To reproduce, rest, feed, migrate or adapt to climate change, animal and plant species, both aquatic and terrestrial, need to be able to move around. But with urbanisation, deforestation, pollution and intensive farming, natural areas are shrinking and fragmenting, threatening biodiversity and the proper functioning of ecosystems as a whole. Ecosystems that are vital for satisfying human needs and improving resilience in the face of climate change…

Connectivity between the various natural habitats must therefore be maintained. This necessary ecological continuity is the subject of various policies, notably the Green and Blue infrastructure and the national plan to restore ecological continuity.

Here are some explanations.

Numerous obstacles to ecological continuity

Ecological continuity can be interrupted by a variety of man-made obstacles: transport infrastructure (roads, railways, etc.), hydraulic dams or weirs, degraded environments, artificial soils, chemical, light and noise pollution, etc. Each of these obstacles acts as an ecological barrier, breaking the continuity of aquatic and terrestrial ecosystems and reducing or preventing the free movement of animal and plant species. The consequences for biodiversity can be far-reaching: extinction of species, increased vulnerability to disease or climate change, loss of genetic diversity (by isolating populations), etc.

For the vast majority of aquatic species, the breeding, feeding and nursery grounds are not the same. The presence of dams, weirs or dykes regulating the flow of watercourses prevents the free movement of fish and organisms such as algae, phytoplankton and zooplankton, diatoms, larvae and invertebrates, by creating barriers that are often impassable.

The accumulation of structures to be crossed particularly affects the movement of migratory fish such as salmon, sea trout, sturgeon and eel, many of which are threatened with extinction, and also increases their mortality rate. The transport of sediments needed to create habitats or purify water is also heavily impacted.

The same applies to terrestrial ecosystems, where urbanisation, soil artificialisation, the construction of transport infrastructures and intensive agriculture are degrading soil quality, reducing natural areas and fragmenting habitats.

Did you know that?

In 2020, the French National Biodiversity Observatory identified more than 100,000 obstacles to water flow in France. That’s one obstacle every 6 km.

The essential ecological continuity of aquatic environments

In addition to their vital importance to the many terrestrial species that feed and reproduce in there, aquatic environments provide us with a large number of free services (known as ecosystem services): they regulate hydrological cycles, reduce the risk of flooding, maintain soil moisture in periods of drought and ensure good water quality by filtering or decomposing pollutants.

According to the French International Union for Conservation of Nature (IUCN), 27% of freshwater species are threatened with extinction worldwide, and in France, only 43% of rivers are in good ecological condition. It is therefore imperative to restore their natural functioning. While, according to the French Ministry for Ecological Transition, the best way of restoring ecological continuity is to remove structures, there are other ways of improving continuity:

  • Reducing the size of certain hydraulic structures.
  • Creating gaps.
  • Installing crossing devices for migratory fish (fish passes, ramps, bypass rivers, etc.).
  • Rehabilitation of river beds and banks.
  • Appropriate management measures, such as temporarily opening floodgates to encourage sediment transport.
  • More environmentally-friendly farming practices.

The national plan to restore the ecological continuity of watercourses

Launched in November 2009 as part of the Water Framework Directive, the French national plan to restore the ecological continuity of watercourses (PARCE) aims to improve coordination and create synergies between the Government, the French Office for Biodiversity (OFB) and the water agencies in order to restore natural habitats and the flow of watercourses, and to improve the movement of fish, particularly migratory fish.

This national plan is based on five fundamental pillars:

  • Improving knowledge by creating a national repository of obstacles to water flow, such as weirs and dams.
  • Defining priorities for action at basin level by establishing a restoration strategy.
  • Revising the programmes of the French water agencies and the contracts of objectives of public establishments to increase their support for actions to restore the ecological continuity of watercourses.
  • Implementation of a water police force responsible for inspections and instructions, with the introduction of a multi-year programme to bring structures up to standard and to remove structures. It should be noted that the water police is made up of the dedicated department of the French Departmental Territories Directorate (DDT), the OFB, the Gendarmerie, the Police and the Mayors.
  • Assessment of the environmental benefits of the measures implemented.

The French Office for Biodiversity (OFB) plays a key role in restoring ecological continuity: at local level, it is responsible for carrying out compliance checks on hydraulic structures, assessing their ecological impact and providing technical advice on the proposed restoration solution. At national level, it implements and/or finances research and development programmes and runs the French Watercourse Resource Centre, which “capitalises, shares and disseminates guides, feedback and awareness-raising tools on the restoration of ecological continuity” and helps to improve practices in this area.

Green and blue infrastructure: an integrated policy

At the crossroads of environmental protection and land-use planning, the Green and Blue infrastructure policy aims to limit the loss of biodiversity resulting from the artificialisation and fragmentation of natural areas by restoring or creating networks of terrestrial (green) and aquatic (blue) ecological continuities. Recently, the Black infrastructure has also been introduced to take account of nightlife disturbed by artificial light and to restore areas of darkness.

The various frameworks are identified in the Regional plans for planning, sustainable development and territorial equality (SRADDET) and the Regional ecological coherence plans (SRCE) for the Ile-de-France Region. They are considered at local level in Local urban plans (PLU), Territorial coherence schemes (SCOT) and Communal maps (CC), for example. The implementation of the Green and Blue infrastructure includes the protection of existing ecological corridors, the creation of new continuities and the restoration of degraded habitats.

Businesses, industries and farmers can also take action to preserve ecological continuity and reduce their impact on the environment. A growing number of farmers are planting hedgerows, which can be a source of inspiration.

To find out more, or to keep abreast of developments in ecological continuity policy, a number of resources are available. These include:

  • The French Office for Biodiversity website
  • The French Ministry for Ecological Transition website
  • The Green and Blue infreastructure resource centre

Ecological continuity is essential, now and in the future

Restoring ecological continuity is a major challenge if we are to preserve biodiversity, ensure that ecosystems function properly in the long term and enable us to benefit from the essential services they provide.

Faced with these challenges, France has adopted ambitious policies aimed at restoring ecological continuity throughout the country: the national plan for restoring the ecological continuity of watercourses (PARCE), which aims to restore the free movement of aquatic species and sediment transport, and the Green and Blue infrastructure, the aim of which is to create a truly functional ecological network, linking natural terrestrial and aquatic environments through biological corridors in particular.

Maintaining and preserving ecological continuity is everyone’s business and should ensure that future generations are left with healthy, resilient and interconnected ecosystems, guaranteeing the preservation of our natural heritage and vital resources.

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