Invasive Alien Species

Plants and animals all over the world vary in their competitiveness. Their capacity to spread is normally controlled by their local environment, soil or climatic conditions, or by the interactions with other plants and animals. When a plant or animal is moved to a new environment such as a different country, and that new environment suits them, they can colonise invasively and take over making it impossible for the original, native species to continue living there. In fact, IAS are considered to be the second most important cause of global biodiversity decline after habitat loss.

This problem has become so serious over the last thirty years that Governments across the world have introduced legislation in an attempt to prevent IAS from being introduced to new countries and, once introduced, to actively stop their spread.Legislation varies across countries and continents. Ireland has adopted a suite of EU measures which can be viewed here.

However, some alien invasive species not controlled by  legislation may pose significant problems locally in individual member states.; an example is winter heliotrope. Winter heliotrope (Petasites fragrans) has become severely invasive in Ireland over the last five years but it is not included in EU-wide lists because it appears to be a problem which is specific to this country.

In Ireland, the National Biodiversity Data Centre (NBDC) does a superb job recording our flora and fauna, including the occurrence of non-native species and their potential invasiveness. Well known, highrisk species include Japanese Knotweed, Giant Hogweed, Grey Squirrel, and Mink. There are many others which are less visible initially but cause significant environmental damage; for example, the fungus Aphanomyces Astaci has caused a plague in our native crayfish, and the ash die back fungus Hymenoscyphus Fraxineus, which is thought to have originated in Asia, has nearly destroyed our native ash population within 8 years. Also, there are many invasive alien freshwater aquatic plants and animals which may not become obvious until the native ecosystem is overwhelmed.

All records submitted to the NBDC are mapped on their comprehensive mapping system which can be accessed here.

The table shows the most frequently encountered and highest risk IAS in County Limerick.

Some of these plants, such as Buddleja and Cherry Laurel are still commonly planted in gardens, which is a matter of real concern, as they can readily 'escape' into the countryside where they cause havoc with our native vegetation.