Popular Science: Through categorisation to victory over invasive plants
There are around 12,000 species of alien plants, animals and fungi in Europe. Plants are represented by 4,140 species and more than a half of them are known to influence the environment. The number of alien species is still growing, and we can assume that this trend will continue in the future. It is therefore necessary to improve the effectiveness of management of their invasion, and categorisation of invasive plants might be an effective tool for setting priorities and decreasing environmental damage.
The scientists chose 128 species and evaluated their impact on the society and environment based on established facts from scientific literature. Then they assessed them in 12 categories: 6 evaluated socioeconomic and 6 environmental impact. Environmental influence could be e.g. competing with local plant species, influencing food availability for animals, or transmission of diseases or parasites. Socioeconomic influence was e.g. impact on agricultural or animal production, or on human health.
The results showed that 79% of the tested species influenced the environment, mainly in the category of competition with original species. Socioeconomic influence was found in 75% of species, most of which influenced human health. Among the top European invaders are for example Canadian waterweed (Elodea canadensis), giant hogweed (Heracleum mantegazzianum) or yellow sage (Lantana camara).
Annual plants had a lower impact on the environment than perennials, and the biggest impact was found in aquatic plants. Aquatic ecosystems are highly sensitive to the change of conditions, and even shading of water surface can severely influence other water organisms. People might face economic losses caused by high densities of plants in water dams and reservoirs.
Categorising plants and pointing out the harmful species is very important. After all, only six out of 24 species with the biggest environmental impact are listed among the most harmful plants in European protected areas. Information from these databases can be used as an effective tool for identifying harmful species, evaluating their potential impact in given environments and deciding about the next steps in managing biological invasions of plants.