Historical Land Use,Nitrogen, and Coastal Eutrophication: A Paleoecological Perspective |
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| Authors: | Grace S Brush |
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| Institution: | (1) Johns Hopkins University, Baltimore, MD 21218, USA |
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| Abstract: | Organisms and chemicals preserved in sediment cores from the Chesapeake estuary in mid-Atlantic USA are consistent with a
precolonial landscape covered with a diversity of forests and marshes, large and small. During the past 300 years, many of
the wetlands have been drained, and the landscape was converted to agricultural fields and urban and suburban development.
During this time, sources of nitrogen have diversified, and loadings have increased. Since precolonial time, the mesohaline
estuary has become increasingly eutrophic and anoxic. Estuaries and coastal regions throughout the world have experienced
similar conditions in their recent history. These changes are recorded in Chesapeake sediment cores by increases in ragweed
pollen, dry taxa, sedimentation rates, nitrogen influxes, and a major change in estuarine autotrophs from benthic to planktonic.
In many areas, attempts to reverse estuarine eutrophication and anoxia have centered on restoring streams and riparian areas
and reducing fertilizer use on agricultural lands. However, data from soils and historical reports and the paleoecological
record suggest that to reduce the effects of modern nitrogen inputs, it may be necessary to locate and enhance denitrifying
areas throughout the watershed. |
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