What are Alien Species?

Alien Species are any animal, plant, fungi or other organism, which is introduced, either accidentally or deliberately, into a natural environment in which it is not normally found. Alien species are frequently encountered in Malta, with two of the more popular species being the Chameleon (Chamaeleo chamaeleon) and the North African Hedgehog (Atelerix algirus). The affects these species have on their newly introduced environment varies from species to species, however typically they do not cause significant harm to their newly introduced environment. Some alien species, after becoming integrated into the new ecosystem exhibit invasive characteristics.

What are Invasive Alien Species?

Similarly, Invasive Alien Species (IAS) are any animal, plant, fungi or other organism, which is introduced, either accidentally or deliberately, into a natural environment in which it is not normally found. However, unlike Alien Species, IAS are species that typically have serious negative consequences when it comes to their newly introduced habitats and surrounding biodiversity. The extent of their negative impacts are not limited to the environment and ecological resources; they can also have serious negative impacts on human health and even the economy. This is why IAS are classified as one of the 5 major threats and causes of biodiversity loss (UN Environment Programme, 2024).

Locally the Maltese Islands already suffers from the deleterious effects of various IAS. IAS typically have the ability to spread rapidly and grow their population numbers at a faster rate than native flora and fauna, are resistant to various climate stressors and can thrive in multiple habitats, even those not typical to the species. For example, Procambarus clarkii is established within various Maltese freshwater courses. This species out-competes native fauna, changes the freshwater ecosystem and is incredibly resistant to various environmental stresses, including extensive dry periods. Another local example would be Acacia saligna a very commonly encountered established species within various Maltese habitats. Similarly, the species out-competes native flora creating dense populations with extensive root systems, even in soils with low nutrient levels. The species also produces a large quantity of seeds and is resistant to various climate stresses.

Procambarus clarkii (ENG: Red-swamp crayfish, MLT: iċ-ċkal tal-ilma ħelu)

Overview and Objectives

Given the growing concern over the threats and impacts that IAS may cause, it has led to the enactment of various relevant policies at a global, European Union and national level. At the European Union level, Regulation No.1143/2014 on the prevention and management of the introduction and spread of invasive alien species (EU IAS Regulations) was put in place to help prevent, mitigate and eradicate IAS. This Regulation aims to create numerous restrictions on the handling, importing, selling, breeding, growing and releasing of IAS into the environment. At the core of this Regulation is the List of Invasive Alien Species of Union concern, a list compromising of species that pose, or that could potentially pose, a great threat to European biodiversity and ecosystems. The species included on the list are subject to the aforementioned restrictions. The list compromises of 88 species, with 47 being animals and 41 being plants and can be found here.

Acacia saligna (ENG: Golden wreath wattle, MLT: l-akaċja)

There are currently 9 IAS of Union Concern* present within the Maltese Islands. In no particular order these are:

      • Acacia saligna (ENG: Golden wreath wattle, MLT: l-akaÄ‹ja);
      • Ailanthus altissima (ENG: Tree-of-heaven, MLT: ix-xumakk; ix-xumakk falz);
      • Cardiospermum grandiflorum (ENG: Balloon vine; MLT: it-tuffieħ ir-riħ);
      • Pennisetum setaceum (ENG: Crimson fountain grass, MLT: il-pjuma; il-penniżetum).
      • Pacifastacus leniusculus (ENG: Signal crayfish, MLT: iÄ‹-Ä‹kal tal-ilma ħelu);
      • Procambarus clarkii (ENG: Red-swamp crayfish, MLT: iÄ‹-Ä‹kal tal-ilma ħelu);
      • Procambarus fallax f. virginalis (ENG: Marbled crayfish, MLT: iÄ‹-Ä‹kal tal-ilma ħelu);
      • Gambusia affinis (ENG: Western mosquitofish); and;
      • Gambusia holbrooki (ENG: Eastern mosquitofish).

Methods of Introduction & Entry

Typically, species have a set range of distribution and will rarely, if ever, set foot outside of this range, this, however, varies from species to species as environmental factors, such as Climate Change, which has had impacts on several species’ natural ranges. They extend beyond their range very often through anthropogenic means. It is often the case that such introduction, in terrestrial environments, is the result of the pet or horticulture trade, where the species is either released into the environment deliberately or is introduced accidentally via an escape. Alternatively, certain species may be introduced to new habitats through various other methods; such as transport contaminants, both of goods and soil or even as hitchhikers through common modes of international transport. With regards to marine non-indigenous species in general, pathways for introduction are primarily transport via hull fouling and ballast waters, followed closely by interconnected waterways. Marine IAS associated with Transport as their main vector include the African blue swimming crab (Portunus segnis). Marine IAS associated with interconnected waterways as their main pathway include the Dusky spinefoot (Siganus luridus). IAS may also be introduced to new habitats via the intentional release of the specimen.

What can you do to help?

If you ever encounter IAS, throughout any Maltese habitat, there are numerous ways that you can help. First and foremost you should familiarise yourself with the list of IAS of Union Concern and the regulations associated with these species to ensure that you are not unintentionally aiding the introduction and spread of the species.

You can also notify the Environment and Resources Authority of both the location of the IAS and extent of its population. Lastly, you can also utilise ERAs Species Observation Survey App, found here, to document the sighting of the species.

For any additional queries, you may check the frequently asked questions (FAQs), contact us via e-mail address on [email protected] or through telephone number 2292 3500.

Other links