Efficient Species-Level Monitoring at the Landscape Scale

Monitoring the population trends of multiple animal species at a landscape scale is prohibitively expensive. However, advances in survey design, statistical methods, and the ability to estimate species presence on the basis of detection-nondetection data have greatly increased the feasibility of species-level monitoring. For example, recent advances in monitoring make use of detection-nondetection data that are relatively inexpensive to acquire, historical survey data, and new techniques in genetic evaluation. The ability to use indirect measures of presence for some species greatly increases monitoring efficiency and reduces survey costs. After adjusting for false absences, the proportion of sample units in a landscape where a species is detected (occupancy) is a logical state variable to monitor. Occupancy monitoring can be based on real-time observation of a species at a survey site or on evidence that the species was at the survey location sometime in the recent past. Temporal and spatial patterns in occupancy data are related to changes in animal abundance and provide insights into the probability of a species' persistence. However, even with the efficiencies gained when occupancy is the monitored state variable, the task of species-level monitoring remains daunting due to the large number of species. We propose that a small number of species be monitored on the basis of specific management objectives, their functional role in an ecosystem, their sensitivity to environmental changes likely to occur in the area, or their conservation importance. El monitoreo de las tendencias poblacionales de múltiples especies animales en la escala de paisaje es prohibitivamente costoso. Sin embargo, los avances en el diseño de muestreo, métodos estadísticos y la habilidad para estimar la presencia de especies con base en datos de detección-no detección han aumentado considerablemente la factibilidad del monitoreo a nivel de especie. Por ejemplo, avances recientes en el monitoreo hacen uso de datos de detección-no detección que son relativamente baratos, datos de muestreo históricos, y nuevas técnicas de evaluación genética. La habilidad para utilizar medidas indirectas de la presencia de algunas especies incrementa enormemente la eficiencia del monitoreo y reduce costos de muestreo. Después de ajustes por ausencias falsas, la proporción de unidades de muestreo en un paisaje en los que una especie es detectada (ocupación) es una variable de estado lógica a monitorear.