If a change occurs in nature

Threatened biodiversity : This is how human intervention changes nature

Of around eight million animal and plant species, around one million could become extinct - due to intensive agriculture, industry and traffic, through hunting and fishing to climate change. These figures from the World Biodiversity Council (IPBES) caused a sensation in the summer. But behind the disappearing species, there is an even bigger problem. In the journal "Science" scientists are now warning of dangerous changes in nature.

Accordingly, the number of species in some of the 51,932 areas examined by various researchers has decreased in the course of the investigations. At the same time, however, the composition of the species in all of these areas changed, sometimes at an enormous pace.

Tagesspiegel Background Energy & Climate

Coal phase-out, climate change, sector coupling: the briefing for the energy and climate sector. For decision-makers and experts from business, politics, associations, science and NGOs.

Free test now!

While this change is rather minor in the forests of the temperate latitudes, such as in Central Europe, it is particularly strong in the warm waters off Australia's northwest coast and in the western Atlantic. The study comes from Shane Blowes from the German Center for Integrative Biodiversity Research (iDiv) in Halle, Jena and Leipzig, the University of Halle-Wittenberg and colleagues from Europe and North America.

Such changes can have a significant impact on the respective ecosystem. “This rapid change is fueling the global biodiversity crisis much more than the loss of species,” explain Britas Klemens Eriksson (University of Groningen) and Helmut Hillebrand (University of Oldenburg), also in “Science”.

The number of species says little about the state of nature

“For this extremely complex analysis, the researchers at iDiv and their colleagues examined ecosystems in the sea, on land and in freshwater for the first time using huge data sets,” says Ingolf Kühn from the Helmholtz Center for Environmental Research (UFZ) in Halle. They were not only able to record the loss of species, but also the sometimes severe changes that are already causing considerable problems in some regions today.

In contrast, the number of species alone often says little about the state of nature. "For example, only very few species live in the beech forests that grow on acidic soils in Central Europe," explains UFZ researcher Ingolf Kühn. "Nevertheless, such ecosystems are not only very stable, but also very productive."

This is precisely why iDiv researcher Shane Blowes and his colleagues have investigated the changes. For this purpose, 239 existing studies were analyzed; individual data sets go back to the end of the 19th century.

[More on the subject: No time to adapt - climate change is too rapid for many animal species.]

In 23 marine regions, the number of species actually decreased by up to 20 percent a year, as feared, while on land there were declines of up to ten percent. In other areas, however, the biodiversity hardly changed - or even increased by up to 20 percent in 31 marine regions. While species diversity is decreasing worldwide due to the influence of mankind, in some regions it even seems to be growing in reverse.

A slight increase in species - sounds like a contradiction

Even more: When the researchers working with Shane Blowes looked at all the ecosystems together, they even found a slight increase in species overall. At first glance, this is in complete contradiction to the worldwide decline in species, but it can be easily explained on closer inspection.

Since the 1960s in particular, farmers have been applying more fertilizers such as liquid manure and manure or synthetic products to their fields than the crops absorb. This surplus eventually reaches forests, moors and other ecosystems through water or air, which previously had much less nitrogen available. Similarly, combustion engines deliver nitrogen compounds to the air in their exhaust gases, which in the end overfertilize forests or grasslands, for example.

The plants that specialize in such locations and are adapted to little nitrogen are kept there for the time being. However, plants also settle in the area that require significantly more nitrogen and have therefore not previously been found on the poor grassland or in the forest. In this area, the number of species is increasing first of all. Over time, however, these plants, which have been adapted to a lot of nitrogen fertilizers, overgrow the typical grassland or forest plants, which can ultimately become extinct.

What happens on the peaks of the mountains

"Climate change triggers a similar process on the mountain peaks in various European mountains," says UFZ researcher Ingolf Kühn. Temperatures are rising there, and plants are spreading that previously only grew in lower altitudes with higher temperatures. So far, the specialists of the high altitudes have also stayed on the peaks. In the coming decades, however, many of them are likely to become extinct. "Overall, the composition is becoming more and more similar in different regions, and this homogenization is at the expense of specialized species that are slowly disappearing," explains Helmut Hillebrand.

The number of species has also been increasing in many cities for many decades, say the researchers. Once again it is all-rounders such as wild boars, foxes or domestic pigeons, which cause problems in many places. When iDiv researcher Shane Blowes and his colleagues find a change in the composition of species practically everywhere due to the influence of human economics, they do not consider this to be reassuring. Rather, one has to understand the loss of diversity in a way that is adapted to the context and location. And that is exactly what future measures aimed at countering change must also take into account.

Now new: We give you 4 weeks of Tagesspiegel Plus! To home page