Invasive species could increase as climate warms

Tim Ridle scrapes Elodea out of Anchorage's Sand Lake (Photo by Joaquin Palomino)
Tim Ridle scrapes Elodea out of Anchorage’s Sand Lake (Photo by Joaquin Palomino)

Tim Ridle’s porch overlooks the southern shore of Sand Lake in South Anchorage, a popular destination for fishers, boaters, pilots, and nature lovers. While once relatively pristine, an invasive weed called Elodea has taken over parts of the lake. “It looks like super thick scum,” Ridle said, while examining the green, brown, and yellow muck colonizing the lake in his backyard. “It’s almost like a disaster. You can’t describe it until you see it, and the next thing you say is, ‘wholly cow, how did that happen?’”

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Elodea is the only known invasive aquatic plant in Alaska. Since being discovered near Fairbanks in 2010, it has taken root in 15 of the state’s rivers, lakes and streams. Once established, the weed spreads quickly, crowding out spawning grounds for fish and killing off food sources for birds and other wildlife. Ridle says the plant can also be a pain-in-the-neck for boaters and pilots.

“It stops your boat it’s so thick,” he said. “You have to tilt your motor up and clean out the weeds and keep blasting until you finally get into open water.”

To manage the invasion, the state issued a quarantine on the plant in March, making it illegal to transport Elodea across Alaska’s borders. But the new policy won’t necessarily stop it from spreading. With warmer days and less ice projected for Alaska’s future, researchers worry Elodea will thrive. Increased float plane traffic—a major vector for Elodea—could also help spread the weed even further.

“If there’s less ice on the water or more ice free days, more people are going to want to be out as long as possible while the weather is good,” said Heather Stewart, a researcher with Alaska’s Department of Natural Resources. “There’s going to be more plane activity throughout the season.”

Warmer weather won’t only make it harder to curb Elodea. It could also prompt a sharp increase in other invasive species throughout Alaska. Changing conditions in the Arctic are particularly concerning, especially since melting sea ice has connected the Pacific and Atlantic oceans. The new naval passage will likely lead to an uptick in shipping, thereby increasing the potential for non-native species to be transported from one ecosystem to another. “When invasion scientists see a new corridor or a new pathway opening up by which different biota can be mixed it always sends up a big alarm signal,” said Whitman Miller, a biologist at the Smithsonian Environmental Research Center.

In Anchorage, Tim Ridle is less concerned about the future of the arctic; he’s just waiting for the state to clean out the 85-acre, Elodea-infested lake behind his home. “I [used to be able] to stand on the porch and see fish and the bottom of the lake,” he said. Now all you can see is weeds and that super thick, industrial scum on top.”

State and federal biologists are testing different herbicides in Kenai to try and eradicate Elodea. Once the results are in, they’ll look into tackling the problem in Sand Lake.

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