“Everyday species” on the advance

The growth of the already widespread plant species threatens the diversity of plants in many ecosystems in Europe. (Image: Harald Pauli / OeAW)

Stinging nettles, dandelions and the like are spreading in many places: “Common species” are displacing rare plants in many different ecosystems in Europe, shows a study. The development includes mountain regions as well as forests and meadows of the lowlands and does not stop at protected ecosystems. In addition to the consequences of climate change, increased nutrient inputs via the air could be responsible for the trend, explain the scientists.

The animal world is often the focus – but the diversity of plants on earth is also endangered by the various man-made factors: According to estimates, two out of five species worldwide are threatened with extinction. Regionally, however, there are often very specific developments and causes for the changes in plant biodiversity. The biodiversity researchers led by Ingmar Staude from the German Center for Integrative Biodiversity Research Halle-Jena-Leipzig (iDiv) now focused on developments in Europe. For the first time, they investigated shifts in the species composition in three very different habitats: in alpine summit zones, in the herbaceous layer of forests and in species-rich meadows and pastures in the lowlands.

80 years of biodiversity development in view

The basis of the study was formed by repeated surveys of the species population on 141 study areas in 19 European countries – over a long period of time: The oldest data sets go back to the 1940s. The temporal increases and decreases of a total of 1827 plant species were recorded. “The field work of the numerous vegetation researchers enabled a unique insight into the past in order to study changes in plant communities over the past decades,” says Staude in recognition of the work of those involved.

As he and his colleagues report, the evaluations show clear trends: In forests, meadows and pastures of the lowlands, biodiversity is dwindling due to an increase in populations of already widespread species at the expense of species with small areas of distribution. The “commonplace species” characterize a preference for nutrient-rich habitats, while the specialists are mostly adapted to nutrient-poor soils. In the alpine summit zones, however, there is still an increase in the number of species, the researchers report. As they explain, this is due to the advance of the more widespread species from the lower elevations upwards, where they have hitherto been added to the native species. “In the long term, however, displacement is to be expected here too,” says Staude.

Near-natural regions also affected

The analyzes also showed that the trend does not only affect areas that are heavily influenced by humans: “We observe that this dynamic also unfolds in natural habitats, i.e. in places that we would expect to be safe places of refuge for specialized species and those of high conservation value. This suggests that the Anthropocene does not stop at the doors of the few remaining wilderness areas that we consider protected, ”says Staude. His colleague Henrique Pereira from the iDiv adds: “It is also worrying that species change is very similar in markedly different ecosystems, which is why we have to assume that we are dealing with a very widespread phenomenon”.

According to the scientists, two factors are largely responsible for the trend: The consequences of climate change as well as increased amounts of nutrients in the soil, which can be attributed to nitrogen inputs from agriculture – but also from the air. They come from combustion processes in traffic and industry and are spread everywhere through precipitation. “The plant species themselves are meaningful indicators of high nitrogen levels: There are many species that reliably display nitrogen, such as the nettle,” explains co-author Harald Pauli from the Institute for Interdisciplinary Mountain Research at the Austrian Academy of Sciences in Vienna. As the researchers explain, increased amounts of nutrients can have two negative effects: They promote the growth of the widespread nitrogen-loving species. Their growth then also leads to increased shading, which leads to the displacement of the smaller, rarer specialists.

The scientists conclude that there are complex consequences associated with the loss of plant biodiversity: “Every species that is lost is an irretrievable loss and has an impact on the ecosystem. Because: The different types of plants interact with insects, but also with other living beings, such as soil organisms, ”Pauli points out.

German Center for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, specialist article: Ecology Letters, doi: 10.1111 / ele.13937

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