Loire River Ecosystem

Category: Inland Aquatic Biomes.

Geographic Location: Western Europe.

Summary: A braided river and one of the last wild rivers in Europe, the Loire supports a remarkable array of wildlife.

The Loire River is one of three rivers that rise from the Massif Central, a stark volcanic uplands region in south-central France, noted for its rugged landscape of forests and pasturelands. Several main tributaries feed into the Loire; these include the Allier, Cher, Indre, Vienne, Maine, and Seore Rivers. This freshwater system drains one-fourth of the lands of France. It is approximately 600 miles (1,000 kilometers) in length.

The catchment area, or watershed, of the Loire River encompasses about 45,000 square miles (177,000 square kilometers). It is considered one of the last wild rivers in Europe. The Loire River basin is remarkably rural and fecund; it supports two-thirds of the livestock and half of all grains produced in France. The Loire is used for navigation, for hydroelectric and nuclear power, and for fishing and tourism. Its many lakes and tributaries are linked by natural and manmade canals that have facilitated the production and transport of goods throughout western Europe for thousands of years. Due to it shallow nature, drought such as was experienced in 2022 has a significant impact on navigability, industrial and energy use, and wildlife.

Flowing north and then west from the central region near Orléans, the Loire passes through deep gorges and floodplains at its upper banks, through dikes and levees, across limestone plateaus, forested islands and sandy shores, and down through the Sologne wetlands to fill the brackish estuaries at the Atlantic coast. It transects the French landscape into three geographically distinct areas of urban, agricultural, and industrial development. The upper basin is bound by the Loire from its source in the Massif Central to its juncture with the Allier River. The Loire middle valley stretches from the Allier to the Maine River; it wanders in a broad circular pattern, creating what is known as the Garden of France. The lower Loire flows west across the granite terrain of Poitou and Brittany; it extends to the wetlands on the Atlantic coastline where it empties into the Bay of Biscay.

The climate of the Loire Valley is temperate, considered the most pleasant of northern France. There are hot summers, warm winters, and fewer extremes in temperatures here. Annual average minimum temperature is 45 degrees F (7 degrees C); annual average maximum temperature is 61 degrees F (16 degrees C). The climate is identified as temperate maritime, with rainfall of approximately 24–27 inches (63–69 centimeters) annually.

Biota

The Loire is a braided river, a definition describing the morphology of rivers that flow in multiple channels across a gravel floodplain. Braided rivers create unique and biologically diverse ecosystems including meadows, wetland marshes, forest vegetation, islands, and sedimentary banks. Because of the variability of riverine floodplain habitats, there is a constant redistribution of biological taxa. Along the Loire River, the result of these dynamics is an extraordinarily rich and complex array of habitats and their related biological species. The Loire River biome also encompasses part of an international flyway for migratory birds.

More than 100 algae species have been identified in the Loire, the richest phytoplankton diversity of all the French rivers. This abundance supports thriving communities of fish and migrating land birds. Every fish known to swim in French rivers can be identified in the Loire, including sea trout, shad, lamprey, flounder, mullet, sturgeon, and catfish. However, extensive damming, channel excavation, agricultural and industrial runoff, and overfishing have created migratory obstacles for the great schools of Atlantic salmon that come to these inland waters from as far as the waters off Greenland to spawn their eggs.

Wetlands are essential biofilters whose sediments, organic, and inorganic accretions act as important buffers for saltwater intrusion into freshwater environments; freshwater flooding is an essential dynamic of wetlands and estuaries. The Loire estuary provides habitat for 25 percent of the juvenile fish found in the Gulf of Biscay. The Sologne in the central Loire valley, just south of Orléans, is an internationally recognized inland wetland, a region whose marshes and forests provide valuable habitats for nesting birds and water fowl, including the goshawk, honey buzzard, the whiskered tern, and little bittern.

Similarly, growths of hawthorn, black thorn, and elder bush provide food and shelter for migrating flocks. Mallards, tits, house sparrows, woodpeckers, kites, larks, rails, and martins are common, as are great blue herons, terns, plovers, gulls, geese, and egrets that populate gravel and sand bank areas. Stands of riverine willows, elders, ferns, and climbers provide habitat for all of these bird species and others.

The Loire River valley’s wet heaths, lakes, and flood meadows support a rich and varied number of moths, dragonflies, and butterflies. Common species include hawk moths, the peacock moth, the common winter damselfly, clubtails, and pincertails. On warm spring days, the riverlands teem with insects (beetles, bees, flies, firebugs, and ants are common), an important food source for the migratory birds for which the area is noted internationally.

Finally, the lands contiguous to the Loire River are famous for their displays of orchids. The most common species include the tongue orchid, the violet Limodore, the early purple orchid, the lady orchid, the bee orchid, the early fly orchid, and the greater butterfly orchid. The Loire River is an important migratory system for plant life; species from the Central Massif, the Atlantic, and the Mediterranean have all made their way here, some taking centuries to migrate.

Human Impact

Civil engineering projects date back to antiquity and include dredging; flood control technologies; land reclamation; the extensive excavation of gravels and sediments; and the construction of levees, groins, bridges, dikes, canals, and dams for irrigation, transportation, and erosion control. For centuries, the habitual deposition of industrial, agricultural, and household wastes have contributed to chronic freshwater contamination. Protocols that now govern the management and protection of the Loire River and its internationally recognized habitats include the Ramsar Convention on Wetlands, adopted in 1971; the European Union (EU) Water Framework Directive; the Natura 2000 directives; and the policies of the EU Nature Legislation—its Birds Directive as adopted in 1979 and amended in 2009, and the Habitats Directive as adopted in 1992.

In 1986, the construction of four new dams in the Loire system was proposed by the French government and other private interests. That year, the Loire Vivante (Living Loire) network was established by the World Wildlife Fund and other nonprofit organizations to protest the new dam construction at Serre de la Fare on the upper Loire. As a result of the highly coordinated efforts of the Loire Vivante movement, the dams were either cancelled or substantially revised, and three other dams were demolished. In 1994, the Plan Loire Grandeur Nature initiative was introduced by the French government to implement sustainable programs of flood control and floodplain restoration. Today, the European Rivers Network is an outcome of the Loire Vivante movement.

In December 2000, the Loire Valley between Maine and Sully-sur-Loire was registered as a United Nations Environmental, Scientific, and Cultural Organization (UNESCO) World Heritage Site. This central Garden of France region includes a surface area of approximately 300 square miles (800 square kilometers). It is an exceptionally temperate, fertile area famous for its orchards and vineyards. As with other inland aquatic ecoregions, the lower areas of the river are susceptible to any changes in sea level. Hence, there is the present concern of long-term impact that climate change will have in this area, especially in the estuary habitats.

Bibliography

Gray, Duncan and Jon. S. Harding. Braided River Ecology: A Literature Review of Physical Habitats and Aquatic Invertebrate Communities. Wellington, New Zealand: Science & Technical Publishing, Department of Conservation, 2007.

Hayes, Graeme. Environmental Protest and the State in France. New York: Palgrave Macmillan, 2002.

Hilbers, Dirk and Tony William. Loire Valley: Loire, Brenne & Sologne (Crossbill Guides). Philadelphia: Trans-Atlantic Publications, 2011.

Mahe, Stephane. "France's River Loire Sets New Lows as Drought Dries Up Its Tributaries." Reuters, 17 Aug. 2022, www.reuters.com/world/europe/frances-river-loire-sets-new-lows-drought-dries-up-its-tributaries-2022-08-17/. Accessed 24 Aug. 2022.

Paskoff, Roland P. “Potential Implications of Sea-Level Rise for France.” Journal of Coastal Research 20, no. 2 (Spring 2004).

Tockner, Klement, Urs Uehlinger, and Christopher T. Robinson. Rivers of Europe: First Edition. Waltham, MA: Academic Press, Elsevier, 2009.