Potential for mountaintop boulder fields to buffer species against extreme heat stress under climate change

Species may circumvent or minimize some impacts resulting from climate change by utilizing microhabitats that buffer against extreme events (e.g., heat waves). Boulder field habitats are considered to have functioned as important refugia for rainforest fauna during historical climate fluctuations. However, quantitative data on microhabitat buffering potential in these habitats is lacking. We characterized temperature buffering over small distances (i.e., depths) within an exposed and forested boulder field on a tropical mountain. We demonstrate that temperatures are cooler and become more stable at increasing depths within boulder fields. The magnitude of difference is most pronounced in exposed situations where temperatures within boulder fields can be as much as 10 degrees C lower than near surface conditions. Our data provide a first step toward building models that more realistically predict exposure to heat stress for fauna that utilize rocky habitats.