Ireland's State of the Environment Report 2024

172 Chapter 7: Nature Figure 7.15  Macroalgal bloom in Youghal Bay, Co. Cork, a negative response to high levels of nutrient pollution 10 These species are both originally from the Ponto-Caspian region and are known to cause widespread economic and ecological impacts on affected waters outside the native range. Pollution Clean air is essential for healthy ecosystems. While recent decades have seen significant improvements in air quality in Ireland, air pollution continues to cause damage to both our health and the environment (DECC, 2023). Air pollution in the form of nitrogen deposition continues to affect natural habitats and their plant communities (Aherne et al. , 2021), which, in turn, has consequences for associated sensitive species and biodiversity, namely our butterflies, bees, other insects and birds. Air pollution from sulphur deposition, while much reduced, may still contribute to the acidification of soils and water (Chapter 2). Water pollution in our environment is unfortunately too common, mainly due to nutrient inputs from agriculture and poorly treated waste water (Figure 7.15). For further discussion on this topic, see Chapters 8 and 9. The loss of high-quality unpolluted rivers, lakes and estuaries nationally has consequences for many freshwater species, such as the freshwater pearl mussel, and also for aquatic plants, invertebrates, fish and birds (King et al. , 2011, Kelly-Quinn et al. , 2020, Stroh et al. , 2023). Nutrient pollution in our waters also favours opportunistic invasive species, such as Nuttall’s pondweed, allowing them to outcompete and replace our native fauna (see Figure 7.8). Similarly, nutrient pollution, in combination with invasive species, such as the Ponto-Caspian zebra mussel now widespread across Ireland, can result in significant ecological and economic impacts. Invasive alien species Invasive alien species are those that have become problematic after they have been introduced (deliberately or accidentally) to places where they do not occur naturally. Increased trade, human movement, changes in land use and climate change mean that the risk of invasive species arriving, spreading and becoming established in Ireland is high. Non-native species become invasive because they adapt to their new environment easily, outcompeting native species for resources such as food, light or space, and may have little or no predation (e.g. sika deer; Twining et al. , 2022). These invasive species can have a negative impact on the economy, wildlife and habitats and are one of the top five causes of biodiversity loss across the globe (IPBES, 2019). For example, Stroh et al. (2023) recently highlighted non-native species as one of the main threats to native plant biodiversity in Ireland. Similarly, invasive species can cause environmental and economic damage – for example, both zebra and quagga mussels 10 can block public and private water abstraction in lakes, increasing operating costs. They attach readily to boats (Figure 7.16) and moorings, causing damage and increasing maintenance costs. Invasive species can also contribute to large ecological disasters; for example, in Lough Neagh in Northern Ireland, the combination of nutrient pollution (from agricultural run-off and sewage), the proliferation of invasive zebra mussel populations across the lake (which filter particles from the water, increasing light penetration) and climate change has resulted in extensive blooms of toxic blue-green algae (The Rivers Trust, 2024). Blue-green algae can release toxins harmful to humans, animals and birds.