Dragonflies: cash losses and gains in Germany
Some species of dragonflies and damselflies suffer from habitat loss and degradation, while many species benefit from better water quality and a warmer climate.
Leipzig / Jena. Over the past 35 years, there have been great changes in the distribution of many species of dragonflies and damselflies in Germany. Many standing water habitat species have declined, possibly due to habitat loss. On the other hand, running water species, living in rivers and streams, and heat-adapted species have benefited from better water quality and warmer temperatures. This was discovered by a team of researchers led by the German Center for Integrative Biodiversity Research (iDiv), Friedrich Schiller University in Jena (FSU) and the Helmholtz Center for Environmental Research (UFZ). The study, published in Diversity and Distributions, highlights the importance of citizen science and natural history societies for long-term data collection and nature conservation efforts to improve biodiversity.
Germany is a hotspot for dragonfly and damselfish (Odonata) species in Europe, due to the range of habitats and climates it offers. While many recent and mostly small-scale studies suggest long-term declines in insect populations in different parts of Europe, studies of freshwater insects – including dragonflies and damselflies – suggest that some species have increased in number. Researchers from iDiv, FSU and UFZ have now provided a nationwide analysis of the occurrence and distribution of dragonflies and damselflies in Germany between 1980 and 2016. For this, they analyzed over a million occurrence records on 77 species from different regional databases, of which were collected by citizen scientists and compiled by the Natural History Society of German-Speaking Dentists (GdO).
Habitat loss threatens species in stagnant water bodies
Researchers have seen both losses and gains, but are concerned about the decline of species using standing water habitats. Decreases were observed in 29% of species, mainly in cold-adapted species that prefer stagnant water habitats such as peatlands and fens. Many of these species are already threatened with extinction. These species depend on small or shallow water bodies, which have been vulnerable to droughts and lower groundwater levels. “These species are suffering greatly from habitat loss and degradation. Here we still face serious conservation challenges, ”said first author Dr Diana Bowler of iDiv, FSU and UFZ.
Overall, the analysis suggests that habitat specialists in cold-adapted standing water habitats are likely to be the most vulnerable to other environmental changes, including climate change.
Species adapted to heat and running water on the rise
In contrast, the results of the study show an increase in the occurrence of 45% of all species, generally heat-adapted species. “Previously, rare species such as Crocothemis erythraea and Erythromma viridulum became much more common in Germany,” said Diana Bowler. “These species prefer warmer temperatures and their increase in Germany is therefore most likely the result of long-term climate change.”
Also among the laureates were running water species, a testament to the conservation success that can be achieved through better environmental management. “The increase in these species reflects a recovery from the impacts of past water pollution and the almost complete destruction of natural floodplains,” said Klaus-Jürgen Conze, President of the GoO. In Germany, projects to improve freshwater quality and restore rivers were started in the 1990s and the EU Water Framework Directive was adopted in 2000.
Great value of citizen science efforts
Much of the data has been collected by citizen scientists and natural history societies, such as the GoO. “Our study highlights the great value of these monitoring efforts in assessing changes in species occurrences. We have found signs of accelerating decline over the past decade, which underscores the need to support these companies’ efforts in the future, ”said lead author Prof. Aletta Bonn from UFZ , FSU and iDiv.
This study was funded among others by the Deutsche Forschungsgemeinschaft (DFG; FZT-118) within the framework of “sMon – Biodiversity Trends in Germany”. sMon is an iDiv synthesis project aimed at bringing together exemplary datasets on a variety of taxa and habitats to explore the possibilities and limitations of analyzing changes in biodiversity. On this basis, the prospects for future monitoring programs in Germany must be determined. The sMon brings together government representatives from all federal states, scientists and members of various professional associations.
(Scientists affiliated with iDiv and alumni in bold)
Diana E. Bowler, David Eichenberg, Klaus-Jürgen Conze, Frank Suhling, Kathrin Baumann, Theodor Benken, André Bönsel, Torsten Bittner, Arne Drews, André Günther, Nick JB Isaac, Falk Petzold, Marcel Seyring, Torsten Spengler, Bernd Trockur, Christoph Willigalla, Helge Bruelheide, Florian Jansen, Aletta Bonn (2021). Winners and losers over 35 years of changing distribution of dragonflies and damselflies in Germany. Biodiversity and distributions, DOI: 10.1111 / ddi.13274