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Early Warning Signs of Biodiversity Changes

Over the last century, Germany’s plant world has produced more losers than winners. While frequencies and abundances of several species have decreased, they have increased dramatically in others. As a result, gains and losses have been distributed quite unevenly.

Early Warning Signs of Biodiversity Changes

The cornflower is one of the “losers,” its population has declined sharply over the past 100 years. Image Credit: André Künzelmann/UFZ

Research headed by Martin Luther University Halle-Wittenberg (MLU) and the German Centre for Integrative Biodiversity Research (iDiv) suggests a large-scale loss of biodiversity.

It is an odd paradox: while global biodiversity is depleting at an astounding rate, numerous studies have found no substantial changes in animal and plant species numbers at the local level.

However, this doesn’t mean that the developments are not worrying.

Helge Bruelheide, Professor and Ecologist, Martin Luther University Halle-Wittenberg

Even so, it also depends on the species in question. For instance, if survival artists tailored to peatlands or dry grasslands are replaced by common plants, the overall number of species often remains the same. However, diversity is continually being lost as the once-distinctive flora of diverse ecosystems becomes increasingly similar.

The group led by MLU examined a plethora of local studies to determine the strength of this tendency throughout Germany. Several experts submitted data from almost 7,700 plots where plant populations were measured multiple times between 1927 and 2020.

These investigations, a few of which have not before been published, cover a broad range of habitats and include data on approximately 1,800 plant species. This contains around half of all vascular plant species found in Germany.

Such time series can provide very valuable information. It is highly unlikely that plants disappear or reappear unnoticed in such plots.

Dr. Ute Jandt, Martin Luther University Halle-Wittenberg

This is due to the fact that very precise botanical censuses can be carried out in plots that are often only 10 or 20 square meters in size.

Data analysis reveals a negative trend in abundance for 1,011 of the species analyzed and a positive trend for 719. In other words, throughout the previous century, there have been 41% more losers than winners.

Even more surprising is that the losses were distributed much more evenly.

Helge Bruelheide, Professor and Ecologist, Martin Luther University Halle-Wittenberg

The team utilized the Gini coefficient, which is frequently used to analyze income and property distribution, to determine this. The index, for instance, reveals that the great majority of the poor are getting poorer while only a small percentage of rich people are getting richer.

A very similar pattern is being observed in the German plant world. Although gains are centered among fewer winners, losses are more equally distributed between the numerous losers.

The second group includes, for example, the black cherry and the northern red oak, which originated in North America but have recently spread to several German forests.

The frost-sensitive European holly has also gained traction due to climate change. On the other hand, the vast majority of losers are agricultural weeds like cornflower, meadow species like small scabious, and wetland specialists.

According to the analysis, the greatest disparity in gains and losses happened between the late 1960s and the early twenty-first century.

Bruelheide adds, “This phase started with the strong intensification of land use. Since then, however, there have been successful nature conservation measures that have weakened the still ongoing negative trend to a certain degree.”

Nobody knows if this also pertains to other parts of the world. As a result, the group argues for gathering and analyzing similar datasets from around the globe. This unequal distribution of gains and losses can be seen as an early warning indicator of biodiversity changes that would eventually lead to species extinction.

The new analysis is the result of the iDiv-coordinated project “sMon - Biodiversity Trends in Germany.” Data on the growth of biodiversity in Germany are being compiled and analyzed as part of this initiative. To that purpose, researchers are collaborating with public institutions and conservationists.

Journal Reference:

Jandt, U., et al. (2022) More losses than gains during one century of plant biodiversity change in Germany. Nature.


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