Nature on our doorsteps – The problem of Invasive Species
By Rosaleen Dwyer
Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into the natural heritage around us and the beautiful biodiversity of the plants and creatures
In Nature, armies of predators and grazers act constantly to maintain a delicate balance, ensuring that no single species is allowed to dominate for very long.
This balance can sometimes be upset when a new species is introduced into a totally new habitat.
Japanese Knotweed can spread quickly along roadways and riverbanks
These can become a problem when they grow and spread quickly, particularly if their own natural predators are absent.
Japanese Knotweed and Himalayan Balsam are two such introduced plant species that have become a problem in some of our parks and along our roads and river systems.
Originally introduced during Victorian times to beautify country estates, these plants ‘escaped’ into the wild where they continue to invade natural habitats and shade out native species.
Also, because the above-ground parts of the plants die away in winter, they expose bare riverbank soils to winter rains and floods, contributing to the erosion of river systems.
Himalayan Balsam likes the damp shady riverbanks along the River Liffey
Invasive animal species also occur. American Mink escaped from commercial fur farms in the 1980s. Without any natural predators to control their numbers, they have spread far and wide, preying on native birds, fish and mammals.
Today, as abandoned pet terrapins and turtles continue to turn up in our parks, we really do need to think twice (or three times!) before releasing any more potential problem species into the wild.
