Characterizing drought for forested landscapes and streams

Authors: LUCE, CHARLIE - Rocky Mountain Research Station; PEDERSON, NEIL - Harvard University; CAMPBELL, JOHN - Us Forest Service (FS); HANSON, PAUL - Oak Ridge National Laboratory; MILLER, CONNIE - US Department Of Agriculture (USDA); Kormos, Patrick; VOSE, JIM - US Department Of Agriculture (USDA); WOODS, ROSS - University Of Bristol

Submitted to: Forest Service General Technical Reports
Publication Type: Government Publication
Publication Acceptance Date: 5/16/2016
Publication Date: 1/1/2016
Citation: Luce, C., Pederson, N., Campbell, J., Hanson, P., Miller, C., Kormos, P.R., Vose, J., Woods, R. 2016. Characterizing drought for forested landscapes and streams. Forest Service General Technical Reports. DOI:10.1016/j.foreco.2016.05.020.

Interpretive Summary: The changing nature of drought is a growing global concern (Cook et al. 2015, Dai 2011, Seneviratne et al. 2010, Sheffield and Wood 2008b, Trenberth et al. 2014, Wilhite et al. 2014). Drought can be a severe natural disaster with substantial social and economic consequences affecting large areas with extended durations (Wilhite and Buchanan-Smith 2005). Although it is clear that shifts in circulation patterns, energy for evapotranspiration, and air temperatures are changing in ways that enhance the consequences of drought, there is only weak consensus about the effects of climate change on drought occurrence [International Panel for Climate Change (IPCC) 2013, Seneviratne et al. 2012, Trenberth et al. 2014]. Some of that uncertainty stems from the complex nature of quantitatively defining drought, but also because some of the changes in drought characteristics are only partially reflected in traditional drought metrics [Palmer Drought Severity Index, (PDSI) & the Standardized Precipitation Index, (SPI)]. Furthermore, although these traditional metrics have adequately reflected the consequences of meteorologically derived moisture deficits on agricultural commodities and water supply, there is a poorer (although improving) understanding of how drought interacts with forests and rangelands and their associated aquatic habitats. Understanding the potential impacts of future drought on forests and rangelands, requires knowledge of how droughts impact forest, shrub, and rangeland structure (covered in other chapters in this assessment) and how drought projections are characterized in the General Circulation Model (GCM) output. The purpose of this chapter is to explore drought as a hydrometeorological phenomenon and reflect broadly on the characteristics of drought that influence forests, rangelands, and streams. It is a synthesis of understanding about drought processes, hydrology, paleoclimatology, historical climate variability, and how this understanding can help predict potential future droughts and their consequences to forests and rangelands. It describes alternative approaches for characterizing drought and highlights additional work that could inform projection and adaptation for future droughts.

Technical Abstract: The changing nature of drought is a growing global concern (Cook et al. 2015, Dai 2011, Seneviratne et al. 2010, Sheffield and Wood 2008b, Trenberth et al. 2014, Wilhite et al. 2014). Drought can be a severe natural disaster with substantial social and economic consequences affecting large areas with extended durations (Wilhite and Buchanan-Smith 2005). Although it is clear that shifts in circulation patterns, energy for evapotranspiration, and air temperatures are changing in ways that enhance the consequences of drought, there is only weak consensus about the effects of climate change on drought occurrence [International Panel for Climate Change (IPCC) 2013, Seneviratne et al. 2012, Trenberth et al. 2014]. Some of that uncertainty stems from the complex nature of quantitatively defining drought, but also because some of the changes in drought characteristics are only partially reflected in traditional drought metrics [Palmer Drought Severity Index, (PDSI) & the Standardized Precipitation Index, (SPI)]. Furthermore, although these traditional metrics have adequately reflected the consequences of meteorologically derived moisture deficits on agricultural commodities and water supply, there is a poorer (although improving) understanding of how drought interacts with forests and rangelands and their associated aquatic habitats. Understanding the potential impacts of future drought on forests and rangelands, requires knowledge of how droughts impact forest, shrub, and rangeland structure (covered in other chapters in this assessment) and how drought projections are characterized in the General Circulation Model (GCM) output. The purpose of this chapter is to explore drought as a hydrometeorological phenomenon and reflect broadly on the characteristics of drought that influence forests, rangelands, and streams. It is a synthesis of understanding about drought processes, hydrology, paleoclimatology, historical climate variability, and how this understanding can help predict potential future droughts and their consequences to forests and rangelands. It describes alternative approaches for characterizing drought and highlights additional work that could inform projection and adaptation for future droughts.