Measuring Deterrence: Ranger Patrols Reduce Poaching in Uganda

ABSTRACT

Rangers serve as a primary defense for wildlife conservation, patrolling 21.7 million km2 of protected areas globally to protect wildlife from poaching and other threats. The high cost of patrols is justified by the assumption that rangers deter poachers from returning in the future. While anecdotal knowledge and correlational studies support patrol-induced deterrence, there is currently no causal evidence of deterrence nor a quantification of the magnitude of its effects. Causal inference is especially difficult in this setting because poaching events are only partially observable, and the likelihood of observing poaching depends on patrol effort, thus entangling the treatment and outcome variables.

Using 7 years of ranger patrol data from Murchison Falls Conservation Area in Uganda, we present the first causal evidence of ranger-patrol deterrence. To enable this causal analysis, we leverage a past field evaluation of a machine learning tool for predicting poaching as a source of quasi-experimental variation, used machine learning to produce temporally and spatially granular estimates of site characteristics for matching, and designed a Bayesian inference model to impute true poaching outcomes, which were partially unobserved. We found that increasing patrol effort by 1 kilometer in a 1 km2 area reduced poaching probability in the next month by 45.0%

BIO

Lily Xu is Sun-Wu Assistant Professor of Industrial Engineering and Operations Research at Columbia University. Her research develops AI methods across machine learning, optimization, and causal inference for planetary health challenges, with a focus on biodiversity conservation. Her work provides novel algorithms to enable practitioners to make effective decisions in the face of limited data, taking actions that are robust to uncertainty, effective at scale, and future-looking. Lily holds a PhD in computer science from Harvard University and was a postdoctoral research fellow at the University of Oxford with the Leverhulme Centre for Nature Recovery.