What are invasive plants?
An invasive plant is a highly adaptive plant species that grows and spreads more efficiently than other plants.
Invasive plants usually come from other areas (they are non-native species) that have been introduced to the habitat where they become invasive.
Not all non-native plants become invasive. Many non-native plants coexist with native plants without causing any damage to ecosystems.
However, some non-native plants can have a negative impact on the natural environment where they have been introduced. In this case, a plant is considered invasive.
In Catalonia (NE Spain), a total of 812 non-native plant species have been identified, 90 of them being considered invasive although not all included in any law. Around 30 invasive plant species are present in the Catalan coastline and have especial impact in the habitat of community interest of Mediterranean cliffs with endemic Limonium spp. (HIC 1240), which is representative of the Costa Brava and Cap de Creus areas.
Impact on the natural environment
In any habitat many different native species grow and co-exist maintaining a natural balance, without one species dominating over the others or one species being detrimental to the others.
Among the native species there may be some species that have very few viable individuals that are capable of reproducing and survive in the long term. Such species are the endangered endemism. In the case of flora, endangered endemic species usually produce very few seeds, their seeds are not capable of germinating or their germinate but the young plants do not get the adult stage to produce new seeds. Year after year, this means that fewer new plants can survive, endangering the long-term conservation of such species. This is the case of Seseli farrenyi, Limonium geronense and Limonium tremolsii, plant species with limited wild populations of few individuals growing in a handful of places within the Cap de Creus area.
When a non-native (invasive) plant arrives in a habitat, it can spread and develop in an uncontrolled way because in the place where it has been introduced there are still no natural predators or competitors, which are the only ones capable of regulating its growth and spread.
In this way, invasive plants easily make their way into the habitat where they have been introduced, occupying all available space.
This alteration of the natural balance causes native species and, above all, endangered endemism, to lose the possibility of developing new individuals and, over the years, they end up being lost. This negative effect impacts not only on native plants but also on insects, birds and other habitat-dwelling organisms. Then, there is a biodiversity loss.
Furthermore, when an invasive plant colonises a place, it makes the natural environment extremely uniform, resulting in compact and low-valued landscapes and causing also a social, cultural and economic loss.