Changing biodiversity: contrasting developments in α- and β-biodiversity

The loss of biodiversity is one of the greatest ecological challenges of our time. But what exactly is changing - and how? A new study in Aqua und Gas by authors Nicolas Martinez, Enrica Steiner, Tobias Roth, Christiane Ilg and Nele Schuwirth provides exciting new insights into this key question.

Ten aquatic and terrestrial species groups were analyzed on the basis of data from two national monitoring programs (BDM and NAWA). The results show a complex trend: 

While species diversity within individual habitats (so-called α-diversity) is increasing in many groups, diversity between different habitats (β-diversity) is simultaneously declining in the majority of cases.

The key findings:

• In seven out of ten species groups, α-diversity is increasing: more species occur locally than before.

• At the same time, β-diversity is decreasing or stagnating in many groups: Species communities are becoming increasingly similar - a sign of homogenization of species communities.

• The increase mainly affects common, adaptable and robust species.

• Rare species, on the other hand, remain endangered or are even declining.

This opposing trend - more species at individual sites, but a standardization of habitats overall - shows that a mere “increase” in species does not automatically indicate a positive biodiversity trend. Rather, the results make it clear that the diversity of habitats and specialized species must be specifically protected and promoted in order to maintain functioning ecosystems in the long term.

At the same time, the study shows how valuable reliable data from different habitats is for analyzing such larger ecological patterns.