Saving Europe's freshwaters

The EU Water Framework Directive (WFD), adopted in 2000, took a pioneering holistic approach to water management. This new approach was based on geographical catchments known as River Basin Districts, rather than the traditional use of administrative or political boundaries.

However, the solutions for improvement are complicated, especially when freshwater ecosystems are impacted by multiple pressures and shared by countries with piecemeal management policies. There was a big challenge in harmonising hundreds of national methods developed for assessing the ecological health of water bodies. Our research tackles these challenges, providing solutions that apply across Europe.

Before we can restore rivers and lakes, we have to understand how to assess and monitor their ecological health. We have to understand how species respond to their environment as well as monitoring the impact of pressures, such as invasive species, river engineering and lake water levels which have often been overlooked in the past. We also need to create solutions to the challenges of biomonitoring in densely populated river basins and diagnose why the health of water bodies is deteriorating in order to mend them.

We developed tools that are now used by UK agencies to determine freshwater status. We designed the protocols used by the EU for harmonising national assessment methods, and defined nutrient targets required to improve the health of lakes and rivers. These targets have been adopted across Europe.

This part of our research assesses restoration practices used in lakes and rivers. We can recommend evidence-based actions suitable for the management plans required under the WFD. One example is our review of lake restoration practices for the Broads Authority which shaped their future lake restoration strategy.

Once we understand the relationship between species and their environment, we can better predict how ecosystems will respond to alterations in the environment imposed by management and restoration.

For example, our research and advice on restoring polluted lakes and removing barriers to salmon migration is now being enacted and has been incorporated into management plans in the UK.

Part of our research is looking into the behaviour of an invasive plant, Himalayan balsam, on UK rivers; and how beavers are rewilding habitats on Tayside.

Our study reveals clues as to why the abundance of Himalayan balsam, a notorious invader of river banks, varies dramatically from place to place. The work could help mitigate the impact of this pink-flowered plant, which outcompetes native species, causes shading and reduces the stability of riverbanks, enabling silt to enter the water.

In 2018, our research revealed how beaver-built ponds are far more biodiverse than other wetlands. By cutting trees, beavers create a complex, mosaic of habitats that benefits local wildlife and improves ecosystem resilience. Beaver dams can improve biodiversity, trap pollutants and reduce downstream flooding. Beavers could therefore offer a solution to some of the environmental problems that society is going to face in the coming decades, especially with the effects of climate change. But we have to be careful and weigh these benefits against the potential for occasional negative impacts on fisheries, forestry and farmland.

Nonetheless, this passive restoration approach is now seen as an important part of the rewilding and restoration debate.

See also: Beaver reintroduction key to solving freshwater biodiversity crisis