US Geological Survey


Thresholds of Climate Change in Ecosystems: Final Report, Synthesis and Assessment Product 4.2

Craig D. Allen, USGS
Charles Birkeland, USGS-University of Hawaii
F. Stuart Chapin, III, University of Alaska
Peter M. Groffman, Institute of Ecosystem Studies
Glenn R. Guntenspergen, USGS
Alan K. Knapp, Colorado State University
A. David McGuire, USGS-University of Alaska
Patrick J. Mulholland, Oak Ridge National Laboratory
Debra P.C. Peters, USDA Agricultural Research Service
Daniel D. Roby, USGS-Oregon State University
George Sugihara, Scripps Institute of Oceanography and University of California at San Diego

Document Type Article

Published by U.S. Climate Change Science Program And the Subcommittee on Global Change Research.


As defined in this Synthesis and Assessment Report, ‘an ecological threshold is the point at which there is an abrupt change in an ecosystem quality, property, or phenomenon, or where small changes in one or more external conditions produce large and persistent responses in an ecosystem’.
Ecological thresholds occur when external factors, positive feedbacks, or nonlinear instabilities in a system cause changes to propagate in a domino-like fashion that is potentially irreversible. This report reviews threshold changes in North American ecosystems that are potentially induced by climatic change and addresses the significant challenges these threshold crossings impose on resource and land managers. Sudden changes to ecosystems and the goods and services they provide are not well understood, but they are extremely important if natural resource managers are to succeed in developing adaptation strategies in a changing world.
The report provides an overview of what is known about ecological thresholds and where they are likely to occur. It also identifies those areas where research is most needed to improve knowledge and understand the uncertainties regarding them. The report suggests a suite of potential actions that land and resource managers could use to improve the likelihood of success for the resources they manage, even under conditions of incomplete understanding of what drives thresholds of change and when changes will occur.