462 



Htihiuit Assessmt'iits — Our Llviiii^ Rt'Sfturces 



particular habitat type). Some of these data are 

 already available in digital format over the 

 Internet. 



Loveland and Hutcheson compare the most 

 cuiTcnt picture of general vegetation patterns 

 (taken from the weather satellite, which is at an 

 altitude of 833 km. or 5 1 7 mi. above Earth) with 

 a map of what the vegetation may have been 

 like before European settlement. In addition to 

 providing some idea of the difference between 

 the land cover of today and. hypothetically. pre- 

 settlement land cover, they show conceptually 

 the value of being able to make these kinds of 

 comparisons. The authors carefully point out 

 the limitations of each of the maps they use. 

 then they walk the reader through how such a 

 comparison is made. Because of the coarse 

 geographic scale used, only general patterns can 

 be shown and the results of this comparison are 

 more meaningful when used to estimate large- 

 area carbon tlux, for example, than for calculat- 

 ing changes in biological diversity. The impor- 

 tance of this article is not in the results of the 

 comparison but in the concepts of using large- 

 area land-cover data to assess the past and pre- 

 sent trends of landscape-level ecological condi- 

 tions and processes. 



Wilen"s article cites studies showing that 

 half of the nation's wetlands have been convert- 

 ed to uplands since colonial times. He demon- 

 strates that the apparent slowing trend in overall 

 wetland loss is deceptive because qualitative 

 changes that do not show up as a net loss of wet- 



lands are occurring in different types of wet- 

 lands. For example, in recent times, vast tracts 

 of forested wetlands have been converted to 

 other wetland forms, such as wet meadows. 

 This is especially important because of their 

 complex functions, such as Hood control and 

 pollution abatement, as well as their providing 

 critical wildlife habitat. By using data from the 

 National Wetlands Inventory, Wilen shows that 

 overall, wetlands are losing their diversity. 

 Without systematic science-based efforts like 

 the NWI to map our natural resources, there can 

 be no meaningfully coherent information for 

 making decisions about how to manage them. 



Because the dynamics of larger systems 

 (e.g., landscapes) constrain the behavior and 

 occurrence of the smaller systems that they 

 encompass (e.g., populations or species), by 

 means that are independent of the smaller sys- 

 tems, conservation efforts implemented at the 

 levels of populations or species cannot be effec- 

 tive when systemwide changes are occurring at 

 the landscape level. Environmental changes 

 that were formerly limited to affecting popula- 

 tions and species are now manifest at scales by 

 which natural community and landscape sys- 

 tems function. Therefore, if we are to make sig- 

 nificant progress in slowing the loss of our bio- 

 logical heritage, the basis for solving problems 

 and implementing decisions must be predicated 

 on information derived from multiple scales of 

 geographic resolution as well as of biotic orga- 

 nization. 



The Gap Analysis Program (GAP) is an 

 approach to protecting the nation's bio- 

 logical diversity based on a collaborative 

 effort among citizens, businesses, nonprofit 

 groups, universities, and local, state, and 

 federal agencies. More than anything. GAP 

 is a method of developing information about 

 biological diversity that will enable individ- 

 uals, planners, managers, and policy makers 

 to make informed decisions. Species and 

 habitats not adequately represented within 

 conservation areas constitute gaps in pro- 

 grams meant to prevent species from becom- 

 ing extinct. By providing information before 

 extinction crises, GAP seeks proactive rather 

 than reactive solutions. 



The questions that GAP asks are: How 

 can we prevent the components of biological 

 diversity from becoming endangered with 

 extinction before they reach social and eco- 

 nomic crises? What is the present conserva- 

 tion status of all species and their habitats, 

 not just those currently endangered? 



To answer these questions on a state-by- 

 state basis, people with expertise in geogra- 

 phy, sociology, economics, zoology, botany, 

 statistics, and ecology cooperate in mapping 



Gap Analysis: A 



Geographic Approach to 



Planning for Biological 



Diversity 



by 



J. Michael Scott 



Edward T. LaRoe 



Michael D. Jennings 



National Biological Service 



the distributions of dominant natural vegeta- 

 tion (as habitat types), and the distributions 

 of each vertebrate species. Nationwide stan- 

 dards are used so that the maps of one state 

 will fit with the maps of adjacent states. 

 Because these maps are standardized across 

 the United States, yet based on state and 

 local information, they provide a critical 

 framework for ecosystem management that 

 is integrated across the private and public 

 sectors. For example, these maps help define 



areas with the highest species diversity as 

 well as how these areas match up with pre- 

 sent conservation areas. 



In the process of mapping land cover, 

 GAP provides most states not only with 

 computerized maps of existing conditions 

 throughout the state (most for the first time 

 ever), but also with maps of these same con- 

 ditions across contiguous states, thereby 

 providing context for what occurs within the 

 state. The GAP is not a substitute for 

 detailed studies of any particular site; 

 instead it provides infomiation. focus, and 

 direction for management decisions at the 

 ecosystem level. GAP is now under way in 

 33 states and consists of more than 200 

 cooperating organizations nationwide. It is 

 coordinated by the National Biological 

 Service. 



For further information: 



Gap Analysis Program 



National Biological Service 



Idatio Cooperative Fish and Wildlife 



Research Unit 



University of Idaho 



Moscow, ID 83843 



