Invasive Giant African Land Snails: Anything But a Slow-Paced Invader
BBC UK News reports of the confiscation of 36 live Giant African land snails by officials at the Glasgow Airport, Scotland.
They were found stuffed in the luggage of a Nigerian passenger who came in a flight from Amsterdam. The man, who claimed that he intended to use the snails for food, did not have an import license for carrying live animals and also violated importation controls on products of animal origin. The Border Force officials who confiscated the mollusks turned them over to a rescue organization. If the airport had not done its job properly, there might have been a greater price to pay.
There is a good reason for all the fuss over a few dozen snails. The Giant African land snail is among the top 100 invasive species on the planet, according to IUCN.
Capable of growing up to 20 cm in shell length, Giant African land snails are known not only for their large, generally reddish-brown shells but also for the damage they cause in an area where they become invasives. The IUCN database page on Achatina fulica lists agricultural, economic, disease transmission, ecosystem change, human nuisance, and human health as major areas that the species, when invasive, impacts.
Giant African land snails only travel an average of 250 m a year or a quarter of a kilometer, But what they lack in movement speed they more than make up in their reproduction speed and rate. Giant African land snails start laying egg clutches of 100 in their first year, up to 500 in their second, and may reach an egg clutch of 1,000 in their maturity. This ability to exponentially multiply is all the more devastating when Giant African land snails are introduced in an area where their natural predators are absent to keep their numbers under control. In fact, a single externally fertilized individual can start a founding population of invasive Giant African land snails. This makes it difficult for typical eradication programs to completely eliminate the invasive snail, as 99% of the population eradicated may still not be enough.
The extent and range of damage that invasive Giant African land snails can inflict does not crawl at a snail-pace, either. In agriculture, IUCN records a fourfold impact: loss of crop yield due to herbivory, transmission of plant pathogens resulting in spread of disease, associated costs in pest control measures, and lost agricultural opportunities. The economic costs of invasive Giant African land snails run into millions of dollars if populations are not controlled. They also impact ecosystems through herbivory, alteration of nutrient cycling, and competition with indigenous snail species. Aggregated Giant African land snails have the capacity to cause road slicks simply through the massive amount of slime they leave behind. In some cases, they can also carry serious health risks to humans who come in contact with them.
The invasive snail can find its way to susceptible locations through a number of ways. They can come in shipping containers, aircrafts, and military equipments. The snails can also be introduced to an area by humans, sometimes deliberately. Here are some examples:
As Pets: People may collect Giant African land snails as novelty pets, as what happened in the story of a boy who brought three Giant African land snails as a gift for his grandmother. She threw them in the garden and they spread over the years, incredibly costing $1 million in eradication efforts by authorities.
As Ornaments and Novelty: Giant African land snails may be introduced to a location as decoration and landscape novelties. Its large, colored shell may seem attractive to some people who then collect them.
As Food Resource: In some countries, Giant African land snails are seen as animal food resource, and even food resource for humans (as in the case of the Glasgow Airport incident). Giant African land snails as food resource pose a negative risk to human health. The snails can carry a form of nematode that enters the circulation and travels toward the brain, causing eosinophilic meningitis. This disease causes numbness, headaches, even coma and death. Even touching the snails’ slime and touching food afterwards can result in contraction of the parasites.
These are only some of the pathways that Giant African land snails (and other invasives) can be deliberately introduced by humans to a vulnerable area. While some pathways cannot be completely controlled, there are pathways where our choices can make a difference.
Eradication and Preventive Measures
Invasive species are one of the top threats to biodiversity (WWF). Once invasive species establish a population in a vulnerable area, it can be very difficult to keep their growth and spread, and the damages that result, under control.
In the case of Giant African land snails, several eradication measures have actually proven inadequate instead of effective in dealing with the invasion. Biological control in the form of introducing the rosy wolfsnail proved disastrous and caused even more damage. Razing of an entire area destroyed ecosystems in the pursuit of eradicating only one species. Use of toxic baits also victimized indigenous as well as invasive snails.
Instead, collection and destruction of the Giant African land snails and its eggs are recommended as a form of physical control. As in most cases, preventive measures are always a better option. Guarding pathways through which invasive species like Giant African land snails can pass is much cheaper than pursuing them through biological or chemical controls that might do more harm than good.
Some tips to prevent being an invasive species carrier:
- Check and wash clothing thoroughly when traveling abroad to prevent carrying plant seeds or minute specimen to a location.
- Clean equipment, vehicles, and personal items thoroughly
- Check with border officials on what live animals and products of animal origin you can bring in or take out.
Remember, invasives can arrive in an area as well as come from it through people. A species in its natural habitat serves its natural function and part in the ecosystem beautifully, but when transplanted where it does not belong, it loses that beauty and brings damage instead.
Reasons to JOIN US include:
- It's absolutely FREE!
- Get Green Tips You MUST know about.
- How to's on going green, saving money, and having fun.
- Keep up-to-date on our posts in cased you missed them.