Figure 4.5 



Numbers of Big Game Animals in Populations Relative to Numt>ers of Hunters 

 in the Contiguous United States by Section, Mid-1950's through Mid-1980's 



Index of Animals in Population per Hunter (Mid-1970's = 10) 

 3- 



q I I I I I I I I I I I I I I I I I I I I I I I I I I I I 



50s 60s 70s 60s 503 60s 70s 803 Ms 60s 70s 80s SOs 60s 703 80s 50s 60s 70s 803 50s 60s 70s 80s 50s 60s 70s SOs 



Figure 4.6 



Duck Harvests by Major Flyways, 1955-1975 



Mil. Ducks Harvested 



S \^— .V ,<r ' Cenral 



-■ ^v^-^^-::-;^ ^r.~: 



^— ^ ,^''%,^.i*'''pac"l1; ^_ ,,-' 



.v^- 



Supplies Related to Ecological Perceptions 



Ecological demands are largely focused on insuring 

 the preservation of individual species and of entire 

 communities of species. The Endangered Species Act 

 addressed the first concern. The Marine Mammal 

 Protection Act addressed the second concern by 

 emphasizing that the management of entire ecosys- 

 tems, including communities of wild fauna rather 

 than species-by-species management, offers the best 

 chance to realize the full continuum of wildlife 

 values. 2'' 



The only available direct measure of the degree to 

 which ecological demands are being met is the success 

 (or lack of success) in preventing the extinction of 

 individual species. 



It has been suggested that the historical rate of 

 species extinction in the United States has paralleled 

 the rate of population growth." Fossil evidence indi- 

 cates that in prehuman times mammal and bird spe- 

 cies became extinct at the rate of three per century. The 

 rate of extinction apparently had accelerated to about 

 1 50 species per century by the 1 800's. Eighty-five spe- 

 cies and subspecies of vertebrate animals are known 

 to have been extinguished since 1900. There is general 

 agreement that extinctions are likely to continue to 

 accelerate in the absence of intense (and expensive) 

 corrective actions. ^^ 



Because the present process of defining and listing 

 species as endangered or threatened is quite new, the 

 benchmark for measuring success in preventing 

 extinction is not firm. Efforts are at an early state of 

 development. For endangered species, most available 

 resources are still being devoted to determining 

 exactly where they are found, their habitat require- 

 ments, the potential extent of their range, and strate- 

 gies for their rehabilitation. Since the first official 

 Federal listing of endangered species was made, fewer 

 than 10 species have been delisted because their num- 

 bers have increased to the point where they are no 

 longer endangered. 



Many endangered and threatened species are geo- 

 graphic isolates, the most obvious being those 

 endemic to oceanic islands. Some species never were 

 abundant but developed in severely restricted habi- 

 tats. The "islands" of suitable habitats that support 

 other rare species are remnants of vegetation types 

 that were once much more extensive. A continual 

 subdividing or shrinking of blocks of similar vegeta- 

 tion is one explanation for the decline of carnivorous 

 birds and mammals. 



The remaining endangered species have suffered 

 from a variety of ills, including exposure to chemicals 

 at concentrations greater than could be tolerated. In a 

 number of instances, and particularly in the Pacific 

 and Caribbean Islands, the introduction of compet- 

 ing exotic species and of predators has had devastat- 

 ing impacts on native fauna. 



2'' This has been generahzed to say that management activities 

 should lead to maximizing the total complex of values of an eco- 

 system, that future management options should be preserved, and 

 that the risk of long-term adverse effects should be minimized by 

 explicitly making allowances to compensate for incomplete knowl- 

 edge, for imperfect decisions, and for imperfect implementation of 

 decisions. Holt, S. J., and L. M. Talbot. New principles for the 

 conservation of wild living resources. Wildlife Monograph 59, 

 Wildlife Society. 33 p. 1978. 



25 Opier, P. A. The parade of passing species: a survey of extinc- 

 tions in the U.S. The Science Teacher 44(1):14. 1977. 



26 Fawcett, C. W. Vanishing wildlife and federal protective 

 efforts. Ecology Law Quarterly l(3):520-560. 1971. 



128 



