Edge effects on evapotranspiration from tropical forest fragments

Evapotranspiration (ET) is a key component of the climate-regulating function of tropical forests. In fragmented landscapes, forest edges may significantly influence spatial variation in ET, but this aspect remains insufficiently studied. Here, we examine ET patterns during the wet season across 83 forest fragments in western Ecuador using ECOSTRESS satellite observations. A changepoint analysis showed that the frequency of ET shifts increased toward fragment edges, with 61% of cases displaying higher ET near edges. A random forest model with target-oriented cross-validation achieved a spatial prediction accuracy of 64%, identifying elevation, aridity, and distance to edge as the most important predictors. SHAP analysis further emphasized the role of edge effects, revealing greater ET rates near the edges, particularly at mid-elevations and in areas with high canopy cover. These patterns likely resulted from a combination of factors, including climatic conditions, forest structure, edge orientation, and surrounding land-use types. The high variability observed at edges underscores the need for further investigation. Our findings suggest that forest edges can locally enhance ET under wet conditions, contributing to microclimatic regulation. While this does not substitute for the broader climate function of intact, continuous forest, small remnant fragments may still play a meaningful role in sustaining local hydrological processes in human-modified tropical landscapes. • Evapotranspiration (ET) was assessed in 83 forest fragments in Ecuador. • ET increased nonlinearly toward edges, with enhancement in most cases. • Explainable machine learning, SHAP analyses, indicate edge effects interaction with canopy cover and elevation.