PROMINENT LEADERS IN THE DEVELOPMENT OF ECOLOGY 

 IN AMERICA 



C.C. Adams, animal ecologlst {courtesy Dorothy Kehaya). 



F.E. Clements, plant ecologist 



Aide Leopold, wildlife manager. 



2 Background 



Concentration of studies not on the rare but on 

 the most abundant and influential organisms in 

 the community. 



Measurement and evaluation of physical fac- 

 tors in the actual microhabitat occupied by or- 

 ganisms. 



Correlation of findings of experimental studies 

 of organisms in the laboratory with observations 

 of those organisms in the field. 

 Use of quantitative — not just qualitative — tech- 

 niques in field studies as well as laboratory 

 studies. 



A study of organisms in the field may bring to 

 light problems which will be most expediently worked 

 out in the laboratory ; but field and laboratory investi- 

 gations must be integrated. The investigator must 

 often study the morphology of dead organisms in the 

 laboratory, and there perform experiments on living 

 animals and plants held under carefully controlled 

 experimental conditions. But unless such studies are 

 perspective to the normal life of an organism, as it is 

 lived in natural conditions, they are not ecology. 



The use of exact quantitative techniques is, of 

 course, a general characteristic of all science. But 

 special difficulties arise when such techniques are ap- 

 plied to free-living organisms in natural conditions. 

 For example, size of animal populations has, in the 

 past, often been described in such vague terms as 

 "rare," 'common," or "abundant." These are subjec- 

 tive terms, based largely on an impression gained by 

 the observer of the apparent conspicuousness of the 

 species. As James Fisher, an English naturalist, 

 wrote in 1939, a species has usually been indicated 

 as "rare" when actual numbers expressible in one's 

 and two's could be recorded ; "common" when the 

 observer began to lose count ; and "abundant" when 

 he became bewildered. One of the chief problems of 

 the ecologist is to develop methods by which to meas- 

 ure the absolute size of populations and the produc- 

 tive capacities of different habitats so that the activi- 

 ties of widely varying types of species may be 

 compared. For setting up experiments and organiz- 

 ing and analyzing studies under natural conditions, 

 it is becoming more and more essential that the ecolo- 

 gist become familiar with and employ good statistical 

 procedures (Williams 1954). 



As a contribution to human knowledge and under- 

 standing, ecology is in the fortunate position of being 

 concerned with the most complicated systems of or- 

 ganisation, apart from human societies, with which 

 we have to deal. For this very reason it provides a 

 constant challenge to the imagination as well as to 

 experimental ingenuity. It is more difficult to analyse 

 and isolate the relevant factors in a living community 

 than in a simpler system, but the gain in significant 

 understanding of the material world and in compre- 



