Climate impact or policy choice? The spatiotemporality of thermoregulation and border crosser mortality in southern Arizona

US public officials frequently argue that high temperatures are responsible for increasing mortality of undocumented border crossers (UBCs) in southern Arizona. In this article, we suggest that these kinds of assertions are not only empirically misleading, they also serve to naturalise UBC deaths in the region by helping to obscure their structural causes. Indeed, although heat exposure is a primary cause of death in the region, prior studies have also shown that migration patterns have shifted toward more remote and rugged terrain, characterised by higher elevations and greater shade cover. Using physiological modelling and a spatiotemporal forensic analysis, we assess whether the distribution of recovered human remains has shifted toward locations characterised by environments where the human body is more or less capable of regulating core temperature, and thus succumbing to heat stress. We find that the distribution of recovered UBC remains has consistently trended toward locations where the potential for heat stress is lower, rather than higher. This demonstrates that UBC mortality is not principally a function of ambient or regional temperature, but rather is a result of specific policy decisions that lead to cumulative stress and prolonged exposure due to factors like difficulty and distance of travel. To contextualise these findings, we discuss the evolution of the US Border Patrol's policy of Prevention Through Deterrence, and apply the concepts of structural and cultural violence to theorize its consistently deadly outcomes.