Demography linked to climate change projections in an ecoregional case study: integrating forecasts and field data

Abstract

Anticipating species movement under climate change is a fundamental concern in 21st century conservation. For blue oak (Quercus douglasii), an endemic, flagship species in California, we modeled potential responses to future climate, then tested the fit of those projections to empirical field data from natural populations. Specifically, we tested how well species forecasts captured observed recruitment and adult tree mortality, and whether recruitment was structured spatially as a function of fine‐scale micro‐topographic and hydrologic environments. In this ecoregional case study, observed demographic patterns were broadly consistent with theoretical expectations. Adult survivorship was three times lower in areas forecasted to be least suitable as a result of climate change than in areas projected to become suitable. This novel field validation exercise documents patterns of adult tree mortality consistent with model predictions of an emergent shift in distribution. Seedlings and saplings showed evidence of spatial structuring into local refugia in areas projected to contract, suggesting that climate change may reshape how blue oak associates with California landscapes and highlighting the potential importance of micro‐environmental diversity in enhancing species resilience to warming.