Spatial Demographic Models to Inform Conservation Planning of Golden Eagles in Renewable Energy Landscapes
Spatial demographic models can help guide monitoring and management activities targeting at-risk species, even in cases where baseline data are lacking. Here, we provide an example of how site-specific changes in land use and anthropogenic stressors can be incorporated into a spatial demographic model to investigate effects on population dynamics of Golden Eagles (Aquila chrysaetos). Our study focused on a population of Golden Eagles exposed to risks associated with rapid increases in renewable energy development in southern California, U.S.A. We developed a spatially explicit, individual-based simulation model that integrated empirical data on demography of Golden Eagles with spatial data on the arrangement of nesting habitats, prey resources, and planned renewable energy development sites. Our model permitted simulated eagles of different stage-classes to disperse, establish home ranges, acquire prey resources, prospect for breeding sites, and reproduce. The distribution of nesting habitats, prey resources, and threats within each individual's home range influenced movement, reproduction, and survival. We used our model to explore potential effects of alternative disturbance scenarios, and proposed conservation strategies, on the future distribution and abundance of Golden Eagles in the study region. Results from our simulations suggest that probable increases in mortality associated with renewable energy infrastructure (e.g., collisions with wind turbines and vehicles, electrocution on power poles) could have negative consequences for population trajectories, but that site-specific conservation actions could reduce the magnitude of negative effects. Our study demonstrates the use of a flexible and expandable modeling framework to incorporate spatially dependent processes when determining relative effects of proposed management options to Golden Eagles and their habitats. Los modelos de demografía espacial pueden ser útiles para las actividades de seguimiento y gestión de especies en riesgo, incluso en casos donde faltan los datos de base. Proporcionamos un ejemplo de cómo los cambios específicos en el uso del suelo y las molestias de origen antrópico pueden ser incorporados en un modelo de demografía espacial para investigar los efectos en la dinámica poblacional de Aquila chrysaetos. Nuestro estudio se centró en una población de esta especie expuesta a riesgos asociados con los cambios rápidos ocasionados por el desarrollo de energías renovables en el sur de California, EE.UU. Desarrollamos un modelo de simulación espacial basado en individuos que integró datos demográficos de A. chrysaetos con datos espaciales sobre la distribución de hábitats de nidificación, recursos tróficos y lugares donde se planifica el desarrollo de energías renovables. Nuestro modelo permitió que águilas simuladas de diferentes clases pudieran dispersarse, establecer áreas de campeo, adquirir recursos tróficos, explorar posibles sitios de nidificación y reproducirse. La distribución de los hábitats de nidificación, de los recursos tróficos y de las amenazas dentro del área de campeo individual influyó en el movimiento, la reproducción y la supervivencia. Utilizamos nuestro modelo para explorar los efectos potenciales de escenarios alternativos con presencia de molestias así como para proponer estrategias de conservación sobre la distribución futura y la abundancia de A. chrysaetos en la región de estudio. Los resultados de nuestras simulaciones sugieren que los incrementos probables en la mortalidad asociados con infraestructuras de energías renovables (e.g., colisiones con aerogeneradores y vehículos, electrocución en postes eléctricos) pueden tener consecuencias negativas para las trayectorias de las poblaciones, pero que acciones específicas en cada lugar pueden reducir la magnitud de los efectos negativos. Nuestro estudio demuestra el uso de un marco de trabajo flexible y extensible que integra procesos espacialmente dependientes a la hora de determinar los efectos relativos de las estrategias de gestión propuestas para A. chrysaetos y sus hábitats. [Traducción del equipo editorial]Abstract
Resumen
The Desert Renewable Energy Conservation Plan area of southern California, U.S.A., and encompassing 50-km radius buffer, where we modeled population response of Golden Eagles to renewable energy development and other anthropogenic stressors. We also show spatial data used to inform an individual-based, spatially explicit simulation model for Golden Eagles, including: (A) relative nesting habitat suitability, (B) estimated prey availability, (C) spatial mortality risk from wind turbines, high-risk roads, and powerlines, and (D) locations of planned renewable energy development (Development Focal Areas), off-highway vehicle (OHV) use areas, and sites identified for conservation actions (Conservation Planning Areas; CBI 2014).
Life cycle of the modeled population of Golden Eagles in the Desert Renewable Energy Conservation Plan area, California, U.S.A. Boxes represent the different age- and stage-classes represented in an individual-based, spatially explicit simulation model, where Si is the survival for age-class i, mi is fecundity (mean number of female young fledged per territorial female) for age-class i, and Ri is recruitment for age-class i between breeding and nonbreeding segments of the population.
Modeling sequence of an individual-based, spatially explicit simulation model for Golden Eagles in the Desert Renewable Energy Conservation Plan area, California, U.S.A.
Output from the stable, baseline population simulation model for Golden Eagles in the Desert Renewable Energy Conservation Plan area of southern California, U.S.A, including: (A) total population size and number of territorial females, (B) number of female fledglings produced, and (C) number of fatalities from collisions with wind-turbines, powerline electrocutions, or collisions with vehicles during time steps 150–500. Black lines show median values from 10 replicate simulations, each conducted over 500 time steps (years); shaded areas indicate maximum and minimum values (A, B), or 95% confidence intervals (C).
Predicted spatial distribution of long-term productivity and mortality at breeding territories of Golden Eagles in the Desert Renewable Energy Conservation Plan area of southern California, U.S.A. We show the mean number of births minus deaths per 1-km2 in home ranges established by simulated eagles during 150 time steps (years) and 10 replicate simulations of the stable, baseline population model. Source habitats appear in green, sink habitats appear in red.
Predicted population response of Golden Eagles in the Desert Renewable Energy Conservation Plan area of southern California, U.S.A., to four different risk scenarios associated with planned energy development, including: an increase in mortality risk of 0.0027 in Development Focal Areas (DFAs) with no effect on prey availability (low effect), an increase in mortality risk of 0.0077 in DFAs with a 25% reduction in prey availability (severe effect), an increase in mortality risk of 0.0047 in DFAs with a 25% reduction in prey availability (moderate effect), and the moderate effect scenario coupled with a 99% reduction in mortality risk in Planned Conservation Areas (moderate effect with conservation). Black lines show median values from 10 replicate simulations, each conducted over 500 time steps (years); grey lines indicate maximum and minimum values.
Contributor Notes
Associate Editor: Christopher W. Briggs