Climate change is fundamentally altering the planet's environment, including increased air and ocean temperatures, melting glaciers and icecaps, and rising sea levels. By altering the environment, climate change is likely to have pervasive but currently unknown impacts on the structure and functioning of ecosystems. Coastal zones are particularly sensitive to climate change given that they are generally within a few feet of sea level. Recent estimates call for a 33% loss of coastal wetlands, including salt marshes and mangroves, by 2080 due to rising sea levels. Coastal wetlands provide crucial ecosystem services, including protection from local flooding, filtration of terrestrial runoff, tourism, and provision of habitat for diverse marine vertebrates and invertebrates that support lucrative fisheries. Nearly 70% of the world’s population lives within 50 miles of the shoreline, thus the loss or degradation of wetland services is likely to have substantial impacts on human societies. Responses to climate change are predicted to be most severe along traditional transitional zones. Thus, we focus on the current and future displacement of temperate cordgrass marshes by eight species of invading mangrove trees from lower latitudes in southeastern North America. Cordgrass marshes are among the world's most productive ecosystems and support ecologically and economically important communities, yet in both North America and worldwide they are rapidly being replaced by tropical and subtropical mangroves. We hypothesize that interactions among increased air and ocean temperatures, rising sea levels, and nutrient over-enrichment are shifting cordgrass marshes to mangrove forests and causing substantial impacts on the structure and functioning of coastal wetlands. Our primary objectives are to: 1) link climatic and biophysical observations to changes in the distribution and composition of salt marsh and mangrove wetlands across spatially variable landscapes; 2) determine impacts on key ecosystem services; and 3) model future distributions of salt marsh and mangrove wetlands. First, to create historical time-series of mangrove and salt marsh distributions from the 1940’s to the present (corresponding with the most rapid increases in global temperature), we will use high resolution aerial photography along with remotely-sensed multispectral high-resolution satellite (IKONOS, QuickBird) and Landsat imagery to recreate historical patterns of shoreline vegetation. In combination with precision GPS surveying of fixed landmarks, we can correlate ecological shifts in wetland vegetation to temperature records, sea level, and environmental disturbance (both anthropogenic and natural). Spatial analysis using GIS tools will also permit development of predictive sea-level rise scenarios (east-west continuum) and ecosystem-replacement scenarios in response to global warming (north-south continuum). Importantly, we will be able to complete remote-sensing analyses wherever mangroves exist worldwide, allowing us to rapidly document global patterns of coastal shoreline transformation. To determine how mangrove expansion into salt marshes affects ecosystem services, we will conduct faunal and vegetation sampling along a salt marsh-mangrove chronosequence. Standard community statistics will be used in conjunction with stable isotopic analysis to determine differences in food web structure and nutrient dynamics. Finally, we will combine new data with our existing datasets on mangrove demography to parameterize spatially-explicit, individual-based models (KiWi) simulating the growth, establishment, and death of individual trees for each invading mangrove species. These models will allow us to predict the future structure, composition, and function of mangrove wetlands in a changing climate.

Project PI: Ilka Feller/Smithsonian Institution

Smithsonian Environmental Research Center SERC MRC 540 POB 28 Edgewater, MD 21037



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Started: Mar 31, 2011

Last Activity: Mar 31, 2011


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