Earthworms not always beneficial, may threaten plant diversity

New study suggests a correlation between the number of earthworms and the abundance and diversity of certain understory species.

Toronto: A new study suggests that an abundance of earthworms in soils could lead to reductions in the number of trees and and other plant species.

Contrary to the popular belief that these creatures and beneficial to the natural ecosystem, the scarcity of these invertebrates can be a threat to certain plant species, causing adverse effects on the ecosystem.

Researchers from Canada's Université Laval and Université de Sherbrooke visited sugar maple forests in Quebec province where they found half of which were populated by earthworms.

Their analysis revealed a correlation between the number of earthworms and the abundance and diversity of certain understory species as they found that new shoots of red maple, striped maple, American beech, and two fern species became rarer as populations of these invertebrates increased.

"The most likely explanation is that the earthworms consume organic matter in forest litter," said Line Lapointe, a professor at Université Laval's faculty of science and engineering and the study's lead author.

"This results in soils that can't hold as much moisture, and that in turn interferes with seed germination and the ability of some species' plantlets to survive," she added.

Earthworms have started to change plant composition in sugar maple forests, according to the researchers.

"If nothing is done, these changes could become more pronounced and spread to other forest communities," Lapointe said.

Researchers suggest that earthworms used for bait should never be released in the forest, instead they be thrown into the lake to avoid overpopulation in the ecosystem.

The study has been published in the journal Forest Ecology and Management.

(With Agency inputs)