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RFF REPORT Terrestrial Ecosystem Adaptation Steven W. Running and L. Scott Mills ADAPTATION | AN INITIATIVE OF THE CLIMATE POLICY PROGRAM AT RFF JUNE 2009 Table of Contents Introduction ................................................................................................................................................................ 1 Climatic Means versus Extremes .................................................................................................................. 3 Recent Historical Climate Trends and Variability ...................................................................................... 4 Vegetation Response and Phenology .......................................................................................................... 6 Wildfire and Disturbance ................................................................................................................................. 9 Adaptation to Climate Change in Wild Populations ............................................................................... 11 Adaptation in Place via Plasticity and/or Evolution ......................................................................... 12 Adaptation via Movement and Range Shifts ......................................................................................... 15 The Interaction of Climate Change with Other Human‐Caused Stressors ............................... 16 Expected Future Ecosystem Trends .............................................................................................................. 17 Future Climate Trends ................................................................................................................................... 17 Species Responses Based on Focal Animal Species ........................................................................... 19 Adaptation Options ............................................................................................................................................... 23 Water Management ......................................................................................................................................... 23 Vegetation Management ................................................................................................................................ 24 Manage for Resilience ..................................................................................................................................... 25 Facilitate Connectivity and Consider Assisted Colonization ......................................................... 25 Directed Evolution of Native Animals ..................................................................................................... 26 References ................................................................................................................................................................ 27 2 Terrestrial Ecosystem Adaptation * Steven W. Running and L. Scott Mills Introduction n this report, we evaluate adaptation issues for natural ecosystems. We will specifically focus on Ithe interactions with the abiotic environment of plants and animals, along with other organisms with which they interact (e.g., disease‐causing bacteria and viruses). We further limit ourselves to natural ecosystems in which the predominant vegetation has developed without having been planted, irrigated, or fertilized. Most of the natural lands in the United States are managed by federal or state governments. Agricultural lands—including range grazing lands —are dealt with in a related adaptation report. This will evaluate the potential magnitudes and challenges facing terrestrial ecosystems in the United States in adapting to changing climate over the next 30–50 years. Our report will not address attribution or mitigation of climate change, as these topics have been dealt with in many other forums. We will begin with a brief summary of the current trajectory of the changing climate in the United States, including both temporal and spatial patterns. We will then relate these trends to ecosystem impacts and vulnerabilities. We consider adaptation in the broad sense to include any means by which organisms successfully confront a perturbation such as climate change. This includes both local adaptation in place—either through plastic responses or through evolutionary changes—as well as changes in movements within or outside of the current geographic range. Some species (often invasive and disease species) will adapt spectacularly. By contrast, those unable to adapt will experience decreased average mean fitness, translating into population decline, decreased persistence, and changed community and ecosystem structure (Figure 1). After considering ecological adaptation mechanisms, it becomes possible to consider potential management options to enhance adaptation. We do not make recommendations of specific adaptation activities at this point; rather, we suggest alternatives to begin the discussion. * Department of Ecosystem Sciences, College of Forestry and Conservation, University of Montana, Missoula, MT. swr@ntsg.umt.edu; scott.mills@cfc.umt.edu. This report was prepared for the Resources for the Future project on adaptation to climate change. For more information, see www.rff.org/adaptation RUNNING AND MILLS 1 Figure 1. Response of Biotic Communities as Climate Change Affects Individual Species (which adapt in place, move, or decline toward extinction), Changes in Species Interactions, and Ultimately the Structure and Composition of Communities and Ecosystems Note: Differential adaptation among species leads inexorably to changes in community and ecosystem structure RUNNING AND MILLS 2
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