Will Seasonally Dry Tropical Forests Be Sensitive or Resistant to Future Changes in Rainfall Regime?
A review of scientific literature on responses of seasonally dry tropical forests to changing rainfall.
Seasonally dry tropical forests experience periodic droughts that occur each year, but it is unknown how their organisms and ecosystem processes will respond to increasing climatic variability including extreme droughts and/or changes in the timing, duration, or magnitude of rainfall regimes. This uncertainty has led to two very different predictions: some people argue that seasonally dry tropical forests will be very sensitive to changes in rainfall because they are already at hydrologic thresholds, while others claim that they will be resistant because these species are already adapted to strong seasonal drought. This research reviewed existing studies with the goals of searching for general patterns that could discriminate between these two hypotheses and also identifying gaps in the literature to guide future research.
This review found that there are many potential ways for “drought” to be manifested in seasonally dry tropical forests. Importantly, most of the studies are consistent with the prediction that changing rainfall regimes will have a large effect on species composition and ecological function of these forests.
By the end of the 21st century, climate models predict substantial changes in rainfall regimes across the seasonally dry tropical forest biome, but little is known about how dry forests will cope with the hotter, drier conditions predicted by climate models. The scientists explored two alternative hypotheses: (1) dry forests will be sensitive to drought because they are already limited by water and close to hydrologic thresholds or (2) they will be resistant or resilient to intra- and interannual changes in rainfall because they are adapted to predictable, seasonal drought. In this review of literature spanning microbial to ecosystem scales, most studies suggest that increasing frequency and intensity of droughts in dry forests will likely alter species distributions and ecosystem processes. Though these scientists conclude that dry forests will be sensitive to altered rainfall regimes, many gaps in the literature remain. Future research should focus on geographically comparative studies and well-replicated drought experiments that can provide empirical evidence to improve simulation models used to forecast dry forest responses to future climate change at coarser spatial and temporal scales.
University of Minnesota
The scientists thank the Terrestrial Ecosystem Science (TES) program of the Office of Biological and Environmental Research, within the U.S. Department of Energy Office of Science, under award number DE-SC0014363. JSP also thanks the National Science Foundation for CAREER Award DEB-1053237.
Allen, K. et al. “Will seasonally dry tropical forests be sensitive or resistant to future changes in rainfall regimes?” Environmental Research Letters 12(2), 023001 (2017). [DOI:10.1088/1748-9326/aa5968]