An historical perspective on land-use change
and N loading in the Narragansett Bay watershed

Steve Hamburg and Matt Vadeboncoeur, with Don Pryor

 

Decisions about the management of nitrogen entering estuarine systems are best made in the context of a solid understanding of past inputs. The watershed of Narragansett Bay has a long history of intensive human exploitation, with consequences for the amount of nutrient loading to the bay.

We present a quantitative model based on 150 years of town-level data on population, sewer construction, animal agriculture, the use of commercial fertilizers, and land cover, as well as regional trends in atmospheric deposition. We validated our model results using comparisons of modern and historic river N concentrations where available.

Our results show that N loading increased most rapidly during the late 19th and early 20th Centuries, but that N loads have increased steadily and significantly throughout the 20th Century as well. Additionally, we show that over the 20th Century, N loading to the Upper Bay / Providence River has increased more than in other parts of the bay.

Land-use change in the Narragansett Bay watershed since 1885. Much of the watershed was heavily agricultural in the late 19th Century, while today it is primarily forested.

A conceptual model of changes in the N cycle in the Narragansett Bay watershed since 1885. Waste nitrogen from agriculture has decreased dramatically, but have been omre than offset by increases in human population which relies on food imported from outside the watershed.

This work is in press as of February 2007, and has been presented at the RI Natural History Survey 2006 annual meeting. An update will be presented at the 2007 annual meeting.

Hamburg, S.P., Pryor, D. and M.A. Vadeboncoeur. 2007. Nitrogen Inputs to Narragansett Bay: an Historical Perspective IN Desbonnet, A. and B. Costa-Pierce eds. Science for Ecosystem-based Estuarine Management: Narragansett Bay in the 21st Century Springer New York (in press).

Updated 05/22/2008
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