Ecosystems that are covered in fog or mist for much of the year may be critical for water supply because the presence of fog can increase total water inputs. This can occur because fog condenses on tree leaves and drips to the ground, reduces light and temperature so less water evaporates, and can be directly absorbed by leaves. However, current knowledge about how fog influences ecosystem water balance is extremely poor. This research quantifies the effect of fog on water movement through individual plants to entire watersheds in a cloud forest zone in Veracruz, Mexico. The goal of this project is to determine how conversion of cloud forest to pasture, pine reforestation, and young regenerating forest affects streamflow. This will be accomplished by combining field measurements of hydrological, ecophysiological, atmospheric and soil processes with watershed modeling.
Cloud forests, combined with other fog/cloud inundated ecosystems, occupy over 70 million hectares on earth, yet many have already been deforested or are threatened by conversion and climate change. Loss of fog-vegetation interactions when tall forests are replaced by shorter vegetation may have irreversible consequences for the hydrological balance, thereby affecting water supply to major population centers in lower-lying regions. This research fills an important gap in current understanding of how cloud forests?and their alteration by land use?affect water resources. By identifying the mechanisms that cause changes in water flow amounts and timing, it will be possible to make specific management and policy recommendations for protecting water supply and reversing processes of degradation. Additional support for this research is being provided by the Hydrology Program (GEO), the Office of International Science & Engineering, Emerging Frontiers (BIO/OAD), and the Division of Environmental Biology.
