Study published in Nature concludes that the recovery of European freshwater biodiversity has reached a halt since the 2010s

English version: Diana Taborda

An international study with the participation of Maria João Feio and Manuel Graça, researchers at the Centre for Marine and Environmental Sciences (MARE) of the Faculty of Sciences and Technology of the University of Coimbra (FCTUC), published in Nature, concluded that despite the positive patterns of the 1990s, the recovery of river biodiversity has stalled since 2010.

In Europe, over the last three decades, and especially since the publication of the Water Framework Directive in 2000, there have been several mitigation measures to combat the degradation of rivers and their ecosystems. However, the number of factors threatening these ecosystems continues to increase worldwide.

Therefore, "this study aimed to analyse whether, over the last few decades, there has actually been a recovery in the freshwater biodiversity of river ecosystems over time, as a result of the mitigation measures implemented in Europe, and what factors have determined this," explains Maria João Feio, adding that it was possible to conclude "that there has actually been a small increase in the number of species (0.73% per year), functional richness (2.4% per year) and abundance (1.7% per year) in freshwater macroinvertebrates communities".

However, Feio adds, "despite these positive trends, the number of species still declined at 30% of sites. The ecosystems where there was the least recovery were those located downstream of dams, in urban areas, and on agricultural land. In addition, invertebrate communities located in areas with faster rates of warming recovered less, which shows the impacts of climate change, namely the effect of rising temperatures," she warns.

According to experts, the increase in biodiversity occurred mainly before the 2010s and has since flattened out. The gains in biodiversity in the 1990s and 2000s reflect the improvement in the physico-chemical quality of the water, due to the deployment of more effective treatment systems and ecological rehabilitation or restoration projects. However, the slowdown in the recovery of riverside biodiversity in the 2010s shows that the current measures are not enough, and are translating less and less into positive results in the recovery of biodiversity.

According to the researcher, this slowdown "has occurred because new threats have also surfaced, namely emerging pollutants such as pharmaceuticals and microplastics, climate change and invasive species. In fact, the number of non-native species (found in 69% of the sites analysed) has been increasing strongly (4% per year)," she says.

Considering these results, the researchers believe that " it is urgent to continue ecological restoration based on the renaturalisation and recovery of species, instead of a merely cosmetic approach, or focused on drainage or the removal of nutrients from the water, but also on new planning focused on new impacts, such as emerging pollutants, climate change, and invasive species. In addition, the research also shows the importance of maintaining ecological monitoring of rivers so that studies may address temporal evolutions," they conclude.

The research involved 96 European researchers from 70 institutions and was coordinated by a research team from the Senckenberg Research Institute and the Natural History Museum Frankfurt, Germany.

The scientific article "The recovery of European freshwater biodiversity has come to a halt" is available here.