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The 1:250,000 maps and overlay techniques visually showed the 

 ecologically important and significant features of the area, and 

 areas required for their preservation. 



The Numerical Ranking System 



To set priorities among 232 diverse areas calls for a numeri- 

 cal ranking system whereby one can weight selected criteria that 

 delineate ecological and, in some instances, social values. Some 

 criteria require not only detailed knowledge of the sites in question 

 but also a broad knowledge of the range and rarity of plant and 

 animal species. 



In other words, numerical values were assigned each criterion 

 based on ecological judgment. Modifications were made in the course 

 of the project and testing and further improvements of the system 

 are needed. The weighting system gives greater importance to plant 

 communities or types that are not in the National System of 

 Research Natural Areas, those for which there are already many exam- 

 ples. Also, the factors of diversity, quality, lack of past and 

 present disturbance, protectability, and other factors have been 

 given appropriate weighting. 



Subjective evaluation could be added to take into account 

 species with human emotional or national significance. The condor, 

 whooping crane or bald eagle have higher importance for preservation 

 than a subspecies of sedge which can be identified by only a few 

 specialists. 



