# Sedimentary habitat units in public policies: habitats classifications, correlations and regulatory implications

Marie La Rivière, Thibaut de Bettignies, Salomé Andres, Sophie Beauvais, A-L Janson, Diane Laforge, Laura Thomas-Sleiman

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Marie La Rivière, Thibaut de Bettignies, Salomé Andres, Sophie Beauvais, A-L Janson, et al. Sedimentary habitat units in public policies: habitats classifications, correlations and regulatory implications. Marine sedimentary habitats seminar for European Atlantic Biogeographic region (North Sea, Celtic Sea, South European Atlantic Shelf), Life IP Marha, Mar 2025, Lille, France. pp.82-86. hal-05107681

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Submitted on 12 Jun 2025

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# Sedimentary habitat units in public policies: habitats classifications, correlations and regulatory implications.

Marie La Rivière<fnref n="1" />*, Thibaut de Bettignies<fnref n="1" />,<fnref n="2" />, Salomé Andres<fnref n="1" />, Sophie Beauvais<fnref n="1" />, Anne-Laure Janson<fnref n="1" />, Diane Laforge<fnref n="1" />, Laura Thomas-Sleiman<fnref n="1" />

## Introduction

Marine habitat classification is a fundamental component of conservation planning and policy implementation. It provides a common language between scientists, managers, and policymakers to describe, assess, and monitor marine ecosystems. The need for standardized habitat classification arises from multiple objectives:

* Defining consistent working units at local, national, and regional scales;

* Facilitating data collection and sharing on habitat occurrence, distribution trends, and ecological functions;

* Ensuring coherence between conservation frameworks under European and national regulations.

In Europe, several classification systems have been developed to meet different needs. We are working on harmonizing typological tools to facilitate the identification and monitoring of benthic habitats in France. These tools ensure the harmonization of habitat typologies and improve conservation assessment and reporting at multiple scales.

## European and national habitat classifications (EUNIS and NatHab)

The EUNIS marine habitat classification is a hierarchical European system designed to categorize marine habitats across Europe based on physical, biological, and ecological characteristics. EUNIS aims to provide a standardized framework encompassing the full diversity of marine habitats across European waters. The consistency of the marine section of EUNIS is especially strategic, as it is the official classification used for the implementation of the MSFD (2008/56/CE) and the Nature Restoration Regulation (NRR, EU 2024/1991). EUNIS is also the classification used by the EUSeaMap (European Marine Observation and Data Network), the European broad-scale seabed habitat map.

However, EUNIS' latest revision (2022) only integrated British and Irish marine habitat units for the Atlantic section, leaving out broader European perspectives. This has resulted in a classification that lacks representativity for other Atlantic states, including France and this raised concerns about its adequacy in representing the full diversity of benthic environments across Europe, specially in the light of its crucial role in regulatory compliance and ecosystem monitoring.

To address this, the French national classification, NatHab-Atl, was updated following the new EUNIS hierarchical structure (Michez et al., 2019). The NatHab-Atl typology provides a comprehensive and structured classification of benthic habitats for the French waters of the English Channel, the North Sea and the Atlantic. It includes 106 habitats units at the biocenotic level (hierarchical level 2), including 55 sedimentary habitats (Fig. 1).

<footnote n="1">¹PatriNat (OFB-MNHN-CNRS-IRD), France.</footnote>

<footnote n="2">²Laboratoire Ecologie Fonctionnelle et Environnement, France</footnote>
This typology serves multiple purposes: ensuring accurate habitat description and mapping at the national level, establishing correspondences with other lists or classifications (including EUNIS), and supporting conservation planning at the national level. Moreover, NatHab-Atl is designed to be adaptable, enabling updates based on scientific advancements and conservation needs.

TYPOLOGIE NATIONALE DES HABITATS MARINS BENTHIQUES DE LA MANCHE, DE LA MER DU NORD ET DE L'ATLANTIQUE
(NATHAB-ATL)

<figure><img src="image_1.png" /><figcaption>Figure 1. Extract from the hierarchical classification of benthic habitats NatHab-Atl showing level 2-sedimentary habitat units, available on the INPN (NatHab-Atlantique - Typology).</figcaption></figure>

Each level 2 unit of the French classification has been described with ecological and environmental parameters (La Rivière et al., 2022). All descriptive sheet includes information on abiotic factors, ecological characteristics, spatial variability, geographic distribution, characteristic and associated species, temporal dynamics, associated or neighbouring habitats, potential misidentifications, ecological functions, conservation status, and evolutionary trends. These descriptions provide the necessary foundation for precise mapping, assessment, and conservation planning.

This work, coupled with a correlation between EUNIS and NatHab, highlights the missing elements in EUNIS and will serve as a reference for updating EUNIS and aligning national and European classifications. In the OSPAR convention framework, France and the United Kingdom will be leading a
proposal to update the EUNIS classification for the Atlantic section in 2025. This will also be the
opportunity to address hierarchical discrepancies and precise some unclear units' descriptions.

National interpretation of marine Habitats of Community Interest (HCI)

Under the EU Habitats Directive, specific benthic habitat units are defined as Habitats of Community Interest (HCI), requiring designation of Special Areas of Conservation. However, the broad definitions in the official EU interpretation manual (European Commission, 2013) often lack clarity for national and site-level management.

Therefore, France has developed a refined national interpretation of nine marine HCs. This work provides descriptive sheets detailing habitat identification criteria, potential overlaps, and national specificities (de Bettignies et al., 2021).

A comprehensive correlation effort was conducted with the NatHab typology (345 matches for NatHab-Atl) to identify which habitat units would require management under the Habitats Directive. In the future, this will make it possible to do away with the use of the list of habitats in the Cahiers d'habitats côtiers (Bensettiti et al., 2004), which is commonly used for Natura 2000 site management, but which does not provide a comprehensive list of HCs.

A national-scale mapping initiative was then undertaken to improve spatial delineation of each marine HCI according to their national definition, for the Habitat Directive Article 17 reporting (biogeographical assessments of conservation status) to the European Commission. These refinements will improve coherence in Natura 2000 site management and will facilitate biogeographic-scale assessments. Further validation at the local level is still required to address potential conflicts with existing designations.

Sedimentary benthic habitats in public policies

Atlantic sedimentary habitats are covered by all public policies for marine environment conservation (Habitats Directive, MSFD, Regulation for Nature Restoration, OSPAR, WFD) with different units. For example, the MSFD targets "Broad-Scale Habitats" defined by EUNIS units that encompass all sedimentary habitats, while the HD only targets intertidal sediments (HCI 1140), infralittoral and circalittoral coarse and sandy sediments (HCI 1110) as long as broad geographical units (estuaries, coastal lagoons, and bays).

The OSPAR convention for the protection of the North-East Atlantic identifies a list of threatened and declining habitats (OSPAR, 2008), e.g. "Intertidal Mytilus edulis Beds on Mixed & Sandy Sediments", "Intertidal mudflats", "Maerl beds", "Zostera beds", "Seapen and Burrowing Megafauna".

As for the newly adopted Regulation for Nature Restoration, it targets in its Annex II, a broad group of habitat types (GHT) encompassing sedimentary habitats (Group 7 "Soft sediments not deeper than 1 000 metres of depth"), while more specific sedimentary habitat types are targeted in other overlapping GHT ("Seagrass beds", "Maerl beds", Shellfish beds" or "Sponge, coral and coralligenous beds").

Since the targeted units differ between these policies, it is essential to understand how the units are
defined and correlated. This is crucial to appreciate properly how work conducted on a unit within one
policy can contribute (or not) to the efforts of another to ensure cross-cutting use of data and increase
efficiency in knowledge acquisition and conservation efforts.
## Available tools

All habitat classification data, including correlations and descriptions, are available through the HabRef repository (inpn.mnhn.fr/programme/referentiel-habitats?lg=en, Gaudillat et al., 2023). This database compiles all habitat classifications and lists for metropolitan France and overseas territories, for both terrestrial and marine environments, supporting:

* Cross-referencing between classifications via unique habitat identifiers (CD_HAB).

* Integration with taxonomic databases (TaxRef).

* Public access through the INPN website, offering downloadable datasets and interactive tools for habitat visualization.

The INPN website (Inventaire National du Patrimoine Naturel, inpn.mnhn.fr) provides access to these data through downloadable spreadsheets (HabRef database, individual typologies, and correlations tables between 2 typologies) or through interactive typology trees and habitat pages.

Training sessions on marine habitat typologies were introduced in 2023 and remain accessible as [online webinars](#), ensuring broader engagement in classification methodologies.

## Conclusion

The development of NatHab-Atl and the refinement of HCI classifications have strengthened the scientific foundation for benthic habitat assessment and conservation at the national level. By addressing gaps in the EUNIS classification and aligning national typologies with European frameworks, these efforts contribute to more effective management, regulatory compliance, and international conservation strategies. Moving forward, the 2025 EUNIS revision represents a key opportunity to establish a comprehensive and coherent European classification system. The availability of all these typological tools on the INPN will facilitate their use, as well as the coherent assessment and management of benthic habitats at local, regional and national, and potentially international levels, through the various regulatory policies.

## Acknowledgements

Part of this work was supported by the Life integrated project Marha - LIFE16 IPE/FR001. The authors thank all scientific experts and stakeholders involved in the description of benthic habitats and in the national interpretation of HCs.

## References

Bensettiti F., Bioret F., Roland J., Lacoste J.-P. (Coord.) (2004) - « Cahiers d'habitats » Natura 2000. Connaissance et gestion des habitats et des espèces d'intérêt communautaire. Tome 2 - Habitats côtiers. MEDD/MAAPAR/MNHN. Éd. La Documentation française, Paris: 399 pp. + cédérom.

De Bettignies T., La Rivière M., Delavenne J., Dupré S., Gaudillat V., Janson A.-L., Lepareur F., Michez N., Paquignon G., Schmitt A., De Roton G., Toison V. (2021) - Interprétation française des Habitats d'Intérêt Communautaire marins. PatriNat (OFB-CNRS-MNHN), Paris: 58 pp.

European Commission (2013) - Interpretation manual of European Union habitats. EUR 28. European Commission, DG Environment: 146 pp.
Gaudillat V., Andres S., Decherf B., La Riviere M., Vallez E. (2023) - HABREF v7.0, référentiel des typologies d'habitats et de végétation pour la France. Guide méthodologique. PatriNat (OFB-CNRS-MNHN-IRD), Paris: 38 pp.

La Rivière M., Delavenne J., Janson A.-L., Andres S., De Bettignies T., Blanchet H., Decaris F.-X., Derrien R., Derrien-Courtel S., Grall J., Houbin C., Latryl., Le Gal A., Lutrand A., Menot L., Percevault L., Tauran A., Thiébaut E., 2022. Fiches descriptives des habitats marins benthiques de la Manche, de la Mer du Nord et de l'Atlantique. PatriNat (OFB-CNRS-MNHN), Paris : 578 pp.

Michez N., Thiébaut E., Dubois S., Le Gall L., Dauvin J.-C., Andersen A. C., Baffreau A., Bajjouk T., Blanchet H., De Bettignies T., De Casamajor M.-N., Derrien-Courtel S., Houbin C., Janson A.-L., La Rivière M., Levèque L., Menot L., Sauriau P.-G., Simon N., Viard F. (2019) - *Typologie des habitats marins benthiques de la Manche, de la Mer du Nord et de l'Atlantique - Version 3.* UMS PatriNat, MNHN, Paris: 52 pp.

OSPAR (2008) - *OSPAR List of Threatened and/or Declining Species and Habitats*. OSPAR Agreement 2008-06 amended in 2021: 5 pp.