Background
The authors write that "dryland ecosystems are particularly affected by relatively intense hydroclimatic fluctuations," citing Reynolds et al. (2007); and they say that "there is some concern that the interannual variability of precipitation in dryland regions might increase in the future thereby enhancing the occurrence of severe water stress conditions in ecosystems and societies."

What was done
To further explore what might initially have been expected in the way of negative ecosystem consequences due to greater interannual variability of precipitation in dryland ecosystems, D'Odorico and Bhattachan studied "some of the current patterns of hydrologic variability in drylands around the world," reviewing "the major effects of hydrologic fluctuations on ecosystem resilience, maintenance of biodiversity and food security." And what did they find were the real consequences of enhanced hydrologic fluctuations?

What was learned
The two U.S. researchers report that the preponderance of the investigations they reviewed indicated that random hydrologic fluctuations may actually enhance the resilience of dryland ecosystems by obliterating threshold-like responses to external drivers, and that "by increasing biodiversity and the associated ecosystem redundancy, hydrologic variability can indirectly enhance post-disturbance recovery, i.e., ecosystem resilience."

What it means
In the concluding words of D'Odorico and Bhattachan, they re-emphasize that dryland ecosystem resilience is "enhanced by environmental variability through the maintenance of relatively high levels of biodiversity, which may allow dryland ecosystems to recover after severe disturbances, including those induced by extreme hydroclimatic events."

Reference
Reynolds, J.F., Smith, S.D.M., Lambin, E.F., Turner II, B.L., Mortimore, M., Batterbury, S.P.J., Downing, T.E., Dowlatabadi, H., Fernandez, R.J., Herrick, J.E., Huber-Sannwald, E., Jiang, H., Leemans, R., Lynam, T., Maestre, F.T., Ayarza, M. and Walker, B. 2007. Global desertification: building a science for dryland development. Science 316: 847-851.