Ch. 2— Importance of Biological Diversity • 43 



is half that of grass outside, protein levels and 

 digestibility are significantly higher. In Wind 

 Cave National Park, prairie dog tow^ns occupy 

 less than 5 percent of the area, but bison spend 

 65 percent of their time per unit area in the 

 towns, mostly feeding (28). 



Some species have an unusually prominent 

 position in food webs, being major predators 

 of species on lower levels of the food chain and 

 major prey of species on higher levels. Arctic 

 cod, for example, feed on herbivorous and car- 

 nivorous zooplankton (amphipods, copepods, 

 and decapods). Cod, in turn, is an important 

 food of many bird and marine mammal spe- 

 cies including gulls, narwhals, belugas, and 

 harp seals (25). 



Genetic Diversity 



Intraspecific genetic diversity allows species 

 to adapt to changing conditions, thus sustain- 

 ing ecosystem and species diversity; it also 

 helps produce plants and animals that will sup- 

 port more productive agriculture and forestry. 

 Genetic diversity is distributed unevenly among 



and within species. Some groups of species ap- 

 pear to be more variable than others: reptile, 

 bird, and mammal species have less than half 

 the genetic variation found in invertebrate spe- 

 cies and less than a quarter of that found in 

 many insects and marine invertebrates (34). 



The greater the amount of genetic variation 

 in a population, the faster its potential rate of 

 evolution (7). Certain genes are directly impor- 

 tant for survival (e.g., genes conferring disease 

 resistance). In addition, genetic diversity ena- 

 bles species to adapt to a wide range of physi- 

 cal, climatic, and soil conditions and to changes 

 in those conditions. Genetic diversity is posi- 

 tively correlated with fitness, vigor, and repro- 

 ductive success (7,85). 



Among marine animals, and probably among 

 terrestrial animals as well, high genetic varia- 

 bility is associated with high species diversity, 

 which in turn is associated with a number of 

 spatially different microhabitats (e.g., tropical 

 and deep sea environments). It seems likely that 

 the high genetic variability provides the flexibil- 

 ity to make finely tuned adjustments to micro- 

 habitats. 



BENEFITS TO RESEARCH 



Research may hold answers to many of the 

 questions facing this complex world. The re- 

 sults of research on the patterns and processes 

 of temperate forests have provided methods for 

 sustainable management of those ecosystems. 

 Knowledge of tropical rain forests will result 

 in similar strategies. Without diversity of spe- 

 cies, researchers would not have the needed 

 plant material to develop many vaccines, in- 

 travenous fluid, or other medicines. The poten- 

 tial for further advancement has not been fully 

 realized, yet a loss of species diversity will ad- 

 versely affect future research. Protection of 

 genetic diversity is equally essential, because 

 materials from plants and animals have pro- 

 vided valuable knowledge on viruses, immu- 

 nology, and disease resistance. 



Ecosystem Diversity 



Many contributions of ecosystem diversity 

 to global ecological processes, e.g., the role of 

 wetlands in the Earth's oxygen balance, have 

 yet to be demonstrated quantitatively. But the 

 research required to develop and test these hy- 

 potheses depends on the full range of diversity. 

 By studying natural ecosystems, scientists are 

 better able to understand how the Earth works. 



Knowledge of the role of ecosystem diversity 

 in ecological processes is substantial and grow- 

 ing, largely because of the availability of natu- 

 ral research areas such as the Olympic National 

 Park and the H.J. Andrews Experimental Eco- 

 logical Reserve in Willamette National Forest 

 (42,81). Relatively undisturbed grasslands in the 



