Significance
Recent advances in ecology show evidence that multiple environmental drivers interact and that their impact on community and ecosystem functioning cannot be predicted from single-driver studies. However, ecologists still largely disregard the role that fluctuations in these drivers (i.e., changes above/below mean trends) play in modulating the magnitude and direction of global-change impacts. Through a 30-year quantitative review, we show that contrary to the established paradigm, additive effects are more frequent when environmental fluctuations are considered in multiple-driver (i.e., acidification, hyperpoxia and hypoxia, light, resource supply, or temperature) scenarios, although such effects are strongly dependent on trophic strategy and phylogeny. Our findings stress the need to consider environmental variability in ecological studies and conservation plans to better predict the impacts of global climate change.
Abstract
Jensen’s inequality predicts that the response of any given system to average constant conditions is different from its average response to varying ones. Environmental fluctuations in abiotic conditions are pervasive on Earth; yet until recently, most ecological research has addressed the effects of multiple environmental drivers by assuming constant conditions. One could thus expect to find significant deviations in the magnitude of their effects on ecosystems when environmental fluctuations are considered. Drawing on experimental studies published during the last 30 years reporting more than 950 response ratios (n = 5,700), we present a comprehensive analysis of the role that environmental fluctuations play across the tree of life. In contrast to the predominance of interactive effects of global-change drivers reported in the literature, our results show that their cumulative effects were additive (58%), synergistic (26%), and antagonistic (16%) when environmental fluctuations were present. However, the dominant type of interaction varied by trophic level (autotrophs: interactive; heterotrophs: additive) and phylogenetic group (additive in Animalia; additive and positive antagonism in Chromista; negative antagonism and synergism in Plantae). In addition, we identify the need to tackle how complex communities respond to fluctuating environments, widening the phylogenetic and biogeographic ranges considered, and to consider other drivers beyond warming and acidification as well as longer timescales. Environmental fluctuations must be taken into account in experimental and modeling studies as well as conservation plans to better predict the nature, magnitude, and direction of the impacts of global change on organisms and ecosystems.
Cabrerizo M. J. & Maranon E., 2022. Net effect of environmental fluctuations in multiple global-change drivers across the tree of life. Proceedings of the National Academy of Sciences USA 119(32): e2205495119. doi: 10.1073/pnas.2205495119. Article (subscription required).
