The University of Arizona

National Assessment and Critiques of State-and-Transition Models: The Baby with the Bathwater

Brandon T. Bestelmeyer


On the Ground
• Ecological site descriptions and state-and-transition
models are national-level tools for organizing and
delivering information about landscape dynamics
and management.
• Recent papers criticized state-and-transition models
because they overemphasize grazing, are inconsistently
presented, and do not address climate change.
• I argue that the analysis of Twidwell et al. does not
support an overemphasis on grazing, that inconsistent
presentation is a necessary consequence of early
model development efforts and immature science
concepts, and that climate change effects should not
be addressed in site-level models without evidence.
• Improving these important tools requires fair critique, but
also the strong commitment of scientists and funders.

Keywords: ecological site descriptions, regime shifts,
grazing, thresholds, climate change.

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