Study Alerts to Imminent Alien Earthworm Invasion

A recent study from Stanford highlights the infiltration of numerous non-native earthworm species into North American soil over the past century. The study emphasizes the need for increased awareness of these invaders and their potential significant effects on the continent’s ecosystem.

Since the late 1800s, individuals have been importing earthworms to the Americas from almost every continent to enhance agricultural productivity. These worms are beneficial as they create tunnels that facilitate the penetration of water, nutrients, and air into the soil, while their excrement serves as fertilizer, promoting the growth of crops and other vegetation. Their utility is such that they are even being considered as potential inhabitants for the planet Mars in the future.

Warning of Detrimental Consequences

While the initial intention behind utilizing this natural soil enhancement method has been positive, researchers from Stanford University, in collaboration with colleagues from Sorbonne University and other institutions, now warn of its potentially detrimental consequences. This is because non-native earthworms often consume material from the surface rather than below ground, leading to significant alterations in native ecosystems.

Furthermore, certain earthworm species have been found to modify the pH, texture, and nutrient composition of soils to such an extent that it becomes challenging for native tree species, like the sugar maple, to thrive. For instance, the alien jumping worm has been observed to desiccate the soil to a degree where native vegetation can no longer flourish. These alterations can disrupt the ecological balance and create opportunities for invasive plant species to establish themselves.

According to the researchers, alien earthworms pose additional challenges because they were introduced into new ecosystems without undergoing the natural evolutionary processes that would have occurred in their native habitats.

The researchers highlighted these concerns in a study published in the journal Nature Ecology & Evolution, emphasizing that while soil organisms such as earthworms are traditionally associated with beneficial land management practices, their introduction into ecosystems where they did not co-evolve can result in catastrophic changes. Despite the significance of these findings, they suggest that the issue has often been overlooked in nature management policies due to the positive perception of soil organisms and limited understanding of the extent of soil fauna introductions outside their native ranges.

Earthworm Data Analysis

In order to assess the widespread presence of non-native earthworm species, the Stanford team examined earthworm records spanning from 1891 to 2021 (indeed, there are records specifically dedicated to earthworms). They supplemented this data with statistics on the interception of alien earthworms at the US border between 1945 and 1975. Subsequently, all this information was utilized to train a machine learning model aimed at tracking the dissemination of non-native worms across North America.

The researchers concluded that approximately 70 distinct species of alien earthworms inhabit 97% of the continent’s soils, constituting 23% of the total 308 worm species present. This surpasses the numbers observed for non-native fish by nearly threefold, non-native mammals by fourfold, and insects and arachnids by tenfold. Additionally, the study unveiled that alien earthworms make up 12 out of the 13 most prevalent worm species.

Moreover, the study revealed a higher concentration of alien earthworms in the northern regions of the continent, with Canada hosting an alien worm population approximately three times larger than that of native species.

Urgent Call for Vigilance

While acknowledging that not all alien earthworms pose a threat, the researchers emphasize the necessity for increased scrutiny and research concerning the potential proliferation and significant impact of these non-native species on native ecosystems.

Lead author of the study, Jérôme Mathieu, an associate professor of ecology at the Sorbonne, remarked, “These ratios are likely to increase because human activities facilitate the development of alien species that threaten native earthworm species, a phenomenon still largely overlooked.”

Furthermore, study co-author John Warren Reynolds, from the Oligochaetology Laboratory and the New Brunswick Museum in Canada, commented, “This is most likely the tip of the iceberg. Many other soil organisms may have been introduced, but we know very little about their impacts.“

For an overview of the research, please refer to the following video from Stanford.

Read the original article on: New Atlas

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