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Javier Naves

  Javier durante su visita en el Abril 2005 preparando una de sus  famosas "fabadas a la hostia"

Analyzing extinction, habitat loss and fragmentation of brown bears (Ursus arctos) in northern Spain: recent and historical perspectives

Regression and extinction of populations of large carnivores are complex historic processes derived from the interaction between the species-specific spatial and temporal dynamics and diverse human activities. Main factors of human origin involved are habitat loss and fragmentation and persecution over centuries. Because of the long time-scales involved, there is little information available for studying extinction under an appropriate historic perspective. Additionally, the inherent complexity of the interactions between demographic and spatial processes makes it difficult to analyze the historic patterns of extinction and its causal factors. However, an understanding of this is indispensable for developing an appropriate management, and of high interest for basic and applied ecological research.

Our aims are (1) to describe and understand the relationships between the patterns of historic extinction and current regression of brown bears in northern Spain and processes of habitat loss and fragmentation and deliberate killing of individuals, (2) to analyze the current spatial and temporal dynamics and the status of the population (assess population viability and identify the parameters that most influence on it), and (3) to support bear conservation for finding the best management scenarios of landscape design and development. The fate of the cantabrian brown bears depends on our ability in understanding the influence of landscape design, management and development on their population dynamics.

We combine two powerful methods of analysis usually applied to conservation biology: 

• statistical habitat modeling with aid of Geographic Information Systems (GIS) to analyze factors that determine the distribution and quality of habitat and those human-induced factors that lead to habitat change and increased mortality. Additionally, regional analysis of remote sensed data of the normalized difference vegetation index (NDVI) seasonal dynamics (from 1982 to 2001) and other climatic index provide information on habitat productivity and its interannual and seasonal variation. 

• spatially-explicit, individual-based simulation modeling to analyze the spatial and temporal dynamics of the population (historical and current) under the constraining impacts of a changing habitat and legal (historic) and illegal hunting.

Several historic and contemporaneous data sets offer the unique possibility to perform a detailed study of extinction, habitat loss and fragmentation over the appropriate period of several centuries. In detail, these sets comprise data on (1) historic bear presence/absence in northern Spain during the 14-17th, and the 18-19th century, (2) location and sex of bears hunted in some areas (Asturias: 1751–1756, 19th century), and different mortality series collected locally and for the whole range of the species during the 20th century (1980-1999 whole area, 1950-1980 western León, 1950-1989 central Asturias) (3) bear observations and observations of females with cubs from 1982–1999.

     Carlos Rodriguez, Doug Bruggeman y Javier disfrutando codillo en Leipzig.