Invasive Earthworms Were Introduced to North America for Soil Improvement, Now They Threaten Ecosystems.
New research published in Nature Ecology & Evolution reveals that at least 70 species of invasive earthworms are currently residing in North America, as reported by IFL Science on February 14. To investigate and monitor their spread, a team of experts reviewed documents on both native and non-native earthworms from 1891 to 2021, including reports on preventing non-native earthworm species at the U.S. borders between 1945 and 1975.
Jumping Worm (Amynthas agrestis) is one of at least 70 species of invasive earthworms in North America. (Photo: John W. Reynolds).
Machine learning technology has revealed that invasive earthworms are present in 97% of the studied soils in North America. Scientists estimate that they account for nearly a quarter of the 308 species of earthworms on the continent. In the United States, their numbers far exceed those of invasive fish, mammals, and insects.
The ratio of invasive earthworms to native species is highest in northern regions of North America, and lower in the southern and western areas. “These ratios may be increasing due to human activities that promote the spread of these invasive species, threatening native earthworms,” said Jérôme Mathieu, a researcher at Sorbonne University and the lead author of the study.
Previously, invasive earthworm species were introduced to enhance agriculture because they aerate the soil and provide nutrient-rich fertilizer through their waste. Additionally, they were imported for use as fishing bait.
However, researchers warn that invasive earthworms could pose significant problems by outcompeting native species. Their presence may also impact entire ecosystems. For instance, when they appear near sugar maple trees, invasive earthworms can lead to tree death and disrupt the food chain.
“This is likely just the tip of the iceberg. Many other underground organisms may have been introduced, but we know very little about their impacts,” said co-author John Warren Reynolds.
Research on this topic remains limited, making it difficult to ascertain the true extent of the impacts of invasive earthworms to date. However, the research team believes that their abundant presence and wide distribution in diverse habitats signify that the scientific community needs to pay more attention to them.
