The grassland–shrubland regime shift in the southwestern United States: Misconceptions and their implications for management

Authors: Bestelmeyer, Brandon; Peters, Debra; ARCHER, STEVEN - University Of Arizona; Browning, Dawn; OKIN, GREGORY - University Of California; SCHOOLEY, ROBERT - University Of Illinois; WEBB, NICHOLAS - New Mexico State University

Submitted to: Bioscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2018
Publication Date: 9/1/2018
Citation: Bestelmeyer, B.T., Peters, D.C., Archer, S.R., Browning, D.M., Okin, G.S., Schooley, R.L., Webb, N.P. 2018. The grassland–shrubland regime shift in the southwestern United States: Misconceptions and their implications for management. Bioscience. 68:678-690. https://doi.org/10.1093/biosci/biy065.
DOI: https://doi.org/10.1093/biosci/biy065

Interpretive Summary: Transitions from semiarid grassland to shrubland states are among the most widely recognized examples of regime shifts in terrestrial ecosystems. Nonetheless, the processes causing grassland-shrubland transitions, and their consequences, are incompletely understood. We challenge several misconceptions about these transitions in desert grasslands, including (i) their control by singular “tipping points”, (ii) that they represent catastrophic degradation, and (iii) that restoration of former grassland states is impossible. Grassland-shrubland transitions are the product of multiple drivers acting at multiple scales of space and time. Grass recovery within shrubland states —with and without shrub removal—produces novel ecosystems dissimilar from historical grasslands, but that provide important ecosystem services and biodiversity benefits. Projected climate changes toward greater aridity are likely to promote the displacement of perennial grasses by xerophytic shrubs. This review offers guidelines for managing grassland-shrubland transitions in the face of changing biophysical and socioeconomic circumstances.

Technical Abstract: Transitions from semiarid grassland to shrubland states are among the most widely recognized examples of regime shifts in terrestrial ecosystems. Nonetheless, the processes causing grassland-shrubland transitions, and their consequences, are incompletely understood. We challenge several misconceptions about these transitions in desert grasslands, including (i) their control by singular “tipping points”, (ii) that they represent catastrophic degradation, and (iii) that restoration of former grassland states is impossible. Grassland-shrubland transitions are the product of multiple drivers acting at multiple scales of space and time. Grass recovery within shrubland states —with and without shrub removal—produces novel ecosystems dissimilar from historical grasslands, but that provide important ecosystem services and biodiversity benefits. Projected climate changes toward greater aridity are likely to promote the displacement of perennial grasses by xerophytic shrubs. This review offers guidelines for managing grassland-shrubland transitions in the face of changing biophysical and socioeconomicTransitions from semiarid grassland to shrubland states are among the most widely recognized examples of regime shifts in terrestrial ecosystems. Nonetheless, the processes causing grassland-shrubland transitions, and their consequences, are incompletely understood. We challenge several misconceptions about these transitions in desert grasslands, including (i) their control by singular “tipping points”, (ii) that they represent catastrophic degradation, and (iii) that restoration of former grassland states is impossible. Grassland-shrubland transitions are the product of multiple drivers acting at multiple scales of space and time. Grass recovery within shrubland states —with and without shrub removal—produces novel ecosystems dissimilar from historical grasslands, but that provide important ecosystem services and biodiversity benefits. Projected climate changes toward greater aridity are likely to promote the displacement of perennial grasses by xerophytic shrubs. This review offers guidelines for managing grassland-shrubland transitions in the face of changing biophysical and socioeconomic circumstances.