be detrimental to the conservation status of species' populations. Some decisions to kill animals have triggered litigation regarding how broadly the provision on exceptions can be interpreted.  In Conservation Science and Practice, we review several contested aspects of the law to conclude that it would be very difficult for countries within the EU to allow hunting of strictly protected animals because of the restrictive interpretations supported by prior decisions of the EU Court of Justice and other sources of law.

Epstein, Y, Christiernsson, A, López-Bao, J.-V. & Chapron, G. (2019). When is it legal to hunt strictly protected species in the European Union? Conservation Science and Practice 1:e18.

Nature rights against human wrongs

Our research explores whether and how recognizing rights of nature may effectively contribute to nature conservation. Specifically, we map some of the questions important to rights of nature in various legal systems in a legal-ecological perspective. These questions include what natural entities can have rights, what those rights can be, how these rights can be enforced, and how nature rights will be weighed against human and corporate rights. Triggered by the aggravation of the planetary crisis, a movement that proposes a radically different approach to build a sustainable future for humans and nature is emerging. That movement revisits the premises of our legal system by postulating that nature —or certain aspects of nature— is a moral and legal person and deserves its own rights. The rationale is that by treating the issue of nature destruction as matters for policy debate rather than as an infringement of rights, existing environmental laws may be hindered from achieving their goal. By framing the protection of the natural world as a rights issue, nature conservation may become more effective.

Drawing of a palila (Loxioides bailleui), a critically endangered finch-billed species of Hawaiian honeycreeper. In Palila v. Hawaii Dept. of Land & Natural Resources, Judge O’Scannlain wrote, “As an endangered species under the Endangered Species Act . . . the bird . . . has legal status and wings its way into federal court as a plaintiff in its own right.” 852 F.2d 1106, 1107 (9th Cir. 1988).

Chapron, G., Epstein, Y. & López-Bao, J.V. (2019). A rights revolution for nature. Science 10.1126/science.aav5601.

Population modelling

What are population models? When one thinks that smaller or declining populations have a higher risk of disappearing, one has started to become a modeller. Models are simplified description of the world. Conceptually linking population size with extinction risk is a qualitative model. In ecological sciences, we use more quantitative models where, for example, we would describe the dynamic of a population with equations to be able to give estimates of extinction risk. My research uses a diversity of modelling approaches for conservation populations of endangered wildlife.

Individual-based models

Individual-based models (IBM) are a class of population models where individuals are explicitly described as the functional unit of the model (this is in contrast to e.g. Leslie matrix models where all individuals within a class are assumed to be identical). Additional units such as social groups (packs or prides) can also be added. In an IBM, the population trend is the emerging population level consequence of individual events and is not predefined by equations as in more traditional population models. Such models therefore require a rule-based formalisation of life history and allow to incorporate more explicit biological realities as it is possible to include genetic aspects or spatial dimension (with model outputs being abundance maps).

Figure: Screenshot of Xcode (the integrated development environment for macOS) of a wolf individual-based model written in C. The code shows the functions and structures (i.e. individuals and packs) of the model. Structures are organized into double-linked lists for computational speed. This model is available in my R package ‘pop.wolf’ which allows one to run demographic simulation of a wolf population within R.

Chapron et al. (2016). Estimating wolf (Canis lupus) population size from number of packs and an individual based model. Ecological Modelling 339: 33-44.

Hierarchical models

Another kind of models are Bayesian hierarchical state-space models. As their names tell, they are on Bayesian statistics where everything, data, model, hypotheses and parameters is a probability. Such models allow the mechanistic investigation of ecological processes by combining multiple sources of data in a statistically coherent way. This is very useful to estimate unobserved quantities (such as poaching) and to quantify both process and data uncertainties (such as error in population estimates).

Liberg et al. (2012). Shoot, shovel and shut up: Cryptic poaching slows restoration of a large carnivore in Europe. Proceedings of the Royal Society B: Biological Sciences 279(1730): 910-915.

Hobbs et al. (2012). Native predators reduce harvest of reindeer by Sámi pastoralists. Ecological Applications 22(5): 1640-1654.

Markov Decision Processes

Numerous challenges in conservation involve making decisions about the best choice among a set of competing actions. For example, if you could buy every year some areas each hosting threatened species and convert them into reserves, which areas would you buy considering that you cannot buy all areas at once and areas you did not buy a year will be developed the next year? Finding the sequences of actions to maximise your outcome (the utility function) requires solving a Markov Decision Process (MDP). Our R package ‘MDPtoolbox’ proposes functions related to the resolution of discrete-time MDPs: finite horizon, value iteration, policy iteration, linear programming algorithms with some variants and also proposes some functions related to artificial intelligence (Reinforcement Learning).

Chadès et al. (2014). MDPtoolbox: A multi-platform toolbox to solve stochastic dynamic programming problems. Ecography 37(9): 916-920.

Approximate Bayesian Computation

Model-based inference generally relies on estimating the likelihood function, which is the probability of data given a model and parameters. For example hierarchical state-space models typically require writing the likelihood. However, for complex models (such as IBM), the likelihood function is unknown and cannot be written and Monte Carlo Markov Chain based methods cannot be used. Enters Approximate Bayesian Computation (ABC), a class of computational Bayesian methods that bypasses the direct evaluation of the likelihood function by approximating it and allowing IBM to be fitted to data.

Chapron et al. (2016). Estimating wolf (Canis lupus) population size from number of packs and an individual based model. Ecological Modelling 339: 33-44.

Quantifying extinction risk

When quantifying extinction risk, models – or their use – are often termed a Population Viability Analysis (PVA). A variable of interest returned by these models is extinction risk. There are different methods to estimate this risk, but the most widespread one is to run Monte Carlo simulations. These simulations are repeated stochastic (i.e. random) trajectories where the model starts each trajectory from the same initial conditions and parameters. Extinction is simply the ratio of extinct trajectories divided by the total number of run trajectories. My R package ‘population’ provides population simulations using an Individual-Based Model compiled in C.

Assessment of extinction risk can also be obtained from probability density of the population growth rate. If the distribution contains a substantial area smaller than 1 (i.e. stable growth rate), this indicate a non-negligible extinction risk.

Figure: The density distributions of population growth rates shown here are for populations of African lions and were obtained by fitting hierarchical models to time series. The gray areas under the curves indicate the probabilities of decline with numerical values shown being medians ± SDs of growth rate estimates.

Bauer et al. (2015). Lion (Panthera leo) populations are declining rapidly across Africa, except in intensively managed areas. Proceedings of the National Academy of Sciences of the United States of America 112(48): 14894-14899.

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