'For Love of Lakes" takes on a hefty challenge: how to explain the paradox of why people love lakes, but continue to do things that ruin them.

To search for answers, Darby Nelson, an aquatic biologist, retired teacher and former Minnesota legislator, jumps in with both feet. He snorkels through lily pads, paddles a canoe through dense floating mats of stinky algae, and picks his way along a shoreline crowded with docks, steel cribbing, cement slabs and planking.

Nelson and his wife, Geri, visit lakes in Minnesota, Wisconsin, Illinois, New England and Canada. At Ryan Lake, in the remote corner of Voyageurs National Park, fish contain the highest concentrations of mercury of any lake tested in Minnesota. Nellie Lake in southern Ontario, the victim of acid rain in the 1970s, is stunningly blue and crystal clear to 100 feet deep, but bereft of life on all but its edges. And there's Walden Pond, where Nelson reflects on Henry David Thoreau, "our first and foremost lake watcher."

As the journey progresses, Nelson weaves in details of the underwater world's plants and creatures, and the ecological pioneers who advanced understanding of how lakes work.

Not all stops are depressing tales of lakes gone bad, and some scenes inspire poetic description. At Lake Winnipeg, a small island "glistens white" with pelicans, gulls and terns.

"They rise in an alabaster cloud and drift out over the lake as though the land itself has levitated and floated away. Only the cacophony of bird voices reveals the truth."

Nelson is not afraid to be personal, as when he describes his life-changing discovery of tiny lake creatures on a college biology field trip, and when he reflects on how profoundly lakes attract people, including his mother. "Although Alzheimer's had erased much of her mind, it had failed to dislodge the powerful images of times at the lake. The quiet water had penetrated to the depth of her being."

Nelson does not resolve the paradox, but concludes that part of the problem is that lakes are mostly invisible, and people don't understand their vulnerability to all manner of damage: overbuilding on lakeshores, uncontrolled runoff and erosion, invasive species, and pollutants from cars and power plants that drift thousands of miles to contaminate remote watersheds and fish.

He acknowledges that changing how people treat lakes is difficult because "preexisting notions may well trump hard evidence."

"For Love of Lakes" is an ode to the beauty of lakes and the high stakes of what we have to lose; it's also an eyes-wide-open cautionary tale of how things are changing for the worse, and what has already been lost.

Tom Meersman is a Star Tribune metro reporter.