Much of the variability in how drought is characterized depends on definitions for terms, reference conditions, and the methods used for developing drought indices. The direction of trends in recent history varies from region to region, with the Western United States showing a trend toward dry conditions while trends in the East are more variable and complex (5). Historical and paleoclimatic evidence shows that drought has always impacted the physical environment and will continue to do so (4). For example, meteorological or hydrologic drought may presage or correlate to fire events (2) or insect outbreaks (3). For forest and stream ecosystems, meteorological and hydrologic drought frameworks are useful for characterizing impacts of a given drought event. In systems with perennial vegetation (both natural and agricultural systems), characterizing and assessing drought impacts is complex, as responses can vary in space, time, and among species.
Meteorological and hydrologic droughts relate water availability to a reference condition (e.g., long-term mean precipitation or streamflow) agricultural and socioeconomic droughts relate to impacts.
Droughts are generally identified as one of four types: meteorological, hydrologic, agricultural, or socioeconomic (1). Drought becomes most obvious when large-scale changes are observed (e.g., insect outbreaks or wildfires) or when water requirements for human or agricultural needs are not met however, even moderate drought can have long-lasting impacts on the structure and function of forests and rangelands without these obvious large-scale changes. Drought can be a severe natural disaster with substantial social and economic consequences. In simple terms, drought is a lack of water over a given temporal and spatial scale. This topic page was adapted from the executive summary of the report Effects of Drought on Forests and Rangelands in the United States: a comprehensive synthesis (WO-GTR-93b) IssuesĬharacterizing and Predicting Future Drought Toral Patel-Weynand, Sustainable Forest Management Research, USDA Forest Service James Clark, Nicholas School of the Environment, Duke UniversityĬharles Luce, Rock Mountain Research Station, USDA Forest Service James Vose, Center for Integrated Forest Science, Southern Research Station, USDA Forest ServiceĪdditional editors of the original publication:
0 kommentar(er)
