Controlling invasive species in wetland areas on the Balearic Islands

What exactly is COFIB and how has it evolved since its creation?

The Balearic Island Wildlife Recovery Centre (COFIB) was created in 2004 as a consortium between the Regional Ministry of Agriculture, Fisheries and the Natural Environment, and the Natura Parc Foundation, with the aim of recovering wildlife. But over time it’s grown a lot. Today, it deals not only with injured animals, but also with invasive alien species control, sea turtle management and many other branches of the environment. This has all resulted from government demands and the evolution of the work over the last 20 years.

What exactly do we mean by ‘invasive alien species’?

It’s a species that, when introduced— intentionally or not—into a new territory, leads to alterations in local biodiversity. It affects not only the environment, through the displacement or extinction of local species, but also the economy, health and even agriculture and livestock farming. Technically, an introduced species is not the same as an invasive species. Introduced species don’t always cause damage, but invasive species have been shown to negatively impact local biodiversity.

What are the most problematic invasive species around the Balearic Islands?

At COFIB, we focus mainly on animals and certain plants. We’re talking about snakes such as the horseshoe snake or ladder snake in Ibiza and Formentera. In Mallorca we have animals such as the raccoon, the Asian hornet (Vespa velutina), the Argentine parrot, the Kramer parrot, and even fish such as carp. There are also significant insect species. The list is long, but these are the ones that are of most concern today and where most resources are invested.

What real impact do they have on our biodiversity?

On islands, local species are more fragile because they’ve evolved in isolation for thousands of years, without competition or natural predators. This makes them more vulnerable. For example, the Ibiza wall lizard is very trusting and has no escape mechanisms, because it has had no predators. When predators like snakes are introduced, it has no tools to defend itself. This leads to local extinction and severe disruption to ecosystems.

How do these species get there and why do they spread so fast?

Some arrive naturally, such as on a floating branch, but that’s anecdotal. Today, most of them are brought by humans. Sometimes they are bought as pets and then escape or are released. Other times they are hidden in goods, plants, soil or even building materials. We import a lot of things from the continent and, as a result, species enter without us realising. Once here, if they find an advantageous ecosystem without predators, they expand rapidly.

In the case of the raccoon, what problems has it caused in Mallorca?

It’s an animal that didn’t exist in our wildlife before. It’s opportunistic, feeding on everything: fruit, carcasses, rubbish, etc. It has a high reproduction rate and has no predators or natural competitors here. This allows it to adapt very well and cause problems: for farming, by attacking orchards; and for biodiversity, by preying on eggs, birds, amphibians, and more. It can displace local native species that are not prepared to face such a mammal.

Another case is the Florida turtle. What’s the situation there?

It’s been a very common pet species for years. It’s been released or escaped and is now found in wetlands in Mallorca, Menorca and some parts of Ibiza. It’s highly territorial, large and aggressive. It competes directly with our own water turtle, the European pond turtle, which is smaller and less hardy. It also preys on fish larvae, amphibians and even small birds. It displaces our species without giving them a chance.

What kind of measures does COFIB take to control these species?

Our work is on the ground: control and containment. We use species-specific traps like turtle traps and raccoon traps, and run snake trapping campaigns. This is all under the direction of the regional government. We also work on prevention, although it’s not our direct responsibility. Prevention is key: if new species continue to enter, control efforts will never be enough. We need to stop it at the source, not just deal with what’s already here.

Which natural areas are under the greatest threat from these invasive species?

The most sensitive are those with a high level of biodiversity or that host endemic species. For example, at ponds known as gorgs, home to the Mallorcan midwife toad, a unique amphibian that only lives around a few ponds in the Tramuntana Mountains. If a snake or a raccoon gets in there, the threat is very serious. Although we need to respond comprehensively by understanding where these species move and on what type of surface they’re found, it’s not enough to act only on specific points.

What about invasive plant species?

This is a somewhat less developed area, but also an important one. Some of the most problematic are the century plant (Agave americana) and clawberry (Carpobrotus), known as ‘cat’s claw’ on the island. They’re much more difficult to detect than animals because they’re usually found in gardens, roundabouts, roads, and so on. Often nobody realises that this plant is a problem. Control is complex and less visual, but also essential.

Is it realistic to think of eradicating these species completely?

It depends. Some species have been eradicated: the Argentine parrot, the coati, even the Asian hornet. But others are more difficult because of their biology, distribution or numbers. In these cases, we work on population control, which means keeping populations at low levels so that our species can survive. Total eradication isn’t always possible, but we can reduce the impact through proper control.