Directional climate change and potential reversal of desertification in arid and semiarid ecosystems

Authors: Peters, Debra; YAO, JIN - New Mexico State University; SALA, OSVALDO - Arizona State University; ANDERSON, JOHN - New Mexico State University

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2011
Publication Date: 1/1/2012
Citation: Peters, D.C., Yao, J., Sala, O.E., Anderson, J.P. 2012. Directional climate change and potential reversal of desertification in arid and semiarid ecosystems. Global Change Biology. 18:151-163.

Interpretive Summary: Our objective was to determine if long-term increases in precipitation associated with climate change can maintain grasslands susceptible to desertification, and initiate a reversal of historic regime shifts in shrublands. Our approach was to combine maps of dominance beginning in 1858 with 15 years of detailed plant production and biodiversity responses for five ecosystem types in the Chihuahuan Desert during a 10-year drought (1994-2003) followed by a 5-year wet period (2004-2008). We addressed four questions: (1) What are historic trends in these ecosystems? (2) How do these ecosystems differ in production, richness, and rain use efficiency during drought compared to a wet period? (3) Does the response to increased precipitation reflect grass recruitment or growth of existing woody plants? (4) How are these systems expected to change in the future under directional changes in climate? Our results show that production responses by most Chihuahuan Desert ecosystem types to an extended wet period cannot be linearly extrapolated from historic or drought-based relationships. The production response in wet years was primarily an increase in herbaceous plants, and the most pronounced responses occurred on sandy sites with little or no slope. Our results are important and timely because they suggest directional increases in precipitation can provide an opportunity for state changes that are thought to be persistent under current climate. Recovery of grasses would influence the nearly 250 million people affected by desertification globally.

Technical Abstract: Our objective was to determine if long-term increases in precipitation can maintain grasslands susceptible to desertification, and initiate a reversal of historic regime shifts on desertified shrublands. Long-term trends in desertification were documented using vegetation maps beginning in 1858. These trends were compared with herbaceous and woody species responses to a sequence of dry (1994-2003) and wet years (2004-2008) for two grassland (uplands, playas) and three desertified shrubland types (honey mesquite, creosotebush, tarbush) in the Chihuahuan Desert. Analyses showed that both types of grasslands decreased in spatial extent whereas areas dominated by mesquite or creosotebush increased. Production of upland grasslands in the wet period was greater than expected based on responses during the dry period whereas the relationships between species richness and precipitation was the same for both periods. Precipitation was not important to responses in playa grasslands in either period. For all ecosystem types, the production response in wet years was primarily an increase in herbaceous plants, and the most pronounced responses occurred on sandy sites (upland grasslands, mesquite shrubland). Results suggest that multiple wet years are needed to initiate a sequence of grass establishment and survival processes that can maintain upland grasslands without management inputs and lead to a state change reversal in desertified shrublands. Restoration strategies need to take advantage of opportunities provided by future climates while recognizing the importance of ecosystem type.