Dr Jarkko Koskela
email: j.koskela@cgiar.org

François Lefèvre
email: francois.lefevre@avignon.inra.fr

Silvio Schueler
email: silvio.schueler@bfw.gv.at

Hojka Kraigher
email: hojka.kraigher@gozdis.si

; Ditte

C Olrik

Jason Hubert
email: jason.hubert@forestry.gsi.gov.uk

Roman Longauer
email: longauer@nlcsk.org

Michele Bozzano
email: m.bozzano@cgiar.org

Leena Yrjänä

Paraskevi Alizoti

Peter Rotach
email: peter.rotach@env.ethz.ch

; Lorenzo

Sándor Bordács
email: bordacss@mgszh.gov.hu

; Tor

Thröstur Eysteinsson
email: throstur@skogur.is

Oudara Souvannavong
email: oudara.souvannavong@fao.org

Bruno Fady
email: bruno.fady@avignon.inra.fr

Bart De Cuyper
email: bart.decuyper@inbo.be

Berthold Heinze
email: berthold.heinze@bfw.gv.at

Georg Von Wühlisch

Alexis Ducousso
email: alexis.ducousso@pierroton.inra.fr

Bjerne Ditlevsen
email: bjerneditlevsen@gmail.com

Ditte C Olrik

Lorenzo

Tor Myking
email: tor.myking@skogoglandskap.no

Ditlevsen

Translating conservation genetics into management: pan-European minimum requirements for dynamic conservation units of forest

Keywords: Forest genetic resources, genetic diversity, genetic conservation unit, genetic management, in situ Forest genetic resources, genetic diversity, genetic conservation unit, genetic management, in situ 65 66

review of theoretical and practical aspects related to genetic management 44 of forest trees. The implementation of international commitments on forest genetic diversity has

management of forest trees. The implementation of international commitments on forest genetic diversity has been slow and partly neglected. Conservation of forest genetic diversity is still riddled with problems, and complexities of national legal and administrative structures. Europe is an example of a complex region where the distribution ranges of tree species extend across large geographical areas with profound environmental differences, and include many countries. Conservation of forest genetic diversity in Europe has been hampered by lack of common understanding on the management requirements for genetic conservation units of forest trees. The challenge resides in integrating scientific knowledge on conservation genetics into management of tree populations so that recommendations are feasible to implement across different countries. Here, we present pan-European minimum requirements for dynamic conservation units of forest genetic diversity. The units are natural or man-made tree populations which are managed for maintaining evolutionary processes and adaptive potential across generations. Each unit should have a designated status and a management plan, and one or more tree species recognized for as target species for genetic conservation. The minimum sizes of the units are set at 500, 50 or 15 reproducing individuals depending on tree species and conservation objectives. Furthermore, silvicultural interventions should be allowed to enhance genetic processes, as needed, and field inventories carried out to monitor regeneration and the population size. These minimum requirements are now used by 36 countries to improve management of forest genetic diversity.

Introduction 67 68

Forests harbour most of Earth's terrestrial biodiversity (Millennium Ecosystem Assessment, 2005) 69 and trees are the keystone species of forest ecosystems maintaining their structure and function. 70

Between 50 000 (National Research Council, 1991) and 100 000 [START_REF] Oldfield | The World List of Threatened Trees[END_REF] tree species variation in trees valuable for present or future human use (FAO, 1989). Lack of research on the 79 minimum size of a genetic conservation unit for forest trees was recognized early as a problem 80 (FAO, 1975). Later on, the concepts of minimum viable population (MVP, a population size that 81 ensures the persistence of a population for a given period of time) [START_REF] Shaffer | Minimum population sizes for species conservation[END_REF] and 82 evolutionary significant units (ESU, populations having independent evolutionary histories) (Ryder, 83 1986) paved the way to incorporating genetics into conservation work and developing a dynamic 84 approach to the conservation of genetic diversity (e.g. [START_REF] Lande | Effective population size, genetic variation, and their use in 861 population management[END_REF]. 85 86 Soon after the MVP and ESU debate started, the dynamic conservation approach was also applied 87 and further developed for forest trees [START_REF] Ledig | Conservation strategies for forest gene resources[END_REF][START_REF] Eriksson | Dynamic gene conservation for uncertain futures[END_REF][START_REF] Namkoong | A gene conservation plan for loblolly pine[END_REF]. It is 88 based on managing tree populations at their natural sites within the environment to which they 89 are adapted (in situ), or artificial, but dynamically evolving populations elsewhere (ex situ). Ex situ 90 conservation stands of forest trees contribute to dynamic conservation only if natural selection 91 predominates. Climate change makes it even more important to apply the concept of dynamic 92 conservation to ensure the long-term sustainability of tree populations. 93 Many countries have developed specific national programmes or strategies for managing their 95 forest genetic diversity based on the dynamic conservation approach (e.g. [START_REF] Graudal | A systematic approach to the conservation of genetic 787 resources of trees and shrubs in Denmark[END_REF]96 Behm et al., 1997;[START_REF] Teissier Du Cros | Forest Genetic Resources Management and Conservation. France 963 as a Case Study[END_REF]. Unfortunately, the progress in implementing these 97 programmes and strategies has been slower than expected and the practical conservation of 98 forest genetic diversity is still riddled with methodological and political problems, and complexities 99 of national legal and administrative structures [START_REF] Geburek | Why the conservation of forest genetic resources has not worked[END_REF]. These problems are 100 not uniquely related to forest genetic diversity but to genetic conservation in general. As a result, 101 many national and international actions on biodiversity conservation have largely neglected 102 genetic diversity [START_REF] Laikre | Neglect of 857 genetic diversity in implementation of the Convention on Biological Diversity[END_REF]. 103 104The lack of genetic management in biodiversity conservation is no longer due to a lack of research 105 or guidelines, but due to failure to incorporate genetic aspects into practical management 106 [START_REF] Frankham | Challenges and opportunities of genetic approaches to biological conservation[END_REF]. In case of trees, forest conservation genetics has improved the theoretical basis 107 of genetic management of tree populations (e.g. Young et al., 2000;Geburek and Turok, 2005;108 Hamann et al., 2005) and various guidelines are available for this purpose (e.g. FAO, DFSC, IPGRI, 109 2001;[START_REF] Fao | Overview, 758 concepts and some systematic approaches[END_REF]. However, a persisting problem is that the national programmes 110 apply the theory and the guidelines in different ways. As a result, the effectiveness of the 111 conservation efforts varies to a large degree between countries. This has also led to difficulties in 112 assessing the status of genetic conservation of forest trees as they often have large distribution 113 areas covering several countries, sub-regions or even continents. Furthermore, without a common 114 and operational definition for the genetic conservation unit, it is impossible to develop range-wide 115 conservation strategies for forest trees. 116

Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P. Europe is an example of a complex region where the distribution ranges of forest trees extend 118 across large geographical areas with profound environmental differences, and include many 119 countries with different forest management practices and forest owners. Conservation status 120 assessment of forest genetic diversity in Europe has been hampered by a lack of common 121 understanding on the management requirements for the genetic conservation units. This has also 122 made it difficult to identify gaps in the conservation efforts and to develop genetic conservation 123 strategies at the pan-European level. 124 125 In this paper, we discuss theoretical and practical aspects of genetic management of forest trees. 126

We use Europe as a case study and present pan-European minimum requirements for genetic 127 conservation units of forest trees that are scientifically sound and practically feasible to implement 128 in different countries. We also suggest further actions for improving the genetic management of 129 tree populations. The term "dynamic conservation of genetic diversity" used throughout the text is 130 defined as in situ or ex situ conservation aimed at conserving evolutionary processes and adaptive 131 potential of natural or man-made tree populations across generations. 132 133

Methods 134 135

This review was carried out in the context of the European Forest Genetic Resources Programme 136 (EUFORGEN) and the EUFGIS project (Establishment of a European Information System on Forest 137 Genetic Resources, 2007-2011). The process of developing the pan-European minimum 138 requirements for dynamic conservation units of forest tree genetic diversity is presented in Figure 139 1. The inputs to the process included relevant literature and various results of EUFORGEN, such as 140 species-specific requirements for the units (unpublished), conservation guidelines (e.g. [START_REF] Lefèvre | EUFORGEN Technical Bulletin: In situ conservation of Populus nigra[END_REF] and descriptors for inventories of forest genetic resources (e.g. Jensen, 142 1998;[START_REF] Kleinschmit | Inventories of Noble 825 Hardwoods genetic resources: basic requirements[END_REF][START_REF] Alba | Standardized list of descriptors for inventories of Populus nigra L. stands[END_REF]. Furthermore, a large group of experts contributed to a 143 survey and a workshop organized as part of the EUFGIS project. A smaller group of experts then 144 reviewed all input information and drafted the minimum requirements. The drafting process 145 included pilot testing of the minimum requirements in six countries (Austria,Denmark,France,146 Slovakia, Slovenia and the United Kingdom) before they were finalized. The literature selected for 147 the review focuses on key issues, i.e. genetic diversity and related processes in tree populations, 148 dynamic conservation of genetic diversity, sampling for genetic conservation, forest management 149 and monitoring (Figure 1). We considered these as the most important issues for integrating 150 genetics into the management of the conservation units and we only referred to main publications 151 (in our opinion). 152 153

Conservation of forest tree genetic diversity 154

Genetic diversity in forest trees 155 156

Forest trees differ from other plant species in their capacity to maintain high levels of genetic 157 diversity within populations rather than among populations [START_REF] Hamrick | Response of forest trees to global environmental changes[END_REF], with some 158 exceptions to the rule (e.g. [START_REF] Vendramin | Genetically dipauperate but widespread: The case of an emblematic 971 Mediterranean pine[END_REF]. This is partly due to extensive gene flow as 159 dispersal distances of effective pollen flow (i.e. pollination leading to successful mating) and seeds 160 can reach up to 100 km and tens of kilometres, respectively (Kremer et al., 2012). Trees also have 161 a long generation time, characterized by a long juvenile stage and overlapping generations 162 [START_REF] Austerlitz | Effects of colonization 707 processes on genetic diversity: differences between annual plants and tree species[END_REF]. However, despite the extensive gene flow, tree populations also 163 demonstrate adaptation to local environmental conditions [START_REF] Aitken | Adaptation, migration or 698 extirpation: climate change outcomes for tree populations[END_REF] [START_REF] Savolainen | Gene flow and local adaptation in trees[END_REF]. 167 168 It seems that the counter-acting processes of extensive gene flow and local adaptation (through 169 strong selection pressures on seedlings and young trees in each generation) have shaped the 170 genetic constitution of European forest trees during their range expansion after the last glaciations 171 to a high degree. Extensive gene flow is constantly mixing genes and alleles, offering a multitude 172 of new combinations for selection. In contrast, forest trees have low evolutionary rates at the DNA 173 sequence level [START_REF] Petit | Some evolutionary consequences of being a tree[END_REF]. The rapid local adaptation is most likely caused by the 174 intergenic allelic associations created in this constant 'mixing' process facilitated by high gene flow 175 rates (e.g. De [START_REF] De Carvalho | Admixture facilitates adaptation from standing 731 variation in the European aspen (Populus tremula L.), a widespread forest tree[END_REF]. These associations explain the coexistence of phenotypic 176 differentiation among tree populations in the presence of extensive gene flow (Kremer et al., 177 2010). An epigenetic mechanism may also play a significant role in the rapid local adaptation of 178 forest trees, as shown in Norway spruce (Picea abies). Variation in environmental signals, such as 179 temperature, during embryo development influences the expression of adaptive traits in the 180 offsprings [START_REF] Kvaalen | Timing of bud set in Picea abies is regulated by a memory of 837 temperature during zygotic and somatic embryogenesis[END_REF]. This epigenetic mechanism in Norway spruce seems to be 181 controlled by a set of largely unknown genes, which have been identified by microRNAs (Yakovlev 182 et al., 2010). 183 184 During the past 2.6 million years (Quaternary Period), the distribution ranges of tree species have 185 not been stable but dynamically contracting, expanding or shifting as a response to climate 186 changes. These changes had a profound impact on boreal and temperate tree species but they 187 also influenced the distribution of tropical forests [START_REF] Hewitt | The genetic legacy of the Quaternary ice ages[END_REF] as well as the migration of 188 tropical tree species (e.g. Kadu et al., 2011;[START_REF] Logossa | Molecular data reveal isolation by distance and past population expansion for the shea 880 tree (Vitellaria paradoxa C.F. Gaertn) in West Africa[END_REF]. Genetic and paleoecological studies have provided insights into the past dynamics of the distribution ranges by locating refugia 190 areas and postglacial migration routes [START_REF] Petit | Identification of refugia and post-glacial colonisation routes of European white oaks 928 based on chloroplast DNA and fossil pollen evidence[END_REF][START_REF] Magri | 889 A new scenario for the quaternary history of European beech populations: palaeobotanical 890 evidence and genetic consequences[END_REF][START_REF] Cheddadi | Imprints of glacial refugia in the modern 726 genetic diversity of Pinus sylvestris[END_REF]191 Liepelt et al., 2009). Refugia populations, which are often found at the current low-latitude regions 192 of temperate tree species' distribution ranges, have been assigned a high priority for the long-193 term conservation of genetic diversity [START_REF] Hampe | Conserving biodiversity under climate change: the rear edge matters[END_REF]. In Europe, the refugia populations 194 are mostly found in the Mediterranean Basin which harbours high within-population genetic 195 diversity in vascular plants [START_REF] Fady | Macroecological patterns of species and genetic diversity in vascular 747 plants of the Mediterranean Basin[END_REF] and where species introgression took place 196 during the last glaciation [START_REF] Hatziskakis | High chloroplast haplotype 806 diversity in Greek populations of beech (Fagus sylvatica L.)[END_REF]Scaltsoyiannes et al., 1999). However, recent 197 studies have provided evidence that small tree populations also survived at intermediate or even 198 high latitudes throughout the Quarternary glacial episodes [START_REF] Hu | Paleoecology meets genetics: deciphering past vegetational 812 dynamics[END_REF]Parducci et al., 2012). 199 200 Range expansions generally reduce genetic diversity along the migration path owing to recurrent 201 bottleneck effects and they can also create patterns of genetic diversity that can be difficult to 202 separate from adaptive events [START_REF] Excoffier | Genetic consequences of range expansions[END_REF]. However, when multiple founder events are 203 unrelated, due to long distance dispersal, a high level of genetic diversity is conserved in the 204 colonisation domain [START_REF] Fayard | Long distance dispersal and the fate of a gene from the 761 colonisation front[END_REF]. Successful migrating tree populations obviously 205 maintained sufficient genetic variation to allow them to adapt to newly colonized areas (Hamrick, 206 2004). Furthermore, so called mid-or high-latitude contact zones, where different refugial 207 lineages mixed, had an important role in creating new gene combinations and adaptations to 208 environmental conditions along the migration routes [START_REF] Liepelt | Postglacial range expansion and 876 its genetic imprints in Abies alba (Mill.) -A synthesis from palaeobotanic and genetic data[END_REF]De Carvalho et al., 209 2010). Tree populations in the contact zones still harbour high levels of genetic diversity (Petit et 210 al., 2003;[START_REF] Liepelt | Postglacial range expansion and 876 its genetic imprints in Abies alba (Mill.) -A synthesis from palaeobotanic and genetic data[END_REF][START_REF] De Carvalho | Admixture facilitates adaptation from standing 731 variation in the European aspen (Populus tremula L.), a widespread forest tree[END_REF] given environmental conditions [START_REF] Eriksson | Evolution and evolutionary factors, adaptation and adaptability[END_REF]. Thus, the goal of genetic conservation of forest 222 trees should be the maintenance of a diverse group of mating individuals and populations across 223 different environmental gradients to ensure continued evolutionary processes, not only the 224 preservation of the existing frequencies of alleles and genotypes. 225

226

In situ conservation is commonly the preferred approach for maintaining the genetic diversity of 227 forest trees and other wild plant species, while domesticated plants are conserved in genebanks 228 (ex situ) or on farms (circa situm). Genetic material of forest trees is also conserved ex situ in seed 229 banks, seed orchards, clone collections, provenance trials, planted conservation stands and 230 botanical gardens to complement in situ conservation efforts (particularly when population size is 231 critically low in the wild). In situ conservation of forest trees has several advantages as compared 232 to ex situ conservation [START_REF] Rotach | In situ conservation methods[END_REF]. Firstly, in situ conservation is dynamic allowing temporal 233 and spatial changes in genetic diversity while ex situ conservation is mostly static maintaining the 234 once-sampled genetic diversity. The second advantage is that trees within in situ conservation 235 units remain exposed to evolutionary processes, as they continue interacting with their 236 environment and competing with individuals of the same or other species. Thirdly, it is easier and protected areas and forests used for different purposes (FAO, FDL, IPGRI, 2004). However, from 244 the genetic management point of view, both protected areas and managed forests often have 245 some limitations. Most protected areas are established for conserving endangered animal and 246 plant species or specific habitats, and their suitability for long-term genetic conservation of forest 247 trees has rarely been assessed prior to their establishment. It is assumed that habitat conservation 248 and natural regeneration also maintain the genetic diversity of tree populations in an optimum 249 and stable state. However, this assumption has been challenged by many theoretical and empirical 250 studies (e.g. [START_REF] Rauch | Estimating the total genetic diversity of a spatial field population 940 from a sample and implications of its dependence on habitat area[END_REF][START_REF] Faith | Getting biodiversity intactness right: ensuring that 749 'biodiversity' reflects 'diversity[END_REF]. Furthermore, genetic conservation of 251 forest trees often has a low priority in the management of protected areas and typically no 252 silvicultural treatments are allowed in these areas to enhance genetic processes within tree 253 populations. 254 255 When protected areas or genetic conservation units in managed forests are being established, it is 256 commonly assumed that seemingly natural forests consist of autochthonous, genetically diverse 257 tree populations. However, historical records show that forest reproductive material (typically 258 seeds or seedlings) has been traded and distributed across Europe for hundreds of years (König, 259 2005). There is usually no documentation available where the transferred material was planted in [START_REF] Fineschi | Chloroplast DNA polymorphism 763 reveals little geographical structure in Castanea sativa Mill. (Fagaceae) throughout southern 764 European countries[END_REF][START_REF] Vendramin | Genetically dipauperate but widespread: The case of an emblematic 971 Mediterranean pine[END_REF]. 262 263As part of today's forest management, stands are often regenerated by planting or seeding with 264 genetic material originating from other locations but the use of forest reproductive material is still 265 poorly documented in most countries. Of the whole silvicultural chain, the regeneration phase is 266 the most significant one as it largely determines the amount of genetic diversity in subsequent 267 mature stands while other phases, such as thinning, have a lesser impact on genetic diversity 268 [START_REF] Savolainen | Effect of forest management on gene pools[END_REF][START_REF] Lefèvre | Human impacts on forest genetic resources in the temperate zone: an updated 869 review[END_REF]. The impact of forest management on genetic 269 diversity depends on the silvicultural system applied and many systems actually maintain genetic 270 diversity rather well [START_REF] Geburek | How can silvicultural management contribute to genetic 782 conservation?[END_REF]. However, forest management usually focuses on 271 one or relatively few tree species and may even aim at removing non-commercial species from 272 production stands. 273 274 A particular concern is the use of non-certified reproductive material for amenity tree planting 275 along roads and for other similar purposes. These activities rarely follow well-regulated forestry 276 practices and they often use reproductive material which does not comply with the international 277 labelling schemes of the material, such as those developed by the European Union or the 278 Organization for Economic Co-operation and Development (OECD) [START_REF] Ackzell | International legislation with implications on the exchange of forest 695 genetic resources[END_REF]. 279

Assisted migration can enhance adaptation to climate change [START_REF] Hewitt | Taking stock of the assisted migration debate[END_REF] but in case of 280 amenity tree planting, the risks of introducing alleles resulting in maladaptive traits into nearby 281 genetic conservation units is higher than in the forestry operations which are obliged to use well-282 documented reproductive material that is usually also tested in different site conditions prior to its 283 deployment. In Europe, most national conservation strategies for forest genetic resources are based on the 286 dynamic approach and several countries have also revised their strategies based on the expected 287 impacts of climate change (e.g. [START_REF] Hubert | The Role of Forest Genetic Resources in Helping British Forests 814 Respond to Climate Change[END_REF][START_REF] Lefèvre | Conservation of forest genetic resources under climate change: the case of 871 France[END_REF]. The national strategies 288 aim at conserving dynamically a representative sample of the genetic diversity found within a 289 country and for this purpose, many countries have created a network of genetic conservation units 290 [START_REF] Graudal | A systematic approach to the conservation of genetic 787 resources of trees and shrubs in Denmark[END_REF][START_REF] Behm | Concept for the 711 conservation of forest genetic resources in the Federal Republic of Germany[END_REF][START_REF] Teissier Du Cros | Forest Genetic Resources Management and Conservation. France 963 as a Case Study[END_REF]. The networks are typically based 291 on ecogeographical zonation and the distribution of tree species in a given country. In other 292 regions, such as Asia and Africa, similar conservation networks have also been established for 293 some commercially important species (FAO,DFSC, IPGRI, 2001). However, these networks are still 294 largely based on tree populations occurring in protected areas and production forests (see Eyog-295 Matig et al., 2002;[START_REF] Luoma-Aho | Forest genetic resources 882 conservation and management[END_REF] rather than populations which are specifically managed 296 for genetic conservation. Ideally, if all countries had national conservation strategies in place, the 297 conservation networks would cover the whole distribution range of a tree species. In practice, 298 however, countries have different priorities for implementing genetic conservation and selecting 299 tree species, as well as different levels of resources available for this work. As a result, there are 300 often gaps in genetic conservation networks in Europe and elsewhere. 301 recognized by the appropriate authorities or agencies in a country to ensure its long-term 309 management for this purpose. The designated status does not necessarily mean that the units 310 should have a legal status. As countries have organized their conservation work in various ways, 311 the designated status can also be based on an administrative decree or other similar arrangement. 312 313 Secondly, the units should have a basic management plan that includes generation turnover and 314 genetic conservation of forest trees should be recognized as a major management goal. All 315 management efforts carried out within a unit should also be documented in detail and the records 316 should be maintained either by the landowner, the organization responsible for the management 317 of the unit or a relevant national authority. The management plan should be updated based on 318 systematic field inventories conducted every five or ten years, depending on the planning cycle. 319 320

The third basic requirement is related to tree species and the genetic background of their 321 populations. For each unit, one or more tree species should be recognized as target tree species 322 for genetic conservation in the management plan. This means that management efforts to 323 maintain genetic processes are applied to favour these species. If a genetic conservation unit has 324 several target species, each target species must meet the appropriate minimum population size as 325 described in detail below. 326 327

The target tree species can be either native or introduced ones. In the case of native tree species, 328 the units should ideally consist of autochthonous tree populations but well-adapted populations 329 originating from other locations can also be designated as conservation units. Several introduced 330 tree species have been used for forestry and environmental restoration in Europe for decades or 331 even hundreds of years. Many of these species have developed into landraces that are adapted to European conditions and have, in some cases, developed distinct characteristics from their original 333 source populations [START_REF] König | Provenance research: evaluating the spatial pattern of genetic variation[END_REF]. Such landraces constitute a valuable genetic resource that needs 334 to be managed according to the principles of dynamic conservation. Furthermore, genetic material 335 of both native and introduced tree species conserved in Europe may be useful in the future for 336 restoring lost tree populations in their original locations [START_REF] König | Provenance research: evaluating the spatial pattern of genetic variation[END_REF][START_REF] Chalupka | Reconstitution of a lost forest tree 722 population: A case study of Norway spruce (Picea abies [L.] Karst.)[END_REF]. The 337 target tree species may grow in pure or mixed stands and a unit may consist of one or more stands 338 of different age classes. No unknown or maladapted genetic material of the target tree species 339 should be growing within a unit. 340 341

The reasons for establishing genetic conservation units often depend on where a country is 342 located in respect to the distribution range of a target tree species. Many stand-forming tree 343 species have large, continuous populations at the centre of their distribution range while they 344 grow in disjunct populations at the margins. There are scattered tree species which rarely, if ever, 345 form stands and subsequently their population density is low throughout their distribution range. 346 Furthermore, a tree can be rare or endangered in one country but more common in another 347 country. There are also endemic tree species which may occur only in specific areas within a 348 country. Thus conservation objectives for tree species often vary among countries. The objectives 349 for the genetic conservation units can be classified into the following categories; 1) to maintain 350 genetic diversity in large tree populations, 2) to conserve specific adaptive or other traits in 351 marginal or scattered tree populations which are often relatively small, and 3) to conserve rare or 352 endangered tree species with populations consisting of a small number of remaining individuals. 353

The fourth basic requirement is that one of these objectives has been clearly stated for each target 354 tree species within a unit. 355

Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady

Size of a dynamic conservation unit 357 358

The size of conservation populations is commonly determined with two goals in mind; 1) to 359 increase the probability of capturing the existing diversity of alleles (sampling perspective), and 2) 360 to reduce the risk of loosing genetic diversity during the course of evolution (dynamic 361 perspective). To our knowledge, no theoretical or let alone practical recommendations have yet 362 been elaborated based on the concept of allelic associations which play an important role in 363 adaptation of forest trees [START_REF] Kremer | Historical and contemporary dynamics of 848 adaptive differentiation in European oaks[END_REF]. 364 365 4.2.1. Sampling perspective 366 367 [START_REF] Marshall | Optimum sampling strategies in genetic conservation[END_REF] presented a conceptual framework for prioritizing genetic 368 conservation efforts and grouped alleles into four classes, 1) common and widespread, 2) common 369 and local, 3) rare and widespread, and 4) rare and local. They argued that common and local 370 alleles should be given a priority in genetic sampling as this class presumably includes those alleles 371 behind adaptation to the local conditions. [START_REF] Brown | Sampling the gene pools of forest trees for ex situ 717 conservation[END_REF] recommended that a 372 sampling strategy targeting this same allele class is also well suited for forest trees as their 373 populations demonstrate geographical patterns in adaptive traits. However, recent work based on 374 DNA sequencing suggests that these highly differentiated adaptive alleles are also rare (Grivet et 375 al., 2011). Any sampling strategy will capture the first allele class while the sampling of the third 376 allele class depends on the number of units within the species' distribution range and not on the 377 number of trees within a unit [START_REF] Brown | Sampling the gene pools of forest trees for ex situ 717 conservation[END_REF]. 378

The alleles in the fourth class are the most difficult ones to sample but they are of low priority for 380 two reasons [START_REF] Brown | Sampling the gene pools of forest trees for ex situ 717 conservation[END_REF]. Firstly, conserving all rare and local alleles is practically 381 impossible considering the resources available for conservation work and secondly, even with 382 unlimited resources available to sample all these alleles, it would be difficult to maintain them in 383 the long-term as they include recent and deleterious alleles which are likely to be eliminated by 384 natural selection. [START_REF] Yanchuk | A quantitative framework for breeding and conservation of forest tree 979 genetic resources in British Columbia[END_REF] calculated that almost 280 000 trees would need to be sampled 385 to include 20 individuals with recessive alleles of low frequency (less than 1%). This would require 386 an area of nearly 700 ha (assuming an average density of 400 reproducing trees per hectare) and 387 would make the establishment of genetic conservation units nearly impossible not only for most 388 tropical tree species but also for many scattered or rare tree species in the temperate and boreal 389 zones. 390 391 In forest trees, some 10-20% of allozyme alleles are common and local [START_REF] Brown | Sampling the gene pools of forest trees for ex situ 717 conservation[END_REF]. 392

Considering this, the same authors defined an adequate sampling strategy as one that captures 393 with 95% certainty at least one copy of alleles with a frequency of 0.05 and stated that this 394 requires 59 unrelated gametes. Taking into consideration differences in the breeding systems of 395 trees, [START_REF] Brown | Sampling the gene pools of forest trees for ex situ 717 conservation[END_REF] recommended that a sample should include a minimum of 50 396 random and unrelated trees. As a worst-case scenario, [START_REF] Brown | Sampling the gene pools of forest trees for ex situ 717 conservation[END_REF] concluded that 397 open-pollinated seed collected from a minimum of 15 maternal trees would sample a large part of 398 genetic diversity within a population. 399 400

Dynamic perspective 401

Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady Applications of MVP and ESU to improve the genetic management of conservation populations 403 have been debated extensively during the past 30 years (see [START_REF] Traill | Pragmatic population viability 968 targets in a rapidly changing world[END_REF] and Flather et al. 404 (2011) for MVP; [START_REF] Fraser | Adaptive evolutionary conservation: towards a unified concept 778 for defining conservation units[END_REF] for ESU). Various MVP and ESU approaches have 405 been defined using different criteria but they all have a common goal, i.e. long-term conservation 406 of evolutionary processes and adaptive diversity. However, no single ESU approach is the best one 407 for all situations [START_REF] Fraser | Adaptive evolutionary conservation: towards a unified concept 778 for defining conservation units[END_REF] and there is no universal threshold for MVP either 408 [START_REF] Flather | Minimum viable populations: 766 is there a "magic number" for conservation practitioners?[END_REF]. MVP also depends on context-specific factors [START_REF] Traill | Minimum viable population size: A meta-analysis of 30 966 years of published estimates[END_REF]. 409 410The minimum size of a genetically viable population is commonly defined using effective 411 population size (N e ), which is a parameter measuring the intensity of random genetic drift in the 412 Wright-Fisher model population (e.g. [START_REF] Hartl | Principles of Population Genetics[END_REF]. Based on theoretical studies, 413 recommendations for the minimum population size range from N e =500 [START_REF] Franklin | Evolutionary changes in small populations[END_REF]Soulé, 414 1980;[START_REF] Lande | Effective population size, genetic variation, and their use in 861 population management[END_REF] to N e =5000 [START_REF] Lande | Mutation and conservation[END_REF] when the goal is to maintain 415 evolutionary potential. A meta-analysis by [START_REF] Traill | Minimum viable population size: A meta-analysis of 30 966 years of published estimates[END_REF] found a median, standardized MVP 416 estimate of 4169 individuals based on published studies on 212 species (mainly animals). If the 417 goal is to maintain reproductive fitness in the short term (over a few generations), the minimum 418 population size of N e =50 has been suggested by many studies (see [START_REF] Frankham | Introduction to Conservation Genetics[END_REF]. 419 420The question of how many individuals should be included in a conservation unit has also been 421 studied extensively in forest trees. However, as N e is extremely difficult to determine accurately in 422 tree populations, it is frequently approximated by the number of reproducing trees (N r ), i.e. the 423 effective size of an observed biological population instead of a model one (e.g. Hattemer, 2005a). 424

The recommendations for N r range from 50 (e.g. [START_REF] Brown | Sampling the gene pools of forest trees for ex situ 717 conservation[END_REF] to 500 (e.g. Hattemer, 425 2005b) and 1000 [START_REF] Lynch | A quantitative-genetic perspective on conservation issues[END_REF]. (1980) and many other theoretical studies on MVP are based on the assumption that 428 additive genetic variance (V a ) rather than allelic diversity determines evolutionary potential, and 429 that its level depends on the balance between random genetic drift and mutation. The change in 430 additive genetic variance (ΔV a ) is calculated as the difference between the increase in genetic 431 variation per generation due to mutation (V m ) and the loss of additive genetic variation per 432 generation due genetic drift (V a /2N e ) (e.g. [START_REF] Frankham | Introduction to Conservation Genetics[END_REF]. At mutation-drift equilibrium 433 (ΔV a =0), N e equals V a /2V m . Various theoretical studies have estimated V m differently and this 434 explains the large variation in the recommended minimum population sizes. These 435 recommendations can thus be debated until it is better known which mutations are always 436 deleterious, and which ones are deleterious in some conditions and beneficial in others (Frankham 437 et al., 2002). 438 439Expected heterozygosity (H e ) and V a are expected to decline in a population by a factor of 1-1/2N e 440 per generation (e.g. [START_REF] Hartl | Principles of Population Genetics[END_REF]. The assumptions of this model include equal sex ration, 441 random mating and non-overlapping generations, and that no selection, mutation or migration 442 take place. However, these assumptions do not often hold in case of tree populations. 443 Furthermore, this model probably over-estimates the decrease of V a because they do not take into 444 account the role of linkage disequilibrium and interactions among loci [START_REF] Carter | The role of epistatic gene interactions in the response to 720 selection and the evolution of evolvability[END_REF]Kremer 445 and Le Corre, 2012). 446 Genetic conservation is obviously more secure with a population size of a few thousand trees 450 instead of a few hundred or tens. However, setting thousands of trees as the minimum population 451 size is not practically feasible. The size requirement should be reasonable and flexible for different 452 kinds of tree species. It should also take into account different conservation objectives across 453 species' distribution ranges. Considering resource allocation at the range-wide level, the size 454 requirement for a unit needs to be set at a level which allows establishment of a network of units 455 to cover all ecogeographical zones within a species' distribution range. 456 457 Considering the real-life fact that resources are limited for conservation, Frankham et al. (2002) 458 proposed that maintaining 90% of genetic diversity for 100 years is a reasonable goal for genetic 459 management of conservation populations. Using this goal, we first considered how long period is 460 100 years in terms of tree generations (t), and then calculated, based on the random genetic drift 461 model, the decline in genetic diversity during this period as (1-1/2N e ) t using different values of N e . 462 463 Generation time in forest trees, i.e. the time from seed to seed [START_REF] Petit | Some evolutionary consequences of being a tree[END_REF], is 464 somewhat difficult to establish accurately for a number of reasons. Temperate and boreal tree 465 species, for example, reach reproductive maturity typically at the age of 20-30 years but in open 466 and dense stands, this takes place several years earlier or later, respectively. The reproductive 467 cycle usually takes two or three years, year-to-year variation in seed production is large and mast 468 years occur infrequently. It may then take several years, decades or even centuries before a new 469 tree generation has been established successfully, depending on whether a species is a pioneer or 470 climax one, and how a forest is managed. The life span of individual trees can extend up to several 471 hundreds of years and as a result, tree populations often consist of overlapping generations. 472

Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady However, assuming that the average generation time of a European tree species is 50 years, a 474 model population with N e =500 would maintain 99.8% of its original genetic diversity after 100 475 years. Smaller populations with N e =50, 15 or 5 would maintain 98.0%, 93.4% and 81.9% of their 476 genetic diversity, respectively. These calculations do not take into account any outside gene flow 477 which is likely to offset some part of the loss of in genetic diversity, nor bi-parental inbreeding 478 that, on the contrary, can reduce the diversity. Furthermore, spatial genetic structure is not 479 considered. Using a simulation approach and the most realistic seed dispersal functions for a 480 model population, [START_REF] Sagnard | Effects of seed 947 dispersal, adult tree and seedling density on the spatial genetic structure of regeneration at 948 fine temporal and spatial scales[END_REF] showed that a spatial genetic structure (non-random 481 distribution of related genotypes in space) could result from a single mating event when N e < 16. 482 483 Migration can play a significant role in maintaining genetic diversity in tree populations. Long-484 distance gene flow via seed and pollen dispersal increases genetic variation in tree populations in 485 two ways (Kremer et al., 2012). Firstly, long-distance effective pollen dispersal increases the 486 genetic diversity in seeds produced by the current tree generation. Secondly, migrant seeds can 487 accumulate in a population over many years, increasing the number genotypes in the next tree 488 generation. This suggests that long-distance gene flow can compensate partly or fully the loss of 489 genetic diversity due to genetic drift in small tree populations or even increase their genetic 490 diversity, depending on the situation. 491 492 Based on the theoretical considerations and practical aspects, we propose that the minimum size 493 of a genetic conservation unit should be either 500, 50 or 15 reproducing individuals depending on 494 tree species and conservation objectives (Table 1). As some tree species are capable of vegetative 495 reproduction (through root sprouts or partially buried shoots), efforts should be made to check if In Cases 1 (N r =500) and 2 (N r =50) (Table 1), the minimum number of reproducing trees can be 500 temporarily lower than what is indicated if it is necessary to create gaps to promote natural 501 regeneration, for example. The prerequisite is that the minimum number of reproducing trees has 502 contributed to mating (and seeding depending on the species) before the regeneration process 503 has been initiated with silvicultural measures. Furthermore, N r should recover to the minimum 504 level or above in the near future after a management intervention. We consider Case 3 (N r =15) as 505 an exceptional case. All units with such a low number of reproducing trees should be subjected to 506 appropriate measures to increase their population size. Furthermore, seed or other reproductive 507 material from these units should be collected urgently for ex situ conservation. 508 509

Management of dynamic conservation units 510 511

Management of the units should aim to maintain and enhance the long-term evolutionary 512 potential of the target tree populations. Subsequently, two management objectives are necessary 513 for reaching this goal (Table 1). Firstly, management should ensure the continued existence of 514 target tree populations and secondly, it should create favourable conditions for growth and vitality 515 of the target tree species and their natural regeneration [START_REF] Rotach | In situ conservation methods[END_REF]. This means that 516 management should be active, i.e. various measures and silvicultural techniques are applied, 517 whenever needed, to enhance genetic processes that maintain the long-term viability of the target 518 tree populations. The management interventions should also favour all tree species that have 519 been recognized as target species and result in adequate natural regeneration, both in terms of quantity and genetic quality. In some particular cases, such as riparian pioneer tree species, 521 ecological engineering may be needed to ensure natural regeneration [START_REF] Lefèvre | EUFORGEN Technical Bulletin: In situ conservation of Populus nigra[END_REF]. 522 523 Under the first objective, management efforts should aim to protect the units against natural or 524 man-made catastrophes. Obviously, the units can never be fully protected against these stochastic 525 events but management can increase the resilience of the tree populations so that they can persist 526 during a catastrophe and recover from it. In the absence of any catastrophe, successional 527 development may also threaten the existence of tree populations and management efforts are 528 needed to halt or reverse this natural process, depending on the target species. 529 530 Under the second objective, silvicultural techniques, such as thinning, are often needed to 531 maintain the vitality of the target tree populations and to avoid stands becoming too dense with 532 reduced health, vigour and seed production. Thinning typically removes out-competed individuals 533 or it can be applied in a systematic way but as long as stand density remains above a certain 534 threshold, thinning usually has limited genetic consequences [START_REF] El-Kassaby | Effects of commercial thinning on genetic, plant 734 species and structural diversity in second growth Douglas-fir (Pseudotsuga menziesii (Mibr.) 735 Franco stands[END_REF]535 Lefèvre, 2004). After thinning, target tree populations should still have a sufficient number of 536 effectively mating and reproducing trees to prevent reduction of genetic diversity through 537 demographic bottlenecks and consanguineous mating, and to maintain genetic diversity. 538 Furthermore, the spatial distribution of trees should be such that it is reasonable to assume that 539 sexual reproduction takes place randomly, and that the level of relatedness among the next 540 generation of trees, or spatial genetic structure, is as low as possible [START_REF] Sagnard | Effects of seed 947 dispersal, adult tree and seedling density on the spatial genetic structure of regeneration at 948 fine temporal and spatial scales[END_REF]. 541 542 Silvicultural techniques should be applied in such a way that they support reproductive processes 543 and result in adequate regeneration of the target tree species. Natural regeneration should be favoured as a regeneration method, but tree populations can also be regenerated by planting or 545 seeding. If stands are regenerated artificially, the reproductive material should originate from the 546 same genetic conservation unit, or, if not available, from another autochthonous stand nearby. In 547 this case, the number of trees which contributed to the artificial regeneration process should also 548 meet the minimum requirements. If a unit is large, different selective cutting and regeneration 549 techniques could be used within and among the units to promote variability in mating patterns 550 (e.g. clustered, random and regular spacing of seed trees). 551 552 Genetic conservation of forest trees can be integrated fairly easily with other management goals 553 of forests and it does not prevent forests from being used for different purposes. As dynamic 554 conservation of genetic diversity may require active management, it can be easier to implement it 555 in forests that are managed for multiple-uses as compared to nature reserves and other protected 556 areas which are often managed passively without silvicultural interventions. However, it is 557 important to note that genetic conservation of forest trees cannot be practised in all managed 558 forests. For example, stands established using reproductive material from unknown sources do 559 not meet the minimum requirements. Furthermore, seed orchards and many seed stands, i.e. 560 areas identified as being suitable for seed collection for forestry, do not meet the requirements for 561 dynamic genetic conservation either. 562 563 Detailed guidelines for field-level management of the units are already available (e.g. Koski et al., 564 1997;[START_REF] Fao | In 755 managed natural forests and protected areas (in situ)[END_REF][START_REF] Lefèvre | EUFORGEN Technical Bulletin: In situ conservation of Populus nigra[END_REF][START_REF] Rotach | In situ conservation methods[END_REF] so we do not discuss them here. 565 However, we want to highlight the importance of relevant practices and policies in supporting 566 management of the units. As countries are ultimately responsible for conserving genetic resources 567 within their territory, management of the units needs overall coordination at the national level. The management of networks of units across a country is best undertaken by a designated 569 authority working in collaboration with relevant agencies, forest owners and other interested 570 parties. This often facilitates the process of obtaining the designated status for a unit and 571 incorporating genetic conservation as a management goal into the management plan. 572 Furthermore, conservation of forest genetic resources should be incorporated into relevant 573 national policies, such as national forest programmes, national biodiversity action plans and 574 national adaptation strategies to climate change (see Koskela et al., 2007). 575 576

Monitoring of dynamic conservation units 577 578

Monitoring is crucial for the successful management of the units. Once basic information on the 579 target tree populations has been collected for the establishment of the units and for the 580 development of a management plan, field inventories should ideally be carried out every five or 581 ten years to assess the success of the conservation work and to update the management plan. 582 583 As a minimum level of monitoring, the field inventories should collect data on natural 584 regeneration of target tree species and their population sizes. In case natural regeneration is 585 inadequate or if the number of reproducing trees has decreased, urgent management 586 interventions may be necessary to improve the situation. Between the inventories, the units 587 should also be visited regularly to check for any damages caused by storms, forest fires or insect 588 outbreaks, for example. Regular visits can also detect problems in the viability or reproduction of 589 target tree populations before they become a serious threat. 590

Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre As development of more powerful and affordable molecular markers and novel statistical and 615 modelling tools is making genetic monitoring more feasible and cost-effective, it is reasonable to 616 expect that an operational genetic monitoring system can be established for the dynamic 617 conservation units in the near future. Genetic monitoring systems have also been proposed for 618 other plant species and animals [START_REF] Schwartz | Genetic monitoring as a promising tool for 957 conservation and management[END_REF][START_REF] Laikre | Potentials for 852 monitoring gene level biodiversity: using Sweden as an example[END_REF]. 619 620

Deployment of the pan-European minimum requirements 621 622

The pan-European minimum requirements for genetic conservation units of forest trees are now 623 being used by 36 countries to improve management of forest genetic diversity. To support the 624 related documentation efforts, the countries have also agreed common data standards for the 625 units. The data on those units which meet the minimum requirements was collected by a network 626 of national focal points for the EUFGIS Portal (http://portal.eufgis.org). This new database 627 provides geo-referenced data on the genetic conservation units based on 26 data standards at the 628 unit level (geographical area) and 18 data standards at the population level (target tree species 629 within a unit). In January 2012, the portal contained data on 2369 units, which are managed for 630 genetic conservation of nearly 100 tree species in Europe. The units harbour a total of 3154 tree 631 populations. In addition to conservation work at the national level, the countries have used the 632 EUFGIS Portal for international reporting efforts, such as the State of Europe's Forests 2011 report 633 [START_REF] Forest Europe | State of Europe's Forests[END_REF] and the forthcoming State of the World's Forest Genetic Resources 634 report. 635 636

Conclusions 637

The pan-European minimum requirements for genetic conservation units of forest trees presented 639 in this paper constitute a major step in improving genetic management of forest trees in a large 640 geographical scale. They provide managers, forest owners and policy makers with practical, 641 science-based recommendations for implementing dynamic conservation of forest trees in a 642 coordinated manner across different countries and situations. The presented requirements were 643 developed for the European tree species and conditions so they cannot be applied to other 644 regions without modifications. However, we believe that they provide other regions with a useful 645 example on how such requirements can be developed through regional collaboration. 646 Furthermore, as range-wide genetic studies and mapping of valuable populations are increasingly 647 carried out also for tropical and sub-tropical tree species (e.g. Kadu et al., 2011;van Zonneveld et 648 al., 2012), countries in other regions would also benefit from having common requirements for 649 genetic conservation units of forest trees modified for their conditions. 650 651 In addition to secured regeneration and adequate number of reproducing trees within a 652 conservation unit, it is crucial that a network of the units has a sufficient coverage of the spatial 653 genetic variation present in a given species [START_REF] Koski | Technical guidelines for genetic 834 conservation of Norway spruce (Picea abies (L.) Karst.)[END_REF][START_REF] Crandall | Considering 728 evolutionary processes in conservation biology[END_REF]. As it is very 654 difficult to define a universal minimum number of units for a conservation network that could be 655 justified for all tree species [START_REF] Brown | Sampling the gene pools of forest trees for ex situ 717 conservation[END_REF], we did not include this aspect to the 656 minimum requirements. Instead, we argue that the minimum number of units for conservation 657 networks of forest trees should be defined species by species using available data on the existing 658 conservation units, species distribution, range-wide genetic diversity studies and results of 659 common garden tests or other information on adaptive traits. This would also allow assessment of 660 duplication in conservation efforts between countries and, considering the level of threats for a Table 1. Pan-European minimum requirements for genetic conservation units of forest trees.

Requirement group Detailed requirements Basic requirements

The unit has 1) a designated status as a genetic conservation area of forest trees, recognized by the appropriate authorities or agencies in a country. 2) a management plan in which genetic conservation of forest trees is recognized as a major management goal.

One or more tree species have been recognized as target tree species for genetic conservation in the management plan.

One of the following conservation objectives has been clearly stated for each target tree species within a unit: 1) to maintain genetic diversity in large tree populations; 2) to conserve specific adaptive or other traits in marginal or scattered tree populations; or 3) to conserve rare or endangered tree species with populations consisting of a small number of remaining individuals.

Population size

The minimum population size depends on the conservation objective as follows:

Case 1: If the purpose of the unit is to maintain genetic diversity of widely occurring and stand-forming conifers or broadleaved species, the unit must consists of 500 or more reproducing trees. Case 2: If the unit was established to conserve specific adaptive or other traits in marginal or scattered tree populations, the unit must harbour a minimum of 50 reproducing trees or, in the case of dioecious tree species with sexual dimorphism, 50 seed bearing trees. Case 3: If the unit is aiming to conserve remaining populations of rare or endangered tree species, it must harbour a minimum of 15 unrelated reproducing trees.

Management

Silvicultural interventions are allowed within the unit and they are actively applied, as needed, to: 1) ensure the continued existence of target tree populations; and 2) create favourable conditions for growth and vitality of the target tree species and their natural regeneration.

Monitoring

Field inventories are carried out every five or ten years to assess regeneration success and the population size, and to update the management plan.

Between the inventories, the units are visited regularly to observe that they still serve their purpose and that they have not been damaged or destroyed.

  and thus they are considered of a high 211 conservation priority in addition to the refugia areas. 212 Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : both the diversity of alleles and the diversity of genotypes, i.e. allelic 216 combinations. The diversity of genotypes is particularly important for organisms having long 217 generation time, such as forest trees, because they have few opportunities of recombination to 218 create new allelic associations. The frequencies of alleles and genotypes are continuously changing 219 over time as a result of evolutionary processes (natural selection, genetic drift, gene flow and 220 mutation) and tree populations have rarely, if ever, reached an optimum degree of adaptation to 221

  Comment citer ce document : Koskela, J. (Auteur de correspondance),Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 11cheaper to conserve tree populations in their natural habitat than under ex situ conditions. Finally, 238 larger population sizes can be managed in situ than ex situ. genetic diversity can be integrated into the management of both 243

  forest trees requires long-term commitment, planning and action. 306 Therefore, we identified several basic requirements for genetic conservation units of forest trees 307 (Table1). Firstly, each unit should have a designated status as a genetic conservation area, Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 14

  Comment citer ce document : Koskela, J. (Auteur de correspondance),Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 15

  447 4.2.3. Recommendations for the sizes of the dynamic conservation units of forest trees 448 Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 20

  , B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 21

  Comment citer ce document : Koskela, J. (Auteur de correspondance),Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 22 there are identical genotypes (clones) of such tree species present within a unit and take this into 497 consideration when estimating the number of reproducing genotypes. 498 499

Figure 1 .

 1 Figure 1. Illustration of the development process of the pan-European minimum requirements for 690

2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 6

, Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (

Biological Conservation (2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 8 local

  Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Version définitive du manuscrit publié dans / Final version of the manuscript published in : adaptation, genetic variation in adaptive traits is generally maintained at a high level within 166 tree populations

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Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L.,

Biological Conservation (2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 9

  Version définitive du manuscrit publié dans / Final version of the manuscript published in :

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		Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C.,
		Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L.,
		Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von
		Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into

2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 12

Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (the past. Genetic studies have shown that such human interventions have shaped the pattern of 261 genetic diversity in forest trees in Europe (e.g.

2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 13 285

Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (

2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 16

, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (

2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 18

, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (

2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 19 427 Franklin

Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (

2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 25

	Manuscrit d'auteur / Author manuscript
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Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (

2013), 157, 39-49, DOI : 10.1016/j.biocon.2012.07.023 Journal homepage: www.elsevier.com/locate/biocon 27

	Manuscrit d'auteur / Author manuscript
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, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady, B., De Cuyper, B., Heinze, B., von Wühlisch, G., Ducousso, A., Ditlevsen, B. (2013). Translating conservation genetics into Version définitive du manuscrit publié dans / Final version of the manuscript published in : Biological Conservation (

Finnish Forest Research Institute, Box 18, 01301 Vantaa, Finland (leena.yrjana@metla.fi)

Aristotle University of Thessaloniki, PO Box 238, 54124 Thessaloniki, Greece (alizotp@for.auth.gr)

been slow and partly neglected. Conservation of forest genetic diversity is still riddled with

problems, and complexities of national legal and administrative structures. Europe is an example

adaptation can develop rapidly, i.e. within one or a few generations[START_REF] Namkoong | Forest genetics and conservation in Europe[END_REF]. Despite of

Regulation (EC) No 870/2004 (EUFGIS action, Contract No AGRI-2006-0261) and the member

Comment citer ce document : Koskela, J. (Auteur de correspondance), Lefèvre, F., Schueler, S., Kraigher, H., Olrik, D. C., Hubert, J., Longauer, R., Bozzano, M., Yrjänä, L., Alizoti, P., Rotach, P., Vietto, L., Bordács, S., Myking, T., Eysteinsson, T., Souvannavong, O., Fady The minimum requirements have prompted various actions by European countries to improve the 665 management of their forest genetic resources and to better document their conservation units. 666

They have been particularly useful for countries with limited budgets and human resources 667 available for genetic conservation by focusing their efforts to key issues. In other countries, they 668 have increased collaboration between forest owners and managers, forest geneticists and the 669 broader biodiversity conservation community to explore whether existing protected areas or 670 production forests meet the minimum requirements and whether such areas can also obtain 671 designated status as genetic conservation units. There are a few countries which have no units 672 that meet the minimum requirements. The reason for this is usually missing designated status or a 673 management plan which includes genetic considerations. Therefore, the minimum requirements 674 have also been useful for pointing out these shortcomings to managers and policy makers.


Marcel Kuntz
email: kuntz@ujf-grenoble.fr

John Davison
email: jrndavison@gmail.com

Agnès E Ricroch

What the French ban of Bt MON810 maize means for science-based risk assessment

The French arguments presented in February 2008 were derived from a draft document of an official (although short-lived) scientific committee, of which most of its members subsequently rejected this interpretation 1 . To understand the reasons for governments to produce their own 'scientific' assessment, it is important to stress that, in Europe, GMOs are regulated by EU law and that a ban on GMO cultivation must have scientifically justifiable reasons. However, bans (now implemented by 9 European Member Another part of the EM document is on dissemination and persistence in soil or aquatic environments of the insecticidal protein produced by MON 810 (termed Cry1Ab).

However, no scientific publications are cited showing such an impact in nature. A 9-year study on Bt-maize cultivation in 4 different sites found that the Cry1Ab protein was not present in the soil in the spring of the following year [START_REF] Gruber | Determination of insecticidal Cry1Ab protein in soil collected in the final growing seasons of a nine-year field trial of Bt-maize MON810[END_REF] . This article was not cited in the EM document and neither was additional literature, including long term results from the USA (see Supplementary Information 2 for references).

Similarly, the invoked risk for non-target arthropods is allegedly substantiated by meta-analyses but none (not even the most recently cited) actually provides « new data » from field studies (that is to say, information or data not previously examined by EFSA). These meta-analyses (e.g. [START_REF] Naranjo | Impacts of Bt crops on non-target invertebrates and insecticide use patterns[END_REF] ) only point to the following phenomenon: when pest management is efficient (due to either pesticides or to Bt plants), an unavoidable effect is to reduce presence of arthropods that depend on the target host, either as predators or as parasitoids. Actually this effect is found mainly for a parasitoid which has not been reported in French fields.

Finally, it should be mentioned that many of the cited articles are laboratory studies (often worst-case scenarios) which, as is well accepted from the Monarch butterfly controversy [START_REF] Sears | Impact of Bt corn pollen on monarch butterfly populations: A risk assessment[END_REF] , cannot alone be used to infer a risk in a natural context.

In conclusion, the French EM document not only contains no new scientific evidence, It is significant that the French Biosafety Authority ('Haut Conseil des Biotechnologies', HCB) was not consulted on this EM. Consequently, the Chairman of the HCB wrote to the French Prime Minister expressing the "emotion" of the HCB members and their shock that "other expertise" was seemingly used for the preparation of the document and that the conclusions of previous HCB reports had been ignored. The Prime Minister did not reply. The actual authors of the EM document, as well as their scientific qualifications, if any, remain unknown; which transgresses scientific ethical norms.

Following the release of the EM document (whose purpose was to inform the EC, according to European law), a national ruling ('arrêté') was published on March 16, 2012 reimplementing a moratorium irrespective of the EC decision on the EM (again without consultation of HCB). This ruling includes a recent laboratory study claiming to observe a deleterious impact of Cry1Ab on ladybirds [START_REF] Hilbeck | A controversy re-visited: Is the coccinellid Adalia bipunctata adversely affected by Bt toxins?[END_REF] . The conclusions of this study are inconsistent with numerous other publications on this topic and with the meta-analyses cited in the EM document, and it has already been criticized (see [START_REF] Romeis | Putative effects of Cry1Ab to larvae of Adalia bipunctata -reply to Hilbeck et al[END_REF] ). EFSA has rejected the arguments presented by the French government [START_REF] Efsa | Scientific Opinion on a request from the European Commission related to the emergency measure notified by France on genetically modified maize MON 810 according to Article 34 of Regulation (EC) No 1829/2003[END_REF] .

The history of the bans in EU, cited here, documents a pattern of behaviour in which politicians cite and/or misuse scientific publications to suit their political desires. Risk analysis is divided into risk assessment and risk management. The former being an exclusively scientific process and is the domain of scientists and not politicians. Unlike risk perception, risk assessment, and science in general, is not a "social construct" (despite what the postmodern school of thought often claims 10 ): risk assessment is the implementation of the scientific method. Risk is a scientific term defined as risk = hazard x exposure to hazard.

In contrast, risk management may operate in a broader context: technological, political and It is a general trend that decisions for regulations specific to GM crops are getting increasingly non-science-based in the EU [START_REF] Morris | EU GM crop regulation: a road to resolution or a regulatory roundabout?[END_REF][START_REF] Ricroch | Is the German suspension of MON810 maize cultivation scientifically justified?[END_REF][START_REF] Davison | GM plants: science, politics and EC regulations[END_REF] . This trend would be amplified should Member States be given the possibility of banning GMO cultivation on their own territory without having to provide any scientific evidence relating to new risks, as proposed by the EC in 2010 [START_REF] Sabalza | EU legitimizes GM crop exclusion zones[END_REF] . Implications for such political decisions go far beyond GMOs.

EFSA is an independent scientific body founded in 2002 by the European Parliament and the Council of Europe following a proposition of the EC. The current burden of safety assessment of transgenic crops in Europe is probably too stringent [START_REF] Giddings | Confronting the Gordian Knot[END_REF] , and in a context dominated by the precautionary principle, EFSA's advice is certainly obligatory and necessary for risk-evaluation of GMOs. Nevertheless, EFSA is under constant politically motivated criticism from some environmentalist NGOs and EU Member States, including

France. GMO approvals must pass by the Council of Agricultural Ministers though this body has never been able to reach agreement with a qualified majority [START_REF] Davison | GM plants: science, politics and EC regulations[END_REF] . In such case, the decision reverts to the EC which usually agrees with the EFSA recommendations (although often with delays counted in years). This has caused antagonism towards EFSA, resulting in unjust accusations of being biased and in league with the biotechnology industry (see EFSA's response 15 ). Such accusations degrade the validity not only of EFSA opinions but of scientific risk assessment in general.

One may wonder why, after more than one year of such malpractice of scientific expertise, as is contained in the EM document, these events have not triggered wide criticisms.

Of course criticisms will not originate from the new French government which follows the

  agnes.ricroch@u-psud.fr Université Paris-Sud. CNRS. AgroParisTech. UMR 8079 Laboratoire d'Ecologie, Systématique et Evolution Bâtiment 360 91405 Orsay cedex France Telephone +33 (0)1 69 15 56 65 Fax +33 (0)1 69 15 46 97 *Correspondence to: agnes.ricroch@u-psud.fr In February 2012, the French government, at that time under Nicolas Sarkozy, sent a document called 'emergency measures' (EM; see Supplementary Information 1 for an English translation) to the European Commission (EC), supposedly providing new information on environmental risks of genetically modified (GM) MON810 maize varieties (MON810 is a trait developed by the Monsanto Company to control some Lepidoptera insects). The release of this document was followed by the publication in March 2012 of a national ruling prolonging the existing ban on their cultivation. This ban has not been discontinued by the new French government under François Hollande, who nonetheless cancelled many other actions of the Sarkozy government. The present commentary examines the EM document to analyze its scientific validity and consider the widespread implications for science-based risk assessment, since not only the French Government but also other European governments (i.e. Austria, Germany, Greece, Hungary, Luxembourg, and more recently Italy) invoked 'scientific' data to justify their own ban. Previously, in February 2008, the new elected President Sarkozy formally suspended the cultivation of the MON810 maize varieties on alleged data concerning the potential negative environmental impacts of these varieties. These hypothetical environmental impacts have always been rejected by EFSA (European Food Safety Authority), e.g. in its recommendation (June 2009) on the renewal of the approval for the cultivation of MON810 maize. It became clear that the French position was largely "biopolitical" posturing as part of a green-washing political move 1 . It stimulated the German government to follow a similar path: in April 2009 it formally suspended the cultivation of the MON810 maize varieties and justified this by citing alleged new data concerning potential negative environmental impacts. These claims were rejected by both a scientific publication 2 and the German Central Committee on Biological Safety (ZKBS) in July 2009. Like the French EM document (discussed below), the German document was produced by anonymous authors, bypassing the official biosafety national agency.

  States) on the commercial cultivation of EC-approved MON 810 maize had only political or economical motives. The French refusal of MON810 cultivation in 2008 was declared illegal in November 2011 by the highest judicial authority ('Conseil d'Etat') in France, following the deliberations of the European Court of Justice in September 2011. Not discouraged by adverse rulings in French and European law courts, Nathalie Kosciusko-Morizet (then Minister of Ecology), immediately decided on a prolongation of the prohibition of MON810 cultivation. Her Ministry was at the origin of the EM document released in February 20, 2012 (see Supplementary Information 1) which the Ministry of Agriculture submitted to the EC. This Comment citer ce document : Kuntz, M., Davison, J., Ricroch, A. E. (Auteur de correspondance) (2013). What the French ban of Bt MON810 maize means for science-based risk assessment . Nature Biotechnology, 31 (6), 498-500. DOI : 10.1038/nbt.2613 Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Manuscrit d'auteur / Author manuscript Version définitive du manuscrit publiée dans / Final version of the manuscript published in: Nature Biotechnology (2013), Vol. 31, N°.6, p. 498-500, DOI: 10.1038/nbt.2613, Journal homepage: http://www.nature.com/nbt/journal/v31/n6/full/nbt.2613.html text purportedly contains new and crucial scientific data regarding environmental risks, not previously examined by the EFSA GMO Panel. The invocation of environmental claims supposedly overlooked by the competent scientific authority, EFSA, has profound implications. Either these claims are true, which means the European risk evaluation system is faulty for not having identified them. Or they are false and this means that the French government (as well as others) is seeking to ban GMO cultivation by deliberately imagining new specious allegations when the previous ones have been rebutted. We have performed a point by point science-based analysis (see Supplementary Information 2) of the French EM document. Its first part presents EFSA's opinion (December 2011 3 ) as follows: « In contrast to their previous conclusions on Bt11 or on MON810, EFSA underlines […] the existence of environmental risks linked to the culture of these GMOs ». While, in reality, EFSA stated 3 : « The EFSA GMO Panel concludes that, subject to appropriate risk management measures, maize Bt11 [and MON810] cultivation is unlikely to raise additional safety concerns for the environment compared to conventional maize ».Two additional arguments found in the EM document, namely the possibility of appearance of resistance amongst pests targeted by MON 810 and of resurgence of minor pests (previously controlled by broad-spectrum insecticides), which can become major pests, are relevant to risk management and to integrated pest management strategies. This type of argument cannot be used to justify a ban, which needs to be based on an immediate and serious risk to the environment.

  but authentic scientific reports, including those of the EFSA GMO Panel, are distorted, misquoted and falsely interpreted. Other scientific articles (at least 8 since 2008) relevant to the subject and providing a different picture are ignored. On the most important points we have obtained direct supporting evidence from several authors of the cited scientific articles and from other experts in the field (see Supplementary Information 2).

Nature Biotechnology (2013), Vol. 31, N°.6, p. 498-500, DOI: 10.1038/nbt.2613, Journal homepage: http://www.nature.com/nbt/journal/v31/n6/full/nbt.2613.html legal

  Comment citer ce document : Kuntz, M., Davison, J.,Ricroch, A. E. (Auteur de correspondance) (2013). What the French ban of Bt MON810 maize means for science-based risk assessment . Nature Biotechnology, 31 (6), 498-500. DOI : 10.1038/nbt.2613 Version définitive du manuscrit publiée dans / Final version of the manuscript published in: means are used to control risks and alleviate them. What is criticized here is that governments interfere with science to justify their political handling of risk management and bypass European and national agencies in charge of risk assessment of biotechnology under the European directives. This behaviour seems to become the norm since the Italian government used a simple translation of the French EM in its justifications sent to the EC for its ban on April 4, 2013 11. The Italian government could not ignore that the French EM had already been rejected by EFSA almost one year previously. The new French ban was imposed only a few months before important political elections in spring 2012 (in which the government was defeated). Declarations to the press of the Minister of Ecology in February 2012 openly admitted that a national ruling will be imposed "in case of failure of the Commission to react" (that is to say that the Minister was disregarding, in advance, potential opinions by official EC bodies) in order to stop farmers planting GM maize this season.

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Comment citer ce document : Kuntz, M., Davison, J., Ricroch same anti-GMO policy. We propose that the silence of the media and of scientific institutions, etc. is, at least partially, attributable to the diffuse contemporary postmodern and relativist ideology that science is a "social construct", a particular "framing" of truth, and finally is simply an opinion, no better than any other opinion [START_REF] Kuntz | The post-modern assault on science[END_REF] . In such a context, those who insist on scientific truth will inevitably face accusations of 'positivism' or 'scientism' [START_REF] Kuntz | Why the postmodern attitude towards science should be denounced[END_REF] . It is a great contradiction of the EU policy, that it simultaneously defends a 'science-based' approach while, at the same time, it is stuck in a postmodern framing which denies that science can approach objective truths.

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The authors declare no competing financial interests.

Supplementary Information 1 Translation of the EM document

Supplementary Information 2

A point by point analysis of the arguments put forward by the French government on the 20th February 2012, for a case of emergency concerning maize MON 810