Stanford scientists have warned that an “alien invasion” is underway in the United States that could leave a trail of destruction across the country.
The team identified 70 species of exotic worms imported from Asia, Europe and South America that pose a threat to the ecosystem.
The invasive species consume more aerial leaf litter than native North American earthworms, potentially destroying plants and starving amphibians and insects.
Exotic earthworms make up 23 percent of the continent’s 308 native species, more than any other imported creature on record.
The maps show how the alien worm population has expanded dramatically every 20 years.
Exotic species, as the researchers called them in their new study, have been largely overlooked because of the positive effects earthworms have on farmers’ and gardeners’ crops.
This is because they create tunnels of air, water and nutrients that crops need to thrive, while their waste also serves as a rich fertilizer.
The researcher combined the records with documents of extraterrestrial worms that were intercepted on the United States border between 1945 and 1975.
Using machine learning, the team combined the two databases to map where the alien worms originated and how they spread across the US.
The resulting data set provided a look at the estimated number of exotic species versus the total number of native and exotic earthworm species, using data from 2000 to 2021.
Then the team met They collected data on both species from 2,510 geographic areas in North America and broke them down to look at the name of the species, the area and date of its observation, and the characteristics of the surrounding habitat.
Their findings revealed that exotic earthworms reside in 97 percent of North American soil and represent 23 percent of earthworm species.
The jumping worm, also called Amynthas spp., is one of the invasive species that has invaded Washington, DC, killing plants and trees by draining nutrients from the soil.
The jumping worm is one of 70 exotic species that could wreak havoc on the North American ecosystem by altering soil nutrients, pH and texture, which can lead to poorer crop quality.
The researchers collected information on interceptions of exotic worms on the U.S. border between 1945 and 1975. They documented how the species arrived, weather by plane, boat, automobile, or some other unknown means of transportation.
Exotic species were brought to North America from all over the world. The researchers looked at how many species were brought to North America from each continent and the total number of species that now reside in the US, Canada and Mexico.
Exotic earthworms are most widespread in Canada, where the population is three times that of native earthworms, while there is only one exotic earthworm for every two native earthworms in the lower 48 US states. USA and in Mexico.
“These proportions are likely to increase because human activities facilitate the development of exotic species that threaten native earthworm species, a phenomenon that is still largely overlooked,” saying Jérôme Mathieu, lead author of the study and associate professor of ecology at the Sorbonne.
Exotic earthworms are mainly distributed when people market them as fish bait or for vermicomposting, which converts organic waste into fertilizer.
Canada exports more than 500 million exotic worms each year to other countries, particularly the United States.
The researchers created a map of where exotic earthworms primarily reside, and the colors indicate the proportion of exotic species in the area compared to native earthworms.
One of the main concerns for exotic earthworms that are becoming widespread in North America is their diet, the researchers said in the study.
Native earthworms feed primarily on soil, but exotic species feed on litter, suggesting they increase litter decomposition.
Exotic earthworms in the broadleaf forests of the United States and Canada are putting pressure on trees (such as sugar maples) by altering soil microhabitat, which can then help invasive plants spread.
Further increases in litter decomposition (the breakdown of organic materials) could lead to changes in ecological function and biodiversity.
According to the study, this decay has already caused a decline in the salamander population in the northeastern United States.
He added that exotic earthworms can also alter soil nutrients, pH and texture, which, despite increasing crop productivity, leads to poorer crop quality.
The researchers suggest that policymakers adjust current laws surrounding the distribution of exotic worms by encouraging people to switch to using native worms for composting and fish bait.
More research is needed to understand the full effect exotic worms have on the ecosystem.
“This is probably the tip of the iceberg,” said study co-author John Warren Reynolds of the Laboratory of Oligochaetesology and the New Brunswick Museum in Canada.
“Many other soil organisms may have been introduced, but we know very little about their impacts.”
