Gaëlle Kotbi

Gudule Kisempa Muyuala

Loïc Sauvee

L'exemple de l'avenir de la filière Betterave-Sucre de Picardie

Introduction

Dans un contexte de changement institutionnel et concurrentiel radical, faisant suite à la réforme de l'OCM Sucre en 2006, une profonde restructuration des filières betteraves européennes a été entamée et les territoires français de l'économie sucrière redessinés.

Compte tenu des prochaines échéances de politique agricole européenne attendues à compter de 2013, l'incertitude domine et les acteurs de la filière Betterave-Sucre Française poursuivent leurs efforts pour atteindre un niveau de compétitivité mondiale. Financé par le Conseil Régional de Picardie, le projet « Diagnostic Prospectif de la Filière Betteravière Picarde » (DiProBe) mené en partenariat avec l'Université Jules-Verne de Picardie de 2007 à 20111 avait pour but d'analyser et de comprendre les facteurs agissant sur la dynamique productive de la filière betteravière picarde, d'en proposer un diagnostic et d'élaborer des scénarios d'avenir. Cette dernière étape, sur laquelle nous nous proposons de concentrer la présentation, a donné lieu à la construction de trois scénarios à l'horizon 2020 en adaptant la méthode des scénarios de l'Ecole Française de Prospective. Après avoir explicité le contexte et la méthode appliquée, nous exposerons pas à pas la construction des trois scénarios. [START_REF] Godet | Manuel de prospective stratégique. L'art et la Méthode[END_REF] préconise une construction des scénarios en plusieurs étapes (cf. tableau ci-après). Véritable boîte à outils, cette méthode offre une souplesse d'utilisation ayant permis au groupe de recherche de tenir compte des spécificités du cas de la filière betterave-sucre picarde et de capitaliser les travaux menés durant tout le projet en sélectionnant les étapes et les outils méthodologiques en vue de la construction de scénarios.

Réflexion collective face aux mutations de l'environnement stratégique, la méthode des scénarios doit éclairer le décideur dans sa prise de décision en lui permettant de déceler les tendances lourdes, les zones d'incertitude majeures, les risques principaux de rupture, les défis auxquels il risque d'être exposé, ainsi que les stratégies qui pourraient être adoptées, leurs avantages et inconvénients respectifs [START_REF] Godet | Manuel de prospective stratégique. L'art et la Méthode[END_REF] . Sur la base de représentations matricielles construites à partir de l'observation du présent avec la participation active des différents acteurs, les scénarios proposent une image, à un horizon donné, du système étudié en fonction des hypothèses d'évolution de certaines variables clés. Etape 4 : Cette quatrième étape consistait à l'élaboration des hypothèses, les futurs possibles étant le résultat de différentes combinaisons des sous-systèmes. La méthode utilisée pour appréhender l'éventail des futurs possibles est l'analyse morphologique [START_REF] Ritchey | FRITZ ZWICKY,Morphologie and Policy Analysis[END_REF].

Elle vise à explorer de manière systématique les futurs possibles à partir de l'étude de toutes les combinaisons issues de la décomposition d'un système. La première phase d'application de cet outil est la construction de l'espace morphologique. Les variables clés et les enjeux identifiés associés aux objectifs dans l'étape précédente ont été regroupés en quatre soussystèmes dont les composantes8 sont les suivantes :

-Un Sous-système Institutionnel : le Cycle de Doha, la PAC, les réformes de l'OCM, les accords interprofessionnels ;

-Un Sous-système Production : les coûts de production, la législation nationale sur l'environnement, la réglementation nationale sur les OGM, le rendement de la betterave -Un Sous-système Socio-économique : le taux de syndicalisation, l'évolution des comportements alimentaires, les politiques nationales de santé publique, le nombre et l'organisation des acteurs de la filière, les niveaux de profit des acteurs de la filière.

-Un Sous-système Technico-économique : les politiques relatives aux biocarburants, les politiques industrielles régionales, les droits de douanes, l'utilisation du sucre dans l'IAA, le contexte économique français, la valorisation des coproduits.

Etant donné le poids et l'influence des variables réglementaires, le Groupe de Recherche a fait le choix de construire les scénarios d'évolution de la filière betterave-sucre de Picardie à travers le sous-système institutionnel (cf. tableau 3).

Tableau 3 : Présentation des composantes retenues et des hypothèses associées Avec les 16 hypothèses associées à ces 4 composantes, plusieurs combinaisons sont possibles.

Il faut donc ensuite réduire l'espace morphologique.

Etape 5 : Cette étape consiste à probabiliser les scénarios. Le but est de conduire l'expert à révéler le niveau de cohérence de son raisonnement [START_REF] Godet | Manuel de prospective stratégique. L'art et la Méthode[END_REF]. Le principal critère de choix de ces combinaisons a été la possibilité de susciter la réflexion collective sur l'avenir de la filière. Vient ensuite la rédaction des scénarios. D'après les résultats des ateliers de travail avec les acteurs auxquels quatre scénarios ont été présentés, trois scénarios ont été retenus (cf. tableau 4 ci-après). Ces trois scénarios présentent trois situations différentes. Le scénario 'tendanciel' décrit une situation de relatif statu quo ; le scénario 'politique agricole environnementale' représenterait une alternative pour éviter le scénario 'marché libre et concurrentiel' qui peut être considéré comme la situation de libéralisation totale.

Conclusion

Permettant une approche globale mariant le quantitatif et le qualitatif, la formulation en « boîte à outils » de cette méthode de prospective stratégique facilite sa mise en oeuvre en fonction de différentes contraintes d'organisation, de budget et de temps, ce qui permet une facilité d'appropriation pour une prospective territoriale appliquée ici à une filière dominante des territoires agricoles picards.

2.

  Contexte et méthode de Diagnostic Prospectif de la filière Betteravière Picarde Jusqu'au milieu des années 2000, l'Organisation Commune de Marché du sucre (OCM Sucre) européenne, mise en place à la fin des années 1960, était réglementée par un système de quotas. Ce système avait pour corollaire la fixation d'un prix annuel du sucrequota et d'un prix hors quota. Dans un contexte européen de stabilité de la consommation annuelle totale long terme mais aussi de la production annuelle totale, les fabricants industriels français de sucre se partageaient le marché sans plus de concurrence qu'une « compétition entre les équipes marketing et commerciales qui verse davantage dans l'émulation que dans la véritable concurrence » 2 . Du fait du maintien d'un prix européen à plus de 600€ la tonne (très au dessus du prix mondial de marché aux environs de 250-300€ la tonne), et compte tenu de la surproduction mondiale de sucre ainsi auto-entretenue, le volet Sucre de la Politique Agricole Commune Européenne est réformé en 2006 3 et 2007 4 dans le but de conduire au rétablissement du prix d'équilibre et à une meilleure gestion des quantités. Promouvant l'abandon des quotas par les planteurs et la réduction d'activité des transformateurs via des mesures d'aide, 75 des 180 sites industriels sucriers européens sont fermés 5 et l'Union Européenne passe d'une position exportatrice nette de sucre à une position d'importatrice. Ce changement institutionnel et concurrentiel a impliqué pour les principaux acteurs de la filière une réponse immédiate sous peine de disparaître. Historiquement ancrés dans les bassins d'approvisionnement et de production situés à 80% au Nord de la Loire et en premier lieu en Picardie (37% de la SAU cultivée en betterave en France à elle seule, 22% des établissements dédiés à la fabrication de sucre et 26% des effectifs salariés 6 ), la filière betterave-sucre française a non seulement dû adapter ses structures productives mais aussi initier les voies de développement pour une compétitivité désormais mondiale. Les prochaines échéances annoncées à partir de 2013 permettront de sanctionner le succès ou l'échec des choix stratégiques des différents acteurs lors de cette réforme mais seront également déterminantes du réaménagement des territoires betteraviers picards et français. Les parties prenantes de la filière picarde dont le Conseil Régional de Picardie, participent directement à l'élaboration des programmes d'action venant soutenir et favoriser les progrès technico-économiques de la filière (cf. structuration de la filière figure 1 ci-après) en termes d'innovation et de compétitivité. 2 Propos issus d'un des entretiens menés auprès de directeurs de sucrerie en février 2008. 3 Règlement européen n°318/2006 du 20/02/2006. 4 Règlement européen n°1182/2007 du 26/09/2007. 5 Données CEFS, 2009. 6 Données XERFI, 2009.

Figure 1 :

 1 Figure 1 : Structuration de la filière betterave-sucre française

Figure 2 :

 2 Figure 2 : Méthodologie du projet DiProBe

  Véritable boîte à outils ou boîte à méthodes pour chaque étape de la construction, cette méthode des scénarios a le mérite de proposer une souplesse et une adaptabilité à tout secteur d'activité et tout niveau de réflexion spatiale(local, national, international), ce qui a autorisé le groupe de recherche à échafauder des scénarios d'évolution de la filière à l'horizon 2020 avec -malgré-les spécificités fortes de la filière explicitées dans la première partie de cette communication. Cette approche insiste également sur les interactions et rapports de force entre les acteurs, clé de voûte du redécoupage des territoires betteraviers français faisant suite à la réforme (cf. la disparition de territoires betteraviers entiers dans le centre de la France). Systémique, elle présente enfin l'avantage d'impliquer la participation des acteurs eux-mêmes à la construction des scénarios et de permettre ainsi une réflexion collective entre différents acteurs qui partagent le même intérêt pour le sujet abordé, de créer ainsi une intelligence territoriale et une dynamique collective. Bibliographie AGRESTE. (2009, Décembre ). « La Picardie est la première région betteravière de France ». les feuilles de liaisons n°32 . ARCADE, J., GODET, M., MEUNIER, F. & ROUBELAT, F. (2003). « Structural analysis with the MICMAC Method & Actor's strategy with MACTOR Method". in J. C.GLENN, & T. J.GORDON, Futures Research Methodology. Washington .

  Tableau 1 : Méthodologie de construction des scénarios mise en oeuvre7 La prochaine réforme de l'OCM Sucre en 2014 sera fortement influencée par la réforme de la PAC de 2013 elle-même en partie influencée par le Cycle de Doha. L'UE en tant que membre de l'OMC s'est en effet engagée dans le Cycle de Doha visant la suppression des restrictions d'accès et des distorsions de marché. Depuis son lancement en 2001, les quotas et du prix minimum est en train de se fissurer. La suppression des quotas et du prix minimum entraîneraient en effet une modification du rapport des forces entre les planteurs de betteraves et les fabricants de sucre. Pour les fabricants de sucre, supprimer les quotas et le prix minimum pourrait se traduire par une augmentation des exportations et une possibilité plus étendue de négocier le prix de la betterave alors que pour les planteurs de betterave, la suppression des quotas et du prix minimum représenterait une baisse du niveau de revenus et une perte de débouchés. Ceci est renforcé par le fait que, depuis 2009, les pays de l'Afrique Caraïbes Pacifique (ACP) peuvent exporter dans l'UE sans limitation de quantité. Compte tenu de ces trois politiques, la protection des intérêts des planteurs par la Confédération Générale des Betteraviers (CGB) qui regroupe près de 90% des planteurs Les dispositions de cette contractualisation permettraient en effet aux agriculteurs de peser davantage dans la fixation du prix avec les industriels. La réalisation ou non de cet objectif est par exemple une hypothèse d'évolution à retenir pour la construction des scénarios. C'est le cas aussi de tous les objectifs identifiés à partir des enjeux de la filière. La réduction des aides de la PAC 8. Le renforcement de la prise en compte des critères environnementaux et alimentaires dans les modalités de la distribution des aides de la PAC Les accords interprofessionnels 9. La fixation bi partite du prix de la betterave hors quota 10. La non-validité de la contractualisation agricole (LMA) Les politiques de Santé Publiques 11. Le renforcement des critères de conditionnalité sur la santé et la production végétale (paquet hygiène) 12. La réduction de la consommation du sucre et des produits sucrés

	multiplication matricielle appliqué à la matrice structurelle qui permet d'étudier la diffusion
	des impacts par les chemins et les boucles de rétroaction et par conséquent de hiérarchiser les
	variables. Le principe de MICMAC s'appuie sur les propriétés classiques des matrices
	booléennes.
	Etapes En partant d'un répertoire de quatre-vingt quatorze variables identifiées grâce au Objectifs Outils Outils utilisés Résultats obtenus Tableau 2 : Enjeux et Objectifs associés
			proposés
	Etape 1. modèle PESTEL qui « repartit les influences environnementales en six grandes catégories : Définir le Ateliers Enquêtes Limite temporelle : Enjeux Objectifs associés
	Se poser les bonnes Le développement du politiques, économiques, socioculturelles, technologiques, écologiques et légales. » (Johnson, périmètre de l'étude prospectifs menées dans les phases 1 et 2 du Horizon 2020 Limite 1. La promotion du bioéthanol (taux d'incorporation, campagnes bioéthanol publicitaires, soutien de l'ADEME,….)
	questions. Scholes, Whittington, & Fréry, 2008), une liste de vingt-trois variables clés a été obtenue et projet + actualisation des géographique : Filière betterave-2. La mise en place des mesures de soutien au bioéthanol (droits de douane élevés, subventions, politiques d'investissement …)
	données Adaptation de la 3. La suppression des quotas de production en Europe sucre française Mettre en MICMAC 23 variables clés retenue. En les classant ensuite par ordre d'influence croissante grâce à la synthèse des Etape 2. Les quotas sucriers 4. La suppression du prix minimum
	Identifier les matrices influence/dépendance, sept variables dont l'influence totale est ≥ à 100 ressortent. évidence les méthode L'ouverture du marché 5. La suppression de la clause de sauvegarde
	européen	variables clés	variables clés 6. La poursuite de l'ouverture du marché européen. MICMAC
	Etape 3. Analyser les stratégies d'acteurs. La Politique Agricole Commune Européenne	Déceler les alliances et les conflits futurs entre les acteurs 7. (PNNS) MACTOR	Monographies des groupes industriels sucriers, Entretiens non directifs, Revue de presse et recherche bibliographique,	Acteurs dominants : planteurs de betteraves et fabricants de sucre 8 enjeux + 18 objectifs associées
	Etape 4. Le respect de	Identifier les 13. La réduction de l'utilisation des produits phytosanitaires (Plan Ecophyto MORPHOL Adaptation de la 4 sous-systèmes
	Balayer les l'environnement	composantes 2018)	méthode
		futurs possibles	des scénarios 14. La réduction de la Tare terre MORPHOL
	Etape 5. Le niveau de compétitivité	Identifier les 15. L'autorisation de la culture des OGM SMIC-PROB-Construction	1 sous-système
		« Probabiliser »	scénarios 16. Le rendement de la betterave EXPERT collective avec	12 hypothèses
		les scénarios	probables et pertinents 17. La valorisation des coproduits les parties prenantes 18. La réduction des dépenses en énergie (PPE) 3 scénarios
	les deux premières phases du projet, la participation active d'acteurs représentatifs des
	différentes parties prenantes, dont la CGB et les groupes industriels, à la construction de
	chacune des étapes de la méthode des scénarios ensuite, puis l'explicitation des points de vue
	compromis sont difficiles à trouver : l'UE fait valoir ses efforts d'ouverture à travers défendus au groupe de recherche enfin, ont permis de valider pas à pas la réflexion.
	Godet et J.C Duperrin au CEA entre 1972 et 1974 (Arcade, Godet, Meunier, & Roubelat, différents accords de Libre-échange alors que les Etats-Unis l'accusent d'utiliser des produits Compte tenu des intérêts défendus par les parties prenantes de la filière, les enjeux
	2003) permet d'identifier les variables clés à étudier en priorité une fois que la liste exhaustive sensibles afin de contrebalancer le niveau d'accès aux nouveaux marchés qu'elle offrait (UE, relatifs aux variables clés ainsi que les objectifs qui leur sont associés peuvent être synthétisés
	des variables à prendre en compte est établie. La méthode MICMAC est un programme de 2006). L'autre point de discorde concerne les subventions, plus particulièrement la PAC. Les comme suit (tableau 2 ci-après). Certains objectifs sont soutenus conjointement par les

Les travaux et enquêtes préalables ayant rempli le rôle d'ateliers prospectifs en permettant de délimiter le champ, de définir le problème et l'horizon de l'étude, la question posée à l'issue de la première étape était : quel est l'avenir de la filière betterave-sucre française à l'horizon 2020 ? Les prochaines échéances de politiques européennes d'une part, le poids et la place des territoires picards dans la France betteravière d'autre part, expliquent ce choix par le groupe. Lors de la deuxième étape, la recherche des variables clés par la méthode MICMAC (Matrice d'Impacts Croisés-Multiplications Appliquée à un Classement) mise au point par M. Parmi celles-ci, les trois premières relèvent des Politiques Agricoles. Elles peuvent être considérées comme des variables structurant la filière. L'importance de l'OCM Sucre est nettement mise en évidence avec une influence totale estimée à 201, alors que l'influence totale de la PAC est estimée à 132. Dans un contexte de demande mondiale croissante (Chine et Inde notamment) et après la réforme de 2006 matérialisée par la baisse de quotas et du prix minimum, le solde commercial de sucre brut de l'Union Européenne est devenu négatif. Le marché reste dominé par le Brésil qui a produit sur la campagne 2008-2009 37,5 millions de tonnes de sucre brut contre 16,58 tonnes pour l'U.E 27. Les exportations du Brésil ont ainsi atteint 25,3 millions de tonnes de sucre brut, très loin devant la Thaïlande, deuxième exportateur mondial pour l'année 2008/2009 avec 5,5 millions de tonnes. La baisse des quotas européens et du prix minimum explique l'essentiel des fermetures d'usines en Europe et l'abandon de la culture de betterave dans certains pays peu compétitifs tels que l'Irlande, le Portugal, la Bulgarie, la Lettonie et la Slovénie. évolutions du Cycle de Doha auront donc des conséquences sur la PAC mais aussi sur l'OCM sucre. Les quotas sucriers et le prix minimum voient par ailleurs leur maintien menacé d'autant que la position unitaire des planteurs de betteraves et des fabricants de sucre pour la défense des français consiste à négocier le maintien du niveau de protectionnisme de l'Union Européenne en limitant l'ouverture du marché à travers entre autres les quotas sucriers et le prix minimum de l'OCM Sucre ainsi que le maintien de l'interventionnisme via les aides de la PAC. Etape 3 : La méthode MACTOR (Matrice, Acteurs, Objectifs, Rapport de force) a été conçue en 1975 par Michel Godet et François Bourse et développée 1990 avec Francis

Meunier

[START_REF] Chapuy | Sécurité alimentaire et Environnement. Analyse du Jeu des acteurs par la methode MACTOR[END_REF]

. Elle permet d'identifier les acteurs qui commandent les variables clés mais aussi d'identifier les principaux enjeux du futur. Dans le cas de la filière betterave-sucre, les jeux de pouvoir sont polarisés autour de trois types d'acteurs : les planteurs, regroupés au sein de la CGB, quatre groupes industriels et les acteurs institutionnels. Les travaux monographiques menés lors de la deuxième phase du projet (cf. figure 2 supra) ont permis de comprendre les principaux points de convergence et de divergence des acteurs ainsi que les modes de coordination et les conventions en place au sein des filières françaises et européennes. Les enquêtes qualitatives et quantitatives menées dans planteurs de betteraves et les fabricants de sucre, à l'image de la promotion des biocarburants qui représentent une opportunité pour le bioéthanol de betterave. D'autres objectifs, tels que la contractualisation proposée par la Loi de Modernisation Agricole (LMA), les opposent.

  Tableau 4 : Synoptique des trois scénarios

			Scénario tendanciel	Scénario « une politique	Scénario « Marché Libre et
				agricole environnementale	concurrentiel »
				pour tous »
			-Accord sur l'ouverture des échanges	-Accord sur l'ouverture des	-Accord sur l'ouverture des
			à Doha	échanges à Doha	échanges à Doha
			-Baisse tendancielle du budget de la	-Reconduction du budget de la	-Forte baisse du budget de la
	Hypothèses		PAC -Renforcement des critères environnementaux dans la distribution des aides de la PAC -Maintien des quotas sucriers au	PAC -Renforcement des critères environnementaux dans la distribution des aides de la PAC	PAC -Renforcement des critères environnementaux dans la distribution des aides de la PAC
			niveau actuel	-Baisse de la quantité des	-Baisse de la quantité des
			-Maintien du prix minimum au	quotas sucriers	quotas sucriers
			niveau actuel	-Baisse du prix minimum	-Baisse du prix minimum
			-Volatilité du prix mondial du sucre	-Volatilité du prix mondial du	-Volatilité du prix mondial
			-Domination du Brésil	sucre	du sucre
	Conséquences possibles		-Développement des partenariats de R&D -Augmentation des coûts de production du sucre en Europe -Diminution de l'activité en Europe l'interprofession -Légitimité renforcée de	-Domination du Brésil -Développement des partenariats de R&D -Développement des biocarburants production -Soutien de l'UE pour développer l'agriculture -Augmentation du coût de	-Marché mondial fortement concurrentiel -Baisse des revenus -Baisse de la production -Développement des aides régionaux et nationaux
				raisonnée
				-Interprofession fragilisée
	Image	finale	Une filière betterave-sucre de moins en moins compétitive à l'international	Une filière betterave-sucre à l'international pérenne et moins compétitive	Une filière betterave-sucre qui risque de disparaitre
			Ce scénario reprend la situation	Ce scénario reprend les	Ce scénario suppose un
			actuelle avec le renforcement de	souhaits de la commission	désengagement presque total
			critères environnementaux et la	européenne sur la prise en	de l'Union Européenne. Sa
	Probabilité		baisse de la PAC qui influent sur la compétitivité de la filière au niveau international. Sa probabilité de réalisation est faible par rapport aux deux scénarios en raison des	compte des considérations climatiques, écologiques et alimentaires dans la réforme de la PAC. Ce qui laisse penser que c'est	probabilité de réalisation reste faible en raison de l'implication forte de certains Etats Membres dans la défense de
			modifications de l'OCM sucre.	le scénario le plus probable	l'interventionnisme de l'UE
				des trois.	et particulièrement de la
					PAC.

Les auteurs remercient le Conseil Régional de Picardie, les acteurs de la filière qui ont accepté de collaborer avec le groupe de recherche ainsi que Lily Horcholle, Delphine Loze, Hadrien Piot et Aurore Vernet, étudiants de master qui ont participé à l'élaboration et l'administration des différentes enquêtes. Les auteurs restent néanmoins et bien entendu seuls responsables des interprétations et opinions défendues dans cette communication.

Une méthode en cinq étapes a été mise en oeuvre, une sixième étape est préconisée par Michel Godet afin que soient conçus les plans d'actions. L'adaptation de la méthode à la demande du Conseil Régional supposait de s'arrêter à la cinquième étape. Néanmoins la journée d'études qui réunit cinquante professionnels de la filière en février 2011 permit une réflexion et un travail collectifs préparatoires à la décision.

Ces composantes sont les reformulations et/ou les regroupements de certaines variables et/ou objectifs associés aux enjeux.


domain: sde sdu

text:
Jean-François Doussin
email: jean-francois.doussin@lisa.u-pec.fr

Paolo Prati

Piero Lionello

J.-F Doussin

The Mediterranean Region Under Anthropogenic Pressures

. Evidence has been found of an organized society structured as an extension of the Neolithic trend, from as early as the 8th millennium BC, with the rise of proto-urban centers on the Eastern shore (Langer 1972). While sometimes presented as a sea that separates Europe from Africa, the Mediterranean Sea has, on the contrary, mostly been a sea that relates and unites three continents, namely Europe, Asia, and Africa, a superhighway allowing the transportation of goods, technologies, and ideas. Since millennia, its shores have been an area of settlements and development.

Population, Density, and Urban Area

Nowadays, the Mediterranean basin is surrounded by 22 countries, which together share a coastline of 46,000 km. These coasts are home to ca. 400 million people (UNEP/MAP Plan Bleu 2009) living across three continents: Africa, Asia, and Europe. It is still one of the world's busiest shipping routes, with about one-third of the world's total merchant shipping crossing the sea each year.

The total population of the Mediterranean countries grew from 281 million in 1970 to 419 million in 2000 and from 472 million in 2010 to 521 million in 2020 (United Nations 2019). The population is predicted to reach 572 million by 2030. Approximately one-third of the Mediterranean population is concentrated along its coastal regions, whereas more than half of the population resides in the coastal hydrological basins (Fig. 1). Based on the United Nations world population prospect and national population census, the population of the coastal areas grew from about 100 million in 1980 to 150 million in 2005, and it could reach 200 million by 2030 (United Nations 2017). The concentration of population in coastal zones is the highest on the western shore of the Adriatic Sea, the Middle East shore, and the Nile Delta. Overall, the population density in the coastal zone is higher in the southern Mediterranean countries. While the population share in the northern coastal area was 59% in 1970, a demographic transition is in progress, and the southern coastal area is expected to represent more than 62% in 2030 [START_REF] Matteudi | Demographic transition in the Mediterranean: between rising risks and the necessary adaptations of humanitarian practices[END_REF]. Interestingly, this is also where the variability of the population density in the coastal zone is highest, ranging from more than 1000 people km -2 in the Nile Delta to fewer than 20 people km -2 along parts of coastal Libya.

While the population in the north is almost stagnant, one observes a strong population growth in the southeast resulting in overexploitation of water, marine, and land resources, and also leading to increasingly problematic air quality issues in cities (EAA 2015). The southern and eastern countries of the Mediterranean are AU2 Fig. 1 Major urban areas and cities larger than 100,000 inhabitants. Circles: city data from JRC/ GHS Urban Center Database 2015 (see [START_REF] Florczyk | Description of the GHS Urban Centre Database 2015, Public Release 2019[END_REF]) superimposed over population density across the Mediterranean basin. (Data: Global Human Settlement Layer produced by the European Commission JRC and the CIESIN Columbia University, https://ghsl.jrc.ec.europa.eu/. Cartography: D Smith CASA UCL, https://luminocity3d.org/) Fig. 2 The urban population growth in the Mediterranean area from 1960 to 2011. European Union Mediterranean Group: Cyprus, Spain, France, Greece, Croatia, Italy, Monaco, Malta, and Slovenia; western Balkans and Turkey Group: Albania, Bosnia and Herzegovina, Montenegro, and Turkey; European Neighbourhood Policy (ENP) South Group: Algeria, Egypt, Israel, Jordan, Lebanon, Libya, Morocco, Palestine, Syria, and Tunisia. (Figure provided by the European Environment Agency data visualization system based on data from the Mediterranean strategy for sustainable development follow-up provided by UNEP/MAP Plan Bleu; https://www.eea.europa. eu/ds_resolveuid/B054CPK1NW) rapidly urbanizing (Fig. 2), with almost all of the future population growth projected to be in the cities-while urbanization rates in the north are quasi-constant at moderate values. Coastal areas historically rich in natural resources are now providing opportunities for economic activities such as tourism, oil and gas extraction, and maritime transport that tend to be located in these areas (EEA 2015). As a consequence, around 40% of the total coastal zone is estimated to be under some form of artificial land cover (concrete, asphalt…). Close to 100% of the population in the coastal region resides in urban localities. The Mediterranean catchment area includes 39 cities or agglomerations that are expected to be over one million inhabitants in 2030, and already more than 200 cities are larger than 100,000 people (see Fig. 1). The issue is further amplified by the increase in the fraction of urban population. Hence the urbanization phenomenon is not only due to the general increase of the population but also to a concentration process in cities and mega-cities. Mediterranean coastal areas are threatened by coastal development that modifies the coastline through the construction of buildings and infrastructure needed to sustain residential, tourism, commercial, and transport activities. Coastal man-made infrastructures can damage landscapes in the long term, habitats and biodiversity, and shoreline configuration by disrupting sediment transport. These densely urbanized areas are also intense emission "point sources" for atmospheric pollutants that tend to accumulate and react over the basin atmosphere (see Giorgi and Raffaele this volume; Dayan this volume).

Industry

When considering the impact of human activity on the atmosphere, large industrial installations fall upon the primary sources to be considered. While being quasipoint sources at the regional scale, their intensity often allows them to affect atmospheric composition at a very large scale.

Being both densely populated areas and the terminal of many marine routes, the Mediterranean coastal regions include several large industrial sites that often gather over a few square-kilometers installations from the chemistry sector, oil and gas terminal, power production, steel production, cement production… (e.g., Fos-Berre area near Marseille in France, Genoa area or Taranto in Italy, or Cairo in Egypt; Fig. 3). The western Mediterranean basin is especially concerned by these high industrial emission areas. These activities often involve combustion processes and emitting CO, CO 2 , NO x , unburnt volatile organic species, and combustion particles, but they also involve direct emission of hydrocarbons (HC) from tank leakages. www.carbonbrief.org, www.industryabout.com, www.powerplantmaps.com) Some of these industries also involve releases of chemical compounds (HC, NOx, SO 2 , or CO 2 ) produced in their processes.

As the formation of secondary atmospheric pollutants such as ozone, photooxidants, and secondary organic aerosol (SOA) is extremely sensitive to the NO x /HC ratio, the dual nature of the industrial emission has diverse effects at diverse scales. Locally, where the ozone and photooxidants production is generally limited by the availability of volatile organic compounds (VOCs), the VOCs that they emit allow a sustained high efficiency of secondary pollutants production in the atmosphere. For example, in the Fos-Berre region near Marseille, France, where lies a very large industrial complex, a record ozone rate production has been recorded: the study of [START_REF] Lasry | An insight into the formation of severe ozone episodes: modeling the 21/03/01 event in the ESCOMPTE region[END_REF] reports an unforeseen ozone episode in the outflow of the Fos-Berre industrial area where concentration as high as 450 μg m -3 and ozone production rates larger than 130 μg m -3 h -1 . They demonstrate that it could be attributed to the combination of breeze dynamics and industrial release of reactive VOCs such as acetylene. At the regional scale, particularly offshore, ozone production is generally NO x limited. The NO x emission by these large industrial sites contributes to the general nitrogen oxide burden and hence to large-scale atmospheric chemistry.

Industrial activities also induce direct emission of semi-volatile persistent organic pollutants (POP) (e.g., [START_REF] Esposito | Dioxins from industrial emissions to the environment: The Taranto case study[END_REF] as well as heavy metals, which are found both in the airborne particulate matter and in the sediments [START_REF] Trifuoggi | Distribution and enrichment of trace metals in surface marine sediments in the Gulf of Pozzuoli and off the coast of the brownfield metallurgical site of Ilva of Bagnoli (Campania, Italy)[END_REF]. Further, both the refinery and cement industry often involve large SO 2 emissions that will later contribute to the secondary sulfate aerosol formation and fine particulate burden [START_REF] Esposito | Dioxins from industrial emissions to the environment: The Taranto case study[END_REF].

Ship Traffic

While being highly interlinked with industrial activities, ship traffic delivering freight and raw material has a specific impact on the Mediterranean atmosphere due to the distributed nature of its emissions and the weak regulation of ship emissions in international waters. In a quite deleterious way, they worsen the effect of industrial areas and megacities by emitting reactive species in a relatively pristine area: the offshore marine atmosphere.

Being a route for exchanges of manufactured products between Europe and Asia through the Suez Canal and for the supply of gas and oil to Europe from the Gulf countries, the Mediterranean Sea is amongst the world's busiest waterways [START_REF] Piante | Blue growth in the Mediterranean Sea: the challenge of good environmental Status, Rept. Project MedTrends[END_REF]. Intra-Mediterranean fluxes illustrated in Fig. 4 account for less than a quarter of the total Mediterranean maritime traffic (REMPEC 2008) that is largely dominated by international fluxes. Following a general global trend, vessel activity in the Mediterranean Sea has recorded a rise of 58% in transit capacity, combined with an increased size of vessels by 30% between 1997 and 2014 (UNEP/MAP-Plan Bleu 2014). It is expected that shipping in the Mediterranean basins will increase in the coming years, both in the number of routes and traffic intensity. Maritime traffic towards and from EU Mediterranean ports will be influenced by the The Mediterranean Region Under Anthropogenic Pressures doubling of the Suez Canal that will allow a proportional traffic increase, but also by key drivers such as weak oil refining capacity outlook for Europe, a changing energy mix, the global demand for Liquified Natural Gas (LNG) as a fuel for maritime shipping, etc. (UNEP/MAP-Plan Bleu 2014).

Fortunately, the Mediterranean Sea is not totally without regulation with respect to atmospheric ship emissions. In 1997, the International Marine Organisation (IMO) through its Marine Pollution Convention (MARPOL) has defined various emission limit values for atmospheric pollutants emitted by shipping activities and forbidden releases of substances likely to affect the stratospheric ozone layer. In October 2016, IMO decided to lower the global sulfur limit in marine fuels to 0.5% by 2020.

The impact of ship emissions on the Mediterranean atmosphere is discussed in a recent study aiming to evaluate the feasibility of emission control over the Mediterranean Sea [START_REF] Rouïl | ECAMED: a Technical Feasibility Study for the Implementation of an Emission Control Area (ECA) in the Mediterranean Sea, synthesis report[END_REF]. Indeed, as Appendix 3 of Annex VI of the MARPOL Convention gives the possibility to define Emission Control Areas (ECA) where sulfur oxides (SO x ) and nitrogen oxides (NO x ) emitted by maritime traffic should be reduced, they consider the benefit of implementing even stricter emission control over the Mediterranean Sea. Their findings demonstrate that controlling ship emission alone, by further reducing the sulfur content of fuels and equipping ship engines with depolluting devices compliant with TIER III cleaner technologies (Wik and Niemi 2016), would lead to a substantial air pollutant concentration reduction. Through a careful ship emission inventory and an advanced modeling approach, they calculated that such a regulation would lead to a reduction by up to 11% in annual average fine particulate matter (PM 2.5 ) concentration, 70% in nitrogen dioxide (NO 2 ), and 11% in ozone (O 3 ) over the coastal areas. [START_REF] Rouïl | ECAMED: a Technical Feasibility Study for the Implementation of an Emission Control Area (ECA) in the Mediterranean Sea, synthesis report[END_REF] conclude that such a regulation would avoid over 6200 premature deaths per year, mainly in Italy, Algeria, Egypt, and Greece. Being limited to coastal areas, these results are relevant to air quality but do not allow further evaluation of these emission impacts on the regional climate (see the two other Chapters of this book by [START_REF] Mallet | Aerosol and ozone direct radiative impact[END_REF] and [START_REF] Nabat | Aerosol-cloud interactions and impact on regional climate[END_REF] for interactions between air pollution and regional climate).

Off-Shore Gas and Oil Production

Among the potential sources of atmospheric pollution located away from the seashore, one must cite offshore extraction of fossil fuels even if, so far, the Mediterranean region has been a relatively small producer of offshore oil and gas. Total offshore oil and gas production in the Mediterranean region was estimated in 2011 at 87 million tons of oil equivalent (TOE), including 19 million TOE for crude oil and 68 million TOE for natural gas. Nevertheless, the oil and gas industry is clearly looking at offshore developments as they represent 9400 million TOE, equivalent to 4.6% of world oil reserves [START_REF] Piante | Blue growth in the Mediterranean Sea: the challenge of good environmental Status, Rept. Project MedTrends[END_REF].

Until 2011, 94% of Mediterranean offshore oil reserves were held by Libya, Algeria, and Egypt, and only very limited quantities were available in EU Mediterranean countries (UNEP/MAP-Plan Bleu 2014). Italy operates approximately 100 offshore installations, mainly for gas extraction and exploration. These facilities are located in the Adriatic Sea, the Ionian Sea, and the Sicily Channel. Spain also has two installations in the Mediterranean Sea (EMSA 2014). Until 2015, no active offshore installations were reported by the Cypriot, French, Maltese, and Slovenian sectors, but this situation is rapidly changing. In Greece, the average production of 2014 was 75,900 TOE of crude oil and 4870 TOE of natural gas. Since then, a new investment program has been implemented in order to increase the current crude oil annual production up to one million TOE. To this end, the Greek authorities have leased new blocks in western Greece: one onshore in Ioannina and two offshore in the Gulf of Patraikos and in Katakolon (January 2015). They also invited applications for bids for 20 blocks in the Ionian Sea and south of Crete (July 2015) [START_REF] Papailias | Atmospheric emissions from oil and gas extraction and production in Greece[END_REF].

For several years, the far eastern basin (in particular, Cyprus and Israel coasts) has been the subject of an intense investigation to identify potentially hydrocarbonrich off-shore areas (Deloitte 2018). In addition to Libya, Algeria, and Egypt, offshore oil and gas activities also take place in the waters of other North African states and the non-EU Member States around the Mediterranean Sea, such as Israel and Tunisia. In March 2013, production started at the Israeli offshore Tamar gas field, the first ultradeep field (below 1500-m depth) in the Mediterranean. In the last 15 years, oil production has remained relatively stable, whereas gas production has steadily increased with a doubling of gas production in the Mediterranean region between 2000 and 2009 [START_REF] Papathanassiou | Preliminary identification of pressures of the coastal seas in socioeconomic terms. Gap analysis on data and knowledge[END_REF]. With respect to the atmospheric environment, the consequences of such development lie in the multiplication of sources from "controlled" burns at extraction platforms, which emit both NO x and unburnt VOCs, as well as soot and SO 2 leading after oxidation to sulfate particles [START_REF] Papailias | Atmospheric emissions from oil and gas extraction and production in Greece[END_REF]. Indirectly, this also implies the development of additional ship traffic.

Tourism

According to EEA (2016), the Mediterranean Sea attracts millions of visitors every year. It is the world's leading tourism destination as it accounts for about one-third of all global tourism. In 2014, it accounted for more than 300 million international tourist arrivals, to which domestic tourism must be added. International tourist arrivals have grown from 58 million in 1970 to nearly 314 million in 2014, with a forecast of 500 million by 2030. About 50% of these arrivals are in coastal areas. Tourism is a major pillar of Mediterranean economies, offering consistent employment (11.5% of total employment in 2014) and economic growth (11.3% of regional GDP). In the Mediterranean basin, tourism is vital for many countries: considering exclusively the coastal areas' economy, tourism represents over 70% in terms of production value and gross value added. It is a major pillar of several countries' economies, such as Spain, Italy, Greece, or Turkey. The interlinkage between touristic activities and air pollution is dual: on the one hand, they contribute to air pollution in particular with the car traffic and aircraft-related emissions, and on the other, they require large infrastructures that are often highly demanding in energy through leisure activity and air conditioning. Further, these large infrastructures are leading to the urbanization of the coastlines bringing originally semirural areas to the emission levels of urban centers.

Tourist transport by car causes the largest impact on air quality (EEA 2015), whereas air transport accounts for the largest share of tourism-related greenhouse gas emissions (80% in 2000) in the EU-25. On the northern shore of the Mediterranean, rail, coaches, and ferries account for only 20% of all tourism trips AU3 and are responsible for a very small percentage of environmental impacts. Between 2005 and 2013, motor vehicles (private or rented) were the main means of transport (65.0%) used by tourists, followed by air and railway transport (15.3% and 11.4%, respectively). Not surprisingly, air transport was the preferred means of transport for outbound trips (53.2%), while for domestic trips, EU residents traveled mainly by motor vehicles (76.4%), followed by rail (13.6%) (EEA 2015). Obviously, the situation is different for islands as air transport accounted for more than 90% of all intra-EU inbound flows (94% to Malta and 91% to Cyprus (91%), for example). While little or no data concerning the southern shore of the Mediterranean are available, one can certainly consider that the share of ground-based motor vehicles (cars and coaches) for inbound tourist transportation is even larger than in the north due to the lack of railroad infrastructure.

In the last decade, an intensely emitting mode of transport has strongly developed: tourist cruise ships. In 2012, there were 207 cruise ships active in the Mediterranean with a capacity of 249,000 passengers and an annual total of 5.7 million passengers and 28.7 million visits to its ports [START_REF] Cari | Cruise tourism environmental impacts -The perspective from the Adriatic Sea, Ocean Coast[END_REF]. The European market has grown by 162% over the 10 years from 2002 to 2012, and despite the economic downturn, European cruising is expected to reach ten million passengers by 2020 (ECC 2012). Tourist cruise emissions must not only be considered as offshore emissions contributing to the general background of air pollution over both the western and the eastern basin but also as being significant in ports when maneuvering or because of hoteling activities. Emission estimates when cruising the Mediterranean sea are scarce in the literature, while the in-port emission is well documented (see APICE project; http://www.apice-project.eu, last access 1 Aug. 2021; [START_REF] Cari | Cruise tourism environmental impacts -The perspective from the Adriatic Sea, Ocean Coast[END_REF][START_REF] Papaefthimiou | Evaluation of cruise ships emissions in the Mediterranean basin: The case of Greek ports[END_REF][START_REF] Murena | Impact on air quality of cruise ship emissions in Naples, Italy[END_REF][START_REF] Ruiz-Guerra | Prediction of the impact on air quality of the cities receiving cruise tourism: the case of the Port of Barcelona[END_REF]. As an example, for the Greek ports only, the emissions from international cruise ships in 2013 were estimated [START_REF] Papaefthimiou | Evaluation of cruise ships emissions in the Mediterranean basin: The case of Greek ports[END_REF], NO x being found dominant (2488 tons), followed by SO 2 and PM 2.5 (995 and 121 tons respectively), while the total emissions of greenhouse gases (GHG) were 124,768 tons of CO 2 -equivalent. Emissions during cruise ship hoteling in harbors significantly outweighed their emissions during maneuvering (89.2% vs. 10.8% of total).

Wildfires

When discussing the anthropization of the Mediterranean atmosphere, one has to consider the occurrence of wildfires as a significant contributor to atmospheric composition. Indeed, even if the fire has always been part of the natural forest life cycle and can even contribute to a form of regeneration, it must be recognized here that it has become an anthropogenic phenomenon. From the analysis of data in the European Fire Database on fire causality during the 2006-2010 period, Ganteaume et al. (2013) have shown that, among the 71% of forest fires in the Mediterranean

The Mediterranean Region Under Anthropogenic Pressures countries for which the cause was identified, more than 95% of fires were directly or indirectly caused by human agents.

In Europe, the Mediterranean gathers the large majority of forest fires: on average, 85% of the annual burned area (San-Miguel-Ayanz and Camia 2010). Because of the characteristics of the Mediterranean climate (summer dryness, occurrence of strong winds linked with a marked orography) and the nature of its vegetation, the Mediterranean area is naturally prone to wildfires, as one can verify by observing the summer average of the Fire Weather Index (Fig. 5), a parameter that combines both weather, vegetation and vegetation stress components to assess the risk of fire outbreak. As seen in Fig. 5, the hilly regions surrounding the western and eastern Mediterranean basins are especially at risk.

In addition to these risks, the main drivers of fire ignition are strongly interconnected to the evolution of the human society and, particularly, its use of forest resources. Socioeconomic developments in recent decades have led to changes such as enhanced mobility, development of tourism, and recreational activities, increasing the number of visitors to high fire-risk areas such as the Mediterranean forest or dry lands. Additionally, in many rural areas of Mediterranean Europe, fire is a AU4 traditional and long-established management tool. Further, the traditional rural socioeconomic systems that once characterized the Mediterranean region collapsed in the last few decades, resulting in a rural exodus in the northern part of the Mediterranean basin, such as in Spain, Italy, or Greece leading to desertification, which favors wildfires (see e.g., [START_REF] Hill | Mediterranean desertification and land degradation: Mapping related land use change syndromes based on satellite observations[END_REF]). On the other hand, in the eastern regions, the overexploitation of natural resources (Turkey, Lebanon, or Cyprus) has led to land degradation, which is also increasing the risk of fire (Marquina 2004). Consequently, as shown by the 11-year record of fires by the MODIS satellite (Fig. 6), the shore of the Mediterranean basin encounters regular outbreaks of wildfires during the dry season.

The past 10-15 years have shown a relative stagnation of the total burned area over the Mediterranean (Darques 2016) and even a small decrease in Mediterranean EU countries (de Rigo et al. 2017). Recently, Turco et al. (2018) provided an estimation of the future trend in wildfire occurrence over the Mediterranean in the context of climate change. They conclude that the observed trend towards warmer and drier conditions in southern Europe would possibly lead to an increased risk of large fires.

The Mediterranean Region Under Anthropogenic Pressures Under 1.5-3 °C global warming scenarios, the summer burned area in Mediterranean Europe would increase in the future from ca. 40% to 100%.

Wildfires are leading to a massive injection of reactive matter in the atmosphere. This comprises not only soot, ashes, and CO 2 but also CO, NO y , and a large variety of non-methane organic compounds (NMOC). For example, [START_REF] Alves | Smoke emissions from biomass burning in a Mediterranean shrubland[END_REF] have analyzed gaseous and particulate samples from smoke from prescribed burnings of a shrub-dominated forest with some pine trees in Lousã Mountain, Portugal. Under a very strong predominance of flaming combustion, gaseous compounds, such as CO 2 , acetylene, and propene, were found with emission factors higher than those proposed for savannah and tropical forest fires. The emission factors of species that are favored by the smoldering phase (e.g., CO and CH 4 ) were below the values reported in the literature for biomass burning in other ecosystems. Approximately 50% of the particulate mass was carbonaceous in nature, with a clear dominance of organic carbon. The organic carbon-to-elemental carbon ratios up to 300, or even higher, measured in the present study largely exceeded those reported for fires in savannah and tropical forests. For Portugal, Rosa et al. (2011) report that pyrogenic emissions represent 1-9% of the total greenhouse gas emission from the various economic sectors.

In fact, biomass burning (BB) is the second largest source of trace gases and the largest source of primary fine carbonaceous particles in the global troposphere (Akagi et al. 2011). Further, large NMOC emission strongly influences secondary organic aerosol (SOA) and ozone formation. This contributes to the large-scale impact of forest fire plumes over several days after their emission. These impacts involve the degradation of air quality, especially close to the fire themselves, and are particularly detrimental when the plume trajectory reaches densely populated areas. For example, Di [START_REF] Di Carlo | Wildfires impact on surface nitrogen oxides and ozone in Central Italy[END_REF] sampled air masses from a site located 30 km downwind of a large forest fire in the Abruzzo region (Italy) and observed a massive increase in NO 2 mixing ratio and PM 2.5 concentration. Concerning secondary chemistry, by comparing observations and simulations on different days with and without a fire plume during a case study, they deduced an impact of fire emissions on the O 3 mixing ratios of about 10%.

Several studies have also been performed on the impact of biomass burning on air quality in Greece. The contribution of forest fire pollutant emissions to the total anthropogenic and natural emissions has been estimated in detail by Lazaridis et al. (2008) for a specific period during July 2000 when widespread forest fires occurred in the Greek mainland (269 fires recorded). Mesoscale air quality modeling was used to quantify the contribution of forest fire emissions to the air pollution levels in Greece. Forest fire emissions were found to be the largest contributor to air pollution in regions tens of kilometers away from the fire source. The wildfire emissions were calculated to cause an increase in the average PM 10 concentration, organic aerosol mass, and gaseous concentration of several pollutants, among them CO, NO x , and NH 3 . An average contribution of 50% to the PM 10 concentration over the region around the burnt area and downwind of the fire source (up to approximately 500 km) was calculated with a maximum of 80%. The average contribution of wildfires to CO was also 50%. The large wildfire events that struck Peloponnese during the summer of 2007 have also allowed a series of case studies [START_REF] Liu | Analysis of the impact of the forest fires in August 2007 on air quality of Athens using multi-sensor aerosol remote sensing data, meteorology and surface observations[END_REF][START_REF] Athanasopoulou | Fire risk, atmospheric chemistry and radiative forcing assessment of wildfires in eastern Mediterranean[END_REF]Majdi et al. 2019a, b). They have shown that in rural areas impacted by fires, gaseous chemistry resembles that in urban environments and led to nitrogen dioxide and ozone exceedances in several cities in proximity to and downwind the fire spots. Due to the atmospheric dynamics, the influence was found significant in Athens from the smoke plume originating from Evia (45% of total surface PM 10 ) and small (5%) from the fires in Peloponnese. Overall, during these events, fire emissions would contribute up to 90% of surface PM 2.5 concentrations in the fire regions (Balkans and Greece), with a significant regional impact associated with long-range transport. From a detailed analysis of the 2009 fire events over Peloponnese, [START_REF] Amiridis | Impact of the 2009 Attica wild fires on the air quality in urban Athens[END_REF] also pointed out that fires burning near urban environments may produce particularly dense pollution plumes. They carry a mixture of anthropogenic and biomass burning pollutants, resulting in chemical processes different from those within a pure biomass burning or pure anthropogenic pollution environment and impacting very large areas.

Voluntary agricultural practices also contribute to the fire emission burden over the Mediterranean basin. Among those, one counts the use of prescribed burning to minimize the risk of wildfire and clear surfaces for pastoral activities (e.g., [START_REF] Favez | Seasonality of major aerosol species and their transformations in Cairo megacity[END_REF][START_REF] Fernandes | Prescribed burning in southern Europe: Developing fire management in a dynamic landscape[END_REF]. Other contributions come from regular open fire to get rid of agricultural residues, such as on the coast of Spain, where biomass residues originating from orange-tree plantations and rice fields are burnt in the open air every year during March-April and September-October. In Valencia (Spain), for example, [START_REF] Viana | Assessment of source contributions to air pollution in Beirut, Lebanon: a comparison of source-based and tracer-based modeling approaches[END_REF] have shown that open burning of rice field residues increased daily PM 10 concentrations on a regional scale by 10-15 μg m -3 on average, with a maximum of 30 μg m -3 on peak episodic days impacting an area of ca 18,000 ha and leading to the exposure of ca. 2.5 million inhabitants.

The impact of wildfire on the atmospheric environment is not limited to air quality reduction. By contributing to the aerosol burden at a larger scale, wildfires exhibit a significant climate impact at the basin scale (see for review the Chapter by [START_REF] Mallet | Aerosol and ozone direct radiative impact[END_REF].

Anthropization of the Mediterranean Region as Detected from Space Measurements

Aside from the bottom-up approach that we have followed so far in the present chapter, which consists of identifying sources, their related strength and temporal/ spatial distribution, another strategy becomes available to assess the anthropization of the Mediterranean Sea: the top-down use of satellite remote sensing. Indeed, the past 20 years have seen the development of several satellite-borne instruments such as GOMOS, MIPAS, and SCIAMACHY on board of ENVISAT (launched in 2002), IASI and GOME2 on board of the MetOp series (launched in 2006, 2012 and 2018), or TROPOMI on board of Sentinel-5P (launched in 2017) that exhibit powerful capabilities for the monitoring of both particulate and gaseous species of air quality interest. These sensors are often limited to the retrieval of the total atmospheric column of the relevant species (Doche et al. 2014)-even if recent improvements in the combination of complementary signals allow measurements in the lowermost layers of the troposphere (Cuesta et al. 2013). Nevertheless, the total retrieved column is generally useful to detect the regional pattern of the emission of those species and often reveals their anthropogenic nature. It has become a very powerful tool to explore the chemical background of the basin, especially where no or little in-situ measurements were available.

Nitrogen Dioxide

Among various other pollutants, the TROPOMI instrument on board Sentinel-5P can deliver tropospheric nitrogen dioxide (NO 2 ) column measurements with a resolution of up to 7 × 3.5 km 2 . As shown in Fig. 7, TROPOMI provides a striking view of the anthropization of the Mediterranean Sea. Indeed, NO 2 is mostly produced during combustion and so can be directly related to human activities, including both ground transportation (cars and trucks) and ship traffic, but also industrial activities, electricity production, and residential heating. NO 2 has only limited natural sources, its atmospheric lifetime toward oxidation is only of the order of a few days, and its vertical profile is such that one can consider the pattern drawn by the tropospheric column density as a trustful reflection of the lowermost troposphere concentrations.

Figure 7 reveals the strong footprint on the atmospheric environment of major cities such as Madrid, Barcelona, Marseille, Turin and the Po Valley, Rome, Naples, Athens, Izmir, Istanbul, Ankara and the Iskenderun Bay on the northern side of the basin, Algiers, Tunis, Tripoli, Cairo and the Nile Delta on the southern coasts, Beirut and Israel on the eastern shore. Urban centers and population densities provided in Fig. 1 can almost perfectly be superimposed on this remote sensing product revealing how Megacities act as hot spots of air pollution all around the Mediterranean [START_REF] Kanakidou | Megacities as hot spots of air pollution in the East Mediterranean[END_REF]. In North Africa and the Middle East, the background level seems generally lower than in the North, which is probably due to the lower level of distributed infrastructures, but the urban centers seem much more intense emitters than in the northern shore. Here the lack of regulation coupled with a more difficult access to the latest technologies as well as the greater use of individual power production systems to the detriment of common and more effective infrastructures probably explains this situation (e.g., see Waked et al. (2015) for Beirut).

Major waterways can also be detected, demonstrating how the high NO 2 emission rate of cargo ships coupled with the high density of the major routes across the Mediterranean Sea (see Fig. 4) are strongly impacting the nitrogen dioxide background even far away from the urban centres. The major ground transportation networks are also well visible. Major roads, railways, freeways, industrial sites, and power generation installations often gather in the same valleys. It is hence remarkable to observe how the Po valley is a source of nitrogen oxides for the Adriatic Sea, and the Rhone valley pollution is spread towards Corsica and the Ligurian Sea following the mistral pathways.

Combined with the close sea nature of the Mediterranean and its peculiar aerology (Dayan this volume), all these features contribute to a significant nitrogen oxides background over the Mediterranean basin, twice as high as the one found in the eastern part of the Atlantic Ocean (Fig. 7). With respect to the atmospheric chemistry of the Mediterranean area, this high background is not without consequence. Nitrogen oxides (NO x ) photo-interconversion (Finlayson-Pitts and Pitts 2000) is, indeed, the propagating force that drives the radical oxidation of pollutants during their atmospheric transit leading to oxidized species, secondary aerosols, and ozone. Being bathed with these anthropogenic emissions of nitrogen oxides and naturally gifted with sunlight, the Mediterranean area is exhibiting a very active photochemistry that governs the fate of many atmospheric pollutants such as volatile organic species of both biogenic and anthropogenic origins or SO 2 , leading to high ozone (e.g., Butkovi et al. 1990), and secondary organic, nitrate, and sulfate aerosol (e.g., Simó et al. 1991;Kostenidou et al. 2015;Drugé et al. 2019) concentrations.

Sulfur Dioxide

Sulfur dioxide is an irritating gas that is well placed among the list of regulated species by air quality regulation. It is also a very efficient precursor of particles: its oxidation by atmospheric oxidants such as OH radicals and ozone leads to sulfuric acid that has a sufficiently low vapor pressure to condense and form secondary sulfate over preexisting particles or even to form new ultrafine particles during nucleation events [START_REF] Sellegri | Nucleation in the Mediterranean atmosphere[END_REF]. As a strong acid, it also contributes to the acidification of precipitation (Avila and Rodà 2002) and is prone to react with atmospheric bases such as ammonia to form new particles [START_REF] Koçak | Ionic composition of lower tropospheric aerosols at a Northeastern Mediterranean site: implications regarding sources and long-range transport[END_REF]. SO 2 emissions are strongly regulated in Western Europe by controlling the sulfur content of fuels which is much less the case in eastern Europe, the Middle East, and North Africa, as well as in offshore areas (see above Ship traffic Sect. 4).

Instruments such as TROPOMI, IASI, or GOME-2 have the ability to retrieve sulfur dioxide vertical columns. Here we focus on reanalysing 2004-2009 OMI data on-board the AURA satellite by Theys et al. (2015). Results presented in Fig. 8 illustrate very well the anthropization of the Mediterranean basin. If volcanic sulfur dioxide emission from Mount Etna in Sicily is well visible, this long-term average brings evidence that non-volcanic sources are also significant, if not major, for the SO 2 contamination of the eastern basin. It illustrates how the mid-troposphere and boundary layer circulation patterns described in [START_REF] Lelieveld | The Mediterranean Region Under Anthropogenic Pressures[END_REF] are efficient in bringing towards the Mediterranean area the pollution emitted in central and eastern Europe. Sulfur emissions from the Danube valley and Balkans are then recirculated from the southern Black Sea area and feed the Aegean and Levantine areas with sulfur dioxide. Beyond the fact that these emissions lead to the formation of particulate sulfate, SO 2 can be seen here as a tracer, and one should consider that many other co-emitted reactive species and contaminants are transported along the same routes. Local industries nevertheless can have a major impact, as demonstrated by the clear detection of the lignite-based Megalopolis power generation center in the central Peloponnese (Fig. 8).

Conclusion

We have reviewed here in a non-exhaustive way the major sectors responsible for the main anthropic pollutant sources in the Mediterranean area. This overview is not only intending to provide starting points for a more targeted and thorough evaluation of anthropic sources, it also depicts a critical panorama of the human activities over the Mediterranean. Indeed, in addition to exhibiting a very peculiar geographical pattern (see Sect. 1.2), in addition of being an interface between Africa and Europe and between Asia and the Atlantic, in addition of being a tipping point area in the context of climate change, the Mediterranean area is under the pressure of unprecedented anthropic forcings that strongly impact the composition of its atmospheres. All sectors of human activities seem to have reached such levels of development-and sometimes of non-regulation-that they present acute impacts on the atmospheric environment. Considering the relatively small size of the basin and the mix of recirculation processes, this variety of sources leads to a strong complexity of the Mediterranean background atmosphere. Moreover, the extrapolation of temporal trajectories of the various emission sources is a dreadful scenario: population, tourism, ground transportation, sea transportation, and fossil fuel extraction are expected to increase in the coming years, preparing the Mediterranean atmosphere to be the place of a future silent environmental disaster.

Fig. 3

 3 Fig. 3 Major industrial sites in the Mediterranean region. (Plotted data from the mixed sources:www.carbonbrief.org, www.industryabout.com, www.powerplantmaps.com)

Fig. 4

 4 Fig. 4 Top density of cargo traffic as extrapolated from the density of automatic identification system (AIS) signals from cargo ships in 2014 (total number of tracks: 13,144; color scale: logarithmic; AIS data http://www.navama.com/). Bottom density of oil tanker traffic as extrapolated from the density of AIS signals from oil tankers in 2014 (total number of tracks: 38,897; color scale: logarithmic); oil refineries are indicated by red droplets. The blue area and red circle in the northwestern Mediterranean indicate particularly sensitive areas. (Reprinted from Piante and Ody (2015), Ⓒ WWF-France)

Fig. 5

 5 Fig. 5 Top Geographical distribution of the three main vegetation types as derived from 1-km resolution Global Land Cover 2000 (GLC2000) dataset as derived from SPOT-4 VEGETATION. Bottom Geographical distribution of mean values of the Fire Weather Index over July-August 2007 to 2009. (Reprinted from DaCamara et al. (2014))

Fig. 6

 6 Fig. 6 Land cover types in 2012 (classified as plant functional types, PFT) and wildfires as detected from 2002 to 2013 from MODIS (Moderate Resolution Imaging Spectroradiometer) satellite-derived data, in the Mediterranean region. (Reprinted and adapted from Figs. 4 and 7 by Darques (2016))

Fig. 7

 7 Fig. 7 Nitrogen dioxide column over the Mediterranean region averaged over April 2018, derived from Sentinel-5P/TROPOMI data (http://www.tropomi.eu, last access 01 Aug. 2021). (Reproduced after https://eoportal.org/documents/163813/4638036/Sentinel5PStatus2018-2017_AutoA.jpeg (last access 01 Aug. 2021), Ⓒ modified Copernicus Sentinel data (2018) processed by KNMI)

Fig. 8

 8 Fig. 8 Vertical column density (VCD) of SO 2 in Dobson unit (DU), as retrieved from space by OMI/AURA, averaged for the 2004-2009 period on a 0.25° × 0.25° grid, and showing emission hot spots over Europe. Cloudy pixels and measurements affected by strong volcanic eruptions are excluded from the analysis. (Reprinted from Fig. 6 in Theys et al. (2015))

The Mediterranean Region Under Anthropogenic Pressures


W Oukil

Non trivial zeros of the Zeta function

Keywords: Riemann hypothesis, Zeta function, Non trivial zeros, Riemann functional equation

published or not. The documents may come

AMS subject classications: 00A05

Consider the representation of the Riemann Zeta function ζ dened by the Abel summation formula [ [START_REF] Titchmarsh | The Theory of the Riemann Zeta-Function[END_REF], page 14 Equation 2.1.5] as

ζ(s) := - s 1 -s -s +∞ 1
{t} t 1+s dt, ℜ(s) ∈ (0, 1), ℑ(s) ∈ R * , [START_REF] Titchmarsh | The Theory of the Riemann Zeta-Function[END_REF] where {t} is the fractional part of the real t. In order to simplify the notation, denote [START_REF] Oukil | Non trivial zeros of the Zeta function using the dierential equations[END_REF] that the zeros of the function ζ and the function f : B → C coincide on B, where the function f is dened as

B := {s ∈ C : ℜ(s) ∈ (0, 1), ℑ(s) ∈ R * }. It is proved in
f (s) := 1 -4s(1 -s) j∈N * 1 (j2π) 2 k∈N * 1 (2k)! (-1) k (j2π) 2k 2k -1 -s , ∀s ∈ B. ( 2
)
We prove the following theorem Theorem 1. Consider the function f given by the Equation [START_REF] Oukil | Non trivial zeros of the Zeta function using the dierential equations[END_REF]. Any zero of the function f in B is of real part equal to 1

2 .

1

In order to prove the previous Theorem, we need the following Lemma.

Lemma 2. Consider the function f given by the Equation (2). Suppose that s ∈ B is a zero of the function f . Then, one of the following statements is true

• 1 -2ℜ(s) = 0, • |h s (t)| = 0, ∀t ∈ (0, 1), where h s (t) := 1 s(1 -s) - 1 (1 -s)s t + 4 j∈N * 1 (j2π) 2 k∈N * 1 (2k)! (-1) k (j2π) 2k t 2k-1 (2k -1 -s)(2k -2 + s) .
Proof. Let be s ∈ B. In one hand, for every t ∈ (0, 1) we have

1 t u -2-s u 0 (v - 1 2
)dv du = 1 2

1 t u -2-s u 2 -u du = 1 2s(1 -s) - 1 2 t -s t 1 -s + 1 s .
(3)

We recall that the function p : R → R, dened as

p(t) := t 0 {u} - 1 2 du, ∀t ∈ R is a continuous 1-periodic function and satises p(t) = 2 j∈N * 1 (j2π) 2 cos(j2πt) -1 = 2 j∈N * 1 (j2π) 2 k∈N * (-1) k (j2π) 2k t 2k (2k)! , ∀t ∈ R.
On the other hand, for every t ∈ (0, 1) we have

1 t u -2-s u 0 (v - 1 2 )dv du = 2 1 t u -2-s j∈N * 1 (j2π) 2 k∈N * (-1) k (j2π) 2k u 2k (2k)! du = 2 j∈N * 1 (j2π) 2 k∈N * 1 (2k)! (-1) k (j2π) 2k 2k -1 -s -2 j∈N * 1 (j2π) 2 k∈N * 1 (2k)! (-1) k (j2π) 2k t 2k-1-s 2k -1 -s . ( 4
)
Suppose that s is a zero of the function f . Then the Equations ( 3) and (4) implies that

1 2 t 1 -s + 1 s = 2 j∈N * 1 (j2π) 2 k∈N * 1 (2k)! (-1) k (j2π) 2k t 2k-1 2k -1 -s , ∀t ∈ (0, 1).
It is proved in [START_REF] Oukil | Non trivial zeros of the Zeta function using the dierential equations[END_REF], that the zeros of the function ζ and the function f : B → C coincide on B. Thanks to the Riemann functional equation, the point 1 -s is a zero of the function ζ and f . Then

1 2 t s + 1 1 -s = 2 j∈N * 1 (j2π) 2 k∈N * 1 (2k)! (-1) k (j2π) 2k t 2k-1
2k -2 + s , ∀t ∈ (0, 1).

The subtraction implies that

|(1 -2ℜ(s))h s (t)| = 0, ∀t ∈ (0, 1),
where

h s (t) := 1 s(1 -s) - 1 (1 -s)s t + 4 j∈N * 1 (j2π) 2 k∈N * 1 (2k)! (-1) k (j2π) 2k t 2k-1 (2k -1 -s)(2k -2 + s)
.

Proof of the Theorem 1. Let be s ∈ B and suppose that s is a zero of the function f . Prove the present Theorem by contradiction. Suppose that 1-2ℜ(s) ̸ = 0. Thanks to the Lemma 2, it sucient to prove that there exists t ∈ (0, 1) such that |h s (t)| ̸ = 0. By contradiction, suppose that |h s (t)| = 0 for all t ∈ (0, 1). Then

4|s(1 -s)| 2 j∈N * 1 (j2π) 2 k∈N * 1 (2k)! (-1) k (j2π) 2k t 2k-1 (2k -1 -s)(2k -2 + s) , (5)
= s(1 -s)t -s(1 -s), ∀t ∈ (0, 1).
In order to simplify the notation, denote for every t ∈ (0, 1) the function Ψ s as follow

Ψ s (t) := 4|s(1 -s)| 2 j∈N * 1 (j2π) 2 k∈N * 1 (2k)! (-1) k (j2π) 2k t 2k |(2k -1 -s)(2k -2 + s)| 2 .
The imaginary part of the equation (5) implies

2 d dt Ψ s (t) -3t -1 Ψ s (t) = t + 1, ∀t ∈ (0, 1).
Then there exists a constant c s ∈ R such that

Ψ s (t) = c s t 3 2 + t 2 -t, ∀t ∈ (0, 1). (6)
The real part of the equation (5) implies

4 j∈N * 1 (j2π) 2 k∈N * (2k -1)(2k -2) (2k)! |s(1 -s)| 2 (-1) k (j2π) 2k t 2k-1 |(2k -1 -s)(2k -2 + s)| 2 +(ℜ(s) -|s| 2 )t -1 Ψ s (t) = (ℜ(s) -|s| 2 )(t -1), ∀t ∈ (0, 1).
Then for all t ∈ (0, 1) we have

Integrate, for all [t 1 , t 2 ] ⊂ (0, 1) we obtain

d dt Ψ s (t 2 ) -2t -1 2 Ψ s (t 2 ) - d dt Ψ s (t 1 ) -2t -1 1 Ψ s (t 1 ) = 2c s t 1 2 2 -t 1 2
1 .

Using the Equation (6) and t 1 ≈ 0, we obtain a contradiction.

s( 1 - 2 ,

 12 s)| 2 (-1) k (j2π) 2k t 2k-1 |(2k -1 -s)(2k -2 + s)| 2 = cs t 1 cs := (ℜ(s) -|s| 2 )c s .