Comparing impacts to shallow-water habitas through time and space |
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| Authors: | Karim A Abood Susan G Metzger |
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| Institution: | 1. Lawler, Matusky & Skelly Engineers, Environmental Science & Engineering Consultants, One Blue Hill Plaza, 10965, Pearl River, New York
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| Abstract: | Impacts to shallow-water estuarine habitats should be assessed in a holistic context reflecting both the interrelatedness of habitats that characterize these environments and the history of impacts, human and natural, that have shaped their present ecology. In a holistic context these habitats are considered to be dynamic associations of macrohabitats and micro-habitats, interacting through time to affect the quantity (Q1), quality (Q2), and timing (T) of material and energy transfer within the system. Where data are available, this holistic approach (Q1, Q2 and T or Q2T) allows impacts to be evaluated in a multidimensional framework of time and space. Unfortunately, few data are available to evaluate the long-term implications of timing, the T factor. Recorded observations of most estuarine systems cover tens of years, periods not extensive enough to assess long-term changes to the environment or to distinguish man's impacts from those of nature. Sustained droughts, for example, can cause massive disruption in estuaries, altering habitats and species composition. When these changes occur over periods of 5–10 yr, the changes are difficult to identify and may be attributed to man's activities rather than nature's Using the Hudson River estuary as an example, we have knowledge of historical impacts extending back to the 1700s, ranging from dredging to major droughts. For the Hudson River, recorded observations of rainfall and river flow extend back about 70 yr; however, tree rings provide a more extensive record since tree growth increments are directly dependent upon rainfall. The Hudson River drought record was extended back to 1694 using tree rings. Using the reconstructed record, the relationship between today's conditions—flow and average location of the ocean-derived salt front—can be placed in a historical context. This historical perspective allows us to place present-day human impacts into the contex of long-term natural impacts and to discriminate among these effects. The drought example is particularly relevant to shallow-water habitats because these habitats provide an interface between fresh and marine waters. *** DIRECT SUPPORT *** A01BY074 00008 |
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