Human-facilitated invasions

To investigate how earthworms spread in forests, we surveyed earthworms near lakes across northern Alberta. At each lake, we sampled near a boat launch, road, seismic line, and near remote sites farther from human disturbances (lake shores and forest interiors).

Earthworm sampling locations around one of the seventeen lakes sampled.

Earthworms were more likely to be found at boat launch and road plots (54%) than at the other plots (13%). Species commonly used as fishing bait also were found more frequently near boat launches (18%) than near roads alone (1%). These results suggest that transport by vehicles and bait abandonment are both important mechanisms of earthworm spread.

Proportion of plots containing earthworms at the six types of sampling locations.
Proportion of plots containing bait species of earthworms. Bait species were not found at sampling locations other than boat launches and roads.

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