Afforestation, as a key nature-based solution for regulating local and global climate, yet their biophysical effect and how drought modulates it in high latitude regions remain debated. This study using eddy covariance observations from six paired forests–grasslands sites, aims to investigate forests produce warming or cooling effect in high latitude of Europe and examine the impact of drought on this effect and underline mechanisms. Results show forests exhibit an annual mean cooling effect of approximately −1.3 K, driven primarily by enhanced sensible heat flux (−3.7 K) and emissivity-induced cooling (−2 K), which offset albedo-driven warming (+4 K). Furthermore, drought weakens forest cooling by an average of 0.3 K during growing season, primarily due to increased warming from latent heat flux and reduced cooling from sensible heat flux. These findings confirm that afforestation cools high latitude Europe, but drought diminish this cooling benefit, highlighting the inevitability of extreme climate in forest-based climate mitigation strategies.

biophysical effect,drought,Europe,afforestation