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Friday Evening Lecture Series
08/11/06
"Disappearing Streams: The Hidden Casualty of Deforestation in the Amazon"
Linda A. Deegan, Marine Biological Laboratory
Lecture Abstract
The clearing of Amazon River lowland rainforest represents one of the largest and potentially most important land conversions on Earth. The Amazon basin contains almost 1.5 million kilometers of rivers and streams surrounded by 4 million square kilometers of tropical forest. This rainforest is being cleared at the fastest rate in the world, primarily for cattle pasture. While the world's attention has been focused on the effects of forest clearing on land plants and animals, a hidden casualty has been the function of earth’s largest river network. Despite the significance of the Amazon River, relatively little is known about the effects of rainforest clearing on the nutrient cycling, food webs or diversity in the small streams that are the direct connection between tropical forests and aquatic ecosystems. These small streams exchange nutrients and organic matter with the land and larger rivers, and serve as habitat for the richest diversity of fishes in the world. I will describe how transforming rainforest into pasture leads to dramatic differences in streams that alters food webs, decreases the number and kinds of species that can survive and changes the supply of nutrients to larger rivers. The magnitude of the changes to streams, and the extent of clearing, suggests that deforestation may be altering stream hydrology and biogeochemistry over many thousands of kilometers of primary and secondary stream channels, potentially affecting the sustainability of Amazon River ecosystem.
Linda A. Deegan is a Senior Scientist at MBL's Ecosystems Center. Dr. Deegan works on marine and freshwater ecosystems, with a special interest in fishes. Dr. Deegan received a B.S. in Biology from Northeastern University, a M.S. in Zoology from the University of New Hampshire, and a Ph.D. in Marine Science from Louisiana State University, Baton Rouge. She is an alumnus of the MBL course in Ecosystem Ecology. She joined the staff of the Ecosystems Center in 1989. In 2004, as part of the new MBL program with Brown University, she was appointed to the rank of Professor in the Department of Ecology and Evolutionary Biology. She is also an Adjunct Professor in the Department of Natural Resource Conservation and Management, University of Massachusetts, Amherst, where she worked prior to joining the MBL. Dr. Deegan is on the editorial board of Ecological Applications and is scientific co-chair of the International Estuarine Research Federation Meeting. She is a member of the MBL Corporation, the Ecological Society of America, the International Estuarine Research Federation, and the American Fisheries Society. Dr. Deegan recently received a Fulbright Fellowship and will spend four months in Brazil in 2007 working with her Brazilian colleagues on the effects of rainforest clearing on the biodiversity of streams in the Amazon River ecosystem.
Dr. Suzanne G. Ayvazian will introduce Dr. Deegan. Dr. Ayvazian is Chief of the Population Ecology Branch at the U.S. EPA’s Atlantic Ecology Division in Narragansett, Rhode Island. After graduating with a B.A. degree in zoology from the University of New Hampshire, a M. S. degree in biology from the University of Massachusetts-Lowell, and a Ph.D. in zoology from the University of Rhode Island, she conducted postdoctoral research with Dr. Deegan at the University of Massachusetts-Amherst and the MBL. In 1991, she was accepted as a postdoctoral fellow at The University of Western Australia, Perth, Western Australia. Upon completion of this fellowship, Dr. Ayvazian accepted a position as a research scientist at the Western Australian Department of Fisheries. In 2003, she was awarded an MBL fellowship to conduct research with Dr. Deegan and Simon Thorrold (Woods Hole Oceanographic Institution). Dr Ayvazian joined the U.S. EPA in 2003. She has served as an international advisory panel member for the journal Marine and Freshwater Research and currently serves on the editorial board of the journal Estuaries.
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