Emerging Threat: The Rise of the Garden Snail

Once primarily found in Skåne until the 1970s, the garden snail, or Helix aspersa, has seen a dramatic increase in its population across Sweden. Its presence is now reported as far north as Umeå, raising concerns among experts.

Ted von Proschwitz, a mollusk expert at the Natural History Museum in Gothenburg, noted a particularly alarming situation in Örebro County a few years ago, where the population surged into the tens of thousands. This rapid spread mirrors trends observed in other European nations, attributed to climate change and human activities that inadvertently facilitate the dispersal of these creatures.

The garden snail, originally from Central Europe, bears a resemblance to the common garden snail found in many backyards. However, distinguishing features, such as the coloration of the shell's aperture, set them apart. Once the shell has fully developed, a distinct thickening occurs; this is white in the common garden snail, while the garden snail presents a brown or black hue.

Experts express concern that the garden snail could potentially displace the common garden snail, causing disruption in gardens and parks. However, it is not considered a direct equivalent to the notorious Spanish slug, or Arion vulgaris. Von Proschwitz clarifies that the reproductive cycle of garden snails is slower; they need at least two years to reach maturity, unlike their more aggressive counterparts, which reproduce more rapidly and in greater numbers.

Despite their differences, garden snails contribute to the destruction of ornamental plants and crops, prompting the museum to enlist the help of local schoolchildren in monitoring their spread. The initiative encourages students to capture images of the snails for identification purposes, as they can now be found in surprising locations.

How to Identify Garden Snails

• Look for snails from May to October, as they hibernate during the winter months.
• Snails are most active after rainfall; dry conditions make them harder to find.
• They thrive in areas inhabited by humans, such as gardens and parks.
• To differentiate between garden and common snails, observe the inside of the shell's opening: the garden snail has a dark band, while the common snail displays a lighter one.
• When encountering these snails, it is advisable to return them to their original habitat to avoid contributing to the spread of invasive species.

As the population of garden snails continues to rise, monitoring efforts will be crucial in understanding their impact on local ecosystems and agriculture.