RESUMEN
Biodiversity is declining worldwide. Because species interact with one another and with their environment, losses of particular organisms alter the function of ecosystems. Our understanding of the global rates and specific causes of functional decline remains limited, however. Species losses also reduce the cumulative amount of extant evolutionary history ("phylogenetic diversity" [PD]) in communities-our biodiversity heritage. Here we provide a global assessment of how each known anthropogenic threat is driving declines in functional diversity (FD) and PD, using terrestrial mammals as a case study. We find that habitat loss and harvest (e.g., legal hunting, poaching, snaring) are by far the biggest drivers of ongoing FD and PD loss. Declines in FD in high-biodiversity countries, particularly in Southeast Asia and South America, are greater than would be expected if species losses were random with respect to ecological function. Among functional guilds, herbivores are disproportionately likely to be declining from harvest, with important implications for plant communities and nutrient cycling. Frugivores are particularly likely to be declining from both harvest and habitat loss, with potential ramifications for seed dispersal and even forest carbon storage. Globally, phylogenetically unique species do not have an elevated risk of decline, but in areas such as Australia and parts of Southeast Asia, both habitat loss and harvest are biased toward phylogenetically unique species. Enhanced conservation efforts, including a renewed focus on harvest sustainability, are urgently needed to prevent the deterioration of ecosystem function, especially in the South American and equatorial Asian tropics.
Asunto(s)
Biodiversidad , Evolución Biológica , Conservación de los Recursos Naturales , Ecosistema , Mamíferos/crecimiento & desarrollo , Animales , Asia Sudoriental , Australia , Extinción Biológica , Bosques , Actividades Humanas , Humanos , Mamíferos/genética , Filogenia , América del SurRESUMEN
Mitigating the massive impacts of defaunation on natural ecosystems requires understanding and predicting hunting effort across the landscape. But such understanding has been hindered by the difficulty of assessing the movement patterns of hunters in thick forests and across complex terrain. We statistically tested hypotheses about the spatial distribution of hunting with circuit theory and structural equation models. We used a data set of >7000 known kill locations in Guyana and hunter movement models to test these methods. Comparing models with different resistance layers (i.e., different estimates of how terrain and land cover influence human movement speed) showed that rivers, on average, limited movement rather than serving as transport arteries. Moreover, far more kills occurred close to villages than in remote areas. This, combined with the lack of support for structural equation models that included latent terms for prey depletion driven by past overhunting, suggests that kill locations in this system tended to be driven by where hunters were currently foraging rather than by influences of historical harvest. These analyses are generalizable to a variety of ecosystems, species, and data types, providing a powerful way of enhancing maps and predictions of hunting effort across complex landscapes.
Comprensión de la Distribución de los Esfuerzos por Obtener Carne de Caza a lo largo de un Paisaje Mediante la Comprobación de Hipótesis sobre el Forrajeo Humano Resumen La mitigación de los impactos masivos de la defaunación sobre los ecosistemas naturales requiere de comprensión y predicción de los esfuerzos de caza a lo largo del paisaje. Dicha comprensión se ha visto obstaculizada por la dificultad que representa la evaluación de los patrones de movimiento de los cazadores en bosques densos y a través de un terreno complejo. Analizamos estadísticamente las hipótesis sobre la distribución espacial de la cacería mediante una teoría de circuito y modelos de ecuaciones estructurales. Usamos un conjunto de datos de más de 7000 localidades conocidas de sacrificios en Guayana y los modelos de movimiento de los cazadores para probar estos modelos. La comparación entre modelos con diferentes capas de resistencia (es decir, diferentes estimaciones de cómo el terreno y la cobertura de suelo influyen sobre la velocidad del movimiento humano) mostró que los ríos, en promedio, limitaron el movimiento en lugar de funcionar como arterias de transporte. Además, ocurrieron mucho más sacrificios cerca de las aldeas que en las áreas remotas. Lo anterior, combinado con la falta de apoyo para los modelos de ecuaciones estructurales que incluyeron los términos latentes para la reducción de presas causada por la sobrecaza pasada, sugiere que las localidades de sacrificios en este sistema tendieron a ser seleccionadas por la ubicación actual en la que los cazadores se encontraban forrajeando y no por la influencia de la cosecha histórica. Estos análisis son generalizables para una variedad de ecosistemas, especies y tipos de datos, lo que proporciona una manera poderosa de mejorar los mapas y las predicciones de los esfuerzos de cacería a través de paisajes complejos.