Narrow thresholds of canopy disturbance determine the microclimate buffering potential of tropical forests

The importance of protecting logged and recovering tropical forests has gained much attention. Disturbed forests can, however, have hotter microclimates, exacerbating the effects of future climate change. Using thermal imaging we captured understory surface temperatures along a gradient of tropical forest disturbance, and compared these to the upper thermal limits (CTmax) of invertebrates within the same forests. Surface temperatures exceeding the CTmax of invertebrate groups occurred once canopy cover fell below 76%. In highly degraded forests, surface niche space was reduced by 22% for the most sensitive taxa, and this doubled following simulated warming of +3°C. In contrast, all invertebrate groups were buffered in sites that retained 80% canopy cover or higher even following severe warming. We demonstrate a narrow threshold of canopy disturbance beyond which microclimate buffering is significantly diminished. These findings illustrate the importance of conserving high canopy cover forests to protect tropical biodiversity in a hotter future.