Nonlinear and Threshold Responses to Environmental Stressors in Land-river Networks at Regional to Continental Scales

EPA Grant Number: R833261
Title: Nonlinear and Threshold Responses to Environmental Stressors in Land-river Networks at Regional to Continental Scales
Investigators: Melillo, Jerry , Felzer, Benjamin S. , Kicklighter, David Wesley , McClelland, James , Peterson, Bruce J. , Vörösmarty, Charles J. , Wollheim, Wil
Institution: Marine Biological Laboratory , University of New Hampshire
EPA Project Officer: Hiscock, Michael
Project Period: September 1, 2007 through August 31, 2010 (Extended to August 31, 2011)
Project Amount: $899,191
RFA: Nonlinear Responses to Global Change in Linked Aquatic and Terrestrial Ecosystems and Effects of Multiple Factors on Terrestrial Ecosystems: A Joint Research Solicitation- EPA, DOE (2005) RFA Text |  Recipients Lists
Research Category: Global Climate Change , Ecosystems , Climate Change


Ecosystems of the US are subject to a variety of human caused stressors including changes in climate, changes in the chemistry of the atmosphere, changes in the chemistry of precipitation, and changes in land cover and land use. These stressors can act singly or together to elicit nonlinear and threshold responses in freshwater ecosystems, and alter their capacity to deliver ecosystem services such as sufficient quantities of clean water. In this research, we will explore how a set of environmental stressors act to affect the physical, chemical, and biological integrity of linked land-river networks using a coupled terrestrial-aquatic ecosystem model that is process-based and is applied in a georeferenced context within drainage basins across the US. The research will have two parts; building the linked land-river network model, and using the model in both retrospective and prospective studies.


Our use of the model will be guided by two hypotheses: 1) nonlinear and threshold responses in the coupled land-water systems are key to defining the observed variations in water quality across the U.S. during the last 100 years, transformning and intensifying local and in some cases regional-scale problems to fully continental-scale syndromes; and 2) future policy interventions can slow and sometimes reverse these problems and syndromes, but the interventions will be complicated by the reality of new stable states and the heritage of existing threshold responses requiring many years to reverse. Our research plan includes two workshops involving our science team, resource managers and policy makers. At the first workshop we will develop a set of "what if' scenarios that include specific policy interventions and then we will use them in simulations. At the second workshop we will analyze how these interventions affect nonlinear and threshold behaviors in the freshwater ecosystems within drainage basins and what the consequences will be for ecosystem services.

Expected Results:

This research will contribute significantly to the development of a theoretical basis for effectively protecting and managing ecological systems that exhibit nonlinear and threshold responses to environmental stressors. The successful development of research and management tools, such as the ones we are proposing, will help scientists to predict ecological thresholds before they are observed. These research tools will also help resource managers and policy makers select among alternative courses of action as they work to maintain, and in some cases enhance, the services provided to us by ecosystems.

Publications and Presentations:

Publications have been submitted on this project: View all 28 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 13 journal articles for this project

Supplemental Keywords:

global change, multiple stressors, nonlinear ecosystem response, threshold response, river network, drainage basin, land cover change, ecosystem services, water quality, hydrologic regime, hydrological modeling, mltiple scales,

Progress and Final Reports:

  • 2008 Progress Report
  • 2009 Progress Report
  • 2010 Progress Report
  • Final Report