Humans and climate are among the most powerful forces affecting global biodiversity today, and their influences are likely to increase in the coming decades. How humans affect wildlife may be associated with their socioeconomic conditions because such factors may determine peoples’ propensity to contribute to conservation, their choice of where to live, and the quality of backyard habitats available for wildlife. Temperature may affect productivity and food availability for wildlife, and the interactive effects of socioeconomic factors and temperature may be greater than their additive effects. For eight forest bird species, we explored the influence of four socioeconomic factors (median age, median income, percentage of the population with a college education, and percentage of the population that was female) and their within-scale interactions (WSIs) and cross-scale interactions (CSIs) with breeding-season temperature on avian persistence. Our study area involved fourteen EPA Level III ecoregions in the eastern United States. We used AIC statistics to compare nine a-priori models for each combination of species and socioeconomic factor. We assessed the relative importance of the variables in the best models using incidence-rate ratios (for negative binomial models) and coefficients of partial determination (for ordinary least-squares models).
Results/Conclusions
Median income positively influenced seven species (four WSIs) and negatively influenced (CSI) one species. College education influenced four species (two WSIs) positively and one negatively. Median age had positive influences on three species (including one WSI and one CSI) and a negative influence on one. Percent female negatively influenced one species. For the remaining 14 models, the socioeconomic variables were either not in the model or were unimportant. In most models, the socioeconomic factors were less important than were habitat and weather variables, but in two models involving median income, WSIs had the highest relative importance. These results demonstrate that human socioeconomic factors can affect forest bird persistence, that breeding-season temperatures at different spatial scales can modify the effects of these factors, and that the effects of socioeconomic and climate variables as well as their interactions may be species-specific. Studies of how climate and socioeconomic factors affect species, especially species of conservation concern, should consider the potential interactions of these factors. Failure to consider interactions may result in misleading interpretations about the influences of main effects and, consequently, ineffective use of limited conservation resources.