The U.S. experience is particularly interesting with respect to the assessment and approval of Conservation banks[6]. On ecological perspectives, the Guidance for the Establishment, Use, and Operation of Conservation Banks (USFWS 2003) notes that “the best way to justify approving a bank is to evaluate whether the bank fits the overall conservation needs of the listed species the bank intend to cover”. Updated in 2016 (USFWS 2016), this document particularly highlights the importance and the compatibility of:
- the project ecological gains strategy (or management plan)
- the site(s) characteristics (intrinsic and landscape context)
Step 2: Articulating these two pillars around the four main components of an ecologically relevant mitigation bank project
On the basis of the elements above and the different criteria identified in literature, the notion of "ecological relevance of a MB project" can be articulated around four main components.
A MB project is ecologically relevant when:
- (1) Its ecological gains strategy is based on acceptable objectives and the mitigation and monitoring measures to achieve them are realistic and operational;
- (2) This strategy must be consistent with the intrinsic characteristics of the host site(s);
- (3) And with the landscape context in which the MB project is located;
- (4) Eventually, it must respect the regulatory principles of biodiversity offsetting[7] (additionality, efficiency and sustainability).
In the section below, we come back on the ecological criteria that compose the four previous components.
Step 3: Describing the criteria of an ecologically relevant mitigation bank
IS THE ECOLOGICAL STRATEGY OF THE MB PROJECT RELEVANT?
Assessing the ecological gains strategy intends to identify the needs and threats associated with the targeted biodiversity components. It also evaluates the planned response to generate, manage and monitor the desired ecological gains. These elements guides the characteristics of the mitigation site(s) required to achieve them. In this section, we emphasize the need to:
- clearly define the targets components and objectives of the project;
- justify that the MB project is ecologically desirable;
- demonstrate that the MB project is coherent with its objectives and technically feasible;
- check the methods used allow to establish the initial state of the site and to monitor gains and project objectives’ achievement throughout time.
- control the management measures are adapted and adaptive to maintain the quality of the site and respond to the threats that could impact the project’s success.
In order to evaluate the ecological relevance of a MB project, it is first necessary to identify what constitutes the core of the project. To do so, the biodiversity components targeted by the mitigation operations (habitats, ecological functions, species and/or species assemblages) must be detailed. The long-term objectives as well as the ecological performance indicators necessary to evaluate their achievement throughout time (expected results, indicators, magnitude of effect, timeframes) must be clearly defined (DOI 2016, Gann et al. 2019). These three key elements allow the MB operator and the state regulator to agree on the nature and issues of the MB and assess the relevance of the project with regard to its targets and objectives. It also draws the outline of future mitigation credits available for sale.
A MB project is ecologically desirable when it contributes to the achievement of the two objectives of compensation: the no net loss of biodiversity and the ecological equivalence between losses and gains (Article L110-1 II 2° du Code de l’Environnement[8]). These objectives can be achieved with projects that improve the conservation status of local impacted specie(s) population in the future. The targets defined in the MB’s offer (mitigation credits) must therefore be adapted and justified in terms of the ecological issues encountered on the territory: meets a local need for offsets that is compatible with the expectations and practices of local authorities (particularly in terms of functional proximity). The level of ecological challenge associated with the biodiversity components targeted (rarity, vulnerability, maturity, etc.) (BBOP 2009, Brownlie et al. 2013) as well as the scientific knowledge available on their ecological needs (USACE and EPA 2008, USFWS 2016) also support the acceptability of the project. The influence of climate change and its consequences on the evolution of the distribution ranges of the targeted biodiversity components is also to consider (Scheffers and Pecl 2019, Gann et al. 2019). At this stage, it should be verified that the MB mechanism is the appropriate solution rather than a punctual and demanding “project by project” offset solution (van Teeffelen et al. 2014). The purpose of these criteria is to anticipate future issues regarding the ecological gains implementation and sustainability. It is also linked with economic and territorial planning aspects such as disturbance of the mitigation hierarchy, economic viability, social acceptance, etc. Depending on the level of challenge encountered, additional technical and financial guarantees could be necessary.
A MB operator must be able to demonstrate the feasibility of its project and the coherence of the proposed mitigation measures (CGDD 2018). It is thus essential the planned restoration operations be sufficiently detailed to meet the ecological requirements of the biodiversity components targeted (nature, targets, objectives, schedule, etc.). The technical feasibility of the measures should be assessed in particular with regard to their nature, available feedbacks experiences (e.g. scientific literature, restoration feedbacks, etc.) and the technical capacities of the operator. The level of technical and temporal uncertainty must also be taken into account in order to rule out projects that are too risky (Moilanen et al. 2009, Maron et al. 2012, Pilgrim et al. 2013). Nevertheless, risky projects supported by scientific experiments should be considered in order not to close the door to innovative and large-scale projects.
In order to justify an ecological gain, it is essential to carry out an initial assessment of the key ecological components of the offset site (physical characteristics of the environment, species composition, functionalities, etc.) and to propose methods and indicators to monitor their evolution over time (Gardner et al. 2013, Gann et al. 2019). To do so, protocols and metrics must be robust, transparent and mobilizable both on the MB and on future impacted sites. This way, one can compare losses and gains in a similar manner (Dorrough et al. 2019) and propose the purchase of the appropriate number of mitigation credits. The use of control sites or reference data (e.g: via partnerships with biodiversity observatories for example), offers the possibility of contextualizing and justifying the gain actually generated on the MB by comparison with reference states (e.g.: plots left to evolve freely vs. plots with mitigation measures, restoration objective site, etc.).
Ecological engineering operations generally involve the introduction of living material. To ensure project suitability, the genetic and geographic origin of this material must be appropriate. It has to fit the host site’s characteristics and comply with permits for movement or introduction of individuals where needed (Rohr et al. 2018, Gann et al. 2019). Adapted and adaptive maintenance measures that address the issues that the site is facing are also necessary. These measures are intended to limit or eliminate potential threats, to ensure the habitats quality is maintained over time, and to preserve any biodiversity of concern present on site during restoration operations (USFWS 2003, 2016, Salafsky et al. 2008). The level of intervention required to maintain the restored ecosystem in the desired trajectory once the bulk of the work has been completed is also to consider. It allows estimating the sustainability of the project and its level of dependence with respect to external interventions and actors.
If at this stage the project's ecological gains strategy is considered clear, coherent, desirable, technically feasible and operational, it is then necessary to determine whether the selected mitigation site(s) is suitable for its implementation.
II. ARE THE INTRINSIC CHARACTERISTICS OF THE MITIGATION SITE CONDUCIVE TO ACHIEVING THE MB PROJECT'S ECOLOGICAL GAINS STRATEGY?
Sites hosting MB projects have specific characteristics that contribute to the nature and magnitude of the biodiversity gains that can be expected. In this section, we preconize to:
- Analyze the ecological potential of the site(s) through habitats conservation status, ecological trajectory and surface area;
- Identify the type of threats and internal pressures that could affect the success of the MB project;
- Ensure the MB project does not significantly impact patrimonial biodiversity components initially present on the host site.
MB should be carried out on sites with physical characteristics (soil, hydro, climate), conservation status, trajectory and surface area which are conducive to the creation of ecological gains and adapted to the desired gains strategy (Rohr et al. 2018, Gann et al. 2019). In order to be viable, restoration operations must be implemented over a sufficiently large area, which varies according to the considered ecosystem (Moreno-Mateos et al. 2012, Theis et al. 2020). The configuration of the MB is also important since it partly conditions the quantity of habitat exploitable by the species: a MB can be in one piece, made up of several independent sites or linked to each other by ecological continuities. In order to ensure the ecological viability of the project, sites with sufficient habitat area to allow the targeted species to complete their entire life cycle should be preferred. When the MB surface alone is insufficient, it must be part of a larger reachable network of habitats (see next part). These criteria require a good understanding of the needs and dispersal capabilities of the targeted species.
The identification of threats and sources of pressure within the MB is of major importance. These may be anthropogenic (due to linear transport infrastructures, activity zones, motorized vehicles, etc.), biological (due to invasive exotic species, predators, etc.) or natural (due to climatic events, topography, etc.). They are likely to impact the quality of the habitat and the quietude of the targeted species, to induce competition for resources, to generate excess mortality, etc. (Salafsky et al. 2008, Gann et al. 2019). Depending on their nature and the biodiversity components targeted, their impact may be more or less significant for the success of the project. When needed, these issues require adapted management measures.
The impact of restoration operations on the biodiversity at stake initially present on the site must be taken into account and their good conservation status guaranteed. Indeed, one of the MB’s objectives is to generate ecological gains without impacting otherwise patrimonial biodiversity components. When necessary, preservation measures must be planned before the beginning of the works, and the administrative authorizations be asked.
At this stage, the MB’s intrinsic characteristic should bring more elements to assess the ecological relevance of the project. The landscape context assessment will provide further additional information, especially regarding the site’s insertion in viable larger habitat networks and potential external threats.
III. IS THE LANDSCAPE CONTEXT CONDUCIVE TO ACHIEVING THE MB PROJECT'S ECOLOGICAL GAINS STRATEGY?
Many ecological processes occur at the landscape, regional, or watershed scale (Hanski 1998). In this section, we highlight the importance of:
- Assessing the ecological potential of the MB host area through its integration into a larger network of habitats
- Describing what threats and external pressures may impact the site but also the neighboring biodiversity reservoirs and ecological corridors.
- Ensuring that the MB project does not disrupt the ecological processes in the host area.
A MB should be located within a landscape context with favorable ecological potential where targeted species assemblages and habitats are naturally present (USFWS 2003, Pärtel et al. 2011, Lewis et al. 2017). In this situation, spontaneous dispersal events are more likely. Also, biotic and abiotic conditions are more likely to accommodate and enable the development of the targeted biodiversity components within the MB. When this ecological potential is unfavorable, assisted migrations or translocations of species may support recovering some biodiversity components. However, the viability and landscape integration of such operations should always be rigorously demonstrated (Lunt et al. 2013, Williams and Dumroese 2013, Wang et al. 2019).
To ensure the sustainability of this ecological potential, the nature, number and level of protection of the surrounding biodiversity reservoirs (e.g. Natura 2000 zone, ZNIEFF[9] I or II, etc.) should be taken into account (Peterson and Lipcius 2003, USFWS 2003, Fox and Nino-Murcia 2005). A large number of habitats "sources of biodiversity", under little pressure and with a high level of protection provide additional guarantees with regard to the MB landscape integration. However, the mere geographical proximity of the MB to these biodiversity reservoirs is insufficient to judge the ecological potential of the site. It must be completed by a study of the connectivity of the MB with these reservoirs. As this is species-dependent, it will be necessary to know the habitat requirements and dispersal capacities of the targeted species (possibly by guild or model species). The objective should be to demonstrate that flows of individuals are possible within the landscape unit in which the MB project is located (Hanski 1998, Bakker et al. 2000, Saura and Pascual-Hortal 2007, Saura et al. 2011, Velázquez et al. 2017).
An ecologically relevant MB project takes into account the threats and sources of pressure that exist outside the site and impact it, either directly or indirectly (Reiss et al. 2007, Salafsky et al. 2008, Gann et al. 2019). These may impact:
- the MB itself by degrading the quality of the restored habitats and by disturbing the species it supports;
- the continuity elements connecting the MB to the surrounding biodiversity reservoirs (risk to weaken the connectivity and viability of the MB);
- biodiversity reservoirs on which the MB project may depend to ensure its functional viability (e.g: provide additional habitats for species to accomplish their life cycle).
Depending on their nature and the targeted biodiversity components, their impact may be more or less significant. When significant, they should be taken into account in the project success conditions.
Finally, we suggest ensuring that the MB project does not disturb the ecological integrity of the landscape area in which it is located. To this end, studies or management measures that ensure the project does not contribute to the degradation of surrounding ecosystems should be expected (e.g, dissemination of invasive exotic species, modification of flow dynamics and bank erosion, disruption of ecological continuity, etc.).
IV. ARE THE REGULATORY OFFSET PRINCIPLES RESPECTED?
At this stage, states services and MB operators should have sufficient information to verify/justify that the MB project is ecologically relevant and respects the offset principles. These principles are: administrative and ecological additionality, sustainability of land ownership and site management, likelihood of effectiveness of the mitigation measures. The principles of proportionality and ecological equivalence can only be assessed in relation to future development projects that will use the MB’s mitigation credits. They are therefore outside the scope of this evaluation.
The ecological relevance assessment approach and the criteria previously mentioned are summarized in Table 1.
Table 1: Summary of the selected ecological relevance criteria
MAIN COMPONENTS
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SUB-COMPONENTS
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ASSOCIATED ECOLOGICAL RELEVANCE CRITERIA
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I. ECOLOGICAL GAINS STRATEGY
Is the ecological gains strategy based on acceptable objectives, realistic and operational restoration and monitoring measures?
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I.A. Clear project core
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I.A.1 Targeted biodiversity components (BC)
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I.A.2 Long-term objectives
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I.A.3 Ecological performance indicators
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I.B. Desirable / acceptable project
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I.B.1 Response to a local compensation need
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I.B.2a Level of patrimoniality of the targeted habitats
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I.B.2b Level of patrimoniality of the targeted species
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I.B.3 Knowledge of the ecology of the targeted BC
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I.B.4 Influence of climate change
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I.C. Coherent and feasible project
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I.C.1 Planned Mitigation Measures and coherence with the project objectives
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I.C.2 Technical feasibility of mitigation measures
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I.C.3 temporal uncertainties of mitigation measures
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I.D. Relevant assessment methods
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I.D.1a Methods for assessing the initial state
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I.D.1b Transposability methods on impacted sites
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I.D.2a Monitoring methods
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I.D.2b Transposability methods on impacted sites
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I.D.3a Methods for evaluating gains and ecological equivalence
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I.D.3b Transposability methods on impacted sites
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I.D.4 Control sites / baseline data
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I.E. Appropriate maintenance measures
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I.E.1 Respect for indigeneity
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I.E.2 Site quality maintenance and pressure management
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I.E.3 Level of post-work intervention required
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II. LOCATION - INTRINSIC CHARACTERISTICS
Is the ecological gains strategy being implemented on a site with attractive ecological characteristics for creating the desired ecological gains?
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II.A. Potential for ecological gain on site interesting
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II.A.0 Soil-hydro-climatatic characteristics
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II.A.1 Conservation status of the site
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II.A.2 Dynamics/Ecological trajectory of the site
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II.A.3a Area and functional viability of restored habitats
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II.A.3b Functional unit of the MB
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II.A.3c Surface allowing the realization of the biological cycle of the species
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II.B. Threats and sources of internal pressure under control or limited
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II.B.1 Threats and sources of anthropogenic pressures
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II.B.2 Threats and sources of biological pressures
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II.B.3 Threats and sources of natural pressures
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I.C. Risque de perturbation de la biodiversité à enjeu pris en compte
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II.C.1 Risk of disturbance to biodiversity at stake taken into account
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III. LOCATION - LANDSCAPE CONTEXT
Is the ecological gains strategy implemented in a landscape context of insertion favorable to the creation of the desired ecological gains?
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III.A1. Ecological potential of the reception area
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III.A.1a Ecological potential (habitats)
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III.A.1b Ecological potential (species)
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III.A2. Favorable relationship to ecological reservoirs
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III.A.2a Nature and Sustainability of Ecological Reservoirs
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III.A.2b MB Connectivity - biodiversity reservoirs
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III.B. Threats and sources of external pressure under control or limited
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III.B.1 Threats and sources of anthropogenic pressures
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III.B.2 Threats and sources of biological pressures
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III.B.3 Threats and sources of natural pressures
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III.B.4 Risk of MB isolation
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III.C. Risk of disruption to the hosting area taken into account
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III.C.1 Disruption of the hosting area
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IV. REVIEW OF OFFSET PRINCIPLES
Does the MB project respect the offset principles?
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IV.A. Verified additionality
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IV.A.1 Administrative additionality
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IV.A.2 Ecological additionality
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IV.B. Probable effectiveness
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IV.B.1 Effectiveness of mitigation measures
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IV.C. Assured Sustainability
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IV.C.1 Sustainability of land ownership
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IV.C.2 Sustainability of site management
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Step 4: Organizing the ecological relevance criteria into an operational assessment grid
In order to support mitigation bank operators and state regulators, we organized the previous ecological relevance criteria into a qualitative reading grid (available in French in the supplementary material). We linked each criterion to different “response modalities” (favorable, favorable with caution, danger, no data) defined on the basis of scientific literature, guidelines and various situations encountered in a sample of mitigation projects. Depending on the project and the available information, the evaluator attributes a response modality to each criterion. These response modalities are guidelines and can evolve after considering other criteria (e.g: a small site that does not support the life cycle of the targeted species (criterion II.A.3c) but which is connected to a larger habitat network (criterion III.A.2b)). In the end, a result can be obtained for each one of the four components assessed (Tableau 2).
Table 2: Attribution of the response modalities to the ecological relevance criteria (Legend: Green: favorable, Orange: favorable with caution, Red: danger)
Step 5: Decide on the approval of the Mitigation Bank project
Used in the MB assessment procedure, the reading grid we propose could assist stakeholders for the future agreement on ecological aspects with the following approach (Figure 4).
After reading the MB application file (A) and assigning (B) a modality response to each ecological criterion, a presentation of the result and a phase of dialogue are necessary (C). Different situations might be encountered that require additional precisions, arguments, data, etc. For example:
- An irrelevant ecological gains strategy might lead the bank operator to modify or precise his project on the identified blocking points.
- A strategy of ecological gains that is relevant but not adapted to the characteristics of the selected site and/or to the landscape context in which it is located might lead to find a more suitable site or to revise the strategy of ecological gains accordingly.
- Non-compliance with or excessive uncertainty about compliance with the offset principles should also lead the state regulator to ask for clarification or additional guarantees before considering issuing MB approval.
During the phase of dialogue between stakeholders, the assessments results can be argued. When justified, it can lead to some change in their rating and requires a completion of the project file (D). These new information allows for a more informed opinion of the state regulator and assists the MB approving decision (E and Tableau 3).
Table 3: Agreement decision based on the result of the MB ecological relevance assessment
At the end of the assessment, one should be able to demonstrate/determine to some extent that the MB project has reasonable chance of generating the expected ecological gains. In this case, the project should receive the MB agreement on ecological aspects.
[6] Conservation banks are mitigation banks in which creation, restoration/rehabilitation measures are carried out targeting species and/or "terrestrial" environments (excluding aquatic environments and wetlands). They are issued from a posterior regulation from Mitigation banks (targeting wetlands)
[7] Ecological equivalence and proportionality principles are not evaluated because the development projects and their residual impacts to compare with the gains of the MB are not known at this stage.
[8] https://www.legifrance.gouv.fr/codes/section_lc/LEGITEXT000006074220/LEGISCTA000006129022/#LEGISCTA000006129022
[9] Zone Naturelle d'Intérêt Ecologique, Faunistique et Floristique