Cloud forests

Watershed function

Cloud forests play a disproportionately important role in the regional hydrological cycle relative to their small global extent. The cloud-stripping mechanism — whereby tree canopies intercept wind-driven cloud moisture — can effectively double rainfall inputs during dry seasons and add approximately 10% to wet-season totals. Experiments by Costin and Wimbush (1961) demonstrated that the canopies of non-cloud forests intercept and evaporate 20% more precipitation than cloud forests do, meaning that cloud forests deliver a larger net water input to the land surface. This function makes cloud forests critical catchment areas for rivers and groundwater systems serving large human populations, particularly in seasonally dry regions such as coastal Peru and northern Chile where cloud forests are virtually the sole source of freshwater.