The recovery of European freshwater biodiversity has stopped in the 2010s
But a recent study in the prestigious journal Nature reveals a stark truth. Rivers are now plagued by new problems such as increased land use, invasive species and climate change, which have led to the loss of many inland habitats. The old measures, mainly aimed at controlling nutrient loads, are not sufficient to tackle the new environmental risks and new, more effective methods are needed. "In Finland, the darkening of inland waters, mainly due to large-scale drainage, is a problem that requires restoration and protection measures on the scale of entire catchments," says researcher Kaisa-Leena Huttunen from the University of Oulu (currently with Finnish Environment Institute).
Most benthic animals, such as mayflies, stoneflies and caddisflies, spend most of their lives in inland waters. In particular, stream invertebrates are a very species-rich group of organisms. "Benthic organisms are an important part of river ecosystems because they maintain many key ecosystem functions. They decompose organic matter, filter fine particles from the water and transfer algal food to higher levels in the food web," explains Huttunen.
The study consisted of more than 1800 time series and nearly 27 000 benthic samples from 22 European countries from 1968 to 2020. This international study made use of monitoring data from the Oulanka River tributaries started in 2000 by the Stream Ecology Research Group at the University of Oulu and the Oulanka Research Station. These Finnish streams have remained almost unchanged throughout the monitoring period and describe the situation in areas with low human activity. "Such data collected from near-natural environments are needed to describe variability independent of human activity. There is also a need for biological time series of heavily modified water bodies. It is a pity that more effort has not been put into this in Finland," says Riku Paavola, Director of the Oulanka Research Station.
According to Paavola, the data collected in the Oulanka area is one of the few monitoring data sets worldwide that focuses on assessing the status of the northern river environment. "The uniqueness of the data is illustrated by the fact that we constantly receive enquiries from researchers who not only want to integrate our data into larger, global frameworks, but also use it as a model for establishing long-term monitoring," says Paavola. "This biological monitoring of the Oulanka streams, started 23 years ago, has opened up opportunities for the Stream Ecology Research Group to engage in extensive international cooperation and networking," adds Huttunen.
Research article: Haase, P., Bowler, D.E., Baker, N.J. et al. The recovery of European freshwater biodiversity has come to a halt. Nature (2023). https://doi.org/10.1038/s41586-023-06400-1