Earthworms breaking down compost.

MN Impact: Exotic earthworms continue to expand their reach and effects on forest ecosystems

June 9, 2020

Issue

Exotic earthworms exert major controls over how soils function. Non-native geoengineering earthworms, which rapidly consume organic matter while burrowing through soils, speed up decomposition and nutrients losses. In a warmer and wetter world, their habitats and numbers are likely to grow increasingly faster. 

What has been done

Researchers at the University of Minnesota have been exploring the invasion and ecosystem impacts of exotic earthworms in Minnesota’s forests for more than a decade. Recently, they extended their research to even colder climates. In 2019, after several years of intensive earthworm surveys in the arctic Sweden, they began to examine the introduction, dispersal, and ecological impacts of European earthworms in Alaska.  

Results

They found in Alaska, active earthworm invasion and dispersal occurs through many different types of human activities such as gardening, fishing, and road building. Although earthworms’ aggressive invasion into otherwise undisturbed boreal forests is active only in Alaska’s warmer southern coastal areas, the repeated introductions of earthworms do occur locally throughout the entire Alaska. Ongoing climate change will likely boost the survival and further dispersal of earthworms in the northern and interior Alaska soon. 

Non-native earthworms result in a cascade of ecosystem effects. These impacts include changes in carbon sequestration, forest disturbance regimes, soil and water quality, forest productivity, plant communities and wildlife habitat. Invasive earthworms further facilitate other invasive species. Considering the massive ecological cascades that exotic earthworms cause to the soil carbon and nutrient cycles, understanding the dynamics of earthworm invasion should be a key component of future climate-related conservation efforts in both boreal and temperate forest ecosystems.