For the estuaries in the lower 48 states, the risk of current habitat degradation in each estuary was assessed by mapping national datasets of disturbance variables measured within estuaries and their adjacent watersheds. Disturbance variables were summarized into the following four disturbance categories:
A relative disturbance index was assigned to each estuary for the four categories. The four indices were then combined to calculate a disturbance score for each estuary, which is a measure of the current risk of degradation to that habitat.
Some important threats to fish and their habitat could not be incorporated in this analysis due to data limitations. These include, but are not limited to, benthic habitat loss and disturbance due to dredging and fishing practices, percentage of shoreline armoring, sedimentation and erosion trends, contaminant concentrations in fish and shellfish tissue, and status of biogenic habitats (e.g. oyster reefs and shellfish beds, coral reefs, kelp forests, and seagrass beds). These additional sources of disturbance will be addressed in future revisions of the coastal assessment.