In Europe alone, there are around 16,000 plants, animals, fungi and micro-organisms that are alien to their natural environment. Of these, 15% pose a threat to biological diversity and can defined as invasive species.

Besides their impact on biodiversity, invasive alien species (IAS) can have enormous economic ramifications. According to European Commissioner for Environment, Karmenu Vella, the damage caused by IAS to property, crops and livelihoods amounts to €12 billion  every year.

Following our last post on Unwanted Aliens, this week we assess some of the national and worldwide conservation strategies being used to combat the introduction and spread of IAS. Then we’ll suggest a few ways that you can join the fight!

Territorial surveillance

The first step in controlling invasive species is surveillance. For a few years, legislation has been in place to ensure that EU countries take this issue seriously. As with all fauna and flora, IAS don’t tend to stop at country borders, therefore a coordinated, pan-European approach is essential.

As part of this surveillance, the European Commision has compiled the Union List, an index of Europe’s 49 most (un)wanted plants and animals. Resources have been made available to prevent, detect, eradicate or manage them. Keep reading to see how you can help with this!

International waters

Invasive species affect terrestrial and marine ecosystems alike. One of the greatest risks to the world’s coastal and marine environments comes from the global shipping industry. Large ships take on a tremendous amount water, called ballast water, to aid their stability. Ballast water, containing plants, animals, viruses, and other microorganisms, is taken from one region and is discharged at the next port, often thousands of miles away.

Last month, however, a global treaty was introduced specifically to promote technological solutions to tackle this problem and prevent aquatic invasive species.

Boat moored above coral reef in ocean. Pic by Rich Carey |
Boat moored above coral reef in ocean. Pic by Rich Carey |

Necessary eradication

While environmental management requires a multifaceted approach, in some cases the most effective method of controlling IAS is eradication. It may seem counterintuitive – ‘killing to conserve’ – but it’s a strategy that has proved successful.

On the isle of Anglesey, for example, a conservation project has led to the complete eradication of grey squirrels. For obvious reasons, such a project is easier to carry out on an island. Nevertheless, it took them no less than 18 years to declare the island free of greys!

Apparent competition

Another fascinating example is that of caribou conservation in North America. Having detected a rapid decline in native woodland caribou, scientists believed it was due to direct competition from invasive prey, such as moose and deer. However, as a recent study shows, it’s not quite that simple.

“If the invasive species is abundant, the native species can go extinct because predator numbers are propped up by the invading species…it ‘appears’ that the invading and native prey directly compete with each other, but really the shared predator links the two prey.”

In this case, wolf numbers increased dramatically because of the abundance moose, and caribou populations suffered as a consequence. In light of this, the initial idea to cull the wolves would have proved to be ineffective. In fact, researchers showed that the only sustainable conservation method was a reduction of moose.

3 ways you can join the fight against invasive species

This is a call-to-action but, don’t worry, there won’t be any violence. There’s a lot you can do without having to chase grey squirrels around your local park!

  • Brush up on biosecurity

You’re probably not going to be captaining a cargo ship across the Pacific Ocean any time soon, but you might be planning a hiking trip sometime soon. Remember, the simple act of going for a walk in a foreign national park could lead to the introduction of an invasive species. Soil or seeds in the tread of your boots could be all that it takes. So next time you’re off on holiday, be sure to give your boots a good clean!

  • Get to know your aliens

Surveillance is everything but, grey squirrels aside, how many IAS do you think you could recognise? Identifying plants and animals isn’t easy, but with the help of technology we can all become alien experts. Here are two apps to get you started:

Invasive Alien Species in Europe

Plant Tracker

  • Keep tabs on your tabby

Domestic and feral cats may not appear on the list of invasive alien species, but the damage they cause to biodiversity is staggering. Last week a study announced that cats were responsible for killing 1 million birds a day in Australia alone.

It’s important to highlight that feral cats are the main perpetrators, killing 316 million birds a year, compared to 61 million by pet cats. So we’re not suggesting you get rid of your felines, quite the opposite. Keep your cat happy and well fed to make sure it doesn’t become a stray.

And if you really want to keep tabs on how your cats spend their time, you could even invest in a GPS cat tracking system – the wonders of technology!


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James is a freelance language professional based in Barcelona. Besides writing articles for Zoo Portraits, he writes about education and teaches English as a foreign language in businesses, universities and other institutions around the city.


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