A storm was coming one evening in July when a half dozen people boarded a pontoon boat at the public boat landing on Big Carnelian Lake, north of Stillwater. They were welcomed by Mike Isensee, administrator of the Carnelian-Marine-St. Croix Watershed District, who was hosting a tour of the troubled lake.

Dark clouds formed a sharp straight line stretching across the sky directly overhead. To the south, it was blue skies and white clouds. To the north, ominous gray thunderheads were collecting themselves into a maelstrom.

Even when not on a storm line, Big Carnelian is a lake on the edge, with its health showing an alarming decline over the past two decades. State officials consider Big Carnelian a lake almost impaired, meaning one more bad survey and it could be listed as degraded. Simply put, the number of fish is shrinking as the overall aquatic ecosystem has been hit by habitat loss.

Several studies of the lake have found that the primary problem is that Big Carnelian is rapidly losing its natural shoreline to new, lifeless trends in property development. It’s part of a broader trend in Minnesota, which is losing two percent of its natural lake shorelines every decade. Destruction of natural shorelines can hurt fish and much more.

Big Carnelian is a beautiful and beloved body of water, 457 acres in size, with five miles of irregular shoreline—bays and peninsulas breaking it into a few basins. It reaches 66 feet deep near its middle. It’s long been known for largemouth bass and northern pike fishing, as well as a popular place for homes and cabins, which ring its shoreline.

According to National Weather Service radar, there was still a little time before the storm would hit, so the group set off on a quick tour of the lake to look at some of the problem spots and some of the ways people are working to protect and restore aquatic habitat. A steady breeze followed the boat east across the water.
There are several ways to study and monitor the health of a lake. One is to take water samples and analyze the nutrients and other material in it. Another method is to measure its clarity with something called a Secchi Disk. Those are valuable measures of water quality, but a lake is much more than its water. Fish, aquatic insects, other animals, vegetation that grows under and above the water are all part of the lake, too. Tracking trends in living things is a useful way to monitor the lake’s overall health. The diversity and abundance of different species generally rise and fall as the lake functions better or worse, respectively.

Isensee explained that Big Carnelian first set off alarm bells 10 years ago. DNR fishery managers conducting a routine survey that summer found the lowest numbers of several species in decades. The lake’s popular walleye, pike, and bass all showed drastic declines.

The DNR followed it with supplementary surveys the following year and in 2019 that focused on shallows near shore, where non-game fish species often live—valuable in their own right, and an important food source for game fish. Many species also use shallow areas for spawning and other activity. In the shallow water surveys, little fish in the darter family, known for not only their rapid movements but also their preference for clean and clear water, were found in low numbers.

“If future survey work by the Minnesota DNR shows the health of the fish community continues to fall, the lake will be listed for not supporting aquatic life,” Isensee warns.

Once a lake gets on the impaired list, it’s hard to escape it. Maintaining a healthy lake is generally much easier than trying to restore one.

Part of measuring the overall health of a lake is not just looking at how many fish are found, but also the mix of species that turns up. Some fish can handle poor habitat or water quality, and others cannot. What the most recent surveys found is that the proportion of organisms that tolerate dirtier water has risen steeply, while more sensitive forms of life have declined.

Combining a lot of data, the DNR gave Big Carnelian a borderline score for the first time, and the trend was heading the wrong way.

The edges of lakes are a not only a key part of its ecosystem, but also where people like to play: swimming, launching boats, and simply being by the water. During open water season, waves from the wind or boat wakes pound turf, sand, and other soft ground. In the winter, fluctuating temperatures and other forces can cause ice heaving, which expands ice sheets with powerful thrust, digging into turf, sand, and other soft shorelines. Either season can result in eroding real estate.

Thus, there is often a conflict between what people want from the shorelines and what fish and other wildlife need.

As we rode across the lake, Isensee pointed out different properties and the many ways their owners have managed the lakefront. Some have a buffer of native vegetation on the banks and cattails, water lilies, rushes, and other vegetation growing from the shallow bottom up into the air. Some houses are barely visible from the water behind rows of trees.

Other properties feature mowed lawns down to the water’s edge, clean sandy beaches, big weedless swimming areas, and heavy rows of rock placed in the shoreline to “harden” it against waves and ice. Placing what is commonly called “riprap” along the waterline locks the shore in place, armoring it against waves and ice.

There also invisible ways people modify the lake and its shorelines. One way is the destruction of aquatic vegetation, some of which can be done without permits, some of which requires a permit. Removal can be done by pulling, cutting, and using herbicides. A 2023 DNR report found 44 permitted vegetation removals on Big Carnelian, most using herbicide, with many more probably possible.

Mowed grass, rock shores, and clean sand are perhaps ideal for human fun, but the increasing popularity of these choices is slowly damaging the whole lake.

“Native plants on the shoreline and shallow portions of a lake provide important habitat for fish,” Isensee told St. Croix 360. “The plants provide shelter, food, and important habitat for the things fish eat to survive, grow, and reproduce.”

He points to crappies as an example. The popular game fish lay adhesive eggs on hard protected surfaces, such as stumps and downed trees. As property-owners remove such objects from the water, fewer and fewer crappies can successfully spawn. Additionally, dragonfly larvae “need emergent vegetation to crawl up out of the water and molt into the mosquito eating machines we all know and love,” Isensee said.

Researchers have also found a correlation between the density of docks on a lake and the health of the ecosystem. Studies show that more than 16 docks per mile are connected to declines in aquatic life. At 24 docks per mile, the amount of living things is low. Big Carnelian has nearly 200 docks on its shores, or 38.4 per mile. The same reasons it’s popular are also causing its degradation.

Since the DNR reported its dire findings about the fish population, the watershed district decided to make the lake’s shoreline a priority. Numerous projects have been undertaken to balance property-owner wants, recreation, fishing, and aquatic habitat.

Near the northeast end of the lake, Isensee pointed out a property with a large house, docks, a lawn, and a rock-hardened shoreline. At first glance, it didn’t look very lake-friendly, but he said it’s actually an example of a design that balances human and aquatic necessities.

This shoreline restoration project was completed just this year, so the extensive native vegetation that has been planted along the water was not very visible in July. The property-owners worked with the Washington Conservation District to design a project that would meet their needs while helping all the other living things that depend on lakeshore habitat, and received a permit from the watershed district.

There were large rocks to protect the shoreline, but primarily placed below the water line, with a vegetated trough behind that can absorb the wave energy. There were also attractive stone stairs between lawn and water, and a shallow swimming area.

”Ultimately, each shoreline landowner just needs to leave a little for the lake.  There are many creative ways to leave or restore some natural shoreline while accommodating views, patios, docks, beaches and lawns; it just takes some planning and acceptance that natural trees, shrubs, and native vegetation are a beautiful and necessary parts of a healthy lake.”

The watershed district and the DNR have also been directly working to improve habitat in the lake. During shoreline surveys in 2022 and 2023, the staff noticed there were few dead trees floating in the lake, creating what are called “loafing logs.” These natural structures are loved by turtles, ducks, insects, and fish. Since then, they have worked with landowners to anchor two dead trees in the shallows, bringing back this ecosystem component.

The boat reached the lake’s north bay and turned around, now facing the wind, and the first few raindrops splattered its surfaces. The clouds were closer, the passengers put on jackets if they had them, and the boat raced back to the landing.

On the return trip, the boat passed another property that had recently been the subject of discussion at the watershed district’s meetings.

In about 2016, the owners had a company lay riprap along hundreds of feet of the waterline and excavated a recessed beach area. They had not received a permit from the DNR or watershed district, and the work would not have been met standards if they had. To the dismay of other lakeshore residents, no fines or restoration were ordered.

But when ice heaving managed to damage the shoreline in the winter of 2024, the DNR and district informed the owners they would need permits to conduct repairs, and the rules didn’t allow restoration of non-permitted and non-standard modifications. It caused some consternation.

At the landing, the boat passengers disembarked and fled to the shelter of their vehicles. The storm lashed the lake briefly with wind and rain, and then moved on. Soon the skies were clear again.

The watershed district has set a goal for its restoration and protection work on Big Carnelian. If 75 percent of properties on the lake leave 50 percent of the shorelines in a natural state, the lake can likely stay healthy. The district has recently implemented new cost-share structures to help reach that goal.

Isensee told St. Croix 360 that he remains optimistic about the future of Big Carnelian.

“Paired with all the great stormwater quality improvement projects landowners have installed, it appears we are headed in the right direction,” he said. “The true measure of success will be the results of the next couple of DNR fisheries surveys.”