Ch. 5— Maintaining Biological Diversity Onsite * 117 



munities representing early stages of succes- 

 sion. For example, savanna ecosystems are 

 maintained by fire, wildlife, and human influ- 

 ence. Management techniques to conserve sa- 

 vanna systems include regulating animal num- 

 bers and species and using controlled burning. 

 Rain forests in a mature successional stage re- 

 quire little intervention, but they are likely to 

 need active protection because they are not gen- 

 erally resilient if cleared in large areas (82). 



Where the U.S. Forest Service manages land 

 with wildlife diversity as a goal, it attempts to 

 provide an appropriate mix of successional 

 stages within each plant community (84). The 

 approach of the U.S. National Park Service is 

 to maintain natural processes to the extent pos- 

 sible, including catastrophic changes such as 

 localized fire, to allow a relatively natural mix 

 of succession stages to occur. 



Management strategies have evolved from 

 strict preservation and protection to multiple- 

 use approaches and, more recently, to inte- 

 grated approaches. Strict preservation strategy 

 entails setting aside large blocks of natural areas 

 where designation and protection alone would 

 be expected to achieve conservation objectives. 

 Protection would mean severely restricting the 

 uses of, and the changes within, an area to en- 

 sure the continued natural condition of its bio- 

 logical resources and regular policing of bound- 

 aries to prevent trespassing or poaching. Where 

 possible, fences would be erected to restrict ac- 

 cess by humans and livestock. 



Moderate versions of this strategy may be ef- 

 fective in some locations, particularly where 

 the land is owned by an individual or nongov- 

 ernmental organization. In many areas, strict 

 controls are impractical. It has not been very 

 successful in developing countries. Moreover, 

 neither fences nor patrols can prevent all ex- 

 ternal influences from damaging a protected 

 area. Regular patrols of a marine sanctuary 

 could not stop the effects of water pollution, 

 for example. 



Strict preservation of biological diversity is 

 not an explicit objective of any federally pro- 

 tected area in the United States. The objective 

 closest to it is protection of "biological re- 



sources" or "ecological processes" on lands in 

 the National Wilderness Preservation System, 

 which is an evolving system of public lands rela- 

 tively undisturbed by humans and large enough 

 to have potential for wilderness recreation. 

 (Most wilderness areas contain at least 5,000 

 acres, although some in the Eastern United 

 States are smaller.) 



Other countries also have extensive areas set 

 aside for preservation while allowing some hu- 

 man access. Examples include large segments 

 of Antarctica and isolated parts of the Amazo- 

 nian forest. Some natural areas, such as Wood 

 Buffalo National Park in Canada and Salonga 

 National Park in Zaire, have wardens to guard 

 the boundaries and prevent trespassing (61). But 

 increasingly, countries cannot afford to desig- 

 nate large areas for strict preservation. Particu- 

 larly in developing countries, adequate fences, 

 patrols, or other means to deny access to desig- 

 nated areas are seldom logistically, economi- 

 cally, or socially possible. In addition, preserva- 

 tion strategies have exacerbated perceived 

 conflicts between conservation and development. 



Another strategy for protected areas is to in- 

 corporate multiple uses or objectives. This strat- 

 egy is usually based on one or two approaches: 

 developing an optimum mix of several uses on 

 a local parcel of land or water; or creating a 

 mosaic of land or water parcels, each with a 

 designated use, within a larger geographic area. 



Developing an optimum mix of uses in an 

 area requires careful incorporation of each ob- 

 jective so that all can be met. This approach 

 is used by the U.S. Forest Service on national 

 forest lands and by most States on wildlife areas 

 and State forests. In national forests, the po- 

 tential of each subsection is evaluated for recre- 

 ation, grazing, timber production, wildlife or 

 fisheries habitat, mineral development, and 

 other uses. Management objectives for each site 

 usually include more than one use. Thus, an 

 area that is managed for timber production may 

 also provide sites for grazing livestock or forag- 

 ing wildlife. Sometimes, mining or another use 

 will be exclusive, at least temporarily. 



The California Desert Conservation Area, 

 managed by the Bureau of Land Management, 



