Researchers Reviving the Danube

Florian Borgwardt and Tibor Erős, ecologists and dedicated freshwater enthusiasts, are focused on restoring the Danube River. They are part of an international partnership involving scientists, conservationists, and local communities to revive the river’s ecosystem and biodiversity.

Flowing through 10 countries and 4 capitals, the Danube is crucial for both nature and people. However, human actions have significantly impacted it. The river is fragmented by dams and barriers, several fish species face endangerment, wetlands have been drained, and pollution affects water quality.

Consequently, fish populations have dwindled, ecosystems have weakened, and communities are increasingly at risk of floods and droughts. Climate change is exacerbating these issues, further threatening biodiversity and water quality.

Tackling a Complex Challenge

Restoring a river as extensive and shared as the Danube is formidable. Pressures and priorities vary between different sections and countries.

This is where the EU-funded DANUBElifelines initiative steps in, assembling experts across the basin to strive for a healthier, balanced Danube.

“Our project focuses on dwindling stocks of fish species that migrate to or within the Danube for stable habitats during their life cycle,” stated Borgwardt, who coordinates the research collaboration.

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Environmental and climate crises are deeply interconnected. Only integrated approaches can address them.

The researchers are targeting eight demonstration areas along the river – from Germany and Austria through Slovenia, Slovakia, and Hungary, reaching Romania and Bulgaria.

Here, teams are removing old barriers, reconnecting side arms and smaller rivers, and enhancing habitats to allow the river to function more naturally. Their efforts contribute to the EU Mission to Restore our Ocean and Waters, aiming to protect and restore aquatic ecosystems by 2030.

Launched in May 2025, the four-year collaboration particularly emphasizes migratory fish and river corridors, reopening migration routes and restoring vital habitats.

The partnership includes universities, research institutes, NGOs, and policy organizations, such as the World Wildlife Fund (WWF) and Wetlands International.

Tracking the Danube’s Revival

The DANUBElifelines researchers are analyzing fish movement patterns, evaluating habitat quality, and collaborating with local stakeholders. In one river stretch, the team is experimenting with removing or modifying small barriers to restore fish movement between spawning and feeding areas.

Borgwardt, an assistant professor at the Institute of Hydrobiology and Aquatic Ecosystem Management at Vienna’s University of Natural Resources and Life Sciences, champions scientific mapping and modeling to guide restoration.

Having grown up near a river, he developed a keen interest in river protection and later became passionate about leveraging technology to understand ecosystems.

Erős, head of the Fish and Conservation Ecology Research Group at the HUN-REN Balaton Limnological Research Institute in Hungary, shares a similar background.

Raised in a small village on the Hungarian Danube shores, the river has been integral to his life. “I was a passionate fisherman who became a passionate fish ecologist.”

Both scientists advocate a hands-on, demonstration-based approach. Instead of producing reports that gather dust, they engage directly in real locations, learn from the results, and widely share their findings.

Reviving the River’s Flow

The essential element, Borgwardt stated, is interconnectivity: the linkage between river parts. “If fish can’t reach certain habitats at the right time, they can’t complete their life cycle. The aim is to facilitate their upstream journey and safe return downstream after spawning.”

Challenges differ along the river. “We must choose the most appropriate sites for restoration and conservation,” said Erős. “We then provide scientific evaluations and recommendations to stakeholders, along with sustainable management proposals.”

Extending Successful Methods

DANUBElifelines aims to develop solutions applicable beyond the Danube. Methods tested in