Earthworms could threaten plant diversity: Study

A study of correlation between the number of earthworms and the abundance and diversity of certain understory species has found that the earthworm could be a threat to plant diversity in natural ecosystems.

Researchers from Canada's Universite Laval and Universite de Sherbrooke visited sugar maple forests in Quebec province and found that new shoots of red maple, striped maple, American beech, and two fern species became rarer as earthworm populations increased.

"The most likely explanation is that the earthworms consume organic matter in forest litter," said Line Lapointe, a professor at Universite 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.

"Earthworms used for bait should never be released in the forest," Lapointe said. "Anglers who use them for fishing should pack them back out afterwards, or if that's not possible, throw them into the lake," she added.

The study was published in a recent issue of Forest Ecology and Management.