They are a magnet for anglers, iceboaters, swimmers, sailors, paddlers, ice skaters, snowshoeing enthusiasts, Nordic skiers, water-skiers, pleasure boaters, rowers, log-rollers and shoreline hikers. This may be the most underacknowledged fact of life here: The Yahara chain of lakes is our single greatest recreational resource.
But there is a corollary fact: As users of the lakes, and as people who live or work in the Yahara River Lakes District, we are causing changes in the lakes on a regional scale. The plausible consequences of these changes range from habitat loss and declining fisheries to increased water-quality problems.
These possibilities are among the central findings of "Understanding Regional Change: A Comparison of Two Lake Districts," a report from the North Temperate Lakes Long Term Ecological Research Program - the ambitious, cross-disciplinary initiative based at UW-Madison. Focusing on the Yahara River Lake District and Vilas County's Northern Highlands Lake District, the article was published last month in the American Institute of Biological Sciences journal BioScience.
What renders the report significant to those of us who live in the Yahara River Lakes District is the clarity with which it explains how we are, in effect, changing the very resource so many of us use for recreation. And we are changing the resource in ways that may impair both the lakes and their contributions to our quality of life.
Lakes are, in a sense, large-scale natural retention ponds that reflect almost everything that is happening in a region. "They're downhill from everything, so everything runs into them," says UW professor Stephen Carpenter, the report's lead author. "They retain a lot, and almost every major event uphill is reflected in the lake, like a major rainstorm, for example, or the construction of a major new development."
The report provides historical context, noting the 20th-century rise in phosphorus and other nutrient pollution (first from sewage discharges into the lakes, later from fertilizer runoffs), the success of invasive species such as carp and Eurasian water milfoil, and the extensive loss of native fish species in the Yahara chain of lakes.
The report extrapolates these and related trends into the future and lays out plausible scenarios for both lake districts. The picture is not pretty: more urban and suburban development, more nutrient pollution and an explosion of invasive species.
"One careless person can ruin a lake forever," notes Carpenter, 54, a specialist in zoology, sustainability and global environment at the UW's Nelson Institute for Environmental Studies. "One person dumping rainbow smelt in a lake is essentially a death sentence for the walleye fishery. Reversing that once it has happened is very, very difficult."
By the same token, a small number of careless boaters could introduce zebra mussels into the Yahara district, upsetting the lakes' biotic balance to a catastrophic degree.
Lessening our impact on the lakes could prove arduous at best. Even studying such complexities demands patience and persistence - along with a perspective that is both broad in geography and long in chronology.
"I think what you do as a policymaker in those situations is you wait for windows of opportunity to open," says Carpenter, adding that the social and economic benefits of protecting the lakes are quantifiable. One 2001 study, for example, measured the net advantage of mitigating eutrophication - the concentration of nutrients in the lakes - at $50 million per year.
While policymakers wait for windows of opportunity to open, what can the rest of us do to help the lakes? "One thing you can do is cut down runoff from your own property," says Carpenter, who has called Lake Mendota the "poster child for lake eutrophication." Install a rain garden, he suggests. Cut down on fertilizer use.
"The bottom line is to understand that all the water that lands on your property goes down to the lakes," he says. "Clean-up flows from your property. Make sure it's as clean as can be because it's not treated before it goes to the lake."
At 13 concise pages illustrated with full-color diagrams and photographs, "Understanding Regional Change" is essential reading for anyone who wants to understand what we are doing to the lakes and the legacy we are leaving to succeeding generations. The complete report is posted at www.sage.wisc.edu/pubs/articles/F-L/Foley/carpenteretalBioScience07.pdf.
Meanwhile, the North Temperate Lakes Long Term Ecological Research Program is looking ahead, Carpenter says. "I think one of the most exciting things we're talking about is climate change, land-use change and invasive species," he explains. "What can we do with land-use change and managing invasive species and other populations to make the Madison lakes more resilient to climate change?"
The answer to that question may hold the ultimate legacy for our greatest recreational resource.