In the April 2005 issue of Conservation Biology, Wendell Haag and Mel Warren, researchers with the FS Southern Research Station (SRS) unit in Oxford, MS, report results from a study of archaeological data from 27 prehistoric sites in the southeastern United States that shows how the erosion and sediment associated with agriculture affect freshwater mussel populations.
Worldwide, freshwater mussels have proven to be highly susceptible to human-caused disturbance, and represent the most endangered group of organisms in North America. Of 297 species found in the United States, 269 freshwater mussel species are found in the Southeast.
"We can tie declines of specific mussel populations to the construction of dams, stream channelization, or pollution from a specific source," says Haag, "but the worldwide patterns of decline in these animals implies that larger-scale disturbances such as sedimentation and nonpoint-source pollution may have an equal impact."
Among freshwater mussels, members of the genus Epioblasma -- commonly called riffleshell -- are the most endangered. Epioblasma consists of 20 species and eight subspecies; at least 13 of these species and four subspecies are presumed extinct. Of the remaining, the snuffbox mussel (Epioblasma triquetra) is the only species not listed on the Federal endangered list.
"Human population in the Southeast began to increase steadily about 5000 years ago," says Warren. "With increasing population came land disturbance from agriculture. This intensified about 1000 years ago, with the beginning of large-scale maize cultivation. No one has really tried to look at how this change in land use impacted water quality and aquatic organisms such as freshwater mussels."