Dehydration Rate and a Novel Model to Aid Search and Relief for Undocumented Border Crossers in the Sonoran Desert

Abstract

There has been a proliferation of geographic literature exploring the fatal effects of immigration policy since the early 2000s. Studies have used geographic information systems (GIS) and predictive modeling to explore potential relationships between border protection infrastructure, environment, and migrant death. Although some studies have used GIS to determine the probable effects of heat stress, none have included the potential perspiration as a limiting factor to pedestrian travel in an arid environment during daylight hours. Heat exposure is the leading cause of mortality for migrants in the desert regions of the U.S.–Mexico border, and humans rely on water to regulate temperature. For a more systematic methodology and higher precision, we calculated the maximum distances a person could walk in Arizona’s Sonoran Desert accounting for sweat rate. The locations of recovered human remains (RHR) correlate with water usage and increased difficulty of pedestrian travel. Further, our results showed at higher precision a significant correlation of mortality and spatial rates of dehydration and demonstrate that sweat rate is a better predictor of RHR location than heat or slope alone and will be more informative for search and relief operations in the region.

21世纪初以来, 移民政策的致命影响的地理学研究激增。这些研究利用地理信息系统（GIS）和预测模型, 探讨边境保护设施、环境和移民死亡之间的潜在关系。虽然这些研究利用GIS确定了高温的可能影响, 但没有把潜在排汗作为日间干旱环境中的出行限制因素。高温暴露是美墨边境沙漠地带移民死亡的主要原因。人类依靠水来调节温度。为了研究更系统的方法、获取更高的精度, 我们计算了个人在亚利桑那州索诺兰沙漠的最大行走距离和排汗率。人类遗骸回收站（RHR）的位置, 与用水量和出行难度有关。此外, 本文以更高的精度, 显示了死亡率和脱水空间率之间的显著相关性, 证明了排汗率比高温或坡度能更好地预测RHR位置、为该地区的搜救行动提供更多信息。

Desde comienzos de los años 2000 se ha presentado una proliferación de literatura geográfica dedicada a explorar los efectos fatales de la inmigración. Los estudios dedicados a explorar las posibles relaciones entre la infraestructura, el medio ambiente y la muerte de inmigrantes han usado sistemas de información geográfica (SIG) y modelos predictivos. Aunque algunos estudios han usado los SIG para determinar los efectos probables del estrés térmico, ninguno ha incluido la transpiración potencial como factor limitante del viaje peatonal en un ambiente árido durante las horas de luz. La exposición al calor es la principal causa de mortalidad de los migrantes en las regiones desérticas de la frontera Estados Unidos–México, y los seres humanos dependen del agua para regular la temperatura. Para lograr una metodología más sistemática y mayor grado de precisión, calculamos las distancias máximas que una persona podría caminar en el Desierto de Sonora, Arizona, teniendo en cuenta la tasa de sudoración. Las locaciones de hallazgos de restos humanos recuperados (RHR) se correlacionan con el uso del agua y con la mayor dificultad de desplazamiento del peatón. Aún más, a un mejor nivel de precisión, nuestros resultados mostraron una correlación significativa de la mortalidad y las tasas espaciales de deshidratación, y demuestran que la tasa de sudoración es un mejor predictor de la localización de los RHR que el calor, o solo la pendiente, y serán más informativos para las operaciones de búsqueda y ayuda en la región.

Key Words:

• human physiology
• humanitarianism
• immigration
• public health
• spatial analysis

关键词:

• 人体生理学
• 人道主义
• 移民
• 公共卫生
• 空间分析

Palabras clave:

• análisis espacial
• fisiología humana
• humanitarismo
• inmigración
• salud pública

Notes

1 Tobler’s hiking function is appropriate here because it is an exponential function that determines hiking speed while accounting for slope (Figure 4B). We chose Tobler’s function instead of other similar models because it is not only anisotropic (Márquez-Pérez, Vallejo-Villalta, and Álvarez-Francoso 2017) but functions best in predictions for when persons are carrying weight in noncompetitive travel in which navigation by landmarks is required rather than strictly marked trails (Kay 2012; White and Barber 2012; Campbell et al. 2019). It has been tested in this case for time between water sources for pedestrian travel in which physiological capacity was a factor, past (Crabtree et al. 2021) and present (Paez et al. 2020). In addition, the values are consistent with the median walking speeds by age and sex of our study group (Schimpl et al. 2011) and the walking speeds of border crossers in the similar terrain of southern California (Anguelova et al. 2010).

Additional information

Notes on contributors

Samuel N. Chambers

SAMUEL N. CHAMBERS is a scientist in the Department of Epidemiology and Biostatistics, The University of Arizona Zuckerman College of Public Health, Tucson, AZ 85724. E-mail: [email protected]. His research interests include the spatiotemporal patterns of border crosser mortality, the impacts of border surveillance, and the application of human physiology to spatial modeling.

Molly Miranker

MOLLY MIRANKER is a Doctoral Candidate in the Department of Geography and Environmental Studies, Texas State University, San Marcos, TX 78666. E-mail: [email protected]. Her research interests are at the intersection of geography, biological anthropology, and GIScience in both forensic and humanitarian contexts.