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Night Crawlers Are Good for Birds, Fishing and Compost

But not so great for forests

Robins and sparrows sing the praises of our unending rain. Their beaks and bellies are filled with wriggling worms.
    Earthworms surface as wet conditions make easy work of relocating. No, worms don’t come up to escape drowning. They are capable of surviving several days submerged.
    The vibration of raindrops sounds like the predatory rumble of moles looking for a snack, causing the worms to head for the surface, where fishermen and hungry birds find them. Some birds have shifted to eating an earthworm-only diet.
    Gardeners also appreciate the nutrient-rich deposits our red wrigglers leave in our compost and soil. But their presence is causing a bit of havoc in our forests.
    “Every one of those earthworms you see on the sidewalks and driveways after a rain is an invasive,” Melissa McCormick says.
    McCormick is a research scientist with the Smithsonian Environmental Research Center in Edgewater, where she studies the interaction of plants with fungi. Including how invasive earthworms are changing the forest environment.
    “We still have a few native earthworms, but the vast majority are non-natives from Europe and Asia,” she says. It is possible that some of these visitors arrived as early as the first European settlers on this continent.
    As with human invasions, these wormy tourists have pushed out native species and caused trouble in the new land.
    “Forests are adapted to work with native earthworms and fungi to support late successional trees,” McCormick explains. Alien worms eat through leaf litter more quickly, baring soil to invasive plants. By affecting the nutrient cycle in the forest, invasive worms give bacteria and more aggressive fungi a favorable environment.
    The Smithsonian research team looked at populations of earthworms at test sites, digging trenches in blocks of soil and using electroshock to coax the worms out. They then planted tree seedlings to see what fungi grew and how the soil affected their growth. A healthy forest has many diverse layers and ages of trees.
    “Most native plants and trees are dependent on their association with fungi to get their nutrients,” McCormick says. “These large populations of invasive earthworms basically bias the soil against the fungi the trees rely on, especially late successional.”
    The experiment proved that oak, hickory and beech trees did not grow as well with lots of invasive earthworms around. Tulip poplar and red maple — both early successional species — grew just as well if not better.