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Regional Vulnerability Assessment (ReVA) Program
 
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How will the overall condition of the region change by 2020?

One of the advantages of the ReVA approach is the ability to provide an overview of environmental quality across the entire region. This serves to place individual small-scale problems into a larger context. Seeing where the pattern changes may help guide planners and prevent unnecessary degradation.

Two methods are used to examine the overall spatial pattern. The two methods are complimentary in the sense that they are sensitive to different peculiarities in the data set. The two methods are used together because greater confidence can be placed in the results when the methods agree.

The future spatial pattern shows that the poorest environmental quality is found in urban areas including the Philadelphia/Baltimore/Washington complex and in watersheds surrounding Pittsburgh. The watersheds in the best environmental condition remain in the highlands of West Virginia and north central Pennsylvania. Watersheds of intermediate quality are found in the more rural coastal plain and plateau.

Simple Sum Future compared to PCA Future - MAIA region map

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The difference map shows that the PCA/Sum method consistently ranks watersheds as being in better condition because this method accounts for the co-occurrence of stressors. Obviously, many watersheds are being simultaneously impacted by many stressors. The simple sum gives a more conservative picture of environmental quality and perhaps a better picture of where cumulative effects are likely to occur.

A comparison between the current and future scenarios by the simple sum method is shown in the figure below. The difference map shows the general decrease of environmental quality throughout the highlands and foothills areas.

Simple Sum Current compared to Simple Sum Future - MAIA region map

Compared to the simple sum the PCA/Sum methods shows less overall degradation and no longer indicates degradation on all of the highland and foothills watersheds. In general, the overall patterns of change are similar with the pca/sum method showing less degradation where multiple stressors co-occur.

PCA Current compared to PCA Future - MAIA region map

The future scenario devised for this study shows significant reductions in environmental quality that are scattered across the Mid-Atlantic region with the possibility of synergistic effects from multiple stressors degrading all of the highland and foothills watersheds. The changes are not necessarily large, often involving only a small shift, but the degradation is spread broadly across the entire region.

 

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