Portrait Photograph of John J. Magnuson

John J. Magnuson

Professor Emeritus

College of Letters & Science l Center for Limnology, Department of Zoology

Hometown: Gurnee, IL.

John J. Magnuson is an aquatic ecologist and limnologist with a special interest in fish and fisheries ecology. His training is in fish and wildlife management, zoology, and oceanography. Current interests include: long-term ecological research on lake ecosystems, analyses of long-term lake ice time series, climate change impacts and adaptations, thermal ecology of fishes, landscape and invasion ecology of lakes.

Dr. Magnuson is now an emeritus professor at the University of Wisconsin-Madison, residing in the Center for Limnology which he helped form in 1982, and was its first director. His students have received their graduate degrees in Zoology, Oceanography and Limnology, and Water Resources Management. He has had a strong interest in seeing science used in solving real world issues related conservation of species, climate change, and fisheries.



“Please keep speaking. You have a gift of gentle discourse, of humility, that helps the science go down much easier. Great job.” – John Bates, Author and WI Naturalist, Mercer, WI

“Thanks again for a wonderful presentation. I am so impressed with the crowd you drew for such a tiny town and a Saturday night.” – Susan Knight, Interim Director, Trout Lake Station, WI DNR


What Does Lake Ice Seasonality Tell Us About Climate Change?

Lake ice cover provides a clear indicator of climate change and variability. Because human observers have recorded the dates of ice on and ice off on many lakes around the world, lake ice provides a view of what is happening, often well before direct climate measurements of temperature were available. In Wisconsin and other states some records began as early as the 1850s. So what do these records tell us? Professor Magnuson will talk about the changes and variability in ice cover in Wisconsin lakes from the 1850s to the present. Several of our Wisconsin inland lakes now have had one or more winters with incomplete ice cover. One long-term record in Japan comes from a Shinto ceremony on Lake Suwa that began before Columbus discovered America and another in Finland that began before the start of the Industrial Revolution. He will also discuss the value of lake ice to us largely for cultural reasons and as a measure of what is happening to climate.

Slides for this talk

Lakes as Islands, Oceans as Continents
No talk details available.
Changing Climate and Waters of Wisconsin

Wisconsin’s climate is changing owing to increases in greenhouse gases in the atmosphere. Impacts of climate change are affecting Wisconsin lakes, streams, and wetlands through the warming climate and increases in precipitation and extreme rain events. These changes result in declines in ice cover (an early minor canary), flooding by surface and ground waters (major direct effects on us), and habitat for fishes and other aquatic organisms. Adaptation is necessary to reduce impacts on us and the environment we have come to love and on which we depend. However, adaptation is not sufficient; we are having to cope and live with the negative influence of a changing climate. To reduce even more extreme future changes, reductions in the emission of greenhouse gases (carbon dioxide and methane) are required. Again, mitigation alone is not sufficient because the impacts of climate change on Wisconsin’s waters are already upon us.

John J. Magnuson is an Emeritus Professor of Zoology and past Director of the Center for Limnology (interdisciplinary study of lakes, streams, and wetlands) at the University of Wisconsin-Madison. He earned his BS and MS from the University of Minnesota-St. Paul and his Ph.D. from the University of British Columbia, Canada. He played a lead role in the lakes and streams portions of the 1995 and 2001 assessments by Intergovernmental Panel on Climate Change (IPCC). He was a co-chair of the Waters of Wisconsin Project for the Wisconsin Academy of Sciences, Arts & Letters (2001-03) and for the “Wisconsin Initiative on Climate Change Impacts” (2007-2011). Presently, he has been publishing research on climate change and its effects on lake ice seasonality.

Lake Ice and the Loss of Winter

Decline in lake ice is an early influence of climate change. These lakes are scattered across the landscape where people live. Lakes in Wisconsin and around the Northern Hemisphere have been freezing over later and breaking up sooner. Some are even beginning to not not freeze over every winter. Cultural resources such as skating and ice fishing, are being lost in areas where lake ice has been considered a permanent part of their sense of place.