74 • Technologies To Maintain Biological Diversity 



Photo credit: U.S. Fish and Wildlife Service 



Northern spotted owl requires large tracts of Pacific 



Northwest old-growth forest as habitat. If harvesting 



of old-growth continues at current rate, the habitat for 



this species could disappear within the next 



two decades. 



tries need more rapid resource development. 

 A "worst-case" calculation indicates that if the 

 forests were reduced until they covered only 

 National Parks and their equivalents that had 

 been established by 1979 (about 97,000 square 

 kilometers), then the final effect could be as high 

 as a 66-percent reduction (43). 



About 704 species of land birds have been 

 described in the Amazon region of tropical 

 America. Using the same mathematical rela- 



tionship as used for plants, a 60-percent reduc- 

 tion of the original forest area over the next 15 

 to 20 years could be expected to cause even- 

 tual extinctions of 86 bird species. The worst- 

 case calculation, with reduction of the Ama- 

 zon forest to the area of already established na- 

 tional parks, projected that 487 types of birds, 

 or about 70 percent of the species, could be- 

 come extinct (43). 



Several assumptions tend to underestimate 

 extinction rates. For example, extinctions re- 

 sulting from reduced provinciality are ignored 

 in the calculations, as are effects of the narrow 

 endemism that occurs in several parts of tropi- 

 cal American forests. On the other hand, the 

 assumption that none of the plant and bird spe- 

 cies will find habitats they need after deforesta- 

 tion seems an exaggeration. Such projections 

 may be helpful in stimulating institutional re- 

 sponses to prevent the worst cases from occur- 

 ring. Many nations' governments have begun 

 to take steps in the past decade to protect en- 

 dangered habitats. The worst-case calculations 

 are thus not predictions, but indications of the 

 direction and scale of the projected trend. 



Distracting Numbers Game 



Projections of alarming losses in species 

 diversity have attracted attention to this issue. 

 But discrepancies among the estimated extinc- 

 tion rates have called into question the credi- 

 bility of all such estimates. In one sense, the 

 numbers themselves have become an issue, con- 

 fusing policymakers and the general public and 

 possibly detracting from efforts to deal with the 

 causes and consequences of diversity loss (28). 

 This numbers game also has defined the prob- 

 lem of loss mainly in terms of species extinc- 

 tion, which may be the most dramatic aspect 

 of the diversity question, but it is only part of 

 the problem. Further, global and national data 

 and projections may mask the localized nature 

 of resource degradation, diversity loss, and the 

 consequences of both. Large inaccessible areas 

 of forest, for example, may make the global 

 deforestation rate seem moderate, but destruc- 

 tion of especially diverse forests in local areas 

 of Australia, Bangladesh, India, the Philippines, 



