RELATIOSHIPS BETWEEN LAND USE AND ECOLOGICAL
CONDITION INDICATORS IN CHESAPEAKE BAY
Richard Latimer
S. Hale, J. Copeland
R. Comeleo, C. Baker
P. August
U.S. Environmental Protection Agency
Environmental Research Laboratory - Narragansett
27, Tarzwell Drive
Narragansett, RI 02882, USA
ISPRS Commission VII / Working Group 8
ABSTRACT
The U.S. Environmental Protection Agency has implemented the Environmental Monitoring and
Assessment Program (EMAP) to monitor the condition of the Nation's ecological resources. The
estuarine component of EMAP is designed to estimate on a regional basis the status, trends, and changes
in estuarine ecological conditions. Biotic and abiotic condition indicators in the Chesapeake Bay pelagic
and benthic environments have been measured each summer since 1990. One objective of EMAP is to
seek associations between condition indicators and various stressor indicators that may be influencing
changes or trends. Although the idea that watershed land use affects the health of water bodies is
intuitively obvious, it has not always been easy 10 demonstrate direct relationships, partly because of the
scarcity of consistent estuarine monitoring data collected on a regional scale. An analysis of land use
mosaics derived from Landsat Thematic Mapper imagery in the Chesapeake Bay watershed, in
conjunction with a spatial analysis of Bay ecological indicators, revealed various relationships and
patterns. The amount of developed land and annual lead loading from pollution points sources within a
10 km radius, along with sediment percent silt and clay, explained 79% of the variation found in
estuarine sediment lead concentrations. Thirteen other sediment metals and total polychlorinated
biphenyls were also significantly correlated with the amount of developed land in adjacent areas. Stations
in urbanized areas had a higher number of opportunist benthic species and a lower species diversity than
less urbanized areas. These patterns and the probable processes that produced them formed the basis for
testable hypotheses. Spatial analytical techniques provide a useful tool in linking watershed activities
with estuarine effects. Remote sensing and the EMAP sampling program provide a sufficiently large
dataset on a regional scale to be able to apply such techniques.
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