Earthworms introduced into northern North America have a negative impact on the insect fauna above ground.
Earthworms introduced into northern North America have a negative impact on the insect fauna above ground. Soil ecologists, led by the German Centre for Integrative Biodiversity Research (iDiv) and Leipzig University describe this observation in the journal Biology Letters. The researchers found this impact for abundance as well as for biomass and species richness of insects. Their results indicate that changes in insect communities can have causes that have previously received little attention. These should be given greater consideration in nature conservation.
At least since the last ice age, about 10,000 years ago, there have been almost no earthworms in the northern part of North America. However, over the last few centuries, they have been introduced, probably through soil and plant transport from Europe. Since then, they have been dispersed and changed the soil significantly, with far-reaching consequences for the soil ecosystem. What impact these invaders have on the world above ground has, up to now, rarely been investigated.
The study was performed in a forest near Calgary in Canada, which has areas that are either inhabited or uninhabited by earthworms. Here, the researchers used insect vacuum samplers to capture aboveground insects and compared the catches. They discovered that the abundance, biomass, and species richness of insects in areas with invasive earthworms, and those areas without them differed significantly. Where earthworm biomass was highest, the number of insect individuals was reduced by 61 per cent, insect biomass by 27 per cent and species richness by 18 per cent.
Read more at German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
Image: Earthworms are considered essential ecosystem engineers underground. Researchers from iDiv and Leipzig University have now shown that they also play a major role in shaping aboveground communities. (Credit: V. Gutekunst)