Which stressors are most important and which resources are most vulnerable?
It is possible to use the regional data base to estimate which individual stressors are most important. Likewise, it is possible to estimate which resources are most vulnerable in the sense of already being under considerable stress. Because stressors interact and resources respond in complex ways,
the method analyses the data to account for these complex interrelationships.
The most important stressor, accounting for impacts on all regional resources, appears to be the amount of land which has been converted to human uses: urban, residential and agricultural. Limiting further development is probably the greatest challenge facing environmental managers in the region. After land conversion, the most important stressors appear to be nutrients (Phosphorus and Nitrogen) that are being added to the aquatic system. These nutrients result from rainfall washing agricultural and lawn fertilizers and animal waste into the streams and rivers of the region. Nutrient stressors are particularly important because they can cause irreversible changes in the aquatic system, a process known as
Eutrophication.
The ReVA approach can also estimate the resources under the greatest stress, considering all of the stressors. In a decision-making context, these resources might be considered the most vulnerable to further stress and most in need of protection. The most vulnerable resources are small intact forests and habitat for migratory birds. The vulnerability is largely the result of fragmenting forests and converting them to human uses.
These results show the overall result of past and present human stressors operating over the region. Many of the impacts are cumulative and do not necessarily reveal immediate impacts. The top ranked stressors are the most important across time and space but their elimination might well result in little, or long-delayed, responses. Nevertheless, limiting future conversion and fragmentation of forests and reducing nutrient inputs to the aquatic system will probably have the greatest long-range effect on regional environmental quality.
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