Island Time: Returning Biodiversity to Green Bay’s Cat Island Chain |
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Waters of Wisconsin Program Blog


Island Time: Returning Biodiversity to Green Bay’s Cat Island Chain

Tue, 05/12/2015 - 12:40pm -- Moira Harrington

In the waters of Green Bay, a forty-year effort involving many stakeholders is balancing the needs of a modern shipping industry with the preservation of shoreline bird habitat. Thanks to planning conducted by the Cat Island Advisory Committee (CIAC)—the latest interation of these stakeholders—clean-dredged material from Green Bay’s navigation channel is restoring a group of three islands once known for the greatest colonial bird diversity in the Great Lakes.

Cat, Willow, and the Bass Islands—the islands that make up the 272-acre Cat Island Chain—had for thousands of years served as a natural barrier to the waves that buffeted the harbor of Green Bay. Home to a long list of wildlife and plant species, the islands were broken apart and washed away during the 1970s by floods and aggressive spring storms.

Chances are that much of the Cat Islands ended up in the bay.

Green Bay is the port-of-call for more than 180 ships each year. In 2014 it handled 2.3 tons of asphalt, coal, and other products. Moving all those goods requires clear navigation channels, and clear navigation requires dredging. After scooping it up, the next challenge is what to do with the dredged materials.

The more popular option among shipping enterprises is to place the dredged materials in disposal facilities. These facilities can cost up to $50 million to build and many in the Great Lakes are nearing capacity. Moving the heavy, water-logged material is also expensive. In response to these issues, engineers found a way to put clean, uncontaminated dredged materials to a constructive use—such as beach nourishment, habitat restoration, or even habitat creation.

Today the CIAC is overseeing the creation of a 2.5-mile spine of what is slowly becoming the Cat Island Chain. They are using clean dredged materials from the outer shipping channel—2.5 million cubic yards of it. So far, there are “fingers” along that spine that outline the footprint of the island chain. The westernmost cell is already taking shape with fill from last year’s dredging work.

A bird's-eye view of the Cat Island Chain

A birds-eye view of the Cat Island Chain

The delicate, buff-colored piping plover, which is known for the black band encircling its neck, is found on the Atlantic and Gulf coasts, as well as inland. The ground-nesting bird is increasingly scarce in the Great Lakes region as residential and commercial development has limited its shoreline-nesting options. If there is too much activity around nests, a pair of piping plovers will abandon eggs. A 2007 survey found only six nesting pairs of the bird in Wisconsin.

The Cat Island Chain holds hope for a renewed piping plover habitat—and the survival of the species. At least five plovers were sighted following the first fill of dredging materials in 2014.

Other birds are also finding the slowly-emerging islands a haven. Last year, 30 different species of shorebirds were spotted—more than in any other part of lower Green Bay in the last several years. Even the red knot—a bird classified as “threatened” under the federal Endangered Species Act—was also sighted several times.

The piping plover is remerging in the Great Lakes thanks to restoration efforts like that on the Cat Island Chain.

The piping plover is remerging in the Great Lakes thanks to restoration efforts like that on the Cat Island Chain.

The restoration work has involved the U.S. Army Corps of Engineers, Wisconsin Department of Natural Resources, Port of Green Bay/Brown County, and the U.S. Fish and Wildlife Service. Along with a member of the public, these groups make up the five-member CIAC.

Eventually, the CIAC will be responsible for the creation of more than 1,400 acres of shoreline habitat on and around the islands. It is their goal that the restored area will support native fisheries and other wildlife in addition to shorebirds like the piping plover and red knot.

“It’s been rewarding work with the committee,” says Wisconsin Sea Grant water quality specialist Julia Noordyk. “My mentor Vicky Harris spent 30 years working with these groups to see restoration come to life. After all those years of planning, things moved quickly—in 2013, there were 200 dump trucks a day on the site, rumbling back and forth to build the spine of the chain. It’s gratifying to work with partners to make this happen and see Vicky’s and others' investment paying off.”

Noordyk recognizes that her current role is just a part of a long history of Sea Grant involvement in the project. After witnessing the destruction of the coastal wetlands behind the original barrier islands, former Wisconsin Sea Grant coastal engineer Phil Keillor came up with the idea for restoring the island chain back in the 1970’s.

After the International Joint Commission designated lower Green Bay an Area of Concern in the late 1980s, Noodyk’s mentor and Wisconsin Sea Grant’s then water quality specialist Vicky Harris led a team of technical and citizen advisory committees that called for restoring the islands. As the design for restoration took place, Wisconsin Sea Grant coastal engineer Gene Clark provided technical assistance to help translate between the biologists and engineers.

Wisconsin Sea Grant’s Vicky Harris led the original restoration effort on the Cat Island Chain.

Wisconsin Sea Grant’s Vicky Harris led the original restoration effort on the Cat Island Chain.

The success seen so far with shorebirds on the islands have led to an increasingly important conversation about Cat Island management, and the CIAC is developing a public access plan for the island with two primary goals. Because the emerging islands are an active construction site, the first is protecting public safety for researchers as well as members of the general public who may be interested in bird watching or other recreational activities. Dredged materials that will make up the islands are very unstable, much like quicksand.

The second goal is to ensure a successful wildlife restoration effort. As already noted, shorebirds like the piping plover are sensitive to human disturbances. Open public access is already prohibited and more thought will be needed to allow controlled access around breeding season or peak migration times. “Many of the species that we hope come back are endangered or threatened, therefore limiting disturbance will be critical to the effort,” says Noordyk.

Noordyk notes that the access plan will also need to be flexible. “A lot will change in the next 20 years. Trees will be growing on the islands. Invasive species may be a factor. In fact, some phragmite shoots have already been popping up. These invasive plants crowd out a more diverse ecosystem. We have to be able to adjust the access plan and adapt to what’s going on.”


Moira Harrington is the assistant director for communications for Wisconsin Sea Grant and the University of Wisconsin Water Resources Institute, directing the creation of materials to promote science literacy, and overseeing media relations and social media.

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