Some of the animals introduced to the Balearics end up adapting to the environment and compete with the native fauna and flora. They displace them and seriously endanger their population. This happens both inside and outside the Balearics, but due to the insularity the damage is accentuated and can become more serious. Some of the species currently considered native were reintroduced over a hundred years ago from other parts of the world and in some cases have evolved to form subspecies specific to the community. This is the case, for example, of the green toad, the marten, the genet, the Least weasel and the hedgehog. Other species introduced in the past are still considered invasive today, such as rats, mice and goats.
Although the introduction of external species in the Balearics is a practice that has been going on for centuries, globalisation has dramatically increased the risks involved. Not only are they introduced more quickly, but in recent years invasive tropical species, which are less adapted to the environment, have been gaining strength. Some species arrive in the Balearics as pets, which either escape or are released into the wild by their owners, without realising that the consequences can be very serious. Among the mammals, reptiles and birds introduced into the islands as pets and which have ended up in the natural environment, the Florida turtle (Trachemys elegans) stands out. Ducks are one of the birds that most frequently escape from zoos and gardens and end up in the wild. The black-and-white hawk-eagle (Geranoaetus melanoleucus) is another example.
Not all invasive fauna has been previously introduced as pets. Some species end up on the islands accidentally, travelling as ‘stowaways’, hidden in olive trees imported from the mainland and even from other countries. On other occasions they are the result of the importation of soil and other contaminated materials. This is how the horseshoe whip snake (Coluber hippocreppis) and the long-tailed lizard (Psammodromus algirus) arrived in the Balearics.
The administration has banned the importation of olive trees during the horseshoe snake’s hibernation period in an attempt to tackle the problem. This species is a good example of invasive animals adapting to their new environment. In Mallorca, horseshoe snakes swim in the open sea. Among the exotic birds we find the monk parakeet (Myiopsitta monachus), Cramer’s parakeet (Psittacula krameri), the common myna (Acridotheres tristis) and the coral-billed mynah (Estrilda astrild).
In addition to the horseshoe whip snake and the long-tailed lizard, some pests have snuck into the islands in the process of introducing infected plants, logs and soil, such as the pine processionary caterpillar (Thaumetopoea pityocampa) and more recently the red palm weevil (Rhincophorus ferrugineus) or the palm borer (Paysandisia archon). Another invasive invertebrate is the American crayfish (Procambarus clarkii) which is at home in streams, ponds and the Albufera.
The list of fish species introduced into the Balearics that live in the wild includes carp, mosquito fish and pike. Reptiles include the Florida turtle, the horseshoe whip snake and the long-tailed lizard. Birds include the monk parakeet, the coral bunting, the rose-ringed parakeet, the common myna, the cinnamon shrub and the metallic starling. Among the mammals, the wild cat, the raccoon and the coati. Among the invertebrates, the Asian wasp, the tiger mosquito, the river crab, the Argentine ant, the pine processionary caterpillar, the red palm weevil, the palm borer and the water snail.
In addition to invasive fauna, we also have invasive flora in the Balearics. These are plants that affect the ecosystem and are also controlled by the Servei de Protecció d’Espècies. There are 320 species of flora known to have been introduced to the islands. Not all introduced plants end up being invasive, but when this happens they cause significant damage to biodiversity. This has happened with the ice plant (Carpobrotus edulis), a very common fleshy plant known as ‘pigface’. A single cutting is enough for the plant to proliferate rapidly, forming veritable carpets that prevent anything else from growing in the territory they occupy. This represents a serious problem for the coastline as it invades the dune system.
Another example is the aquatic plant cotyledon (Cotula coronopifolia) which grows in ponds, in the canals of the Albufera and in other wetlands. Also the grass Pennisetum villosum, native to the African part of the Eastern Mediterranean. It is recognisable by its white flowers that look like feather dusters.
Experts differentiate between three basic types of introduced plants, according to their degree of adaptation to the environment in the Balearics and their invasive capacity. They are thus classified as naturalised, sub-spontaneous and invasive species.
Species that have become naturalised are those that, after a long process of naturalisation, have become part of our plant communities and ecosystems. They have become naturalised over a long period of time. They are normally species that were introduced for specific purposes, such as the carob tree (Ceratonia siliqua), the almond tree (Prunus dulcis), the prickly pear (Puntia maxima) or the wood sorrel (Oxalis pes-caprae).
Subspontaneous spices are those that we usually find on the edges of fields or in very run-down areas, such as urban parks, farmyards and land with manure. They come from nearby crops and gardens. They normally end up disappearing over time or become naturalised directly if conditions are right. This would be the case of the castor oil plant (Ricinus communis) frequently found in some streams, the Chinese cheesewood (Pitosporum tobira) or the oleander (Nerium oleander). The latter two are commonly used to mark the boundaries of roads and pavements.
Invasive species are those that have naturalised and proliferated rapidly in all kinds of areas, regardless of whether they are degraded or protected spaces. They displace native flora and pose a danger to the environment. Control de Espècies is working to try to eradicate them. The pitch plant (Carpobrotus edulis) and the crown daisy (Cotula coronopifolia) are the most prominent.
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