New Mapping of Great Lakes’ Wetlands

Swamp Stomp

Volume 15, Issue 14

A new and comprehensive map of the Great Lake region’s coastal wetlands has been released by the Michigan Tech Research Institute that manipulates fluorescent bands of color to outline the great lakes. This new map is the first of its kind applied to such a broad scale, and is the only one that outmaneuvers political boundaries by displaying both Canadian and US wetlands along the more than 10,000 miles of shoreline.

The Michigan Technological University focuses a great deal of attention on the Great Lakes, and this coastal map is evidence of years of work expanding on previous maps created through the Michigan Tech Research Institute (MTRI).

Laura Bourgeau-Chavez, MTRI research scientist and the project leader for the wetlands map, claimed that having a standard method of mapping all of the regions wetlands, free of any inconsistencies that could affect data analysis and the implementation of management strategies, was crucial. She said, “This is the first map to span the entire basin, and it’s important to have a consistent map over the entire area.” She continued to claim that inconsistencies occur “if you don’t know the accuracy of the map or how it’s changing from one place to another.”

Wetlands are effect by a lot of change each year, some natural changes, but mainly as a result of human interaction. Bourgeau-Chavez asserted, “We’ve lost more than 50 percent of coastal wetlands in the Great Lakes over the past century. The wetlands are very important because they serve as filtration as well as habitat—and a lot of them are being degraded.”

The map uses satellites that are orbiting at roughly 200 miles above the earth’s surface to map the wetlands using remote sensing, a term used to represent imagery and measurement techniques collectively. By studying the area from a distance, a lot of ground is able to be covered quickly and easily.

Bourgeau-Chavez and her team used three-season PALSAR remote sensing data, a 23 cm wavelength Synthetic Aperture Radar (SAR). SAR is especially helpful for mapping wetlands because the technique is capable of distinguishing flooded ground, vegetation’s vertical structure, soil moisture, and the total mass of vegetation. All of these wetland aspects may vastly differ between seasons, so the satellite data was collected in each season except winter.

Remote sensing is not foolproof, however. Mixed readings, caused by overlapping pixels in data, blurred some of the maps boundaries, and, subsequently, made vegetation difficult to distinguish. Therefore, Bourgeau-Chavez and her team supplemented the remote sensing data with extensive field checking at over 1,400 separate field sites. It is only through field visits that the predominant vegetation, which is important for tracking invasive species like Phragmites and cattails, can be verified.

Field visits also allowed the researchers to map the different types of wetlands that were not separated by remote sensing. For example, the map displays peatlands as separate wetlands, because the bogs are sometimes mined for peat, and, therefore, contain large amounts of carbon.

Bourgeau-Chavez says, “An emergent wetland that doesn’t have any, or very little, peat at the surface is very different from a peatland with peat that is meters deep.”

There are many other factors considered in land use management other than monitoring urban and agricultural proximity, invasive species, and different water types, so a variety of uses were incorporated into the mapping interface. Viewers are also able to simply view the data they are searching for by clicking on the button below the legend.

Susan Hedman, EPA’s Region 5 Administrator and Great Lakes National Program Manager, said, “This Great Lakes Restoration Initiative project—made possible by an EPA grant—produced updated coastal wetlands maps that will help the United States and Canada better target efforts to restore critical habitats and to protect native aquatic and terrestrial spaces in the Great Lakes Basin.”

This map is a step forward in attempts to accurately map out constantly changing wetlands. The satellite imagery is able to stay up-to-date with changes to the region, and thus keep pace with the changing terrain.

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