PS 22-99 - Moving edges: What changing edges tells us about the causes of Salt Marsh loss

Tuesday, August 9, 2011
Exhibit Hall 3, Austin Convention Center
James P. Browne, Ecology and Evolution, Stony Brook University, Stony Brook, NY

Salt marshes are being lost on the Atlantic Coast of North America. Anthropogenic impacts on salt marsh are varied and the causes of marsh loss and occasional gain may be as well. Changes in salt marshes are measured in various ways, growth responses, changes in species composition, changes in food web dynamics, competition between plants, and changes in area. This study takes a different approach, looking at the spatial and temporal pattern of edge changes on a Spartina alterniflora marsh. Located in a highly urbanized estuary on the South Shore of Long Island, New York, the focus estuary still contains roughly 3,000 hectare of Spartina marsh. Using twelve sets of aerial photographs and GIS software, changes over an eighty one year period were measured at over four hundred randomly chosen points along the marsh edges. It is argued that looking at the changes at specific points along edges is highly informative because each point is exposed to a unique combination of potentially causative influences. This study explores the varied changes seen, even at different edges of the same marsh island, and draws conclusions about the patterns formed by the mix of causes and responses within this estuary.


Changes measured at these salt marsh edges were not attributable to any single influence. It was found that edges formed artificially continue to show high rates of loss long after initial damage, however they formed only a small part of the total edge. The distance to borrow pits with still water was also a significant anthropogenic factor, as was heavy boat usage in facing channels. Significant natural influences include unobstructed distance across water and tidal flow rate. A strong gradient in nutrient loading did not reveal either loss or gain resulting from this anthropogenic influence. Other factors will also be discussed. In general, the edges most distant from both natural and anthropogenic disturbance have changed relatively little.

Copyright © . All rights reserved.
Banner photo by Flickr user greg westfall.