Slow and Steady Wins the Race: A Snail's Journey Across the World
By Ember Snook
When you think of garden pests, the images that op into mind are often insects like beetles or caterpillars. Few people imagine going out into their garden only to find their precious plants being terrorized by a nearly foot-long snail – but from Madagascar to Hawaii, and all across the ocean as far as Florida, the giant African snail is a menace. Why is it such a problem?
The
answer is simple: its diet includes a very wide range of plant materiel, not
limited to fruits and vegetables. If it were not the size of a kitten, this
might not be a problem – but combined with the fact that when sexually mature
an adult snail’s average clutch of eggs numbers around 200 (of which an average
of about 180 will hatch) it starts to get rather frightening. Then you realize
that a snail can lay up to six of these clutches every year, and it becomes
quite clear why it might take only a single gravid snail to destroy a forest.
This
would be a problem on its own – but people have a nasty habit of helping this pest
get around. As early as the 1800s, this snail was brought and deliberately
introduced as not just a source of food, but also for the ornamental use of its
shell, the medicinal value of a chemical in its shell, or all too frequently
shipped unknowingly in containers of agricultural produce. All it takes is one
clutch of eggs to start an infestation, which makes it both hard to prevent
from taking hold and incredibly hard to get rid of – which isn’t to say people
don’t try. In Hawaii, it was successfully eradicated in a venture that was both
incredibly expensive, and took the better part of several years.
It’s
easy to hear names like Madagascar or Hawaii and think, “Why does something so
far out there matter to me?” But let me tell you, this snail is not on the top
100 invasive species list of the world for no reason. In just the continental United
States, this species has been found in Florida, Georgia, Maine, Washington and
Oregon, and Colorado. For those who are not up to date on their geography –
that’s a coast to coast problem! Despite careful monitoring, once it does
manage to be introduced, the snail’s population balloons, necessitating
thorough eradication by means of a combination of mulluscicides, by-hand retrieval,
and general public awareness campaigns.
Other
attempts to control the growing population of snails have been incredibly
destructive – specifically, when people tried to introduce predatory snails or
flatworms that ideally would have preyed on these giant snails. Instead, these
creatures drove other native species extinct!
The
giant African land snail has, at least in Brazil, caused tens of billions of
dollars in damage to crops, and a further seven billion in damage. But that’s a
hard number to process. What struck me the most were the simple maps presented in a study done by Silvana Thiengo and her colleagues, showing how
fast the snails can spread in a four year period in Rio de Janiero:
That's just one municipality of Brazil! It's no wonder the snail is so hard to control, after seeing those figures. It's shocking to see how fast they spread - and even more so to learn that they are drawn to urban areas due to the combination of accumulated garbage and vegetation provides them with an ideal source of both nutrients and egg-laying shelter. Then, being drawn so close to civilization, it becomes an easy (and preferred) course of action for them to begin chowing down on our produce - broccoli and peppers and bananas and so much more are being lost to these savage snails.
Stopping the spread of these snails is a much more complicated matter than simply putting into place laws that make it illegal to sell, rear, or transport the creatures and their young. In Brazil, as well as many other places, the best course of action they have is to encourage physical methods of control and removal, where people go in and manually destroy and remove the snails in several sweeps until they are all gone.
What this means is that, for us here in the states, the best way to control these snails is to know they exist, and be able to identify them when they crop up. It's not hard to recognize a foot-long snail - but understanding the danger it poses and getting people to report if they see them is still an ongoing challenge.
Don't just marvel when you see something like a gigantic snail. Stop and think and ask "Is this actively harming my environment?" At the very least, research it - and encourage others to do the same. It'll save you a headache in the long run, when the world is overrun with oversized molluscs.
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