Edge effects on evapotranspiration from tropical forest fragments

Evapotranspiration (ET) is a key component of forest ecohydrological functioning and land–atmosphere coupling in tropical regions. In fragmented landscapes, forest edges may strongly influence the spatial variability of ET and microclimate, yet this aspect remains insufficiently studied. Here, we examine wet-season ET patterns 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 edges, particularly at mid-elevations and in areas with high canopy cover. These patterns likely arise from a combination of climatic conditions, forest structure, edge orientation, and surrounding land-use types in this human-modified landscape. The high spatial variability observed at edges underscores the need to better integrate edge processes into forest hydrology and land–atmosphere models. Our findings suggest that forest edges can locally enhance ET under wet conditions, thereby contributing to microclimatic and hydroclimatic 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 fragmented tropical landscapes.