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The recovery of European freshwater biodiversity has come to a halt

Freshwater biodiversity faces an uphill battle against anthropogenic pressures. 

Freshwater ecosystems are under pressure. These ecosystems play a vital role in maintaining the balance of our planet and provide key ecosystem services such as drinking water, food sources, energy production and recreational opportunities. However, human activities have exerted enormous pressure on these ecosystems; agriculture, urbanization and pollution have accumulated over time and caused significant damage.

The article published this August 9, 2023 in Nature magazine, co-authored with IRBio researcher Núria Bonada, from the FEHM Lab warns that "the recovery of European freshwater biodiversity has stopped". The work has been led by Peter Haase of the Senckenberg Forschungsinstitut und Naturmuseum in Frankfurt with the contributions of Dra. Bonada in the conceptual design of the study and with various macro-invertebrate biodiversity data from the research group itself and from the water administrations (ACA and CH de l'Ebre).

Freshwater invertebrates play a fundamental role in ecosystem processes, including the breakdown of organic matter, water filtration, and nutrient transport. They are also essential for water quality monitoring. The study focused on this group to assess both taxonomic and functional diversity changes.

Due to a long history of anthropogenic pressures, freshwater ecosystems are among the most vulnerable to biodiversity loss.

The research includes five decades of monitoring in 22 European countries, shedding light on the state of freshwater biodiversity and the challenges it faces. The study analyzed 1,816 time series of freshwater invertebrate communities collected between 1968 and 2020, allowing researchers to quantify temporal changes in taxonomic and functional diversity, as well as responses to environmental pressures and gradients.

Encouraging signs of recovery but worrying news

The study showed that there have been overall increases in taxon richness (0.73% per year), functional richness (2.4% per year) and abundance (1.17% per year) in freshwater invertebrate communities. These positive trends are attributed to mitigation measures implemented in the 1990s and 2000s, wastewater treatment and hydromorphological restoration.

Since 2010, these positive trends have stagnated. The slowdown in biodiversity recovery suggests that current mitigation measures may be less effective or that there are new and persistent threats, such as emerging pollutants, climate change and invasive species, that continue to challenge freshwater ecosystems . Climate, dam impacts and the percentage of urban areas and cropland are related to freshwater invertebrate communities in Europe, identifying the drivers of biotic change is essential for management strategies.

-Climate plays an important role and places experienced an increase in air temperature and precipitation over time. Sites in warmer areas were more likely to gain taxa, suggesting that climate warming may not have reached critical levels for many freshwater invertebrates.

-The dams have had a negative impact on the richness, abundance, functional richness and functional redundancy of taxa. They alter sediment loads, reduce connectivity and change the flow of rivers, affecting biodiversity.

-Urban areas and farmland have negatively affected taxonomic and functional richness and abundance.

Mitigation measures and a call to action

Despite the improvements experienced after mitigation measures, the global picture remains gloomy, with increasing stress factors and poor biological quality of rivers. The findings of this extensive study serve as a wake-up call. Freshwater ecosystems are at a critical juncture and recovery requires concerted efforts. To revitalize the recovery of freshwater ecosystems, the study calls for several crucial measures:

  • Targeted Management: Management actions should focus on sites at greater risk of biodiversity decline, such as those downstream of urban areas, cropland, and dams. 


  • Land Management: Substantial, catchment-scale changes in land management are needed to reduce water extraction and inputs of pollutants, including fine sediments, pesticides, and fertilizers. 


  • Wastewater Treatment: Significant investment is required to upgrade sewage networks and improve wastewater treatment plants to better manage stormwater overflow and remove contaminants. 


  • Hydromorphological Restoration: Efforts to reconnect rivers and floodplains should be intensified to improve ecosystem functioning and adapt riverine systems to future climatic and hydrological regimes. 


  • Monitoring: Prioritizing standardized, large-scale, and long-term biodiversity monitoring, coupled with environmental data collection, is essential to characterize temporal changes in biodiversity and identify high-risk sites. 

Looking to the future

The study highlights the need for adaptive environmental management: which recognizes the objectives of conservation and restoration to adapt to global change and protect the Earth's remaining biodiversity. Dr. Bonada commented on the implications of the study: "River biodiversity has been recovering with all the measures that have been taken up to 2010, but from 2010, despite these measures, no improvement has been seen. This is because heavier contamination such as organic matter is easier to remove, but smaller pollution is more complicated. Therefore, specific measures are needed for this type of contamination, aimed at dealing with new disturbances, such as emerging pollutants or the effects of climate change."

Given new and persistent pressures on freshwater ecosystems, including emerging pollutants, climate change, and the spread of invasive species, additional mitigation is called for to reactivate the recovery of freshwater biodiversity.

Source: Haase, P., Bowler, D. E., Baker, N. J., Bonada, N., Domisch, S., Garcia Marquez, J. R., ... & Welti, E. A. (2023). The recovery of European freshwater biodiversity has come to a halt. Nature, 1-7.10.1038/s41586-023-06400-1
Photos: Núria Bonada