R/UC-1

Impact/Outcome:

This section describes how this project has advanced scientific knowledge and/or made a difference in the lives of coastal residents, communities, and environments. Maryland Sea Grant has reported these details to the National Oceanic and Atmospheric Administration (NOAA), one of our funding sponsors.

RECAP: Scientists developed a new analytical approach that improves detection and measurement of changes in biological communities in Chesapeake Bay tributaries over time and at different locations. This line of research may help researchers and local and state officials to plan better to prevent and manage the effects of development and urbanization on that plants and animals in Maryland’s streams.

RELEVANCE: The project’s overall goal is to better understand responses of biological communities to changes in stream water quality caused by urbanization and development in watersheds. Existing methods for detecting these responses have methodological limitations that limit their precision for representing/detecting changes over time, such as the population decline of a species, genus, or family. The new approach developed in this project complements and informs interpretation of those existing techniques.

RESPONSE: The principal investigators -- Matthew Baker of the University of Maryland, Baltimore County, and Joseph Sexton, University of Maryland, College Park – created an annual database of impervious surface maps from satellite images covering a 25-year period for six Maryland counties and Washington, D.C. The researchers linked these maps to existing data sets on stream chemistry and macroinvertebrate abundance in the Chesapeake Bay watershed. The scientists looked for evidence of thresholds, where incremental changes in urbanization and water quality were associated with disproportionately large changes in the composition of biological communities, as reflected in the occurrence and abundance of individual species or other taxonomic groups.

RESULTS: This study provided a proof of principle for a new analytical approach for accurately mapping urbanization and land development and tracking associated changes in biological communities. Of 70 sampling sites where macroinvertebrate species were measured, 16 sites showed evidence of abrupt changes consistent with a threshold response.

The researchers identified several specific cases where threshold responses indicated urbanization was a likely cause, yet other cases showed incremental responses to increasing development. The scientists are working to expand the model’s predictive power by incorporating a larger data set from more Bay tributaries in Maryland.

Knowledge of how ecosystems respond to land-use changes, and how rapidly, has profound implications for mitigation efforts and properly managing those ecosystems. The researchers have begun to disseminate their new analytical approach to local officials and natural-resource managers. It may prove useful for analyzing long-term trends in and effects of development, construction, population growth, and changes in regulatory policy.

The method has spawned research proposals and efforts in other major metropolitan regions of the United States.