Invasive plant species will spread even further in Germany

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Forecast of the spread for Ambrosia artemisiifolia in Germany under current and
Forecast of the spread for Ambrosia artemisiifolia in Germany under current and future climate conditions. Photo: Fabian Sittaro (Graphic)
They are called giant hogweed, Japanese knotweed or ragweed - but they all have one thing in common: they are invasive plant species that found their way to Germany many years ago and are increasingly displacing other plant species. Many of them have not even reached their potentially suitable habitat yet. Geographers at the University of Leipzig have determined this in a recent simulation study. They coupled different data sets to predict the probability of occurrence of selected invasive plant species for each location in Germany. The results were published in the International Journal of Applied Earth Observation and Geoinformation and will be used in an online portal that will enable users to monitor these species.

Actually, Ambrosia artemisiifolia could be dismissed as a more or less annoying field weed. The plant species migrated from North America around 150 years ago and is probably familiar to many allergy sufferers. Ragweed is highly allergenic, and even small amounts of its pollen can cause severe reactions. In addition, the sometimes mass occurrence of ragweed endangers agricultural crops. The plant prefers warm and dry locations and will spread even further in the coming years in the hot and dry regions of Saxony, southern Brandenburg and the Upper Rhine Graben, among others.

Scenarios created for current and future climate conditions.

This is one result of the study by Fabian Sittaro, a doctoral student at the Institute of Geography at the University of Leipzig. The aim of his study was to evaluate suitable habitats for important invasive plant species in Germany under current and future climate conditions up to the year 2080. To this end, the 33-year-old examined a total of 46 invasive plant species in his doctoral thesis, which are at different stages of their spread. -I divided the whole of Germany into quadrants by remote sensing using satellite image data. For each of these quadrants, the environmental data was determined, i.e. information on soil type, land use, climate and elevation data, information on infrastructure and existing plant communities," says Fabian Sittaro, explaining the methodological procedure. Using this data, various machine learning methods were used to calculate whether the respective species would be able to spread in the defined quadrants and thus in certain parts of Germany. These scenarios were created for current and future climate conditions up to the year 2080. The distribution data used come from the FlorKart database for floristic mapping in Germany and the Natura2000 network on nature conservation areas in Europe.

Climate change further favors spread of invasive species

-The study shows that future climate conditions will determine the habitat that individual species can occupy or claim-, says Michael Vohland, professor of geography specializing in geoinformatics and remote sensing at the University of Leipzig and supervisor of the dissertation. -The invasive plant species will have a larger, potentially suitable habitat available to them, because many of them come from regions with dry and warm climatic conditions.- Even under current climatic conditions, most of the species studied have not yet reached their potential habitat. High dispersal potential is found in urban agglomerations and areas with good transport infrastructure. The study provides important information for the targeted implementation of protection and control measures on the basis of monitoring. Fabian Sittaro, who received a scholarship from the Deutsche Bundesstiftung Umwelt (DBU) for his dissertation, is currently working on a web application. In addition to information on invasive plant species, this should also provide maps with current and forecast areas of spread and be available by the end of 2023.

Original publication in International Journal of Applied Earth Observations and Geoinformation.

-Which factors determine the invasion of plant species? Machine learning based habitat modeling integrating environmental factors and climate scenarios- , DOI: 10.1016/j.jag.2022.103158

Dr. Katarina Werneburg