Extreme example of the potential consequences of earthworm invasion. Shown is a maple forest in Minnesota, USA, which has not yet been invaded by exotic earthworms (top), and another maple forest in that region that has been invaded by European earthworms (bottom). Please note that direct comparisons of those two forest stands are complicated and it is hard to identify cause and effect. Experimental manipulations are needed to study earthworm effects. Photo credit: Olga Ferlian (top) and Ulrich Pruschitzki (bottom).

  Part of: Eisenhauer N, Ferlian O, Craven D, Hines J, Jochum M (2019) Ecosystem responses to exotic earthworm invasion in northern North American forests. Research Ideas and Outcomes 5: e34564. https://doi.org/10.3897/rio.5.e34564