# Restoring genetic diversity to facilitate the implementation of the EU Nature Restoration Law

David O'Brien, Tsipe Aavik, Ancuta Fedorca, Martin C Fischer, Robin Goffaux, Sean Hoban, Peter Hollingsworth, Christina Hvilsom, Robert Jehle, Belma Kalamujić Stroil, et al.

► To cite this version:

David O'Brien, Tsipe Aavik, Ancuta Fedorca, Martin C Fischer, Robin Goffaux, et al. Restoring genetic diversity to facilitate the implementation of the EU Nature Restoration Law. Biological Conservation, 2025, 303, pp.110995. 10.1016/j.biocon.2025.110995. hal-05109272

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# Restoring genetic diversity to facilitate the implementation of the EU Nature Restoration Law

David O'Brien<sup>a,b</sup>, Tsipe Aavik<sup>c</sup>, Ancuta Fedorca<sup>d,e</sup>, Martin C. Fischer<sup>f</sup>, Robin Goffaux<sup>g</sup>, Sean Hoban<sup>h</sup>, Peter Hollingsworth<sup>b</sup>, Christina Hvilsom<sup>i</sup>, Robert Jehle<sup>j</sup>, Belma Kalamujić Stroil<sup>k</sup>, Francine Kershaw<sup>l</sup>, Peter Klinga<sup>m,n</sup>, Alexander Kopatz<sup>o</sup>, Deborah M. Leigh<sup>p,q,r,s</sup>, Ivan Paz-Vinas<sup>t</sup>, Marine Robuchon<sup>u</sup>, Gernot Segelbacher<sup>v</sup>, Viktoria Takacs<sup>w</sup>, Cristiano Vernesi<sup>x,y</sup>, Linda Laikre<sup>z,*</sup>

## ARTICLE INFO

Keywords:

NRL

NRR

Regulation

Indicators for genetic diversity

CBD GBF

European Union

## ABSTRACT

Governments and economic blocs are recognising that the world faces a biodiversity crisis. The restoration of biodiversity to the levels prior to widespread human induced damage has been incorporated as a crucial component of conservation in the Global Biodiversity Framework of the Convention of Biological Diversity. The Nature Restoration Law (NRL) forms part of the European Union's response and after its adoption by the European Parliament and the Council of the European Union, it has formally become the Nature Restoration Regulation (NRR). The NRL aims to play a role in restoring ecosystems, habitats and species but does not expressly include genetic diversity, the third biodiversity component. Considering genetic diversity in strategic biodiversity planning is important to help nature adapt to rapid anthropogenic change. We have reviewed the text of the NRL and note opportunities to incorporate genetic diversity in National Restoration Plans to augment its implementation. In particular, genetic diversity assessments are well aligned with the NRL's aspiration to enhance connectivity, and genetic indicators can assess the effectiveness of its implementation. Here we give

<footnote><sup>a</sup> NatureScot, Inverness, UK</footnote>

<footnote><sup>b</sup> Royal Botanic Garden Edinburgh, 20a Inverleith Row, Edinburgh EH3 5LR, UK</footnote>

<footnote><sup>c</sup> Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia</footnote>

<footnote><sup>d</sup> Department of Wildlife, National Institute for Research and Development in Forestry 'Marin Dracea', Brasov, Romania</footnote>

<footnote><sup>e</sup> Department of Silviculture, Faculty of Silviculture and Forest Engineering, Transilvania University of Brasov, Brasov, Romania</footnote>

<footnote><sup>f</sup> Institute of Integrative Biology (IBZ), ETH Zurich, Zurich, Switzerland</footnote>

<footnote><sup>g</sup> French Foundation for Research on Biodiversity, 75005 Paris, France</footnote>

<footnote><sup>h</sup> Center for Tree Science, The Morton Arboretum, Lisle, USA</footnote>

<footnote><sup>i</sup> Copenhagen Zoo, Sendre Fasanvej 79, 2000 Frederiksberg, Denmark</footnote>

<footnote><sup>j</sup> School of Science, Engineering and Environment, University of Salford, UK</footnote>

<footnote><sup>k</sup> University of Sarajevo-Institute for Genetic Engineering and Biotechnology, Bosnia and Herzegovina</footnote>

<footnote><sup>l</sup> Natural Resources Defense Council, New York, USA</footnote>

<footnote><sup>m</sup> Technical University in Zvolen, Faculty of Forestry, T.G. Masaryka 24, 96001 Zvolen, Slovakia</footnote>

<footnote><sup>n</sup> Czech University of Life Sciences Prague, Kamýcká 129, Praha-Suchdol 165 00, Czech Republic</footnote>

<footnote><sup>o</sup> Norwegian Institute for Nature Research, Trondheim, Norway</footnote>

<footnote><sup>p</sup> Swiss Federal Research Institute for Forest, Snow, and Landscape Research WSL, Birmensdorf, Switzerland</footnote>

<footnote><sup>q</sup> LOEWE Centre for Translational Biodiversity Genomics, Senckenberganlage 25, 60325 Frankfurt, Germany</footnote>

<footnote><sup>r</sup> Senckenberg Research Institute, Senckenberganlage 25, 60325 Frankfurt, Germany,</footnote>

<footnote><sup>s</sup> Institute of Ecology, Evolution, and Diversity Faculty of Biosciences, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany</footnote>

<footnote><sup>t</sup> Universite Claude Bernard Lyon 1, LEHNA UMR 5023, CNRS, ENTPE, F-69622 Villeurbanne, France</footnote>

<footnote><sup>u</sup> European Commission, Joint Research Centre (JRC), Ispra, Italy</footnote>

<footnote><sup>v</sup> Chair of Wildlife Ecology and Management, Tennenbacher Str. 4, University Freiburg, Germany</footnote>

<footnote><sup>w</sup> Faculty of Veterinary Medicine and Animal Sciences, Poznan University of Life Sciences, Wojska Polskiego 71/c 60625 Poznan, Poland</footnote>

<footnote><sup>x</sup> Research and Innovation Centre, Fondazione Edmund Mach, 38010 S. Michele all'Adige, Italy</footnote>

<footnote><sup>y</sup> National Biodiversity Future Centre, Palermo, Italy</footnote>

<footnote><sup>z</sup> Department of Zoology, Stockholm University, SE10691 Stockholm, Sweden</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: linda.laikre@popgen.su.se (L. Laikre).</footnote>
examples where restoration has incorporated genetic diversity to ensure long term wide-reaching success. This is of relevance beyond the NRL and applies generally to policy for nature restoration efforts globally, especially those related to the Global Biodiversity Framework.

# 1. Background

In June 2022, the European Commission (EC) proposed a new law "to restore ecosystems for people, the climate and the planet", referred to as the Nature Restoration Law (EC, 2022, hereafter "NRL"). After two years of trilogues between the European Union (EU) institutions, the European Parliament and the EC a revised version of the NRL proposal was adopted in June 2024 which subsequently became the Nature Restoration Regulation. This represents a significant step in EU environmental policy. Whilst this is an EU initiative, the global commitment to biodiversity restoration enshrined in Global Biodiversity Framework Target 2 means that approaches developed in Europe can be applied in any continent, nation or region.

The EC proposes establishing an EU-wide methodology for assessing ecosystem condition, which would allow specific restoration targets and the development of national restoration plans (European Parliament, 2024). These will need to be documented, assessed, and to have a unified monitoring approach. The NRL (and its Annexes) focuses primarily on ecosystems and species, and only one mention of "genetic exchange" is present (Annex VII) with no text on "genetic diversity" or its synonyms ("within species diversity" or "intraspecific diversity", European Parliament, 2024). Both ecosystems and species, however, depend on genetic diversity for resilience to natural biotic and abiotic change as well as to anthropogenic threats, including the five direct drivers of biodiversity loss identified by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES): climate change, pollution, direct exploitation, changing land and sea use, and invasive species (Díaz et al., 2019). Recognising that there are several definitions for 'ecological resilience' (see review by Van Meerbeek et al., 2021), we use it here to mean the ability of populations to return to their reference conditions following a perturbation (Pimm, 1984), and to absorb change and maintain ecological function (Holling, 1973). By extension, resilient populations underpin resilient ecosystems. Maintaining and restoring genetic diversity is needed for long-term successful species and ecosystem restoration. Thus, the effectiveness of the implementation of the NRL would be further enhanced by incorporating within-species genetic diversity restoration actions. Further, genetic diversity should in fact be a key component of any restoration strategy globally. The examples in this paper are focussed on the ecosystems detailed in the NRL. However, these ecosystems are found globally and include those facing the greatest threat (Díaz et al., 2019) including forests, rivers and wetlands and agricultural systems, as well as urban land. The examples also cover all three realms: marine, freshwater and terrestrial.

# 2. Why restoring genetic diversity can improve the implementation of the NRL

Halting and reversing biodiversity loss can only be accomplished by a shift to humanity working more extensively with nature, allowing nature's own tools to be a key part of the restoration process. Genetic diversity is the variation at the DNA level, including differences among individuals and populations Table 1. It gives species the potential and flexibility to respond to pressures through adaptation, while also underpinning fitness of individuals and their populations. Genetic diversity is integral for establishing and maintaining healthy self-sustaining populations. These populations in turn support ecosystem function and resilience to regulation of the environment (e.g. soil fertility, biological control, pollination). Thus, within-species genetic diversity also increases overall ecosystems resilience (Prunier et al., 2023).

Maintaining and restoring genetic diversity is therefore crucial for the implementation of the NRL. Importantly, this can be linked to global efforts to monitor and maintain genetic diversity required by the Kunming-Montreal Global Biodiversity Framework (KM-GBF) of the Convention on Biological Diversity (CBD, 2022a, 2022b; Robuchon et al., 2023). Genetic diversity is fundamentally composed of alleles, heterozygosity and variation in their distribution across individuals or populations. It is important to note that restoration of alleles may not be possible if they have gone globally extinct. However, increasing size and connectivity among populations can help reduce genetic diversity loss, as well as inbreeding, and bolster heterozygosity.

To maximise success, a biodiversity restoration strategy must encompass ecosystems, species and genetic diversity. Restoration may use materials sourced *in situ* (in natural populations) or *ex situ* (in collections). *Ex situ* conservation is particularly useful for restoration action if the whole species has suffered extreme loss of genetic diversity. Further, zoos, botanical gardens and seed banks can preserve genetic diversity *ex situ* and provide insurance against catastrophic events (O'Brien et al., 2022). *Ex situ* populations have played a central role in many restoration projects, conserving unique genetic diversity and preventing extinctions, but they do not necessarily facilitate the same multi-pressured adaptive processes as natural settings (Schoen and Brown, 2001; Smith et al., 2023). By contrast, *in situ* conservation facilitates natural adaptation, if populations are sufficiently large (crucially with effective population size Ne > 500; Hoban et al., 2021), thus supporting the long-term success of restoration, can maintain different genetic lineages compared to *ex situ* populations, and can benefit other organisms in their habitat. Given their complementary strengths, restoration actions should seek to combine both approaches, where relevant. The CBD now calls on Parties, including the EU, to restore genetic diversity within and between populations of native, wild and domesticated species to maintain their adaptive potential (Target 4; CBD, 2022a). Another global commitment of the KM-GBF is to "ensure that by 2030 at least 30% of areas of degraded terrestrial, inland water, and marine and coastal ecosystems are under effective restoration [...]" (Target 2; CBD, 2022a). Integrating genetic diversity conservation, monitoring and management in the implementation of the NRL (Fig. 1) via National Restoration Plans would thus contribute to efforts for reaching KM-GBF targets (Goal A, Target 4; CBD, 2022a) and National Biodiversity Strategy and Action Plans (Hoban, 2024) as well as targets 2.5 and 15.5 of the Sustainable Development Goals (UN, 2015). It would also align with the Habitats Directive in which populations must achieve Favourable Conservation Status, which is sometimes interpreted to include maintaining genetic diversity (Laikre et al., 2009).

Genetic diversity has already been lost in many European species, in part due to pressures from a long history of human settlement combined with species' post-glacial colonisation histories (Hewitt, 2000; Leigh et al., 2019; Pearman et al., 2024). Such a loss of genetic diversity makes European species and populations particularly vulnerable in the face of change. Genetic diversity is not always spatially correlated with species diversity (Schmidt et al., 2022; Marta et al., 2023) and it is unclear how it relates to ecosystems diversity, as a result, it needs specific conservation and policy attention. Nevertheless, specific genetic diversity targets would likely incentivise policy makers and land managers in nature restoration actions. Crucially, *in situ* conservation of genetic diversity in wild species has been shown to be compatible with economic land uses such as farming and forestry, and to be supported by land managers (Minter et al., 2021). As shown in case study 1, land managers can be vital allies when they participate in the co-development of genetic diversity-based restoration (O'Brien et al., 2021). Incorporating
<table><caption>**Table 1**
Glossary of terms and abbreviations used in this paper.</caption><thead><tr><th>Term</th><th>Explanation</th><th>Webpage/reference</th></tr></thead><tbody><tr><td>CBD</td><td>The UN Convention on Biological Diversity; international policy instrument ratified by 196 nations.</td><td>http://www.cbd.int/.cbd.int</td></tr><tr><td>Complementary indicator</td><td>A voluntary CBD GBF indicator. For genetic diversity these indicators are "the proportion of population maintained within species" abbreviated PM indicator and the Scorecard of Genetic Diversity.</td><td>CBD, 2022b; https://www.cbd.int/doc/decisions/cop-15/cop-15-dec-05-en.pdf<br>https://www.nature.scot/doc/scotlands-biodiversity-progress-2020-aichi-targets-conserving-genetic-diversity-development-national<br>www.cbd.int/meetings/COP-15</td></tr><tr><td>COP15</td><td>The 15th Conference of the Parties to the Convention on Biological Diversity. COP15 was held in Montreal in December 2022 hosted by China (the meeting should have been held in Kunming, China, but was changed due to the pandemic).</td><td>O'Brien et al., 2022; Andersson et al., 2022; Dussex et al., 2023; Kurland et al., 2023; Saha et al., 2024</td></tr><tr><td>DNA-based indicators</td><td>Indicators based on assessment of variation in the DNA collected from temporally separated samples of individuals of a species to monitor trends in genetic diversity. EBVs for genetic composition are used for DNA-based indicators<br>Note: this is NOT eDNA which only measures occurrence of species, not the essential variation within species which the present DNA-based indicators focus on.</td><td>https://geobon.org/ebvs/what-are-ebvs</td></tr><tr><td>EBV</td><td>Essential Biodiversity Variable - fundamental metric used to assess and monitor biodiversity over space and time. Different EBVs are applied to ecosystems, communities, species, and genetic composition.</td><td>Hoban et al., 2022</td></tr><tr><td>EBVs for genetic composition</td><td>Essential Biodiversity Variables for assessing and monitoring genetic diversity. These parameters include measures of genetic diversity within populations, between populations and includes estimating Ne. EBVs for genetic diversity are used for DNA-based indicators.</td><td>https://www.stockholmresilience.org/</td></tr><tr><td>Ecosystem resilience</td><td>The ability of an ecosystem to withstand and recover from different types of environmental disturbance.</td><td></td></tr><tr><td>Ex situ conservation</td><td>Conservation of species populations outside their native environment in a human-controlled environment (e.g. zoos, botanical gardens, etc.)</td><td></td></tr><tr><td>GBF</td><td>The Kunming-Montreal Global Biodiversity Framework adopted by the CBD COP15. Includes Goals to 2050 and Targets to 2030. Goal for genetic diversity: "The genetic diversity within populations of wild and domesticated species, is maintained, safeguarding their adaptive potential". Target for genetic diversity: "to maintain and restore the genetic diversity within and between populations of native, wild and domesticated species to maintain their adaptive potential".</td><td>CBD, 2022a<br>https://www.cbd.int/gbf</td></tr><tr><td>GBF Monitoring framework</td><td>Strategy adopted by CBD COP15 to monitor trends in genetic diversity to support implementation of the GBF. Includes Headline indicators that parties need to report on and Complementary Indicators that are voluntarily.</td><td>CBD, 2022b<br>https://www.cbd.int/gbf/related/monitoring</td></tr><tr><td>GCU</td><td>Genetic Conservation Unit - concept used by the European Forest Genetic Resources Programme to describe a forest area aimed to protect forest genetic resources of one or more forest tree species.</td><td>https://www.euforgen.org/forest-genetic-resources/conservation/gcu</td></tr><tr><td>Genetic diversity</td><td>Variation at the DNA-level. Also known as intraspecific diversity. Occurs below the species level as variation within and between separate populations.</td><td>Allendorf et al., 2023</td></tr><tr><td>Goal A</td><td>Goal of the GBF that focuses on the 2050 vision for biodiversity. Goal A for genetic diversity is: "The genetic diversity within populations of wild and domesticated species, is maintained, safeguarding their adaptive potential."</td><td>CBD, 2022a</td></tr><tr><td>Headline indicator A.4</td><td>A mandatory indicator of the CBD GBF monitoring framework which tracks "the proportion of populations within species with an effective population size (Ne) > 500". Implementation can use DNA-techniques, but to allow large scale, global implementation, non-DNA proxies for genetic measurements are needed (proxy-based indicators)</td><td>CBD, 2022b</td></tr><tr><td>In situ conservation</td><td>On-site conservation, conserving biodiversity in the natural site of occurrence</td><td></td></tr><tr><td>IPBES</td><td>The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. An independent body establishes strengthen science-policy in the area</td><td>https://www.ipbes.net/</td></tr><tr><td>KM-GBF</td><td>Same as GBF (above). KM abbreviates Kunming-Montreal since the CBD COP15 meeting was supposed to be held in Kunming, but was finally held in Montreal (see COP15)</td><td>CBD, 2022a<br>https://www.cbd.int/gbf</td></tr><tr><td>Ne</td><td>Effective population size. A standard population genetic parameter that describes the rate of loss of genetic diversity of a population and its adaptive potential. An Ne above 500 is considered to maintain adaptive capacity. Ne is an EBV for genetic composition and can be used in restoration to assure adaptive capacity of key animal and plant populations.</td><td>Allendorf and Ryman, 2002</td></tr><tr><td>Ne indicator</td><td>Indicator based on assessment of the effective population size of populations and for detecting changes of Ne over contemporary time frames. DNA- or proxy-based methods can be applied. In the CBD GBF monitoring framework Ne > 500 is Headline indicator A.4.</td><td>CBD, 2022b; Andersson et al., 2022; Mastretta-Yanes and da Silva et al., 2024</td></tr><tr><td>NRL</td><td>The Nature Restoration Law adopted by the European Parliament and the Council of the European Union in June 2024.</td><td>https://environment.ec.europa.eu/topics/nature-and-biodiversity/nature-restoration-law_en</td></tr><tr><td>NRP</td><td>National Restoration Plan to be prepared by all EU member states and cover the period up to 2050 with intermediate deadlines e.g., 2030. Should include restoration measures necessary to meet the restoration targets and fulfilment of Articles 4-13.</td><td>Chapter III, Article 14 of the NRL https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32024R1991&qid=1722240349976</td></tr><tr><td>NRR</td><td>The Nature Restoration Regulation through which the NRL comes into effect.</td><td>https://environment.ec.europa.eu/news/nature-restoration-law-enters-force-2024-08-15_en<br>Waples and Gaggiotti, 2006<br>https://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2006.02890.x</td></tr><tr><td>Population</td><td>A biological entity below the species level. Species consists of multiple populations that e.g. occur in different regions of the distribution range. Populations can be identified with DNA-techniques as genetically distinct clusters that can reflect genetic adaptation to local conditions. In the absence of DNA-data populations can be identified by demographic, geographic or other information.</td><td></td></tr></tbody></table>

(continued on next page)
<table><caption>**Table 1 (continued)**</caption><thead><tr><th>Term</th><th>Explanation</th><th>Webpage/reference</th></tr></thead><tbody><tr><td>Proxy-based genetic indicators</td><td>Indicators aimed at tracking genetic diversity over time but which do not rely on direct measures of genetic diversity but use substitutes (proxies) for DNA-data such as demographic measures of census size, population occurrence and distribution.</td><td>Mastretta-Yanes and da Silva et al., 2024</td></tr><tr><td>Restoration</td><td>The act of reversing human induced biodiversity degradation and returning ecosystems, species and genetic diversity back to a good state. Includes the recovery of evolutionary processes and diverse and resilient populations, species and ecosystems.</td><td>Hoban et al., 2020; https://environment.ec.europa.eu/topics/nature-and-biodiversity/nature-restoration-law_en</td></tr></tbody></table>

<figure><img src="image_2.png" /><figcaption>**Fig. 1.** The beneficial role genetic diversity can play in facilitating restoration success (left), the key Articles of the European Nature Restoration Law it will aid (centre) and practical examples (right).</figcaption></figure>

genetic diversity in the implementation of the NRL would thus recognise the vital role of land managers and those who rely on marine resources in safeguarding biodiversity, as has been demonstrated by tree Gene Conservation Units (discussed below, Minter et al., 2021).

### 3. Genetic diversity is key to achieving the NRL's ambitions for restoration targets

To maximise future ecosystem resilience, genetic diversity would enhance the proposed EU wide standards for national restoration plans (Articles 14 and 15 of the NRL). NRL Article 14 states that restoration measures should take “into account the latest scientific evidence” (European Parliament, 2024), an evidence need that conservation genetics and genomics can readily fill (Fig. 1). Going through the NRL, Article by Article, genetic diversity has a key role to play.

### 4. Genetic diversity should be an inherent criterion in restoring connectivity under the NRL

Land use change, including habitat fragmentation, is one of the five main pressures on biodiversity noted by IPBES (Díaz et al., 2019). Enhancing ecosystem connectivity is part of the KM-GBF Goal A (CBD, 2022b) and the Convention on Migratory Species (CMS, 2019), and the NRL notes the importance of restoring genetic exchange to improve connectivity across habitats (European Parliament, 2024). Enhancing

connectivity has also been a core target of EU funding through the Common Agricultural Policy (EU CAP Network, 2023). Habitat fragmentation interrupts or limits gene-flow in many species, which can lead to measurable genetic diversity and fitness loss over time. Monitoring change in genetic diversity can therefore assess habitat fragmentation and connectivity restoration success (e.g. Jehle et al., 2023). Genetic data are already being used to monitor population connectivity in dozens of species across the EU, including trees (Fady et al., 2016), freshwater fish (Andersson et al., 2022) and marine species (Assis et al., 2021). A shared approach to monitoring connectivity through genetic means across such projects and directives could support and accelerate the attainment of multiple EU policy goals. It can also provide valuable information to help land managers plan restoration.

### 5. Genetic diversity can be monitored and reported on using direct genetic methods or by using simple non-DNA proxies

Chapter IV of the NRL discusses monitoring (Article 20) and reporting (Article 21). Developments in DNA sequencing technologies are driving down costs and increasing the accessibility of DNA-based monitoring of biodiversity. However, there are still resource and capacity barriers to truly widespread and universal monitoring of genetic diversity through DNA-sequencing and it is still often reserved for selected species or populations. Recognising this, simpler non-DNA based proxies have now been developed (Hoban et al., 2020; O'Brien
et al., 2022; Mastretta-Yanes and da Silva et al., 2024). A key non-DNA based proxy, effective population size (Ne), helps conserve genetic diversity (typically when above 500) and can be inferred from census counts improving accessibility for many animals and vascular plants (Hoban et al., 2020). Consequently, Ne > 500 has been accepted as CBD (2022b) Headline Indicator A.4 for Goal A and Target 4. Importantly for restoration, Ne > 500 can be applied at regional and local levels to assure adaptive capacity is reached for local populations of key species (Andersson et al., 2022; Kurland et al., 2023) following restoration events. Ne, genetic diversity and connectivity have also been considered in other European policies including in setting favourable population conditions for Habitats Directive species (Mehtälä and Vuorisalo, 2007; Wojkiewicz et al., 2021). The Genetic Diversity Scorecard (Hollingsworth et al., 2020; O'Brien et al., 2022) is a related approach made up of six indicators, each of which can be assessed using either direct or proxy-based measures of genetic diversity, and is a CBD (2022b) Complementary Indicator. Genetic diversity monitoring based on different proxies are now already being applied at a national or subnational level within four European countries: Belgium, France, Sweden and the UK (Hollingsworth et al., 2020; Andersson et al., 2022; O'Brien et al., 2022; Hoban et al., 2023; Kurland et al., 2023; Mastretta-Yanes and da Silva et al., 2024). Additionally, DNA-based monitoring is now in the pilot phase in Germany (BIGFOOT), Sweden (SWAM), and Switzerland (GenDiv). Guidelines produced by the International Union for Conservation of Nature (IUCN) on selecting species and population for genetic diversity monitoring (Hvilsom et al., 2022) are already available. Thus, there are practical monitoring methods in place, and there is an opportunity to set simple transparent restoration targets that are meaningful at multiple geographic scales and aligned with the EU's role within the High Ambition Coalition for Nature and People. By setting SMART - Specific, Measurable, Achievable, Relevant and Time-bound - targets for genetic diversity, policy makers and practitioners can measure restoration progress and ensure management interventions are effective.

## 6. Reporting for the NRL can use existing tools

Existing programmes, such as the European Forest Genetic Resources Programme EUFORGEN's network of Genetic Conservation Units (GCU), show that safeguarding genetic diversity at a European scale is practical. The GCU network covers the whole continent, as well as Turkey, and is built around the concept of dynamic gene conservation, maintaining evolutionary processes within tree populations. The genetic resources within GCUs can be a key asset in restoration programmes (EUFORGEN, 2021). The GCU concept could be applied to other habitats and species (Minter et al., 2021). Many marine species have been subject to genetic assessments (Wennerström et al., 2017) and there is an opportunity to develop a systematic programme of monitoring and reporting of diversity (Thomson et al., 2021). This would support the attainment of NRL Article 5 (Restoration of marine ecosystems). Crucially, the GCU approach is also compatible with management of the land for economic gain (Minter et al., 2021). Article 12 of the NRL focuses on forest restoration, and adding consideration of genetic diversity will strengthen the NRL for biodiversity and recognise existing good management.

## 7. Restoration built upon genetic diversity

Since genetic diversity underpins species and ecosystem resilience (Sgrò et al., 2011; Mason et al., 2022), including genetic diversity in restoration plans seems relevant both for biodiversity conservation and securing long-term success for publicly and privately funded projects, thus justifying financial outlay. There are examples within Europe and elsewhere which highlight the effectiveness of projects that explicitly build genetic diversity into their restoration plans.

**Case study 1. Habitat restoration leads to recovery of European Protected Species**

The great crested newt (*Triturus cristatus*) is a European Protected Species. A disjunct range edge population in the Scottish Highlands had been steadily declining until a restoration project that combined knowledge about the species' local habitat requirements and genetic structure. The Highland population is genetically distinct and its extinction would therefore represent the irreversible loss of a unique genetic lineage (O'Brien et al., 2021). Once the status of the lineage had been discovered, a species recovery plan was devised and implemented through collaboration between scientists, local volunteers, farmers, foresters and other land managers. The plan used genetic data to identify priority locations for habitat restoration. The need to safeguard genetic diversity was also a key tool in engaging farmers and foresters, as they are familiar with the importance of genetics in their working lives. An evaluation after six years found a 26% increase in breeding ponds with enhanced connectivity between them (O'Brien et al., 2021). This case study exemplifies NRL implementation of Articles 4 (terrestrial, coastal and freshwater ecosystems), 9 (rivers and floodplains), 11 (agricultural), 12 (forest).

**Case study 2. Post-restoration population growth is enhanced by genetic diversity**

European grasslands are highly threatened and have been the focus of many restoration programmes. Success has varied, leading to evaluations of the importance of different methods and factors (Resch et al., 2022). A study examining the restoration success of the grassland plant devil's-bit scabious (*Succisa pratensis*) in Flanders (Belgium), a key species for pollinators, found faster growing populations had higher genetic diversity, linking genetic diversity with population fitness (Van Geel et al., 2021). Furthermore, devil's-bit scabious genetic diversity also had a small but important impact on below-ground restoration of arbuscular mycorrhizal increasing community diversity (Van Geel et al., 2021). The project relied on stock already *in situ* without taking into account genetic diversity at the beginning of the project. This example shows genetic diversity can impact the speed and overall success of a restoration, as well as the complexity of the community restored, and suggests that greater success could have been achieved if enhancing local genetic diversity had been part of the original project plan. It highlights implementation of NRL Articles 4, (terrestrial, coastal and freshwater ecosystems), 8 (urban), 10 (pollinators), 11 (agricultural).

**Case study 3. Restoring connectivity of fragmented populations**

The Arctic fox (*Vulpes lagopus*) in Scandinavia was severely over-hunted for fur from the early 1900s to the early 20th century. Even after legal protection entered into force, the population failed to recover (Keeling Hemphill et al., 2020). A genetic study found that the Scandinavian population is fragmented into three subpopulations with limited genetic exchange (Keeling Hemphill et al., 2020). Monitoring of the southernmost sub-population since 2000 showed this had led to inbreeding depression expressed as reduced juvenile survival been included throughout the species management and restoration programme. A series of measures have been taken to support the fragmented populations including supplementary feeding, culling of competitive red foxes and an *ex-situ* breeding programme. The *ex-situ* breeding programme was established with wild caught cubs from the nearby region and releases of these captive-bred Arctic foxes introduced locally-new genetic variation and acted as gene flow among subpopulations. These efforts led to a doubling in the population size in the south, the re-establishment of many populations and increased connectivity between them (Keeling Hemphill et al., 2020). This case links to NRL Articles 4 (terrestrial, coastal and freshwater ecosystems), 12 (forest).
Case study 4: Restoration of a species formerly extinct in the wild

European Bison (Bison bonasus) once inhabited much of Europe and northern Asia, but was extirpated over most of its range due to habitat loss and overhunting, with the last three wild populations hunted to extinction in the 19th and early 20th centuries. However, 54 captive individuals remained (Bolbot and Raczyński, 2013). From the 1920s onward, bison were the subject of an ex situ breeding programme which sought to avoid inbreeding depression as well as ensuring that the managed population did not include hybrids with American bison or cattle (Bolbot and Raczyński, 2013). Only 12 of the 54 animals were found to be of pure European Bison origin, leading to a reduced founder base for the breeding programme (Olech, 2023). Reintroduction of captive stock began in the Bialowieża Forest, Poland in 1929 and has continued there and in other European countries. Though historical levels of genetic diversity can never be restored, due to reintroductions, habitat management and the removal of hunting pressure, there are now over 7000 free-living bison across Eastern Europe (Olech, 2023). Despite genetic depletion, the self-sustaining bison populations have had subsequent positive impacts on habitat-level restoration goals, as European bison act as important long-distance seed dispersers (Jaroszewicz et al., 2008), enhance beetle community composition (Schwerk et al., 2021), and preliminary evidence suggests they improve grassland carbon sequestration (Kastovská et al., 2024). There has been consistent emphasis on the management of the remaining European bison genetic diversity throughout, which, combined with natural purging of deleterious genes has minimised the impacts of inbreeding following the population bottleneck (Olech, 2023). This example links to NRL Articles 4 (terrestrial, coastal and freshwater ecosystems), 12 (forest).

8. Conclusion

* Including genetic diversity in national restoration plans is well-aligned with the aims of the NRL and could further enhance its implementation. We have presented examples of how each NRL Article is linked to genetic diversity.

* Our case studies (1–4 above and Fig. 1) show how genetic diversity has been used in practice in Europe in the recent past and these examples can be used as models for future interventions.

* Within the NRL, including genetic diversity in the national assessment of each habitat would be beneficial to ensure adaptability of populations of species, improve resilience of ecosystems and for monitoring success of restoration actions.

* Genetic diversity is a key criterion in restoring connectivity, a central tenet of the NRL.

* Genetic monitoring and target setting are practical and ready to use and can form part of the NRL's contribution to the CBD KM-GBF - at European, national and subnational levels.

* Rapid implementation of genetic diversity monitoring in the NRL using existing DNA-based studies and simpler proxy indicators can help to safeguard Europe's genetic diversity.

CRediT authorship contribution statement

David O'Brien: Writing – review & editing, Writing – original draft, Project administration, Methodology, Investigation, Conceptualization. Tsipe Aavik: Writing – review & editing, Writing – original draft, Investigation. Ancuta Fedorca: Writing – review & editing. Martin C. Fischer: Writing – review & editing, Writing – original draft, Investigation. Robin Goffaux: Writing – review & editing, Writing – original draft, Investigation. Sean Hoban: Writing – review & editing, Writing – original draft, Investigation. Peter Hollingsworth: Writing – review & editing, Writing – original draft, Investigation. Christina Hvilsoim: Writing – review & editing, Writing – original draft, Investigation. Robert Jehle: Writing – original draft, Investigation. Belma Kalamujić Stroil: Writing – review & editing, Writing – original draft,

Investigation. **Francine Kershaw:** Writing – review & editing, Writing – original draft, Investigation. **Peter Klinga:** Writing – review & editing, Writing – original draft, Investigation. **Alexander Kopatz:** Writing – review & editing, Writing – original draft, Investigation. **Deborah M. Leigh:** Writing – review & editing, Writing – original draft, Visualization, Conceptualization. **Ivan Paz-Vinas:** Writing – review & editing, Writing – original draft, Investigation. **Marine Robuchon:** Writing – review & editing, Writing – original draft, Investigation. **Gernot Segelbacher:** Writing – review & editing, Writing – original draft, Investigation. **Viktoria Takacs:** Writing – review & editing, Writing – original draft, Investigation. **Cristiano Vernesi:** Writing – review & editing, Writing – original draft, Investigation. **Linda Laikre:** Writing – review & editing, Writing – original draft, Project administration, Investigation, Funding acquisition.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors acknowledge the following funding support L.L.: Formas [2020-01290], Swedish Research Council [2019-05503], Swedish Environmental Protection Agency, Swedish Agency for Marine and Water Management. The following scientific networks/projects have contributed to this paper: the Coalition for Conservation Genetics (www.coalitionforconservationgenetics.org), EU Biodiversa+ GINAMO (www.biodiversa.eu/2024/04/15/ginamo), EU COST Action GENOA (CA23121; www cost.eu/actions/CA23121). We thank Jerker Lokrantz at Azote for illustrations (Graphical abstract and Fig. 1).

Data availability

No data was used for the research described in the article.

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