Let’s be honest, we humans are pretty stupid sometimes. We wander around the Earth, thinking we own the place. We tear up trees, dam rivers and dig, dig, dig for everything under the sun. We also like to take creatures and nice pretty things from one side of the planet and plop them where they don’t belong. Thus invasive species are born (or rather introduced). When this happens all sorts of fun ensues. Here I’m running through some of our greatest invasive blunders.
First up the "killer algae".
If you live in Europe, chances are you’ve heard of Caulerpa taxifolia, also known as the “killer algae”. C. taxifolia gained notoriety in Mediterranean countries during the 90s due to one unfortunate leakage from a maritime museum. Since then the seaweed has out-muscled native species and killed off fish habitat. When it's not invading other places seabeds, the species is native to the Indian Ocean.
The first stage of the killer’s invasion of the Med was the discovery of a cold water variety that was well suited to aquariums. It became popular, appearing in exhibits including the Oceanographic Museum of Monaco.
The killer algae.
In the 1980s, the first patch of C.taxifolia was found on the museum’s watery doorstep. This was ground zero. At first the seaweed covered one measly square meter. It’s believed that an accidental release of the seaweed in 1984 kick started what became a full blown invasion of the Mediterranean seabed. Thinking that the cold waters of the Med would kill off the tropical invader, the solitary one square meter was left to die in peace. Bad move.
Within ten years of its discovery the seaweed had expanded to cover 30 square kilometers.
Then we took over to help it along its way. C.taxifolia hitched a ride on the anchors of fishing boats and cargo ships to conquer new territory. Now it covers over 130 square kilometres of seabed along 190km of the Mediterranean coastline and can be found off Spain, France, Monaco, Italy, Croatia and Tunisia.
In 2005, C.taxifolia was listed as one of the top five risk species in Europe. Its ability to out-compete other seagrasses (either by crowding them out, or intoxicating them) and its creation of “monospecific meadows” (where few fish species roam) are listed by the IUCN’s Global Invasive Species Database as the species’ worst effects. For us this translates into fewer fish catches, or catches that are riddled with toxins and therefore unfit to eat.
During the early years when it was discovered in the Mediterranean, instead of working together to combat the invasive algae, folks were casually bickering over who released it in the first place. The response to the algae's appearance off the shores of California in 2000 was also heavily criticised.
We just weren't ready for a rapidly expanding killer seaweed that's now made i
t on to the IUCN's 100 worst invasive species, one of only two algae to grace the list. Hat's off, I say.
Next up the American Skunk Cabbage.
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