Editor’s Note: This is one of a series of profiles of the Wisconsin Idea in action. See past profiles we have published.

For well more than 100 years, a succession of eminent biologists and ecologists have used Wisconsin lakes as their laboratory, dissecting their physical attributes as well as the complex interplay of the plants and animals that live in them. A lake, after all, is a busy place, filled with aquatic vegetation, mollusks, microbial communities of all kinds and, of course, fish and the stuff they eat.

In short, a lake is far more than just a wet spot on the landscape. And in Wisconsin, we have more than 15,000 lakes, and there is no question they are a beloved natural resource woven into the cultural and social fabric of our state. Lakes are iconic, used to draw tourists and businesses and to promote our quality of life. They are economically vital, underpinning recreational, real estate and sporting industries, and in some places, they represent a way of life. Up north, for example, in an area bounded roughly by Tomahawk, Eagle River, Park Falls and the Michigan border, is one of the world’s greatest concentrations of freshwater lakes.

But for as much as we know about Wisconsin’s lakes and what makes them tick, it is easy to forget that they are not static features of the landscape. They change naturally, of course, but aquatic environments today are mainly and increasingly shaped by humans. And the simple fact is that while we know a great deal about lakes and their native inhabitants, we know precious little about the interplay of Homo sapiens and the lakes they love.

Limnologist Steve Carpenter came to UW–Madison as a faculty member in 1989, when scientists here were in the thick of an ambitious multiyear experiment on Lake Mendota. The idea was to see if the composition of the lake’s ecosystem could be altered in the interest of reducing the algae blooms that each summer transform the urban body of water into an unsightly and smelly broth. Would it be possible to reduce algae by overstocking the lake with predators — walleye and northern pike — that eat the smaller fish whose menu includes algae-eating zooplankton? The whole-lake experiment, conducted cooperatively by UW–Madison limnologists and the Wisconsin Department of Natural Resources, seemed to be inching toward the predicted result when heavy rains, in effect, short-circuited the effort by washing tons of soil and nutrients from a new golf course into the lake. A boon to algae, the giant shot of phosphorous and other nutrients wiped out the results of the experiment by kick starting large new blooms of the pea-green aquatic organisms.

“I realized then that people are part of the system, too, just like algae, fish and the physical properties of lakes,” says Carpenter, the Stephen Alfred Forbes Professor of Zoology at the UW–Madison Center for Limnology and one of the world’s leading experts on lakes and their ecosystems. “Human systems are turbulent and fast-moving. The human dimension adds a very different flavor to the way ecosystems operate.”

Although trained as a botanist, earning his master’s and doctoral degrees from uw in the 1970s, Carpenter looks at lakes through the companion prisms of ecology and limnology. The big, integrative picture is what matters: “To understand lakes, you need information from different areas — chemistry, biology, ecology — all at once. I’m strongly motivated by basic questions about how ecosystems work.”

Having garnered an international reputation for his direction of large-scale experiments on ecosystems, including manipulations of whole lakes, Carpenter in recent years has expanded his purview to the social sciences, blending the human influence into his studies of lakes and related environments. “In principle, there is no reason why you can’t study a social-ecological system,” he explains. “It’s just that few people do it.”

But it is critical that science do so, he adds, because the natural world is under unprecedented pressure from a burgeoning human population. “Right now, we are seeing the fastest changes in ecosystems since the evolution of the species,” says Carpenter, whose expertise on ecosystem dynamics was used to help forecast environmental change for the Millennium Ecosystem Assessment, a 2001 global inventory of the health and direction of our planet’s ecosystems. Carpenter’s group, composed of 95 researchers — biologists, chemists, political scientists, physical scientists and social scientists — from 24 different nations was charged with envisioning the world in 2050 under different environmental scenarios.

One of the most important lessons of that monumental exercise, Carpenter argues, is that it remains possible for humanity to right the ship. “Surprisingly, we found that we could make things better. It’s not all gloom and doom. For example, if all women were educated to a high-school level within their culture, fertility rates would drop by almost two children per woman. That would put world population on a trajectory for 8.3 billion people by 2050, instead of 11.5 billion people. The world is going to be a lot more pleasant place at 8.3 billion than 11.5 billion.”

While Carpenter has made his mark in science (he is a member of the U.S. National Academy of Science, a foreign member of the Royal Swedish Academy of Science, and is one of the most cited researchers in all of environmental science), his forays into the world of policy are viewed as vital to injecting dispassionate science into the public discussion of how we treat the natural world.

“The work he has published in the realm of the science-policy interface is particularly important because it is scientifically rigorous and so highly policy relevant,” notes Walt Reid, who directs the David and Lucile Packard Foundation’s Conservation and Science Program and who worked with Carpenter on the Millennium Ecosystem Assessment. “He has helped to create a level of acceptance (in the scientific community) that one can do cutting-edge science in highly policy relevant areas.”

For Wisconsin, with its vast lake resource in an increasingly parched world, having scientists like Carpenter at the policy table will only pay dividends as the state’s resource managers face increasingly complex problems. The mix of scientific acumen and accomplishment, a strong desire to see his work improve the outlook for Wisconsin’s and the world’s aquatic resources, and a disarming, friendly and even-keeled nature is a combination that may work well to help establish a framework of policy grounded both in science and an understanding that the growing human influence on water resources is a variable that cannot be neglected.

“Well, by any measure, his work is seminal,” notes T. Douglas Beard, a former doctoral student of Carpenter’s who now is the program coordinator for the U.S. Geological Survey’s Fisheries Aquatic and Endangered Resources Program. “It is not just about publishing papers, it’s about making a difference. Steve is an open-minded, progressive scientist who really wants to make a difference in the world. He really wants to see his work applied.”

Shepherding new knowledge to practice is a path littered with shattered ideas and ideals. While science can teach us about the world, applying that knowledge is another matter entirely. “Many ideas don’t work,” explains Carpenter, who this year became chair of the Program on Ecosystem Change and Society, a project of the International Council of Science. “There is no silver bullet to solving some of these problems and often, when we try something, we don’t know what’s going to happen. So the honest things to say is we’re going to try it and see what the outcomes will be. There is a lot we don’t know, yet it is urgent. We can’t just sit on our hands.”

In his work as a researcher and teacher, Carpenter has been effective in conveying to his students and others the idea that in the details of science, there are lessons that can be extracted and utilized. And while the Wisconsin limnologist and his expertise are in demand nationally and internationally, Carpenter relishes his opportunities to act locally. He works with state agencies, Wisconsin’s Native American nations and private groups to extend the reach of good science. Using the baseline data obtained over many years through the National Science Foundation-funded North Temperate Lakes Ecological Research (LTER) program, for instance, Carpenter has helped guide planning and future thinking for Madison’s Lake Wingra.

Anne Forbes, a former DNR scientist, consultant and a volunteer with the group Friends of Lake Wingra, notes that Carpenter is a deft leader with a key understanding of how to get things done: “He is an excellent ‘process’ person,” says Forbes. “In my professional work, I help build environmental collaborations and it is a rare and wonderful thing when one of the most important experts in a field is also someone who not only values good process when he sees it, but also leads and exemplifies it.”

For Forbes and the Friends of Lake Wingra, Carpenter was able to put the lake into a larger picture, laying out not only its ecological profile, but also the gory social, economic and political details that, like invasive weeds, can bog down the most sincere effort. According to Forbes, making ecological headway on Lake Wingra came as a result of Carpenter’s efforts to make LTER data accessible to students and volunteers; build research and management collaborations between the university, the Friends of Lake Wingra, the DNR and other interested parties; and establish the lake as a lab for graduate seminars to envision the possible scenarios for the lake’s future.

Having lakes in the immediate neighborhood of the university, in addition to their constituting an iconic state resource, has historically been an inspiration for research and university engagement with the community, Carpenter explains, noting that E.A. Birge, Wisconsin’s first great limnologist, had an active interest in applied problem-solving.

“Lakes are really important to us,” says Carpenter. “Many people I run into are fascinated by the science, but they want it boiled down to a practical level.”

In that desire, Carpenter sees the opening for science to spell out the future for an essential resource. Forecasting outcomes given different circumstances — both natural and human — informs policy and gives people the opportunity to make choices about the future. “There are a lot of surprises out there, a lot we don’t know. But there are things we’ve learned that do work. There is a lot that can be done to make the future better.”