Friday, August 7, 2009 - 8:00 AM

OOS 47-1: Bridging the divide: Overcoming barriers to understanding the effects of human activities on environmental outcomes

David Bart and Matthew L. Simon. University of Wisconsin


Generalizations about how human activities affect environmental changes are crucial for effective management, yet few of these generalizations retain clear causal information.  In part, this problem results from the ways that human activities are incorporated into ecological studies.  For example, studies that rank broad activity classes (e.g. agriculture, urbanization, etc.) as “levels of disturbance” do not take into account tremendous variability in these activities, nor do they present mechanisms connecting activities to the change.  Consequently, these generalizations do not contain information specific enough to inform management strategies.  Social scientists have done better in accounting for variations in activities. Nevertheless, their analytical methods are often better suited to studies of practices than of their environmental effects.  Here I summarize three studies in which careful attention to variations in activities and their environmental effects led to robust, management relevant generalizations. These studies were: 1) the effect of salt haying on Phragmites australis invasion in New Jersey brackish marshes, 2) the potential for salt haying practices to control Phragmites re-invasion in restoration sites, and 3) determining whether marsh haying suppressed Phalaris arundinacea invasion in sedge-meadow wetlands.  Each study used sequential exploratory strategies, in which I used farmers’ accounts to form hypotheses about the mechanisms connecting activities to invasions. I then used field and greenhouse experiments to test these mechanisms.


Detailing how and why activities varied was crucial to forming testable hypotheses in each case.  Experimental assessment of the environmental effects of these variations led to clear mechanistic understanding of how these activities affected the invasion.  In turn, this mechanistic information provided the basis to generalize not only about the effects each specific activity, but also to other activities as well.