Chemistry and Water: The Science Behind Sustaining the World's Most Crucial Resource

Forested watersheds offer access to vital natural resources, i.e., water supply for drinking, agriculture and industry, transport routes, and hydroelectric energy. Ecosystem services provided by these watersheds are numerous and, in addition to good quality water, include reduced peak river flow during storms; increased availability of groundwater and base flow in streams during seasonal dry periods and droughts; reduced soil erosion and landslide probability; enhanced resilience to wildfire, pathogens, and invasive species; biodiversity; genetic resources; and recreation [1e3]. These resource and esthetic benefits come with risks associated with floods, landslides, and wildfires, which are episodic natural disturbances in these settings. Furthermore, these disturbances compromise the provision of the ecosystem services listed previously. Nonetheless, natural landscape disturbance by floods has well-known benefits, i.e., delivery of nutrients to flood plains; landslides open forest gaps that create small-scale opportunities for successional vegetation growth, while hurricanes and wildfires similarly serve as large-scale mechanisms for resetting landscapes and creating new habitats. More than half of the world population now lives in urban areas, which are expected to absorb all the population growth expected over the next four decades, mostly in the cities and towns of the less developed regions. The United Nations [4,5] has defined 23 megacities with at least 10 million inhabitants; all but 6 of these are in the developing world. These populations place large stresses on water and other resources.