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Landscape Thresholds and the Condition of Northeastern Estuaries
Citation:
HOLLISTER, J. W. AND H. A. WALKER. Landscape Thresholds and the Condition of Northeastern Estuaries. Presented at New England Estuarine Research Soceity Spring Meeting, Greenland, NH, May 01 - 03, 2008.
Impact/Purpose:
The purpose of this poster is to highlight the use of broad scale monitoring data for use in identifying thresholds in relation to condition of estuaries. This work will impact research on ecoloigcal condition and ecosystem services in that broad scale data has the potential to identify estuaries that may soon transition from an ecosystem capable supporting numerous ecosystem services to one that cannot.
Description:
Anthropogenic impacts to northeastern estuaries have been well documented and many researchers have quantified the associations between broad scale human land uses in contributing landscapes and impacted estuarine condition. However, associations alone are not adequate for identifying thresholds and little work has been done to identify thresholds in the patterns of human use that are indicative of degradation in downstream estuaries. We use conditional probability analysis, non-overlapping confidence intervals, and change point analysis to identify thresholds and explore relationships between patterns of human use in estuarine catchments and the probability of impairment in northeastern estuaries. Preliminary results suggest the following: 1) probability of impairment increases as human use increases, 2) all estuaries with less than approximately 20% human uses are not impaired 3) probability of impairment peaks at intermediate proportions of human use (i.e., approximately between 30-50% of a contributing watershed), and 4) human use alone may not be a tipping point for impairment because non-impaired sites can be found with landscapes dominated by human uses. This last result suggests other factors (e.g. ecoregional variation, estuarine type, habitat differences, etc.) may also play a role in determining how human uses ultimately impact estuarine condition. We expand on these preliminary results with more recent data examined at the individual catchment scale.