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Sanctuary Currents 2003
Threatened and Thriving Species: Lessons from the Sea

General Info & Program | Session Abstracts | Ricketts Lecture | MBNMS Awards | Exhibitors
Poster Abstracts & Awards | 2003 Symposium Poster (PDF)

Ed Ricketts Memorial Lecture


James Estes

Adjunct Professor of Biology
U.S. Geological Survey and Institute of Marine Sciences
Long Marine Lab
U.C. Santa Cruz

Defaunated Food Webs: Vertebrate Consumers and Nature's Balance

Food webs are defined by who eats whom, thus establishing a complex network of pathways by which species may be connected with one another in nature. While this dimension to food web complexity has been well studied in many ecosystems, little is known about how food webs work. For example, ecologists are still struggling to understand such fundamental questions as the relative importance of bottom-up vs. top-down control, and the effects of direct vs. indirect food web linkages in population regulation. My lecture will explore these questions as they relate to large vertebrates, especially apex or high trophic-level predators. The progressive loss of global biodiversity has been disproportionately great for large vertebrates, in part because these animals are intrinsically rare and in part because people selectively exploit them. This pattern is well known for prehistoric, historic, and modern times. But the consequences of these losses to ecosystem function are poorly known, and in truth they have been a matter of minor concern to resource managers and policy makers in the larger scheme of things. I will argue that the selective defaunation of large vertebrates from the world?s ecosystems has been instrumental in a wide array of indirect effects, most of which are undesirable to human welfare. Three examples (two from terrestrial ecosystems, one from the marine realm) will be used to illustrate how changes in the abundance and distribution of large vertebrates may have caused ripple effects?ecological chain reactions?to spread across their associated food webs, sometimes with important yet unforeseeable consequences. These examples, like many others, contain elements of uncertainty. I will conclude with a discussion of the implications of this uncertainty to science and policy, focusing in particular on ocean ecosystems.

About James A. Estes

Jim Estes received a B.A from the University of Minnesota in 1967, a M.S. from Washington State University in 1969, and a Ph.D from the University of Arizona in 1974. Following completion of his graduate studies, Dr. Estes moved to Alaska where he worked for the U.S. Fish and Wildlife Service on a variety of issues concerning arctic marine wildlife until 1978. In 1979 he moved to Santa Cruz. He is currently a research scientist with the US Geological Survey and holds adjunct faculty positions in biology and marine sciences at the University of California at Santa Cruz.

Dr. Estes' primary research interest concerns the nature and importance of species interactions, especially those resulting from the influence of apex predators. He has employed a wide range of experimental, comparative, and historical approaches to understanding the dynamics of species interactions in coastal marine ecosystems. Much of his field research has focused on the direct and indirect influences of sea otter predation in kelp forest ecosystems. This work now provides one of the better-known examples of the keystone species concept, indirect species interactions, and trophic cascades. He has authored or co-authored more than 100 scientific papers and supervised the training of 27 graduate students. He is a Pew Fellow in Marine Conservation, a Fellow of the California Academy of Sciences, and a Distinguished Alumnus of the University of Arizona. He has served on the editorial boards of Ecology/Ecological Monographs, Animal Conservation, Marine Ecology Progress Series, and Frontiers in Ecology and the Environment; on the Science Advisory Board for the National Center for Ecological Analysis and Synthesis; on the Southern Sea Otter Recovery Team; and as a National Research Council Study Panel member.

History of Ricketts Memorial Award and Past Recipients