Case Study: Estimating and mitigating the impacts of climate change and air pollution on alpine plant communities in national parks

Porter, Ellen; Sverdrup, Harald; Sullivan, Timothy

Two of the major stressors affecting plant communities in remote locations are climate change and excess nitrogen input from atmospheric pollution. Both stressors are causing profound changes in ecosystems, and there are strong interactions between plant responses to nitrogen pollution and responses to climate change. Certain native plant communities, notably those found in alpine, desert, and wetland areas, are expected to be very sensitive to both climate change and nitrogen addition. Many plant species in these areas have strict habitat requirements, and as climate change and nitrogen alter physical, hydrological, and chemical conditions, these species are displaced or marginalized. Plant communities located in “edge” or transition zones (e.g., tree line) are expected to be particularly vulnerable. While climate change is disturbing moisture and temperature regimes, nitrogen deposition from air pollution is causing unnatural fertilization (eutrophication) of ecosystems. This enrichment may favor certain species, often invasive weeds, over native plants. Species better able to use nitrogen crowd out native plants adapted to low-nitrogen conditions, making plant communities even more vulnerable to differences in temperature and precipitation expected as a result of climate change. In a workshop held in 2008, National Park Service (NPS) and university alpine plant specialists identified growth requirements of many alpine species in parks, including requirements for light, moisture, temperature, and nitrogen. The information was then used to simulate plant species responses to climate change and nitrogen addition, using the ForSAFE-VEG model. The model was developed in northern Europe to estimate soil chemistry and plant biodiversity responses to climate change and nitrogen pollution. The model is rooted in biogeochemical processes but also includes expert judgment to classify plant species according to their general patterns of response to stress. Based on information from the 2008 workshop, ForSAFE-VEG has recently been applied to a generalized tree line location representing national parks in the central and northern Rocky Mountains. Results of this preliminary model application suggest that ForSAFE-VEG is a useful tool in understanding interactions between nitrogen air pollution and climate change at high-elevation national park locations. For example, reducing nitrogen deposition and its associated stresses may be an effective strategy for increasing the resiliency of alpine plant communities to climate change.

Case Study: Estimating and mitigating the impacts of climate change and air pollution on alpine plant communities in national parks

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