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Several other ecological ranking systems have tried to take 

 into account the factors of man-induced pressures on the land 

 and relative isolation from development. Indeed, one of the 

 original rankings used in this study gave added weight to threatened 

 areas. This seems to make sense for any setting of priorities as 

 far as timing is concerned. But as far as true ecological value 

 is the measure, isolation from threatened destruction should 

 receive greater numerical value. If both of these factors are 

 included in one system, they tend to cancel each other out. For 

 these reasons we have excluded the factors of threat and isola- 

 tion. In the implementation of preservation actions, however, 

 the ecologically important areas that are threatened most should 

 of course be worked on first. 



Selection of Proposed Natural Areas . In making the quantita- 

 tive evaluation of each site considered as a natural area, all of 

 the data in the file for each site were put into a standardized 

 format for natural areas. This is the system jointly developed for the 

 Natural Area Registry by The Nature Conservancy and the 

 Smithsonian Center for Natural Areas. It is compatible with 

 the system used by the U. S. Committee on Conservation of 

 Ecosystems of the International Biological Program. The data for 

 the considered sites for the Chesapeake Bay are shown in the 

 complete print-outs. They also contain the present rating for 

 each site (also shown in the lists in this report) . The ratings 

 are not permanent and can be updated with the addition of further 

 ecological information . 



