This new Sala Lab publication in Global Change Biology addresses the influence of drylands on the global carbon cycle under climate change conditions. Using a data synthesis approach, Lau Gherardi and Osvaldo Sala reached robust conclusions.
Although projections of climate change anticipating increases in precipitation variability and extreme events are part of the public and scientific narrative, the effects of inter-annual precipitation variance per se on ecosystem functioning have been largely understudied.
This global synthesis indicated that increased precipitation coefficient of variation decreased primary productivity in drylands globally. The effect of precipitation inter-annual variability on dryland productivity changes from positive to negative along a precipitation gradient. Desert sites with mean precipitation under 300 mm per year responded positively to increases in precipitation variability whereas prairie sites with mean precipitation over 300 mm per year responded negatively. Given the large extension of dryland ecosystems, increased precipitation variability per se may result in a decline in global C sequestration of about 0.1-0.3 Pg C per year. This decline represents 4-12% of the mean C sink reported by the global carbon project for the last decade.