LIBRARY: Introducing the TETHYS4ADRION Pilot Rivers: The Reno River

The Reno River is one of the five pilot rivers monitored as part of the TETHYS4ADRION project. Located in northern Italy, it stretches for 210 kilometres, from the locality of Prunetta in Tuscany to the south-east of the Valli di Comacchio, near the Torre di Bellocchio, where it empties into the Adriatic Sea. Along its course, it passes through the provinces of Pistoia, Prato, Florence, Bologna, Modena, Ferrara, and Ravenna.

Its network includes eight major rivers, 12 secondary rivers, and 600 torrents. Notable tributaries include the Limentra di Sambuca, the Rio Maggiore, the Silla River, the Limentra torrent, the Rio Groara, the Venola torrent, the Rio del Piantone, the Rio Molinello, and the Setta—the largest mountain tributary—along with the Samoggia, the Idice torrent, the Sillaro torrent, the Santerno River, and the Senio River.

The mouth of the Reno River holds particular ecological importance. It comprises coastal wetlands, dunes, and beaches that are vital for migratory birds and coastal species. These wetlands are recognised as Ramsar sites, underscoring their role in supporting the river’s biodiversity and riparian ecosystem. Within the Reno River sub-basin, 50 sites are designated as part of the Natura 2000 Network: 21 ZSCs (Special Conservation Areas), five ZPSs (Special Protection Areas), and 24 combined ZSC-ZPSs.

Among the most common bird species in the surrounding wetlands are herons and egrets, which find refuge among the reeds. Flamingos, storks, kingfishers, night herons, and various waterfowl also appear seasonally. The reserve hosts fish such as eels and other brackish- and freshwater species, as well as insects including dragonflies and butterflies that thrive in wetland habitats.

The vegetation varies across the region, ranging from open terrain to wooded and reedy areas. The Reno Valley contains the highest percentage of woodland in the Northern Apennines.

Historically, the Reno River was a vital waterway for trade and transport during Roman times, used to move goods and people as part of key communication and commerce routes. Over the centuries, communities along the river developed agricultural, industrial, and navigational activities, relying on its waters to irrigate fields, power mills, and facilitate transport.

Today, the area’s population density is nearly 25 inhabitants per square kilometre. The river continues to be an essential resource, extensively used for drinking water, irrigation, and industry in the populated and industrialised regions it traverses.

The Reno’s course has a distinctive pattern: it first flows from south (the Apennines) to north (the Po Valley), then, after a sharp bend, runs west to east, and finally—along its last kilometre—turns sharply northwards after skirting the Valli di Comacchio. Its path winds through scenic landscapes of lush valleys, quaint villages, and productive farmland.

Monitoring results of floating macrolitter collected at the mouth of the Reno River under the Marine Strategy Framework Directive (2022–2023) revealed that 92.2% of recorded items were plastic, mostly single-use. Of this litter, 15.9% was related to food and 6.1% to agricultural activities, while the source of 74.3% remained unidentified. The summer season alone contributed over 40% of the annual litter load.

The structure, density, and continuity of riparian zones play a key role in intercepting floating debris and enhancing retention, especially during periods of high flow or flooding. Plastic waste poses significant threats to all living organisms in the river and its surroundings. Waterfowl and wading birds may become entangled in fishing lines or plastic rings, or mistake small plastics for food, leading to intestinal blockages or starvation. Litter can block sunlight and smother riparian plants, reducing germination and survival rates.

In wetlands and retention basins, accumulated litter can reduce spawning success or cause deformities in aquatic organisms. Macroinvertebrates, such as insect larvae and molluscs, are also affected as litter alters substrate composition, smothers gravel beds, and reduces habitat quality—often leading to a shift toward pollution-tolerant species.

Finally, accumulated plastic and debris can alter soil permeability and compaction, affecting seedbeds. Urban litter may also facilitate the spread of invasive plants (e.g., Robinia pseudoacacia, Ailanthus altissima) by disrupting native competition and modifying soil nutrients.

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can under no circumstances be regarded as reflecting the position of the European Union and/or IPA ADRION programme authorities.