A new environmental threat map of the Great Lakes serves as a powerful visualization tool for those interested in the challenges facing lake restoration efforts. The map brings to mind the adage, “a picture is worth a thousand words.” But the colorful image is worth even more than that – the red, orange, and blue colors on the map show multiple stressors and represent gigabytes of data from decades of research. It paints an alarming picture about the cumulative effect of stress on such a precious freshwater resource.
The comprehensive map is the product of the Great Lakes Environmental Assessment and Mapping (GLEAM) project. Led by researchers at the University of Michigan, the group published a paper about the ambitious project in last week’s print edition of the Proceedings of the National Academy of Sciences. They also produced a cool interactive mapping tool which is now available on the GLEAM project website. Privately funded by the Erb Family Foundation, the main results of the project are summarized in a press release and were reported in news outlets throughout the Great Lakes region. I recently spoke with several members of the research team to learn more about the project.
“We found that the places where people gain the most benefit from a healthy lake ecosystem are also the ones with the highest levels of stress,” the project’s lead researcher and a professor of aquatic sciences at the University of Michigan’s School of Natural Resources and the Environment, David Allan, told me. “Marinas, boating activities, and public beaches tend to be near population centers where environmental stress also tends to be greatest.”
In addition to a cumulative stress index map, the research team generated separate digital maps for 34 individual lake stressors. Like a digital photo, the maps are made up of individual pixels. One pixel on the map represents one square kilometer of lake surface area. For 94,000 square miles of lake surface area, that’s 34 layers of information for each of the 244,000 pixels that make up the map. For all of its complexity, the visual display is clean and simple.
“Our intent in developing these maps was to give a bird’s eye view of which regions are the most stressed and which regions suffer from a particular stress at the highest levels,” said Peter McIntyre, a co-author of the study and professor at the University of Wisconsin-Madison’s Center for Limnology. “This view from 30,000 feet is most meaningful for making regional comparisons among lakes and for drawing conclusions about the state of the environment at very broad spatial scales.”
While the maps also provide useful perspective for restoration at a more local level, there is a risk of over-interpreting the data depending on how finely you zoom in, especially if viewing individual pixels near color boundaries. “These maps are just one important input into a process informed by local knowledge and additional data gathering,” Allan said.
What the Maps Say About Climate Change-Related Stressors
With recent concern about the role of climate change in exacerbating problems on the Great Lakes, including record low water levels on Lakes Michigan and Huron last month, I was particularly interested in this part of the research team’s analysis.
As with many of the lake stressor maps, the climate change data is displayed in a way that hasn’t been available to date. A quick glance at the warming lake temperature map shows Lake Superior, one of the most rapidly warming lakes in the world, at highest risk. The ice cover map shows the greatest loss in ice cover along the shorelines of the upper Great Lakes, especially in large bays like Grand Traverse Bay, Georgian Bay and on Lake Superior.
Sigrid Smith, a postdoctoral researcher at the University of Michigan, coordinated most of the analysis of the map data. She explained that the water level map is more rudimentary compared to the other two climate maps. “Using bathymetry maps, we simply identified areas of the lake that are less than three meters deep because these will be most susceptible to abnormal fluctuations in water levels,” Smith told me. Compiling the other maps involved serious number crunching to look at real trends. “We used sophisticated computer programming to analyze trends in lake temperature and ice cover from daily snapshots over a couple decades,” she said.
How Well Do the Maps Reflect Reality?
If you think in terms of maps as I do, you may find yourself clicking and zooming around the online maps to find out what they say about your favorite beach, boating harbor, bird watching area or fishing hole. Although the research team cautioned me about interpreting the data at the finer end of the scale, I couldn’t resist zooming in to see what it had to say about a stretch of beach I visited on northern Lake Michigan on a cold, windy day in late November.
First, let me explain the backstory for the photo above. Friends of my family told me of the beach on the Leelanau Peninsula where they had found dead loons and cormorants. I had read an online article in the Detroit Free Press about this tragic die-off and felt compelled to see the evidence with my own eyes.
Finding the frozen carcass of such a majestic bird saddened me beyond words. The story about how such a large water bird – and hundreds like it – ended up on this frigid stretch of rocky coastline read more like a sci-fi novel than a wildlife specialist’s account.
A bizarre set of interactions sealed the loon’s fate. Experts believe that invasive zebra and quagga mussels play a role, by creating suitable conditions for a particular species of algae to thrive. It now grows in mats and in deeper water along the lakeshore. When the mats of algae decompose, oxygen in the water is depleted, and botulism bacteria thrive. Invasive round gobies are well adapted to the new conditions, and they pick up the deadly bacteria, which gets passed up the food chain to the fish-eating loons and cormorants. They then die en masse and wash up on beaches.
Some of the environmental stressors that led to this nightmare scenario are now viewable with the online maps. I was not surprised to find that this area of the lake shows up in red on the cumulative stress map, indicating that it is under high stress compared to the rest of the lakes. I then zoomed in on the stretch of shoreline where I snapped the photo and viewed the individual lake stressors there.
The likely suspects causing the loon’s death seemed to correspond quite well with the lake stressor maps. This area of the lake shows up red and orange on two of the key invasive species maps, indicating that it is on the medium-high to high end of the stress index for round goby and for zebra and quagga mussels. All are suspected culprits contributing to the loon’s death. The maps also identify this part of Lake Michigan as an important area for fisheries, which is why the loons use it as a feeding ground.
In total, the maps showed that 12 of the 34 lake stressors were medium to high on the stress index scale for this one stretch of Lake Michigan coastline. The cumulative stress index map and my photo of the dead loon tell a similar story: the Great Lakes coastline is not only important to humans and wildlife but is under tremendous environmental stress.
High-resolution threat mapping is a technique that’s been used by groups concerned with the world’s oceans and river basins. The GLEAM project is the first time a similar approach has been used to cross-compare environmental stressors and the ecological services provided by lakes.
I asked the team about the applicability of the threat mapping approach for other lake regions. Allan says that it is a generalizable approach that can easily be used elsewhere. McIntyre added that there is a blessing and a curse when placing this study in a global context. “We are blessed to be working in one of the most data rich large lake regions of the world,” he said. “The curse is that we have an immense number of stressors, most of which are not at all unique to the Great Lakes of North America.”
Implications for Great Lakes Restoration Efforts
The team intends for their expansive research effort to help guide future Great Lakes restoration efforts, including the federally funded Great Lakes Restoration Initiative (GLRI) underway since 2009. For the most part, GLEAM researchers found current investments are going to the areas with the highest levels of environmental stress, but they are quick to point out how their maps create opportunities for a more strategic approach to considering future investments.
In addition to helping target specific places, McIntyre explained that the maps could help broaden the portfolio of restoration efforts. “By quantifying each lake stressor independently and placing them on an even playing field in terms of spatial data, our maps highlight the full range of stressors in a given area,” he said. “In some cases, restoration projects may be designed to alleviate only a handful of the few dozen threats that are at moderate to high levels.” He suggests that the maps could point out whether there is still a substantial “to do” list for existing restoration sites.
Another way the maps can be used is to complement restoration initiatives by identifying low-stress sites, places where fewer of the more challenging problems need to be dealt with but where human benefit is also high. “Our first round of analysis helps set the stage for a more systematic and strategic approach to restoration investments down the line,” McIntyre said.
Although the bi-national project team included representatives of some of the federal agencies involved with the GLRI, it’s too early to evaluate how the maps will influence the overall restoration program. Several conservation groups, however, were involved in the project and have already embraced the threat mapping approach, including regional projects of The Nature Conservancy and National Wildlife Federation.
Sometimes a map confirms your thinking about what you see at ground level, and other times, it can challenge your understanding of the world around you. The new environmental threat map for the Great Lakes did both for me. Having grown up in the region and sailed on all five lakes, I would have used a red marker to color many of the areas that the research team found to be high stress. But the precise nature of the patterns created on their maps, backed up by data and careful analysis, was as eerie as the call of a loon on a calm lake after dark. It startled me to see how much of the Great Lakes shoreline is under high stress and how few areas are relatively stress-free.
Record low water levels and dead loons washing up on the beach are two of the more visible indicators of a stressed ecosystem. These events, along with the new map showing the cumulative effect of multiple stressors, create a sense of urgency for the success of Great Lakes restoration efforts. Perhaps in addition to identifying the areas at greatest risk, the new maps will also help guide the way forward.
Lisa Borre is a lake conservationist, freelance writer and sailor based in Annapolis, MD. With her husband, she co-founded LakeNet, a world lakes network that was active from 1998 to 2008, and co-wrote a sailing guide called “The Black Sea.” She is a native of the Great Lakes region and served as coordinator of the Lake Champlain Basin Program in the 1990s.