Relevant habitats neglected by the Directive 92/43 EEC: the contribution of Vegetation Science for their reappraisal in Sicily

Field investigation carried out by the Sicilian botanists in the last 20 years enabled them to identify eight habitat types of high biogeographic and conservation interest, neglected by the Directive 92/43, which deserve ad hoc conservation measures. For each of these habitats, a syntaxonomic interpretation of the corresponding plant communities, their main ecological, physiognomic and syndynamic traits and a list of diagnostic species are provided. Their classification into the macrotypes listed in the Annex I of the Directive 92/43 and the respective correspondence in EUNIS habitat classification are proposed. The habitats here described integrate those already proposed by the Italian Botanical Society, with the hope of an adequate recognition at national at supranational level.


Introduction
The Natura 2000 sites form a pan-European network for the in situ protection of species and habitats, recognized as conservation targets "of Community Importance" on the basis of Directive 92/43 EEC, which represents the most important regulatory instrument for the conservation of natural and semi-natural ecosystems in Europe (Evans 2012).
Designed to support the long-term survival of Europe's most valuable species and habitats, Natura 2000 sites con-stitute an environmental network to be managed through initiatives that should also fulfil socio-cultural and economic requirements at the local scale, with the general aim at achieving the best balance between ecological integrity and requirements of people living and working nearby (Tsiafouli et al. 2013;Linnell et al. 2015).
Even if originating from a species-specific concept (Kirk et al. 2016), the term "habitat" is frequently used to designate an integral unit, supporting ecological functions and species assemblages (Morrison and Mathewson 2015). This happens both in the EUNIS habitat classifi-cation (Rodwell et al. 2018) and in the Directive 92/43 EEC. Vascular plant communities are crucial to define EU habitats, both because plants are the least vagile and most visible component of terrestrial ecosystems, and because the vegetation cover and classification are the criteria by which the habitats of the Directive 92/43 (henceforth: Habitat Directive) are identified, delimited and mapped.
The census of natural habitats from the same Directive has given new impetus to basic taxonomic, syndynamic and ecological research, involving different disciplines (Blondet et al. 2017). Among these, vegetation science offered a significant contribution, considering that the units codified in the Annex I of the Habitat Directive often refer to the species composition and the structure of plant communities and sometimes explicitly refer to phytosociological units (Loidi et al. 2007;Tomaselli et al. 2016;Angelini et al. 2018;Attorre et al. 2018).
The explicit mention of some syntaxa by the Habitat Directive is important, also because this implicitly recognizes one fundamental postulate of phytosociology, that is: each phytocoenosis corresponds to a specific range of variability of environmental factors. Phytosociological studies carried out across the entire Sicilian territory during the last three decades pointed out the biogeographical importance of several habitats that deserve to be included in the Annex I of the same Directive. This paper aims to introduce these habitats and to discuss about the urgent need for their adequate recognition.

Study area
The Sicilian Natura 2000 network counts on 245 protected sites, unevenly distributed throughout the island (Fig. 1). Among the Italian regions, Sicily is the one hosting the largest surface area of Special Areas of Conservation (SAC, based on the Habitat Directive), and Special Protection Areas (SPA, based on the Directive 79/409). These protected areas cover approximately a surface of 4710 km 2 , corresponding to 18.3% of the Sicilian territory, sea excluded (www.mite.gov.it). Altogether, Sicily hosts 71 habitats listed in the Directive 92/43, of which 18 have priority conservation status. Additionally, 46 species from Annex II of the same Directive and 92 birds from the Directive 79/409 are recorded in Sicily.
The main feature of Sicily is a great geomorphologic and bioclimatic diversity, which originate ecological gradients of different intensity, also influenced by the distance from the sea and by the orientation and elevation of mountain ranges. In general, the natural patchiness of the Sicilian landscapes has been increased up to critical levels by human activities (Gianguzzi et al. 2016;. Land use and human demography have significantly changed during the last seven decades, as a consequence of the mechanization of agriculture, the decline of extensive land use and traditional agriculture. Emblematic, in this case, is the almost complete abandonment of terraced fields (Barbera et al. 2009). The development of new economic sectors, like tourist services and infrastructure, promoted the concentration of people within a few miles from the coastline, with an ever-increasing impact on coastal habitats (Guarino and Guglielmo 2010). On the other hand, many lands which were used by agriculture or husbandry until recent times are currently abandoned, particularly in the mountain districts. For these reasons, two main kinds of Sites of Community Importance can be found in Sicily: those occurring on mountains are on average quite large; the coastal ones, instead, are on average rather small and set up in the attempt to save the savable, i.e. the few coastal stretches escaped from the massive urbanization which took place in recent decades as a consequence of the human migration coastwards (Mikhaylov et al. 2018). Indeed, the conservation and management of the Sicilian coastal sites, exposed to the pressure of strong economic interests, is quite problematic and poses several specific issues Sciandrello et al. 2021).

Survey approach
The vegetation survey aimed at identifying the Sicilian habitats neglected by the Directive 92/43 was based both on phytosociological literature and on-site investigations conducted according to the Braun-Blanquet phytosociological approach (Braun-Blanquet 1964;Westhoff and van der Maarel 1978). The habitat description, syntaxonomic classification and designation of diagnostic species was carried out based on expert knowledge, supported by literature data and by the Expert System for the European EUNIS habitats (Chytrý et al. 2020).
The identification and nomenclature of vascular plants was based on Pignatti et al. (2017Pignatti et al. ( -2019, whereas the animal species names mentioned throughout the text follow Ruffo and Stoch (2005). The syntaxonomic nomenclature follows Mucina et al. (2016) and subsequent updates for Sicily . The bioclimatic units refer to Bazan et al. (2015).  (Crisafulli 2007). b) some outstanding habitats barely taken into account by the Directive and not adequately protected by national and regional laws, linked to localized and peculiar geomorphological units and hosting several vegetation units. This is the case of the annual swards and perennial grasslands, the sedge communities and the brackish temporary ponds co-occurring near the mud volcanoes and badlands of Macalube di Aragona, Terrapilata, Vulcanelli di Adrano, etc. (Pasta 2001;Brullo et al. 2010Brullo et al. , 2013; the vegetation of the gypsum outcrops of southern and inner Sicily Musarella et al. 2018). c) traditional landscapes shaped by century-long agro-forestry practices, such as the dehesa-like communities dominated by Ceratonia siliqua on the Hyblaean Plateau (SE-Sicily). This would reinforce the unit 63 of the Directive, i.e., sclerophyllous grazed forests (dehesas), currently recognizing only the habitat 6310 ("Dehesas with evergreen Quercus spp. "). The eight habitats described here integrate those already identified and proposed as additions to the Habitat Directive by the Italian Botanical Society (Table 1; Genovesi et al. 2014). Each of the newly proposed habitats is commented more in detail in the forms reported below.

1) Sicilian gypsum outcrops
Motivation: The plant communities growing on gypsum are a clear example of the strict relationship between substrate and vegetation, as many plant species grow exclusively or preferentially on such peculiar substrates (Escudero et al. 2015, Musarella et al. 2018. Gypsum habitats have historically been perceived as sterile, degraded areas with no special conservation interest that needed to be afforested or that could be used as dumping sites for urban waste (Escudero et al. 2015). Nowadays, they are acknowledged as habitats worth preserving due to their high number of endemic or exclusive plants (Escudero et al. 2015). However, these same communities represent often a largely underrated or ignored habitat, with serious consequences for both flora and fauna conservation (Musarella et al. 2018).
As already highlighted in Musarella et al. (2018), for the vascular flora, and Puglisi et al. (2020) for bryophytes, the Italian gypsum habitats could be included in the Habitat 1520* (Iberian gypsum steppes) extending its current definition in the Manual of Habitat interpretation, also with the addition of the Italian vascular and moss gypsophytes. Similarly, the habitat has been recently recognized in Cyprus (Manolaki Vogiatzakis 2017), at the opposite side of the Mediterranean Basin, and it stretches northwards up to the submediterranean gypsum outcrops of the Northern Apennine.
Macrotype: 15 Salt and gypsum inland steppes Name: Sicilian gypsum outcrops. Description: Garrigues, perennial grasslands and annual swards colonizing gypsum-rich shallow soils and gypsum outcrops in the southern and central part of Sicily, under thermo-and mesomediterraean climatic conditions. These plant assemblages include several gypsophilous species, mainly belonging to the families Lamiaceae (genera Micromeria, Teucrium, Thymus, Thymbra), Cistaceae (Fumana, Helianthemum), Asteraceae (Centaurea, Jurinea, Santolina, Frankenia) and Brassicaceae (Alyssum, Erysimum, Matthiola). All of them are adapted to several environmental stresses, such as: long-lasting seasonal drought, base-rich substrates (especially in the most eroded sites and on lithosols), high solar radiation, exacerbated by the high reflectance of rock outcrops.
Diagnostic sentence: Garrigues, grasslands and annual swards colonizing gypsum-rich substrates of the hilly areas of inner and southern Sicily.
List of diagnostic species: In addition to the species already listed as gypsum-specialists by Musarella et al. (2018) and Puglisi et al. (2020) Dynamic contacts: Although gypsum outcrops have for long time been interpreted as the result of the extreme degradation and erosion of previously forested areas, this is probably true only for gently sloping or almost flat areas. Indeed, some small and scattered evergreen (Quercus ilex) or semideciduous (Quercus pubescens) oak forest fragments still occur nowadays on the deeper gypsum-rich soils of central and southern Sicily (Bazan et al. 2006;Brullo et al. 2009).

2) Mud volcanoes and badlands in the evaporitic outcrops of Sicily
Motivation: Already studied by early naturalists such as Pliny the Elder and eminent geologists like Deodat de Dolomieu and Charles Lyell, around 15 mud volcanoes occur in the inland areas of Sicily. Mud volcanoes alternate an almost continuous degassing activity and episodes with ejection of large quantities of mud. The protection of these absolute naturalistic highlights gave birth to many protected areas worldwide, namely in the SE-European and middle-central Asian countries bordering the Black and the Caspian Sea, in the Indian Ocean and in the Americas. In Italy, mud volcanoes also occur in Emilia-Romagna, Marche, Tuscany and Latium regions. Some of them are nature reserves, such as the "Salse di Nirano" in Emilia-Romagna, whilst many others are lacking any protection.
Like other poorly vegetated but geologically peculiar habitats (e.g. 8320: Fields of lava and natural excavations), the Sicilian mud volcanoes and badlands are worth being included in the 92/43 EEC Directive as a whole, not only for their naturalistic and aesthetic value, but also for their increasing vulnerability, exacerbated by absurd destinations (e.g., waste dumping grounds, go kart and motocross trails) and disturbances such as wildfires, overgrazing by domestic herbivores, unsustainable cereal crop cultivation practices, reforestation with alien trees, which currently compromise many of these unique, hostile habitats by accelerating the natural erosive processes affecting them.
Because many mud volcanoes and badlands are located in poorly investigated areas, their occurrence has often been overlooked and, consequently, they have not been included in the Sicilian Natura 2000 network. Indeed, some Sicilian endemics, like Tripolium sorrentinoi (= Aster sorrentinii), Limonium calcarae, Allium agrigentinum, Malva agrigentina only grow on badlands or close to mud volcanoes. Of these species, Tripolium sorrentinoi is the only one mentioned in the Annex II of the 92/43 EU Directive. All these plant species, classified as critically endangered or vulnerable according to IUCN criteria, are currently experiencing a rapid shrinkage, and some have already gone extinct, as in the case of Puccinellia gussonei. Hence, the inclusion of Sicilian badlands in the 92/43 EEC Directive is urgently required also for plant conservation purposes.
Macrotype: 15 Salt and gypsum inland steppes Name: Mud volcanoes and badlands in the evaporitic outcrops of Sicily Description: Mud volcanoes with almost continuous degassing activity and patchy halo-tolerant xerophitic vegetation colonizing the top, the slopes and the base of the steep to gently sloping and rounded badlands. Such vegetation occurs on marly, clayey-marly and salty-clayey substrates of the geological unit "Formazione Gessoso-Solfifera", including several sedimentary materials accumulated during the Messinian Salinity Crisis. This habitat is mostly concentrated in the inner part of Sicily and hosts both xerophilous and hygrophilous grassland communities, adapted to face different severe and counteracting stress factors (e.g., winter soil waterlogging and oxygen shortage, summer water shortage and cracking). Sicilian mud volcanoes occur in the Province of Agrigento, Caltanissetta and Catania (Cangemi Madonia, 2014). Some of these went destroyed during the last century, including the ones forming the famous lake Naphtia, near Palagonia, home of the divine twins Palikoi, feared and venerated by central-eastern Sicilians already three thousand years ago. Clayey and marly badlands are more widespread throughout the island, particularly in the provinces of Agrigento, Caltanissetta, Enna and Catania, with minor spots in the provinces of Trapani and Palermo (Brullo et al. 2010(Brullo et al. , 2013 Dynamic contacts: Mud volcanoes are bare areas, totally devoid of vascular plant cover, but they may host interesting algal communities. The halo-nitrophilous scrub communities of the harshest badlands (Salsolo oppositifoliae-Suaedion fruticosae, Pegano harmale-Salsoletea vermiculatae) are dominated by few species adapted to face the hyperarid conditions and the intense erosion of the steep slopes. Some sub-nitrophilous plant communities referred to Artemision arborescentis may occur on more humid badlands under meso-mediterranean bioclimatic conditions. The drought stress-tolerant communities, framed into Moricandio-Lygeion sparti (Lygeo sparti-Stipetea tenacissimae), are dominated by few hemicryptophytes and are rich in narrow endemics. On clayey or loamy compact soils, Lygeum-dominated grasslands are often intermingled with halo-subnitrophilous sparse ephemeral swards framed into Frankenion pulverulentae (Saginetea maritimae), also colonising the gently sloping margins of temporary ponds, while the bare ridges and the steepest eroded slopes are characterised by the uneven cover of therophytic assemblages referred to Gaudinio fragilis-Podospermion cani. Badlands and mud volcanoes may form complex landscapes hosting a patchwork of hygrophilous communities referred to Charetea fragilis, Isoeto-Nanojuncetea, Juncetea maritimi, Phragmito-Magnocaricetea and Nerio-Tamaricetea.  Brullo Siracusa 2000, ibidem].

3) Meso-and supramediterranean acidophilous Sicilian broomfields
Motivation: The meso-and supramediterranean acidophilous Sicilian broomfields represent the most south-eastern and isolated stands of pertaining to a group of plant communities with Iberian-Atlantic distribution. The chief species of this vegetation type spread in Sicily during the hypsothermal period following the last glacial event (during the Atlantic and Subboreal chronozones, see Orombelli Ravazzi, 2002) and have persisted in local areas where the summer aridity is buffered by orographic moisture condensation and water-rich acidic soils. This vegetation type migrated through southern France and along the Tyrrhenian side of the Apennines and Calabrian Massifs, until reaching north-western Sicily (De Beaulieu et al. 2005). Here, the isolated populations in some cases gave rise to new, autonomous lineages as a consequence of the geographic isolation and the adaptation to mountain ecosystems (Sciandrello et al. 2015). Owing to the biogeographical interest and the occurrence of exclusive endemic species, this habitat deserves adequate protection.
Macrotype: 51 Sub-Mediterranean and temperate scrub Name: Meso-and supramediterranean acidophilous Sicilian broomfields Description: Mesophilous forest fringes and shrublands dominated by Pteridium aquilinum and genistoid nanophanerophytes with flexible and elongated green branches, growing on humid, non-eroded, nutrient-poor acidic soils. The dominant species, thanks to the symbiosis with nitrogen-fixing bacteria, play an important role in soil-formation processes. Such vegetation s widespread in the western territories of the Mediterranean, sub-Atlantic and Atlantic regions, often as seral stages replacing oak-dominated mixed deciduous woods. In Sicily, it is rather common along the Peloritani and Nebrodi moun-tains and on Mount Etna, on soils deriving from quartz sandstones, metamorphic siliceous rocks and volcanic debris, within the meso-and supramediterranean subhumid to hyperhumid bioclimatic belts (Bartolo et al. 1994;Guarino 1998;Siracusa 1997;Gianguzzi 1999). The vegetation included in this habitat thrives particularly well on sea-facing submontane and mountain slopes, where it benefits from the condensation of moist air currents rising from the sea.
Diagnostic sentence: Mesophilous forest fringes and shrublands dominated by Pteridium aquilinum and genistoid nanophanerophytes, growing on nutrient-poor acidic soils, within the meso-and supra-Mediterranean, subhumid to hyperhumid bioclimatic belt. List

4) Small woods dominated by Celtis tournefortii subsp. aetnensis
Motivation: Celtis tournefortii is a widely distributed species ranging along the south-eastern border of continental Europe, from the southern slopes of Caucasus to the Balkan and Aegean regions (Browicz Zieliński 1984;Tutin 1991;Boratyński et al. 1992). The Sicilian populations of the species, referred to the subsp. aetnensis, represent the most western and isolated outpost of its distribution range, testifying Miocene connections between the Balkan and Tyrrhenian territories (Montelucci 1972;Tomaselli 1972;Pezzetta 2010). These Sicilian populations show a circumscribed and fragmentary distribution, occupying refuge habitats of remarkable phytogeographic interest, worthy to be preserved.
Macrotype: 63 Sclerophyllous grazed forests Name: Small woods dominated by Celtis tournefortii subsp. aetnensis Description: Small woods dominated by Celtis tournefortii subsp. aetnensis, 3-6 m tall, distributed in scattered patches of 200-400 square meters, from 380 m to 1340 m a.s.l., between the upper dry thermomediterranean and the sub-humid supramediterranean bioclimate. The stands occur on stony sites with different outcropping rocks, such as the lava flows (locally named "sciare") on the south-western slopes of Mount Etna, quartz sandstones (southern slopes of the Nebrodi Mts. and Madonie Mts., near Gangi), marly-limestone screes (Sicani Mountains and lower part of the southern slope of Rocca Busambra), up to the summit ridges of Rocca Busambra, on cryoturbated calcareous-dolomitic outcrops (Troia 1997;Schicchi Marino 2011;Gianguzzi et al. 2014).
Diagnostic sentence: Small woods dominated by Celtis tournefortii subsp. aetnensis, associated with Pistacia terebinthus and evergreen species and lianas of the Mediterranean scrub. These woods consist of relict, scattered patches settled in xeric and stony habitats, between the dry thermomediterranean and the sub-humid supramediterranean bioclimatic belts.
Dynamic contacts: The vegetation at issue tends to have a primary character and plays an important ecological role in stabilizing screes and detrital fans, representing the most evolved aspect of the "Sicilian hilly and submontane, detrital, indifferent edaphic, thermo-mesomediterranean subhumid series of the Pistacio terebinthi-Celtido aetnensis sigmetum". This edaphophilous series is strongly affected by frequent rock falls and landslides and by local microclimatic conditions, with remarkably wide daily and annual temperature ranges. Towards the central part of the detrital fan, the Pistacio terebinthi-Celtido aetnensis sigmetum gets in catenal contact with the shrubby and herbaceous vegetation of the scree microgeoseries, while at the edge of the its habitat, the sigmetum can be in contact with woodlands dominated, either by: a) Quercus ilex (habitat 9340), linked to rocky habitats with deeper soil (e.g., Aceri campestris-Quercetum ilicis on the Sicani Mountains, as well as Teucrio siculi-Quercetum ilicis on Mount Etna); b) Quercus pubescens s.l. (habitat 91AA -Eastern white oak woods), on deeper and more evolved soils (e.g., Oleo sylvestris-Quercetum virgilianae on the Sicani Mountains and Rocca Busambra, as well as Celtido aetnensis-Quercetum virgilianae and Festuco heterophyl-lae-Quercetum congestae on Mount Etna). In the upper part of its growing sites, the Pistacio terebinthi-Celtido aetnensis sigmetum can also be in contact with the vegetation of rocky cliffs (habitat 8210, calcareous rocky slopes with chasmophytic vegetation), or with the Mediterranean maquis ascribed to the habitat 5330 (Euphorbia dendroides-maquis), with the perennial and annual dry grasslands of the habitat 6220* (Pseudo-steppe with grasses and annuals of the Thero-Brachypodietea) or with the thermoxeric sclerophillous woods ascribed to the habitat 9320 (Olea and Ceratonia forests).
Phytosociological arrangement: Pistacio terebinthi-Celtidetum aetnensis Gianguzzi Local agro-pastoral practices, mostly based on a biennial rotation system, maintain good levels of productivity with no need of chemicals for soil fertilization or against weeds and pathogens. Such extensive land use, combined with the lower impact of cattle grazing with respect to other domestic herbivores, is responsible for the high species richness recorded within chiuse (Baumel et al. 2018). Although chiuse host few preferential/differential plant species, they are home to many rare, protected, and endemic plants, like the orchids Ophrys calliantha, Ophyrs discors and Ophrys lunulata, the last being a priority species according to 92/43 EEC Directive. Chiuse also represent an important habitat for prey birds (e.g., Buteo buteo, Falco tinnunculus, Tyto alba), for the Sicilian Rock Partridge (Alectoris graeca subsp. whitakeri) and for several important migratory birds (e.g., Alauda arvensis, Coturnix coturnix).
Macrotype: 63 Sclerophyllous grazed forests Name: "Chiuse" with Ceratonia siliqua of south-eastern Sicily Description: The native status of the island's carob populations is still under debate (Ramón-Laca 2004; Viruel et al. 2020): in fact, ancient documents never mention forest communities dominated by carob trees, while many of them attest the extensive cultivation of this species since the XVII century after huge forest clearings (e.g., in the territory of Vittoria, once part of the Countee of Modica). The construction of these fenced areas is intimately related to the stony and rugged characteristics of the Hyblaean Plateau. Since ancient times, to enhance agro-pastoral activities local inhabitants used to create stone mounds along border of their properties. These mounds were gradually transformed into dry limestone walls to delimit crop fields, tree groves, or, more frequently, agro-silvo-pastoral complex ecosystems with crop fields and pastures and an uneven and scattered olive, almond, azerole and more frequently carob tree cover, with average low density of (often huge and aged) individuals (10-20 plants per hectare). This complex landscape and its cultural landmarks (stone walls, terraced groves, etc.) are generally well preserved; they were able to survive across the centuries and to face modernity because local rural economy, after experiencing some decades of economic crisis between 1970s and 2000s, re-started thanks to brilliant marketing initiatives (e.g., eco-tourism) valorising local agro-pastoral activities and products. For instance, the toasted flower obtained from carob pods is used to produce the famous "chocolate of Modica", while these pastures feed the free-roaming cows of a local breed called "modicana", producing the renowned "caciocavallo ragusano" cheese. Another traditional knowledge linked to carob trees is the local culinary use of Laetiporus sulphureus (whose vernacular name is "funcia ri carrùa"), a mushroom frequently associated with Ceratonia siliqua.
During last decades many chiuse located near the coast have been transformed into greenhouses for vegetable production and have been lost forever. Today the major threats to these man-made ecosystems are the abandonment of the land and traditional practices. Due to progressive succession processes, this agro-silvo-pastoral system is slowly changing into an intricate Mediterranean maquis. In addition, another threat for the "chiuse", also featured in the national catalogue of the rural historical landscapes (https://www.reterurale.it/flex/cm/pages/ ServeBLOB.php/L/IT/IDPagina/14376), is the transformation of ancient farms to make new private estates with no respect for traditional building style and/or not using local stone material. Dynamic contacts: Along the south-eastern coast of Sicily the chiuse with carob trees get in contact with the communities of the Periplocion angustifoliae and in particular with the association Calicotomo infestae-Rhoetum tripartitae or with the communities of the Oleo-Ceratonion (Myrto communis-Pistacietum lentisci). In these contexts, the grazed chiuse host a mosaic of communities framed into the Echio-Galactition, perennial grasslands referred to the Hyparrhenietum hirto-pubescentis, annual grasslands (Plantagini coronopi-Catapodietum mari-ni, Anthemido secundirameae-Allietum lehmanii and, on rocky outcrops, Thero-Sedetum caerulei). In the inland, the chiuse are characterized by scattered remnant downy oak forest stands ascribed to Oleo sylvestris-Quercetum virgilianae and perennial grassland communities issuing from woodland degradation (Avenulo-Ampelodesmion mauritanici).
Woodwardia radicans is a conservation target included in Annex II of Directive EEC 43/92 and in the IUCN Red List with the status of "Endangered" for the Mediterranean basin (De Belair 2010) and "Vulnerable" for Europe (Christenhusz et al. 2017). In Sicily, according to IUCN criteria it is considered an "Endangered" species (Spampinato et al. 2008), a status recently confirmed (Crisafulli et al. 2021).
The need for a specific habitat type concerning shady dripping cliffs had already been highlighted by Spampinato Puglisi (2009) in the drafting of the Italian Manual for the Interpretation of habitats under 92/43 EEC Directive. Up to now the bryo-pteridophytic communities of the class Adiantetea are not recognized as a habitat of Community interest, although they are important for the conservation of various hygrophilous and rupicolous species.
Due to climate change and the diversion of water flows for agricultural or urban purposes, the extent of this habitat is continuously decreasing in Sicily: for instance, it has disappeared on Mount Etna since a century and is now found exclusively in a few localities in the Peloritani Mountains (Crisafulli et al. 2021).
Macrotype: 83 Other rocky habitats Name: Shady dripping cliffs with Woodwardia radicans and other large ferns Description: Dense, three-layered vegetation consisting of a dense moss carpet, thickly covered by the fronds of Adiantum capillus-veneris, in turn loosely covered by the fronds of large ferns, such as Woodwardia radicans, Pteris vittata, Osmunda regalis, Phyllytis scolopendrium, thriving near waterfalls and/or on shady rocky faces located in narrow ravines and gorges, constantly dripping with clear and well oxygenated freshwater (Brullo et al. 1989), in northeastern Sicily (Tyrrhenian side of the Peloritani Mountains, no longer present on Mount Etna), within the thermo-and mesomediterranean bioclimate.
Diagnostic sentence: Bryo-pteridophytic communities with large ferns, covering rocky faces located in narrow and shady ravines and gorges within the thermo-and mesomediterranean bioclimate.
List Dynamic contacts: This vegetation may come in contact with the forest communities ascribed to Habitat "9180*: Tilio-Acerion forests of slopes, screes and ravines", mixed mesophilic broadleaved forests growing on steep rocky slopes or gorges and with the evergreen forests dominated by holm oaks of the habitat "9350 Quercus ilex and Quercus rotundifolia forests". In areas affected by frequent fires, this habitat may come in contact with secondary woody communities such as tall shrublands dominated by Erica arborea.

7) Birch woodlands of Mount Etna
Motivation: The Betula etnensis woodlands of Mount Etna represent the most southern and isolated remnants of a vegetation which spread in Sicily during the cold phases of the Pleistocene glacial events and have locally persisted in restricted areas where the summer aridity is buffered by orographic moisture condensation, on welldrained acidic soils. The migration pattern of birch trees developed through southern France and along the Tyrrhenian side of the Apennines and Calabrian Massifs, until reaching Sicily (Agostini, 1981). Here, the isolated populations of birch gave rise to a new lineage, slightly diversified from Betula pendula, as a consequence of geographic isolation and adaptation to the new volcanic habitat (De Dato et al. 2020;Giusso del Galdo et al. 2021).
Owing to the biogeographical interest and the occurrence of narrow endemic species, the habitat dominated by B. etnensis deserves adequate protection.
Macrotype: 92 Mediterranean deciduous forests Name: Birch woodlands of Mount Etna Description: Mesophilous, edapho-xerophilous deciduous woodland physiognomically dominated by Betula etnensis Rafin., a narrow endemic tree species exclusively found on Mt. Etna, where it was probably more widespread in the past and has been exploited for centuries by local people, mainly for charcoal production (Strano 2010). This deciduous plant community is usually represented by open woods growing on volcanic scoriae, where the soil evolution is hampered by the severe climatic conditions and by the frequent volcanic events, such as tephra rains. This woodland type ranges between 1400 and 2000 m a.s.l., chiefly on the north-eastern slopes, showing its optimum within the upper supramediterranean humid-hyperhumid bioclimatic belt, with penetrations towards the oromediterranean belt (Brullo et al. 2012). This community exhibits a remarkably pioneer character, occurring within the area potentially occupied by the beech woods of the Epipactido meridionalis-Fagetum sylvaticae above 1800 m a.s.l. Dynamic Contacts: This association comes in contact at lower altitudes with the edapho-xerophilous vegetation of Daphno laureolae-Pinetum calabricae, at higher altitudes with the hedgehog-heaths ascribed to Astragaletum siculi (Bagnato et al. 2014).

8) Ostrya carpinifolia woods of Sicily
Motivation: Sicily hosts the southwesternmost stands of Ostrya carpinifolia. This species is known for having gone through alternate phases of expansion/regression during the late Quaternary vegetation history of the Mediterranean Basin; last maximum expansion occurred between 8000 and 4500 years ago (Willis 1992;Tzedakis 1994;Denèfle et al. 2000). The current distribution of the species in Sicily is restricted to steep valley slopes scattered in the main mountain ranges of the island, where it participates to extremely localized broadleaved deciduous mesophilic woods. The high biogeographical interest and the relict connotation of these woods impose to consider them an important conservation target for preserving the Sicilian biodiversity.
Macrotype: 92 Mediterranean deciduous forests Name: Ostrya carpinifolia woods of Sicily Description: Three-layered thermophilous and aerohygrophilous broadleaved woods, thriving on steep valley slopes, gorges and tributary detrital fans, scattered in the main mountain ranges of Sicily on different soil parental materials, from limestone to acidic metamorphic and volcanic rocks. The canopy is dominated by thermophilous deciduous (with some evergreen) trees, among which Ostrya carpinifolia and sometimes Acer obtusatum provide the floristic and physiognomic characterization of this habitat. Under conditions of higher edaphic and environmental humidity, Laurus nobilis and Tilia platyphyllos are also frequent, whereas under greater lighting Quercus ilex and Fraxinus ornus also play an important role. These woods largely depend on moist and fresh microclimatic conditions and range between 200 and 1200 m a.s.l., with optimum within the meso-and supramediterranean humid bioclimate. This habitat is well represented in the main gorges of the Hyblaean plateau, along the eastern slope of Mount Etna and in the mountain ranges of NE-Sicily (Peloritani and Nebrodi Mts.; Brullo Marcenò 1985;Bartolo et al. 1992;Brullo et al. 1996;Minissale et al. 2007). The scattered occurrence of many isolated spots of Ostrya carpinifolia in the mounts near Palermo and on the Sicani Mts. (Marcenò and Ottonello 1993;Venturella et al. 1991;Marino and Ilardi 2007;Castellano et al. 2009;Giardina et al. 2015) suggests that this habitat was once more widespread also in western Sicily. Phytosociological arrangement: Aceri obtusati-Ostryetum carpinifoliae Brullo Marcenò 1985, Arabido turritae-Quercetum congestae Brullo Marcenò 1985, Hieracio criniti-Aceretum aetnensis Brullo C. et al. 2012[Tilio-Ostryon carpinifoliae Brullo, Scelsi Spampinato 2001, Fagetalia sylvaticae Pawłowski in Pawłowski et al. 1928

Discussion
The combination of a phytosociological and phytogeographical approach to habitat recognition represents a convenient way to resolve the conundrum of habitat identification. However, some appropriate additions to the Habitat Directive would be highly desirable to ensure adequate and explicit protection to the Sicilian habitats listed above, that host rare species of phytogeographic interest, highly localized edaphic specialists and, also, historical rural landscapes shaped by traditional land uses.
Some of these habitats have been forced into comparable units already codified by Directive 92/43 (http://vnr. unipg.it/habitat/). However, an excessive "stretching" in the habitat interpretation leaves room for ambiguity and uncertainties in the correct identification and designation of the conservation targets (Pasta La Mantia 2009).
For example, the recognition of the habitat here proposed as "Meso-and supramediterranean acidophilous Sicilian broomfields" would eliminate the interpretative impasse that forces some of these formations, either, into habitat 5330 (Thermo-Mediterranean and pre-desert scrub), together with thermomediterranean broom fields (retamares) in Sicily represented by coastal formations dominated by Retama raetam subsp. gussonei or by Genista tyrrhena, or, instead, into habitat 4090 (Endemic oro-Mediterranean heaths with gorse), together with the high-mountain vegetation dominated by Astragalus siculus or A. nebrodensis.
Similarly, the recognition of the habitats here proposed as "Mud volcanoes and badlands in the evaporitic outcrops of Sicily" and "Sicilian gypsum outcrops" would allow to consider as a whole the mosaic of contiguous habitats that characterize these so peculiar geomorphological units (similarly to what happens with the Habitat 8320 "volcanic outcrops and lava fields"). This would en-sure better protection also to the vegetation dominated by some endemic taxa, such as Tripolium sorrentinoi (Asteretum sorrentini, see Brullo et al. 2010) or Astragalus caprinus subsp. huetii (Astragalo huetii-Ampelodesmetum mauritanici, see Minissale 1995), currently lumped into the omni-comprehensive and ubiquitous habitat 6220 (Pseudo-steppe with grasses and annuals of the Thero-Brachypodietea).
The choice of using a "geology-based" criterion to circumscribe the two above-mentioned habitats is justified by the difficulty of separating the tiles of a mosaic in which vegetation units ascribed to different phytosociological classes (such as Pegano-Salsoletea, Lygeo-Stipetea, Saginetea maritimae, Thero-Brachypodietea, Juncetea maritimi and others) intermingle in very close spatial contiguity. The opportunity to propose as autonomous some of these vegetation units would require an in-depth comparative analysis of their physiognomic and structural characteristics, which is not always available apart few exceptions (Brullo et al. 2013;Marcenò et al. 2019) and is adventurous to pretend from an instrument, i.e. the Habitat Directive, whose main purpose is identifying conservation targets in the easiest and most practical possible way. Moreover, designating mud volcanoes and badlands as a whole habitat allows to safeguard the landscape unicum and its root causes, which are eminently geological, and to ensure an unitary impact assessment to any project of "hydraulic-forestry amelioration" with acacias or eucalyptuses or, worst, to any transformation of these sites into landfills, photovoltaic power plants, go-cart tracks and, in the case of gypsum outcrops, also into intensive vineyards after gypsum-grinding.
The habitat "mud volcanoes and badlands in the evaporitic outcrops of Sicily" is akin to the habitat already proposed (Genovesi et al. 2014) as "halophilous and/or subalophilous pioneer vegetation in badlands". However, the badlands of Peninsular Italy host a somewhat different vegetation from that of Sicily, as it lacks the shrub component typical of the Pegano-Salsoletea class. Therefore, it was decided to propose a new habitat for Sicily.
Also, the habitat "Ostrya carpinifolia woods of Sicily" is similar the habitat already proposed (Genovesi et al. 2014) as "hop-hornbeam Italo-Balkan woods". However, the latter has a floristic composition and ecological settings quite different from those in Sicily and, with reference to the EUNIS habitat classification, it is to be classified among the "temperate and submediterranean thermophilous deciduous forest" (code: G1.7a) rather than the "Mediterranean thermophilous deciduous forest" (code: G1.7b), as it happens for the Sicilian stands.
Lastly, the habitat "Shady dripping cliffs with Woodwardia radicans and other large ferns" is similar to the habitat "Mediterranean dripping cliffs", also present in Sicily and already proposed (Spampinato and Puglisi 2009;Genovesi et al. 2014) to be integrated into the Habitats Directive. However, it is considered appropriate to treat as a separate habitat the Adiantetea vegetation characterized by the presence of large ferns (such as Woodwardia radi-cans and Pteris vittata) which, due to their extreme rarity, should be pertaining to priority habitat.
To fully understand the obvious gaps of the Habitat Directive in Sicily, it is worth to consider that the Italian botanists did not play a very active role in the definition of the "Annexes" to the Directive, both as regards species and habitats (Biondi et al. 2010). This lack particularly affects the surface areas of the Italian territory belonging to the Mediterranean ecoregion, determining a gap that could not be filled until today. In fact, since the publication of the Habitat Directive, no official integration of its annexes has been allowed, with exceptions reserved only to the countries involved in the EU enlargement.
In recent years, the regional administration of Sicily has put significant effort to ensure the long-term management of the Natura 2000 sites, taking account of all potential sources of EU, national and regional funding. These efforts include the implementation of management plans, the recognition of new sites (Fig. 1) and the establishment of a list of priority actions to be carried out in the next decade. Unfortunately, these efforts are not sufficient to ensure adequate protection to many relevant habitats and species occurring in Sicily, due to the above-mentioned shortcomings of the Habitat Directive and to some inconsistencies in the designation of the habitats already included in the same Directive (Pasta La Mantia 2009).
As it happens for many habitats officially designated as conservation targets, also the "neglected" habitats mentioned in this contribution are declining both in extent and quality for different reasons, related to land abandonment, land-use change, destruction and alteration of the local biota, pollution and eutrophication of water, wetland reclamation, water abstraction, introduction of alien species, urbanisation and infrastructure development. These pressures and threats act at different spatio-temporal scales and vary across different habitat types (Bagella et al. 2016;Gigante et al. 2016Gigante et al. , 2018Angiolini et al. 2017;. In particular, the disappearance or the exacerbation of anthropogenic disturbance (e.g., abandonment of traditional practices, cessation of grazing or, instead, overgrazing and increased fires frequency) can compromise many of the habitats we have proposed.

Conclusions
Aim of every protected area in the world is to promote in situ conservation strategies for threatened habitats and species. This should be done by the set up of a network of stakeholders, administrators and scientific experts which will support capacity building, management and policy actions. Unfortunately, these intentions are inevitably constrained by the lack of scientific knowledge on the ecosystem functioning and by the reality of limited economical resources. Conservation must therefore be based on the establishment of priorities, in order to determine how these limited resources could be best allocated (Guarino et al. 2011).
People's perception of protected areas is, in most of the cases, limited to the recreational or aesthetical function of biotopes and biodiversity: a kind of "playground for ecologists" that can be used for outdoor activities and experiential marketing. This limited view should be widened through the use of protected areas as living labs for the environmental education, to raise the public awareness on the function of ecosystems. Unfortunately, managers and planners seem to be much more sensitive to the marketing and promotion of typical products and to the construction of infrastructure to improve accessibility and usability of these areas. This is not necessarily a negative aspect, but it can be so if it becomes the priority target for the development of protected areas . Too many habitats and natural sceneries have been irreparably spoiled by senseless interventions to "improve" accessibility and usability. This is the case, for example, of the renowned Etnean "Rifugio Sapienza" and surrounding areas, where thousands of absent-mindedly tourists are brought on Mt. Etna "to walk on the lava", with best regards to the superficiality that already characterizes the average way of living of the urban people.
The only way to contrast these dangerous shortcuts is a correct and unambiguous designation of the conservation targets, accompanied by appropriate conservation measures, management plans, prioritized action framework, monitoring and periodical updating of the Habitat Directive in the light of the new achievements emerging from territorial research and thematic in-depth studies. Last but not least, substantial resources have to be invested in education and dissemination campaigns, in order to reach a societal consensus on the need for conservation of the Natura 2000 sites and the Sicilian biodiversity in general.