Defining and quantifying drought is essential when studying ecosystem responses to such events. Yet, many studies lack either a clear definition of drought, and/or erroneously assume drought under conditions within the range of “normal climatic variability” (c.f. Slette et al., 2019). To improve the general characterization of drought conditions in ecological studies, Slette et al. (2019) propose that drought studies should consistently relate to the local climatic context, assessing whether reported drought periods actually constitute extremes in water availability.While we generally agree with their proposal, we argue that standardised climatic indices, such as the Standardized Precipitation and Evapotranspiration Index SPEI (Sergio M Vicente‐Serrano, Beguería, & López‐Moreno, 2010) as highlighted in Slette et al., cannot be recommended as stand‐alone criteria for drought severity, especially when applied in a global context. We base our critique on three major points: (1) standardisation can lead to a misrepresentation of actual water supply, especially for moist climates, (2) standardised values are not directly comparable between different reference periods, (3) spatially coarsely resolved data sources are unlikely to represent site‐level water supply.
Bibliographical noteFunding Information:
We thank Nathan L. Stephenson for useful discussions and comments on the manuscript. C.S.Z., A.B. and A.R. acknowledge funding by the Bavarian Ministry of Science and the Arts in the context of the Bavarian Climate Research Network (BayKliF). A.E.‐M. is supported by the ERC grant TreeMort (758873). A.S.J. acknowledges funding by the Natural Environment Research Council, grant NE/S010041/1.
ASJC Scopus subject areas
- Global and Planetary Change
- Environmental Chemistry
- Environmental Science(all)