PART IX — TERRESTRIAL ECOSYSTEMS 



To these basic parameters must be 

 added the complicating effects of hu- 

 man culture on both man and hi? 

 environment. 



Gross considerations suggest that 

 the unguided technological culture in 

 the hands of a rapidly increasing 

 population is producing an unman- 

 ageable complexity in human society 

 and rapid deterioration in the envi- 

 ronment and its component resources. 

 If man is to endure on earth, the 

 entire biosphere must be his ecosys- 

 tem, preserved and kept productive 

 through conservative use and under- 

 standing management. 



Since man has never created an en- 

 during, self-perpetuating ecosystem, 

 he has much to learn from the study 

 of natural processes. All conditions 

 relative to human use and manage- 

 ment are of interest and should be 

 studied. However, the features of 

 ecosystems that guarantee perpetua- 

 tion are most clearly effective under 

 primitive conditions. Thus, areas 

 where primitive conditions are still 

 operative are of special scientific in- 

 terest. The least-modified communi- 

 ties of living things are likely to be 

 found on lands and waters set aside 

 as "wilderness" or natural reserves 

 of one kind or another. 



Isle Royale as a Prototype 

 Ecosystem 



A roadless island of 210 square 

 miles in northern Lake Superior ex- 

 emplifies the kind of situation where 

 fact-finding is possible under rela- 

 tively undisturbed conditions. Isle 

 Royale is a national park and may be 

 visited by some 10,000 people during 

 the tourist season from mid-June to 

 early September. From the end of 

 October to mid-May it is uninhabited 

 except for a research group, using a 

 small aircraft, that is present for 

 seven weeks in February and March. 



Animal Populations and Associated 

 Vegetation — Lying 15 miles from 

 the nearest Canadian shore, the is- 



land is sufficiently isolated that it has 

 not yet been colonized by certain 

 mammals and birds found commonly 

 on the mainland — especially deer, 

 bear, raccoon, porcupine, and ruffed 

 grouse. Lynx and marten disappeared 

 from the island early in this century, 

 as did coyotes in the mid-1950's. In 

 the latter case, the advent of wolves 

 about 1949 probably resulted in elimi- 

 nation of the smaller competing canid. 

 The fox does not appear to have been 

 affected by such competition. 



The boreal forest and hardwood 

 vegetation of Isle Royale was exten- 

 sively burned over in the past cen- 

 tury. Alteration of "natural" condi- 

 tions by this human disturbance must 

 be considered a matter of degree, 

 since burning also took place in 

 primitive times. The dynamics of 

 forest successions is, in any event, 

 significant. Early successional stages 

 produce food and cover for such crea- 

 tures as snowshoe hare and beaver, 

 as well as browse for the moose. 

 Thus, burning incident to drought 

 cycles renews the habitat of many 

 herbivores and indirectly supports 

 their dependent carnivores. 



The mammal populations of Isle 

 Royale have shown the instability 

 that characterizes simplified animal 

 communities. The moose illustrates 

 this, since it reached the island in the 

 first decade of the century, before its 

 primary enemy, the wolf, was pres- 

 ent. As a result, by the mid-1920's, 

 moose had overpopulated and de- 

 stroyed most of the available browse. 

 In ensuing years, as a result of mal- 

 nutrition and disease, moose died 

 down to a low level. A fire in 1936 

 destroyed forest cover and initiated 

 new brush-stage successions on about 

 a third of the island. Moose were 

 building up again when wolves 

 crossed the ice and became estab- 

 lished in the late 1940's. 



The Meaning of a Dynamic Wil- 

 derness — In areas like Isle Royale, 

 the U.S. National Park Service and 

 other land-management agencies have 

 been enabled to get a new view and 



concept of "wilderness" as a dynamic 

 condition. Thus, a full spectrum of 

 successional stages and habitat condi- 

 tions enables a vegetation zone to 

 support a wide variety of animal life. 

 On any given site, animal life must 

 change with maturation of the forest 

 or other vegetation. In terms of land 

 management, this means that agen- 

 cies charged with the administration 

 of natural areas must regard fire as 

 a part of the primitive scene that 

 should not be totally eliminated, even 

 if this were possible. A strictly ap- 

 plied policy of fire suppression would 

 lead to the development of extensive 

 monotypes representing the "climax," 

 or stability phase, of plant life in a 

 region. This would correspondingly 

 reduce variety in both flora and 

 fauna. 



Predator-Prey Relationships — 

 Biological studies carried out by Pur- 

 due University on Isle Royale over 

 the past twelve years have been sig- 

 nificant in revealing predator-prey 

 relationships. The moose is the larg- 

 est member of the deer family and 

 the gray, or timber, wolf is its only 

 effective natural enemy. In natural 

 communities, large browsing and 

 grazing animals depend in major de- 

 gree on their predators for population 

 control, the alternative being range 

 damage and violent fluctuations in 

 number. When it became known in 

 the early 1950's that wolves had 

 reached Isle Royale, it was evident 

 that this was a situation in which nat- 

 ural relationships of the two species 

 could be studied. 



The major findings of the ensuing 

 research program elucidate a mutu- 

 ally beneficial relationship between 

 predator and prey, an adjustment of 

 relative stability that, by controlling 

 the moose population, protects the 

 habitat from over-use. As of mid- 

 winter, an average population of 22 

 to 24 wolves is being supported by a 

 moose population of about 900. The 

 beaver is a secondary prey species 

 furnishing 10 to 15 percent of the 

 wolf's food. Numbers of the moose 

 and beaver are limited by the wolf. As 



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