24 Humans as Components of Ecosystems: A Synthesis Steward T.A. Pickett and Mark J. McDonnell Introduction The call for including humans as components of ecological research is not new. As we described in Chapter 1, the obvious negative impacts of human activities have been well documented, but the more subtle causes and effects of humans on ecosystems have not traditionally been the subject of study by North American ecologists. Similarly, human populated areas are typically not considered within the research domain of ecologists. Ironically, however, the very first paper published in the Ecological Society of America's journal, Ecology, was on the influence of weather on infection rates of pneumonia and influenza in the citizens of New York City and Boston (Huntington 1920). Since Huntington's paper, there have been relatively few studies that include humans as part of an ecological system published in the journal. The relative lack of ecological research that includes humans may reflect a long-standing tension in ecology (Kingsland 1985) between historical and instantaneous approaches. One of the earliest calls for including humans as components of ecologi- cal study by a North American ecologist was by Charles C. Adams (1935, 1938). Some 50 years ago, Adams (1938:501) stated time is rapidly approaching when ecologists-or others more alert to the true ecological situation-will be called upon to assist in a fresh integration of the biological and the social sciences· in order to more effectively assess the influence of human activities on the environment. This call has been echoed by other ecologists including Curtis (1956), Holling and Orians (1971), Stearns and Montag (1974), Bornkamm et al. (1982), Ehrlich (1985), Brown and Roughgarden (1989), and McDonnell and Pickett (1990). The recent appearance of a new North American journal entitled Ecological Applica- tions is yet another indication that ecologists are willing to broaden the scope of the field to explicitly include human activities. Unfortunately, in 310 M. J. McDonnell et al. (eds.), Humans as Components of Ecosystems © Springer-Verlag New York, Inc. 1993