DULUTH — Interstate island is disappearing into the St. Louis River estuary, threatening one of only two tern colonies remaining on Lake Superior, but a two-year effort to raise the tiny island and help the terns is set to begin.
The $1.4 million project will use sand from on-land sources and dredged from nearby shipping lanes in the Duluth-Superior harbor to raise the island that has succumbed to rising water levels since 2015. Lake Superior is up 14 inches from normal July levels, and that mass of water pushes into the harbor and estuary, inundating the island and wreaking havoc — much as it has along the South Shore, Park Point and along Duluth's waterfront — especially during high winds.
Already crammed onto the five-acre shrinking island with more than 30,000 adult and young ring-billed gulls, the rising water is squeezing about 150 nesting pairs of terns out of their last suitable habitat in the region. The only other nesting colony of so-called common terns on Lake Superior is in Ashland.
The gulls have been eating both tern eggs and newly hatched tern chicks.
“The number of terns is down this summer from recent years because of predation by the gulls," said Fred Strand, a retired Wisconsin DNR wildlife manager who has been working to restore the island’s terns for years. “The island is noticeably smaller than it was just a couple of years ago … there’s now standing water in the interior of the island; we've never seen that before … and that’s pushing the gulls into the tern area.”
Martha Minchak, Minnesota DNR wildlife manager in Duluth, said the island "is eroding more than we've ever seen it before. Every time there's wave action, we lose more of it."
The island sits along the main shipping channels in the Duluth-Superior harbor right on the Minnesota-Wisconsin boundary line, just upstream of the Blatnik Bridge.
Money for the project is coming from Minnesota conservation sales tax funds and from federal wildlife and Great Lakes restoration grants. The Minnesota Land Trust and Minnesota Department of Natural Resources are heading the effort. They hope to get permits, hire a contractor and bring 13,000 cubic yards of sand to the island by autumn, starting as soon as the terns leave to go south.
“That should be enough material to offer some help for next year’s terns. Then we’ll do an even bigger project in 2020," said Melissa Sjolund, who coordinates St. Louis River restoration efforts for the Minnesota DNR. “We’ll also bring in some small gravel that the terns like to use for their nests.”
Organizers hope to raise the center of the island where terns nest amid an elaborate system of wires and fencing erected to keep gulls out. The effort, underway for years, is a joint project by Wisconsin and Minnesota DNR wildlife officials and the Natural Resources Research Institute at the University of Minnesota Duluth. Until high water came, the effort was working to bolster tern numbers. Banding studies show terns hatched on the island are surviving and eventually nesting on their own.
But it’s been getting harder to keep the gulls and terns apart as the island shrinks, Sjolund said.
“There’s less real estate to share," she said.
Sand will be tested to make sure it’s not contaminated. Sand from shipping channels, dredged deep to allow big boats to navigate the harbor, usually is clean because it fills in quickly, swept downstream by the river. Material dredged from boat slips and bays that aren’t flushed by currents often are contaminated with legacy pollutants.
The Interstate Island project will have to compete with several others for what has become valuable sand dredged for the harbor. Dredge material was recently used to fill in parts of the Duluth harbor near the Western Lake Superior Sanitary District sewage plant to restore shallow-water habitat for fish and wildlife. Dredged material also is being used to build dry-land shore area for endangered piping plovers on the bay side of Wisconsin Point.
The Interstate Island project is part of part of the massive Great Lakes Restoration Initiative to dredge or cap legacy pollution, restore fish and wildlife habitat and thwart invasive species across all the Great Lakes. It's one of many restoration projects that’s either already completed, underway or planned in the Twin Ports as officials seek to remove the St. Louis River estuary-Twin Ports harbor from the infamous list of toxic, degraded hot spots across the Great Lakes called Areas of Concern.
Interstate Island is a protected bird sanctuary and is closed to the public from March 1 to Aug. 30 each year, not that you’d want to go there considering the shower of gull guano you’d get.
Interstate Island funding
NOAA Coastal Program: $5,200
Minnesota Outdoor Heritage Fund: $487,000 ($400,000 this year, $87,000 from a previous year)
USF&WS Great Lakes Fish and Wildlife Restoration Act: $145,000
USF&WS Coastal Program: $200,000
EPA Great Lakes Restoration Initiative: $834,650