IV 



PREFACE 



the environmental effects of alternative sources of 

 energy. This exchange of information promotes a proper 

 perspective in which to make critical judgments affect- 

 ing a country's energy and environmental policies. 

 The symposium was ideal for comparing effects of 

 various stressors and for enabling researchers in one 

 discipline to become acquainted with those in another 

 area. Because of the broad nature of the meeting, we 

 were able to define six central topics around which the 

 160 oral presentations were organized. Each of the six 

 core areas was represented by an invited speaker, who 

 reviewed the effects of specific stressors or discussed 

 methods of modeling stress. These speakers were en- 

 couraged to speculate on future avenues of research and 

 to make generalizations where appropriate. Thus, each 

 topic was addressed first by a general synthesis and then 

 by a series of detailed, specific studies. The final 49 

 papers in this volume were selected from an initial group 

 of 80 papers submitted for publication from that 

 symposium and were included only after vigorous 

 review by outside referees. 



The theme of the symposium was environmental 

 stress, but, as evidenced by this volume, little unifor- 

 mity exists in application of the term "stress." Three of 

 the core papers distinguished between the action and 

 response involved in stress, two equating the action with 

 the term "stressor" and the response with the term 

 "stress," but another core paper described action as 

 "stress" and response as "strain." Differentiation in 

 terms may seem superfluous, but the dual meaning is 

 common in the ecological literature and has implications 

 for understanding system specificity in response to 

 environmental fluctuations. For example, Esch and 

 Hazen, in their core paper, characterized the response to 

 a stressor as "either an enhancement or a diminishment 

 in the probability of mortality, natality, or permanent 

 change." This concept of stress as either a positive or 

 negative response is controversial to say the least, but, if 

 the action or stressor is defined as a neutral, time- 

 varying input, then the response to it can be either 

 positive, neutral, or negative depending on the charac- 

 teristics of the receiving system. We believe that stress 

 always represents a negative effect on some specific 

 component of the system but that the ultimate response 



