STRESS AND ECOSYSTEMS 63 



tions to ecosystem structure, function, and stability. Sectors of the 

 biosphere that are relatively more sensitive to human alteration (e.g., 

 atmospheric and aquatic systems) initially received the greatest 

 public attention. Terrestrial systems have been studied in relation to 

 the impacts of ionizing radiation and radionuclide contamination 

 (Woodwell, 1970). Marine and coastal systems are now under intense 

 study as human population centers continue to grow in coastal areas 

 and the demands for fossil fuel increase the intensity and frequency 

 of oil and thermal pollution incidents (Cowell, 1971; Gibbons and 

 Sharitz, 1974; Ferguson-Wood and Johannes, 1975). Another line of 

 research uses laboratory microcosms to study the impact of heat, 

 radiation, oil, and other pollutants on microecosystems (Byers, 1962; 

 Moore, 1964; Copeland, 1965; Ferens and Byers, 1972; H. T. Odum, 

 1974). 



Piatt (1965), H. T. Odum (1967), Woodwell (1970), and others 

 suggested that ecosystem response to external impact follows certain 

 common patterns regardless of ecosystem type or type of impact. If 

 they are correct, it would be unwarranted to continue to duplicate 

 certain types of studies every time a new perturbation to the 

 biosphere is introduced by man. If there are patterns of ecosystem 

 response to stressors, we should use this knowledge to anticipate 

 human impact on natural ecosystems. This paper has two objectives, 

 first, to review the information available on the response of 

 ecosystems to stressors to determine whether there are recurrent 

 patterns of response, and, second, to suggest some approaches for the 

 study of stress and natural ecosystems. The synthesis highlights 

 controversial ideas with the hope of stimulating further research on 

 the issue. 



DEFINING STRESS AND STRESSORS 



The concept of stress is commonly applied to describe the 

 behavior of systems of all kinds. Meier (1972) summarized a number 

 of definitions of stress: Stress was initially defined as "the forces or 

 pressures exerted upon a material." Later, biological stress was 

 defined as "the rate of all the wear and tear caused by life." In social 

 studies, stress characterizes "physical, social, and cultural conditions 

 likely to be discomforting for most people living within a specific 

 group." Stress is also viewed as "a response to external or internal 

 processes which reach those threshold levels that strain psychological 

 and physiological integrative capacities close to or beyond their 

 limits." Finally, stress can be defined as "any force that pushes the 

 functioning of a critical subsystem beyond its ability to restore 



