Evidence of macroclimatic impacts of deploying agroforestry at landscape scale

Agroforestry, integrating trees into croplands, is promoted as a nature-based solution to mitigate climate change by enhancing carbon sequestration, and to improve crop resilience to temperature extremes. However, quantifying its climatic benefits at local and large scales remains challenging, due to antagonistic processes. Moreover, the macroclimatic feedbacks of large-scale agroforestry deployment is poorly understood. Here, for the first time, the micrometeorology is simulated over various agroforestry configurations under summer conditions in a temperate region and contrasting soil moistures, using large-eddy simulations (LES). Unlike previous studies, our approach provides an integrated view of agroforestry effects from the crop microclimate to the atmospheric boundary layer (ABL) macroclimate. Simulations reveal a consistent increase in ABL air temperature with increasing tree cover over cropland, driven by the higher radiation absorbed by agroforestry systems compared to a treeless monoculture. A cooling effect emerges only under dry soil conditions and for a dense tree cover, where the larger tree transpiration offsets the excess radiative absorption. Although agroforestry mitigates crop surface warming on average, the crop surface temperature in sunlit areas near trees can locally exceed those in the treeless monoculture due to additional radiation from adjacent trees. These warmer zones are associated with higher crop net primary production under wet soil conditions, but may also expose plants to increased physiological stress during heatwaves. These findings for a typical summer day require further validation over a longer period, with diverse meteorological conditions, including potential afternoon cloud formation, to conclude on the climatic implications of large-scale agroforestry expansion.