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The extent and expected condition of isolated wetlands in the southeastern and mid-Atlantic states, USA
Citation:
LANE, C. R., E. D'Amico, B. C. AUTREY, AND J. Rhodus. The extent and expected condition of isolated wetlands in the southeastern and mid-Atlantic states, USA. Presented at Society of Wetland Scientists Annual Meeting, Prague, CZECH REPUBLIC, July 03 - 08, 2011.
Impact/Purpose:
The EPA Office of Water has recognized a critical need for states and federal agencies to be able to quantitatively assess the condition of the Nation’s wetland resources. Currently, >85% of states, tribes, and territories are lacking even rudimentary biological assessment methodologies for wetlands. Additional important needs identified include obtaining base line nutrient and physical/chemical conditions to aid in understanding the role of wetland systems (isolated wetlands in particular) in ensuring aquatic life and beneficial uses of lakes, rivers, and streams in the watershed. To address these challenges, the following research on isolated wetlands is proposed: Within a region, 1) Develop a probabilistic sampling design that stratifies isolated wetlands by type and size (also targeting reference conditions); 2) Collect biotic data using macroinvertebrates, macrophytes, and diatoms; 3) Collect abiotic (water and soil chemistry) data to establish base line conditions, quantify wetland contribution to landscape nutrient dynamics, and establish a spectral library for future rapid assessment of nutrient sequestration abilities of isolated wetlands; 4) Assess wetland condition with Level 1 (geographic information systems - GIS) and Level 2 (rapid assessment) characterization methods; 5) Develop metrics and correlate biotic signature to local and landscape assessments; 6) Report on the condition of systems across region and recommend assessment methods to states and tribes; 7) Model isolated wetland contribution to landscape nutrient dynamics based on analyses using visual and near-infrared spectrometer (VNIRS) data. Key outputs for regions and states from the proposed research include: tools for remote GIS-based assessment, tools for rapid on-site assessment, and tools for intensive biological assessment of isolated wetlands; comparison between local and landscape assessment measures; functional assessment of isolated wetland contribution to landscape nutrient dynamics (using VNIRS); baseline water and soil physical/chemical conditions; baseline flora and fauna of isolated wetland systems; and a fuller understanding of watershed condition and regional environmental health.
Description:
In the wake of two United States (US) Supreme Court decisions in the past decade, federal protection for isolated wetlands (i.e., those completely surrounded by uplands) has been severely curtailed. However, the extent of the resource impacted and thus the implications for the change in protected status is unknown. Current estimates from almost a decade ago suggest that no more than 20% of the wetlands of the US are isolated, but that is simply best professional judgment. In this study we used the increasingly available and updated National Wetlands Inventory from the US Fish and Wildlife Service and a 10-m buffer of the US Geological Survey National Hydrography Dataset to mask data where potential wetlands intersected stream, river and lake buffers, thereby identifying potential isolated wetlands in an eight-state region of the Southeastern and mid-Atlantic US, an area of dense isolated wetland occurrence. We additionally applied a landscape-level measure of anthropogenic distubance, the Landscape Development Intensity (LDI) index, to calculate the expected condition of the extant isolated wetlands. Results suggest that over 800,000 isolated wetland features, covering over 1.2 million hectares, are present on the landscape, although the average isolated wetland size is only approximately 1.3 hectares (ranging from <0.01 - 2400 ha). Preliminary expectations of relative condition indicate that <20% of the wetlands, on average, are in the poorest expected condition, while the distribution of high-quality wetlands varies markedly by state from <20% to >55%. Future applications include identifying watersheds of high-quality isolated wetlands, opportunities for restoration, and determining connectivity.