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The Contextual Rating would have a <br />maximal value of about 42 in the extreme case of <br />a tract entirely surrounded by undisturbed hard- <br />wood forest (see Appendix II). It would have a <br />value of 0 in the other extreme case of a tract <br />entirely surrounded by unforested land to a <br />distance of 2 miles in all directions. <br />By adding 1 to the. CR, the target tract in <br />this latter case would have a Total Rating equal <br />to its Intrinsic Rating: when CR = 0, TR = IR x <br />(CR + 1) = IR. Thus when CR = 0, it has no <br />effect on the Total Rating. <br />Total Ratings for tracts of forest in Orange <br />County in 1988 appear in Map 3, and the sites <br />with the highest Total Ratings are presented in <br />Map 4. <br />HOW RATINGS HAVE CHANGED <br />IN THE PAST DECADE <br />The aerial photos used for mapping the <br />forests in Orange County date from 1988, <br />the most recent available. In the past decade the <br />Intrinsic Ratings of some tracts of forest have <br />probably increased and others have decreased. <br />Undisturbed forests have continued to <br />mature, so some have changed from predomi- <br />nantly pine to predominantly hardwood and <br />thus have higher Intrinsic Ratings. <br />Other forests include properties that have <br />been timbered or for which building permits <br />have been issued in the past decade. Although a <br />building permit does not necessarily mean that <br />all forest on the property has been cleared, some <br />clearing is usually the case. These tracts would <br />now have lower Intrinsic Ratings. <br />To estimate the consequences of recent <br />building for the wildlife value of forests, we have <br />recalculated the ratings after subtracting all <br />properties for which building permits were <br />issued between 1988 and 1998 (except those <br />14 <br />tracts in the Chapel Hill Planning District, for <br />which information on building permits was not <br />available). The resulting ratings appear in Maps <br />5 -8. Some statistics for these ratings before and <br />after subtracting properties with building <br />permits appear in Table 3. <br />It is important to emphasize that the statis- <br />tics in Table 3 for forests in 1998 are based on <br />incomplete information: they do not include the <br />effects of timbering, the progressive maturity of <br />undisturbed forests, nor the actual effects of <br />building permits. Accurate assessment of the <br />County's current forests will require an analysis <br />of recent aerial photographs. <br />Male (bottom) and Female Pileated Woodpeckers <br />