Developing and applying an index of environmental integrity for the US Mid-Atlantic region

Environmental conditions in the Mid-Atlantic region of United States are presently being documented in a series of reports that use 'environmental report cards' to summarize the condition of individual natural resources (e.g. estuaries, streams, forests, and landscapes) over the entire region and within major subregions. An 'index of environmental integrity' (IEI) approach has been developed and is illustrated using the information content of these report cards to evaluate the overall condition throughout the region. The IEI approach is a four-step process: (1) select individual components for the index, (2) calculate subindex values for each of the individual components, (3) aggregate the subindex values into the overall index, and (4) interpretation of index values. The IEI approach was illustrated by applying to the Mid-Atlantic estuaries and wadable streams in the Mid-Atlantic Highlands. Because the IEI approach is new, application should not be made without considering issues such as evaluation of the selection of the indicators, weighting scheme, uncertainties, and appropriate way to interpret the values.