Coastal Biodiversity Assessment Aided by Citizen Science Volunteers: A Look at the Italian Central Adriatic

Abstract

Coastal ecosystems, encompassing land and marine environments and hosting substantial biodiversity, are among the most threatened worldwide. The European Habitats Directive prioritises coastal habitats and species, requiring legislative, direct protection, monitoring, and informational measures. Accurate habitat and species monitoring is crucial to conservation efforts, yet biodiversity research in complex, ever-changing environments like coastal areas is difficult. Citizen Science may bridge biodiversity assessment and eco-friendly monitoring by incorporating non-scientists into the data collection for scientists and stakeholders. A Citizen Science approach supported by a dedicated iNaturalist project (called Wild Coast CASCADE) was implemented to obtain a complete monitoring framework that includes observations of many taxa in terrestrial, aquatic, and transitional dynamic coastal environments in the Central Italian Adriatic coast. We explored data gathered focusing on the IUCN Red List species, the species and habitats of European conservation concern, and the non-native species. Between 2020 and 2023, we collected 3784 records covering 742 species, with 81% meeting the “research grade criteria”, and these were retained for subsequent research. Citizen Science volunteers have collected 291 georeferenced animal records from the global IUCN Red List, 51 plant species from 14 species that are indicators of the presence of habitats of European Conservation Concern, and 44 non-native plants and animals. Our results provide evidence that citizen research projects can effectively assist in monitoring coastal–marine habitats and species. They also underline the potential of Citizen Science for biodiversity conservation and emphasize the importance of public engagement in conservation efforts.

1. Introduction

Coastal ecosystems are characterised by dynamic transitional zones between terrestrial and marine environments, exhibiting significant levels of specialised biodiversity [1,2]. Not only do they possess significant quantities of unique flora and fauna, but they also offer a multitude of benefits to society and ecosystem services [3,4]. Simultaneously, coastal areas are ranked as one of the most at risk in the world [5,6], with the Mediterranean region being particularly vulnerable [7,8]. To mitigate the ongoing deterioration of these imperilled habitats, they are subject to conservation restrictions that have been imposed at both the global and regional level. The Convention on Biological Diversity [9] underscores the importance of allocating focused attention and financial resources to the preservation of biodiversity in coastal areas. The Member States of the European Union have collectively embraced the Council Directive 92/43/EEC, more often known as the Habitats Directive (HD). This legislation represents an important step forward in the development of a European approach to nature conservation. The HD designates numerous coastal ecosystems as habitats that require conservation efforts. These habitats are specifically mentioned in Annex I of the directive. Additionally, the HD identifies certain coastal species of flora and fauna that are of conservation importance. These species are included in Annexes II, IV, and V of the Habitats Directive, deserving either direct (the species) or indirect (their habitat) protection. Art. 17 of the directive impose all member states to monitor and report every six years on the distribution and conservation status of all species and habitats listed in Annexes I, II, IV and V. Furthermore, it establishes a comprehensive network of biologically significant areas referred to as the Natura 2000 network, aiming to preserve these ecosystems and species in a state of “good conservation status”. Each Natura 2000 site is obligated to develop and implement the essential measures and actions required to guarantee the enduring preservation of the designated species and habitats as stipulated by HD. These measures must encompass regulatory, direct protection, monitoring, and information-based strategies. The importance of precise monitoring of habitats and species is widely acknowledged as a crucial element of successful conservation strategies [10,11]. However, conducting periodic biodiversity assessments in complex and ever-changing environments such as coastal transitions can be problematic. This difficulty stems from a variety of factors, including the high costs involved [12,13], poor accessibility to specific sampling locations [14], and the intricate nature of organising field campaigns that require frequent and regular intervals [15].

Citizen Science (CS) is a potential solution for bridging the divide between biodiversity assessment and the implementation of efficient and economical monitoring practises [16]. Citizen Science encompasses the participation of non-professional citizens in many scientific activities, including data collection and analysis, technology development, species occurrence assessment, and the dissemination of these endeavours [16]. The continuous expansion of online platforms and the introduction of novel digital technologies are facilitating a significant increase in the engagement of CS activities [16,17]. Volunteer participation in environmental data collection fosters their connection to research subjects, while also raising public awareness about pressing issues such as biodiversity loss, climate change, environmental contamination, and the spread of invasive species [18]. Furthermore, CS efforts have shown favourable improvements in citizen behaviour, encouraging a more environmentally concerned and scientifically engaged citizenry [19]. At the same time, there is empirical support for the impact of data acquired by CS endeavours in the surveillance of distinct ecological systems, such as forests or savannas [20,21,22]. CS may also contribute to increasing public awareness in long-term monitoring areas [23,24]. Certain studies have specifically focused on investigating the application of CS in the monitoring of fauna, e.g., [25,26], or flora [27]. Additionally, there are studies that have explored the use of CS for monitoring specific domains, such as water or land [28,29]. CS initiatives are frequently aimed at specific tasks, such as implementing environmental education for youth [30,31,32], studying the presence of rare or less attractive species [33,34], or even monitoring biological invasions [35,36]. Yet, the studies that simultaneously analyse organisms belonging to distinct kingdoms are still scarce [37,38,39]. Moreover, the use of CS to support the implementation of a comprehensive observation framework, which includes observations of many taxa in various terrestrial, aquatic, and transitional dynamic systems in coastal regions, has not been attempted thus far, and it is necessary to enhance our comprehension of how CS can function in such a context.

iNaturalist [40] is a social networking platform that was founded in 2008 to facilitate the collaboration of individuals from various scientific backgrounds, including professionals and laypeople, to collectively document and disseminate discoveries related to biodiversity [40]. This platform is well recognised as an efficient networking service for the purpose of observing biodiversity and preserving associated data within the realm of CS activities. iNaturalist relies on a substantial user base of over six million registered participants, serving as a hub for scientists, naturalists, biologists, and citizens alike who are interested in advancing online CS endeavours and facilitating the gathering of biodiversity data [40]. The collection consists of more than 160 million verifiable observations, with a continuous growth rate, and each observation is accompanied by details, including the geographic location and date of observation. The dataset excludes observations of organisms that are held in captivity or those that have been cultivated. Notably, around 100 million of these observations have achieved the designation of “research grade”, indicating their credibility and suitability for scientific applications (as of 10 October 2023). The iNaturalist programme has been recognised as a key tool for collecting biodiversity data in multiple nations globally [41]. Moreover, it has gained significant popularity as a social platform for consolidating nature-related data [12]. According to [42], the platform has the capacity to significantly contribute to the implementation of conservation strategies by providing useful data to many stakeholders, including research initiatives, land managers, environmental organisations, and the wider public.

Within this framework, the current study aims to examine the capacity of CS initiatives facilitated by the iNaturalist platform in monitoring biodiversity in coastal–marine regions, with a specific focus on the Central Adriatic Italian coast as a designated experimental site. For this purpose, we established a specialised iNaturalist project known as the “Wild Coast CASCADE” (WCC) and subsequently investigated critical questions pertaining to the preservation of biodiversity within these regions by means of CS. Subsequently, we focused our attention on those data pertaining to taxonomic groups that are of conservation significance. These groups include (a) species that are listed in the IUCN red book and are also present in the annexes of HD, (b) plant species that serve as indicators for the occurrence of habitats that are of conservation concern in Europe (HD), and (c) non-native species. Focusing on these three species groups can meet different needs in conservation biology. Firstly, the updated distribution of vulnerable species might potentially enhance devoted monitoring and conservation efforts. Secondly, investigating the occurrence of plant species that serve as indicators of European habitats may allow us to propose specific management priorities for the analysed coasts. Finally, the inclusion of current and accurate data regarding the occurrence of alien organisms can enhance the effectiveness of the early detection systems for invasive species.

2. Materials and Methods

2.1. Study Area

Biodiversity data were gathered from the coastal areas of the Abruzzo and Molise regions in Central Italy, along the Italian Central Adriatic coast. The study area, spanning a total distance of roughly 166 km and encompassing a landward extent of 300 m and a seaward extent of 500 m, exhibits a Mediterranean climate. This stretch of coast is distinguished by expanses of sandy or gravelly/pebbly beaches that are occasionally interrupted by rocky promontories and interspersed with the mouths of rivers. Previous studies evidenced the high ecological significance of the analysed coasts [43,44]. The southern sector is characterised by seashores mostly composed of gravel and pebbles (Abruzzo), while the southern tract (Molise) is predominantly characterised by low dunes. As far as bathymetry is concerned, the entire study area is characterised by very shallow depths, with the depths sloping gently from the coast towards the open sea [45].

The study area comprises a total of eleven areas under differ types of protection, including 1 marine protected area, 3 regional reserve sites, and 7 Natura 2000 sites (Figure 1), all requiring biodiversity monitoring activities, as mandated national and international regulations. In addition, the area includes two sites of the Long-Term Ecological Research Network (LTER), specifically referred to as “Foce Saccione-Bonifica Ramitelli” (IT20-003-T) and “Foce Trigno-Marina di Petacciato” (IT20-002-T; [46]; https://deims.org/6d7ffd99-40e1-4f0d-ad26-6904581dbe9b (accessed on 1 August 2023)).

2.2. Data Collection

Data were collected through CS initiatives, which included active engagement in public outreach and educational activities that began in August 2020 (for details, see Figure 2). We sent invitations to a diverse group of people, requesting their cooperation and participation in the process of collecting data on the presence of wild species in both natural and semi-natural sites. From 2020 to 2022, a total of 12 CS initiatives along the Central Adriatic coast were coordinated and implemented in collaboration with local NGO’s, such as “Ambiente Basso Molise” (http://ambientebassomolise.blogspot.com/ (accessed on 1 August 2023)) and the Abruzzo Institution for Protected Areas (IAAP, https://www.iaap.it/ (accessed on 1 August 2023)), along with protected area management bodies such as the Marine Protected Area “Torre del Cerrano” and the Special Area of Conservation Punta Aderci–Punta della Penna (IT7140108). Our initiative was partially supported by the INTERREG Italy–Croatia CASCADE project (https://www.italy-croatia.eu/web/cascade (accessed on 1 August 2023)) and the LIFE17 NAT/IT/000565 CALLIOPE project (https://lifecalliope.eu/ (accessed on 1 August 2023)).

2.3. Data Storage and Organization

The WCC records were obtained from a diverse range of sources, including organised CS events and the independent leisure activities of individuals. These records were collected from the beginning of August 2020 to the end of January 2023 and involved the participation of hundreds of observers (Figure 2). Data were systematically collected within a dedicated iNaturalist project known as the “Wild Coast CASCADE” (WCC) (https://www.inaturalist.org/projects/wild-coast-cascade (accessed on 1 August 2023)). Each individual observation submitted to the WCC project consisted of one or more field photographs, precise geographic coordinates, and a proposed taxonomic identification provided by the iNaturalist criteria (for the full explanation of how iNaturalist works, please refer to https://www.inaturalist.org/pages/help#general3 (accessed on 1 August 2023)). In addition to the iNaturalist platform, we established a specialised Facebook webpage that offered people with low computer experience the chance to submit observations that the managers of the WCC will then upload to iNaturalist on their behalf.

The comprehensive evaluation of the quality of each observation involved an initial classification of the newly submitted entry as “Needs ID”, indicating the requirement for verification and potential correction by members of the iNaturalist community who possess expertise in the relevant taxonomic categories.

After achieving a consensus among a majority of specialists (i.e., more than two-thirds) who verified the identification of the organism at the species level, the observation was subsequently elevated to the category of “research grade”. This categorization enhances the suitability of the data for scientific utilisation (Figure 2). The data collected consisted of a wide range of living organisms, representing different taxonomic levels. The aforementioned observations were categorised according to the 13 taxonomic groups acknowledged by iNaturalist, namely Actinopterygii, amphibians, arachnids, birds, chromists, fungi and lichens, insects, mammals, molluscs, plants, protozoa, reptiles, and other animals [40].

2.4. Data Extraction and Analysis

We first classified data on iNaturalist taxonomic groups and evaluated the reliability of the observations collected, keeping for further analysis the records that had reached the “research grade”.

The number of threatened species (Figure 2) collected within the WCC project was assessed by relying on the global [47] and Italian [48] IUCN Red Lists. Additionally, the conservation concern level of these species in Europe was determined by referring to the annexes of the HD. The IUCN Red List provides a comprehensive and up-to-date assessment of the conservation status and risk of extinction for various biological species. These species are classified into nine categories, and, among these, we focused on critically endangered (CR), endangered (EN), vulnerable (VU), and near threatened (NT). The annexes of the HD consist of a list of species that member states of the European Union have agreed to safeguard and regulate through a range of measures. These measures include the designation of Areas of Special Conservation Interest (Annex II), the establishment of stringent protection rules (Annex IV), and the development of national management plans (Annex V).

As for the analysis on plant species that represent “diagnostic taxa” (Figure 2) according to the HD, we followed the nomenclature recommended in the updated checklist of “Flora d’Italia” [49]. These species are of outmost importance in influencing the composition and operation of these habitats. Because of their importance to the general functionality and survival of the ecosystem, they are also known as “focal species” [50]. The identification of diagnostic species was based on the “Italian Vegetation Prodrome” [51] and the European Union’s Habitat Interpretation Manual [52].

Subsequently, we shifted our attention towards an analysis of alien and invasive species (IAS; Figure 2) that are included in the European regulation known as “on the prevention and management of the introduction and spread of invasive alien species” (Regulation (EU) No. 1143/2014, hereafter referred to as the IAS Regulation). The IAS Regulation delineates a catalogue of invasive alien species categorised as being of “Union concern”. These species pose a threat to biodiversity and ecosystem services, necessitating coordinated efforts at the European Union level [53]. The determination of the origin of non-native species was also established by Galasso et al. [54] and Loy et al. [55]. In our analysis of plant species, we incorporated the research conducted by Galasso et al. [54] and its subsequent revisions [56,57]. Regarding the fauna, we conducted a thorough examination of the data provided by the Global Biodiversity Information Facility (GBIF) platform (https://www.gbif.org (accessed on 1 August 2023)). Additionally, we conducted a quick analysis of the plant species that are poisonous to humans based on information from the iNaturalist platform and consulting some of the relevant literature (e.g., [58]).

3. Results and Discussion

As of 31 January 2023, the WCC project has documented a total of 3,784 observations by 250 distinct users pertaining to 742 species across diverse ecosystems (terrestrial and aquatic;

Table 1. Number of observations that are “research grade” and species per iNaturalist taxa, along with the respective percentages.

iNaturalist Macro-Categories	Number of Observations	% of Observations	Number of Species	% of Species
Actinopterygii	168	5%	53	7%
Amphibians	10	<1%	3	<1%
Arachnids	50	1%	18	3%
Birds	434	12%	82	11%
Chromists	8	<1%	2	<1%
Fungi and lichens	11	<1%	2	<1%
Insects	415	11%	161	22%
Mammals	162	4%	8	1%
Molluscs	358	10%	79	11%
Other animals	350	9%	94	13%
Plants	784	21%	230	31%
Reptiles	1034	27%	10	1%
Total	3784		742

). The research has acquired a large number of observations collected systematically through time and across diverse coastal ecosystems (terrestrial and aquatic). These observations provide compelling evidence of the efficacy of the dedicated CS activities, as well as the valuable contributions made by people during their leisure activities. During the summer season, the coastal regions under study attract a significant number of tourists. However, during the winter and fall seasons, these sites are frequented by schools and local people [4]. Scaling with the study area extent, our collection of data showed figures that are comparable to previous studies conducted in various regions, such as California, Scandinavia, South America, and North Asia [59]. Our findings also align with the research conducted by international institutions, including natural history museums [30].

As for the number of records per taxonomic group, reptiles account for 27% of total records, making it the most observed group, followed by plants (21%), birds (12%), and insects (11%). The less represented categories (with less than 1%), include amphibians, fungi and lichens, and chromists (Table 1). A substantial percentage of species is also present among the category of other animals, i.e., 13%. On iNaturalist, this macro-category collects a series of taxonomic categories, such as Cnidaria, Arthropoda, and Chordata, without any distinction and in which we have identified species of considerable importance.

The high number of reptile observations is mainly attributed to records of Caretta caretta. In recent years, this species has been recolonising and returning to historical nesting sites along the coasts of Spain, France, and Western Italy [60], with the WCC project providing evidence of this ongoing process also in the Adriatic.

Plants was the most diverse taxonomic category, with 236 species recorded (31%), followed by insects (163 species; 22%). Birds are another taxonomic group that has a significant number of reports and species (82 species, 11%). In this case, it is highly probable that this pattern is associated with the sea–land ecotone, which provides a diverse range of trophic niches [61].

Conversely, the lowest represented taxonomic groups, each comprising less than 1% of the total, were fungi and lichens (two taxa), chromists (two taxa), and amphibians (three taxa) (Table 1). Such a distribution of reports is congruent with earlier iNaturalist studies that have identified plants and insects as the most often observed groups [59]. Plants and insects in the studied area showed a great species diversity, which is indicative of the extensive ecological mosaic influenced by a pronounced environmental sea–land ecotone. This ecotone, found within relatively narrow coastal strips, facilitates substantial turnover rates of plant species [62] and arthropods [63].

The “research grade” status achievement, indicating species that have undergone thorough review, was observed in 81% of the cases (Figure 3). The “research grade” was reached according to iNaturalist criteria of at least 2/3 of users agreeing on an identification, and, in our case, most of the observations (81%) reached “research grade”, with 1 or 2 users in agreement with the submitting user. Less than 1% of the “research grade” observations showed any remaining disagreement among users on the determination of the specimen. This highlights the significant potential of CS activities in involving a high number of well-trained citizens who are able to improve collected data reliability, thus confirming the usefulness of the iNaturalist platform in the context of future research and conservation endeavours, despite some research highlighting limitations and biases in the iNaturalist approach [64,65,66], including errors or undersampling in less known and charismatic taxa, while well-known taxa or charismatic species might be oversampled. Accordingly, it is worth mentioning that both amphibians and reptiles have attained a “research grade” status of 100% for all their recorded observations (Figure 3). The higher quality of these observations can be primarily attributed to the number of records related to a few easily recognizable species. For example, the abundance of reptile observations at the “research grade” is mainly due to the loggerhead turtle (Caretta caretta) and the Italian wall lizard (Podarcis siculus) records, while for amphibians, it includes several observations of the Balearic green toad (Bufotes balearicus) and the marsh frog (Pelophylax ridibundus).

Among the other macro-categories, most taxonomic groups reached the “research grade” for at least the 50% of the records. Only fungi and lichens had less than 30% of their observations at the “research grade” (Figure 3). As observed by Barbato et al. [34] in regard to marine environments, most of the reports that did not reach the “research grade” (19% requiring identification) are not readily identifiable and classifiable by photographic evidence. The 30% of plant records that have not achieved the research status can be ascribed to the phenology and seasonal variability of species features (e.g., flowers and fruits), which enable identification only within a short time frame [26].

3.1. Species of Conservation Concern

The WCC has documented a total of 291 observations (Table 2) of species that fall within the global IUCN Red List [47]. These observations pertain to 17 species that have been classified as critically endangered (CR—5.9%), endangered (EN—17.7%), vulnerable (VU—47.0%), or near threatened (NT—29.4%). Among the most threatened taxa, we documented the occurrence of one critically endangered species (Fan Mussel—Pinna nobilis) and three endangered (EN) species (namely Testudo hermanni, Cladocora caespitosa, and Chelonia mydas).

The critically endangered Fan Mussel (Pinna nobilis Linnaeus, 1758), the largest long-lived endemic bivalve species in the Mediterranean Sea [67], has faced a significant decline since 2016, primarily attributed to infections caused by pathogens. This infection likely heightened the species’ susceptibility to changes in water temperature, resulting in sporadic occurrences around the Adriatic seashore [68]. The reported occurrence of Pinna nobilis within the WCC project can help enhance scientific research and guide future monitoring efforts. The occurrence areas of Pinna nobilis can serve as pilot sites for implementing reinforcement actions aimed at boosting the population of the species [69]. Moreover, they can guide habitat restoration plans and facilitate the implementation of protection actions required by the HD for species listed on Annex IV.

The Hermann’s tortoise (Testudo hermanni Gmelin, 1789) is an endangered terrestrial Testudinidae that is native to the northern coastal region of the Mediterranean and occurs in Italy with a fragmented distribution [70]. The Hermann’s tortoise exhibits a preference for well-preserved coastal dune mosaics throughout the Adriatic coast that consist of many habitats that are of conservation concern [71]. Being highly susceptible to habitat deterioration [72], its occurrence underscores the high conservation status of certain coastal tracts in the Central Adriatic.

Updated data on the presence of Annex II species outside the Natura 2000 network can also help us organise monitoring campaigns targeted at expanding the network. The occurrence data collected within protected areas can aid in the implementation of targeted conservation measures for species listed on Annex IV of the HD.

The WCC also documented the presence of the endangered green sea turtle (Chelonia mydas Linnaeus, 1758), which has a preferential distribution on tropical and subtropical waters and a reduced presence in temperate regions [73]. The green turtle population in the Mediterranean Sea is highly susceptible to the effects of climate change and human activities, which have a detrimental impact on all stages of its life cycle, from eggs to adult individuals [74]. The significance of our observations is heightened by recent research that highlights the strategic importance of the Adriatic basin for the conservation of green turtle populations [60]. Furthermore, the new data on green sea turtle’s occurrence in the Adriatic coastal area provide valuable insights for planning additional monitoring campaigns and developing specific protection measures, as mandated by the European Union for species listed on Annex IV (HD).

Table 2. Status of threatened species registered on the WCC iNaturalist according to the global and the Italian IUCN Red Lists [48,75] along with their inclusion in HD Annexes II and IV. The number of observations and the iNaturalist taxonomic category are also reported. CR, critically endangered; EN, endangered; VU, vulnerable; NT, near threatened; LC, least concern; NE, not evaluated.

Species	GLOBAL IUCN	Italian IUCN	HD Ann.	No. of Obs.	iNaturalist Category
Pinna nobilis	CR	CR	IV	3	Mollusks
Cladocora caespitosa	EN	LC		9	Other animals
Chelonia mydas	EN	NE	IV	3	Reptiles
Testudo hermanni	EN	EN	II; IV	8	Reptiles
Caretta caretta	VU	EN	II; IV	239	Reptiles
Passer italiae	VU	VU		8	Birds
Streptopelia turtur	VU	LC		5	Birds
Palinurus elephas	VU	NE		2	Other animals
Balaenoptera physalus	VU	EN	IV	1	Mammals
Epinephelus marginatus	VU	EN		2	Fishes
Aythya ferina	VU	VU		1	Birds
Cerambyx cerdo	VU	LC	II; IV	1	Insects
Haematopus ostralegus	NT	VU		3	Birds
Calidris ferruginea	NT	NE		2	Birds
Aythya nyroca	NT	EN		1	Birds
Raja asterias	NT	NE		2	Other animals
Sciaena umbra	NT	VU		1	Fishes

Table 2. Status of threatened species registered on the WCC iNaturalist according to the global and the Italian IUCN Red Lists [48,75] along with their inclusion in HD Annexes II and IV. The number of observations and the iNaturalist taxonomic category are also reported. CR, critically endangered; EN, endangered; VU, vulnerable; NT, near threatened; LC, least concern; NE, not evaluated.

Species	GLOBAL IUCN	Italian IUCN	HD Ann.	No. of Obs.	iNaturalist Category
Pinna nobilis	CR	CR	IV	3	Mollusks
Cladocora caespitosa	EN	LC		9	Other animals
Chelonia mydas	EN	NE	IV	3	Reptiles
Testudo hermanni	EN	EN	II; IV	8	Reptiles
Caretta caretta	VU	EN	II; IV	239	Reptiles
Passer italiae	VU	VU		8	Birds
Streptopelia turtur	VU	LC		5	Birds
Palinurus elephas	VU	NE		2	Other animals
Balaenoptera physalus	VU	EN	IV	1	Mammals
Epinephelus marginatus	VU	EN		2	Fishes
Aythya ferina	VU	VU		1	Birds
Cerambyx cerdo	VU	LC	II; IV	1	Insects
Haematopus ostralegus	NT	VU		3	Birds
Calidris ferruginea	NT	NE		2	Birds
Aythya nyroca	NT	EN		1	Birds
Raja asterias	NT	NE		2	Other animals
Sciaena umbra	NT	VU		1	Fishes

The Mediterranean Pillow Coral (Cladocora caespitosa Linnaeus, 1767) is an endangered long-lived reef-building species indigenous to the Mediterranean Sea, where it forms scattered colonies, beds, or vast banks [76,77]. Cladocora caespitosa is declining in the Adriatic Sea due to its great sensitivity to pollution [78], invasive algae [79], eutrophication [80], trawling, dredging [81], and climate change. Cladocora caespitosa was discovered in the setting of infra-littoral algal biocenosis, providing additional evidence of the presence of the Habitat of European Concern 1170 “Reefs” on several coastal tracts where the habitat had not previously been documented. Moreover, the WCC’s new knowledge may enable future scientific campaigns to adequately record and map the Reef EU habitat, updating its distribution range in the Central Adriatic area and extending the execution of necessary conservation actions [77].

The loggerhead sea turtle (Caretta caretta Linnaeus, 1758) has a broad distribution in the Mediterranean Sea [11]. The Italian breeding population of Caretta caretta plays a crucial role in preserving the genetic diversity of the species [82]. The species is classified in the national Red List as endangered [48], as it suffered a serious decline in Italy that were caused by multiple threats, such as urban expansion, human trampling, and pollution [83]. The recorded occurrences and nesting sites for Caretta caretta in the WWC database fill the information gap concerning the Central Adriatic coast, where, until about ten years ago, there was a lack of recorded nesting sites [84]. Furthermore, the current distribution data can be instrumental in guiding scientific research and the development of suitable conservation measures for Italian populations, as advocated for species listed on Annexes II and IV of the Habitats Directive (42/93/EEC).

The investigation of the WCC database, with a focus on endangered species, demonstrates how CS can be used to monitor various types of wildlife in need of conservation. This indicates an essential issue that necessitates additional research [85]. The abundance of georeferenced recordings of species listed on the IUCN Red List and in the HD annexes allows us to generate a comprehensive picture of the priority areas of the Central Adriatic coast that require concerted conservation efforts. Our findings highlight the potential of CS for biodiversity monitoring, a task that is frequently performed for a single taxon. The biodiversity data acquired in these broad areas can play a critical role in the development of integrated coastal management strategies. These strategies should successfully include the conservation needs of each taxon or group of taxa within the geographical framework offered by protected area networks such as the Natura 2000 network and regional/national protected areas.

3.2. EU Habitats

In WCC, we recorded 51 plant species which are diagnostic of 14 habitats of European Conservation Concern (Table 3). Our results reveal the presence of the typical ecosystems of dune zonation from the halo-nitrophilous formations on the drift-line to the fore dune woody formations (e.g., 1210: Annual vegetation of drift lines; 2110: Embryonic shifting dunes; 2120: Shifting dunes with Ammophila arenaria; 2130 *: Fixed coastal dunes with herbaceous vegetation; 2230: Malcolmietalia dune grasslands; 2250 *: Coastal dunes with Juniperus spp.; 2260: Cisto-Lavanduletalia dune sclerophyllous scrubs; and 2270 *: Wooded dunes with Pinus pinea and/or Pinus pinaster), some cliff formations (1240: Vegetated sea cliffs of the Mediterranean coasts with endemic Limonium spp.), a rich and heterogeneous salt marsh mosaic (1410: Mediterranean salt meadows Juncetalia maritimi; 1420: Mediterranean and thermo-Atlantic halophilous scrubs Sarcocornietea fruticosi; 3170*: Mediterranean temporary ponds; and 6420: Mediterranean tall humid herb grasslands of the Molinio-Holoschoenion), and few river (3250: Constantly flowing Mediterranean rivers with Glaucium flavum) and marine habitats (1110: Sandbanks slightly covered by seawater).

The data acquired validates earlier research indicating the great diversity and well-preserved dune mosaic characterising the Molise coast [86], which, in accordance with HD, is in large part included in the Natura 2000 network [4]. It also points to the necessity of restoration efforts along the Abruzzo coastal dunes, where natural ecosystems are fragmented and poorly covered by European protection areas [87]. Conservation actions aimed at reinforcing populations of dune-building perennial grasses (e.g., Ammophila arenaria and Elymus farctus) and reducing trampling pressure, for example, may play a critical role in dune consolidation, ensuring both biodiversity values and ecological functions [88].

Table 3. List of the recorded diagnostic plant species of habitats of European Conservation Concern, along with the respective habitat code and name [89]. * Priority habitats.

Species	Habitat Code and Name
Cymodocea nodosa (Ucria) Asch.	1110: Sandbanks which are slightly covered by seawater all the time
Cakile maritima Scop. subsp. Maritima	1210: Annual vegetation of drift lines
Salsola kali L.
Salsola soda L.
Crithmum maritimum L.	1240: Vegetated Sea cliffs of the Mediterranean coasts with endemic Limonium spp.
Calystegia soldanella (L.) R. Br.	2110: Embryonic shifting dunes
Elymus farctus (Viv.) Runemark ex Melderis
Eryngium maritimum L.
Euphorbia paralias L.
Euphorbia peplis L.
Lotus creticus L.
Medicago marina L.
Polygonum maritimum L.
Achillea maritima (L.) Ehrend. et Y.P. Guo	2120: Shifting dunes along the shoreline with Ammophila arenaria (white dunes)
Ammophila arenaria LK.
Anthemis maritima L.
Cyperus capitatus Vand.
Echinophora spinosa L.
Eryngium maritimum L.
Lotus creticus L.
Pancratium maritimum L.
Sixalix atropurpurea (L.) Greuter and Burdet
Glaucium flavum Crantz	3250: Constantly flowing Mediterranean rivers with Glaucium flavum
Euphorbia terracina L.	2130 *: Fixed coastal dunes with herbaceous vegetation (grey dunes)
Verbascum niveum subsp. garganicum (Ten.) Murb.
Artemisia campestris L.	2230: Malcolmietalia dune grasslands
Erodium laciniatum (Cav.) Willd.
Lagurus ovatus L.
Malcolmia ramosissima (Desf.) Thell.
Matthiola incana (L.) R. Br.
Ononis variegata L.
Silene colorata Poir.
Verbascum niveum subsp. garganicum (Ten.) Murb.
Asparagus acutifolius L.	2250 *: Coastal dunes with Juniperus spp.
Juniperus macrocarpa Sm.
Myrtus communis L.
Phillyrea angustifolia L.
Pistacia lentiscus L.
Rhamnus alaternus L.
Smilax aspera L.
Asparagus acutifolius L.	2260: Cisto-Lavanduletalia dune sclerophyllous scrubs
Cistus creticus L.
Cistus salviifolius L.
Phillyrea angustifolia L.
Pistacia lentiscus L.
Rhamnus alaternus L.
Rosmarinus officinalis L.
Smilax aspera L.
Phillyrea angustifolia L.	2270 *: Wooded dunes with Pinus pinea and/or Pinus pinaster
Pinus halepensis Mill.
Pinus pinea L.
Pistacia lentiscus L.
Atriplex prostrata Boucher ex DC.	1410: Mediterranean salt meadows (Juncetalia maritimi)
Blackstonia perfoliata (L.) Huds.
Juncus acutus L.
Limbarda crithmoides (L.) Dumort.
Sarcocornia fruticosa (L.) A.J. Scott	1420: Mediterranean and thermo-Atlantic halophilous scrubs (Sarcocornietea fruticosi)
Schoenus nigricans L.	6420: Mediterranean tall humid herb grasslands of the Molinio-Holoschoenion
Scirpoides holoschoenus (L.) Soják
Tripidium ravennae (L.) H. Scholz

Table 3. List of the recorded diagnostic plant species of habitats of European Conservation Concern, along with the respective habitat code and name [89]. * Priority habitats.

Species	Habitat Code and Name
Cymodocea nodosa (Ucria) Asch.	1110: Sandbanks which are slightly covered by seawater all the time
Cakile maritima Scop. subsp. Maritima	1210: Annual vegetation of drift lines
Salsola kali L.
Salsola soda L.
Crithmum maritimum L.	1240: Vegetated Sea cliffs of the Mediterranean coasts with endemic Limonium spp.
Calystegia soldanella (L.) R. Br.	2110: Embryonic shifting dunes
Elymus farctus (Viv.) Runemark ex Melderis
Eryngium maritimum L.
Euphorbia paralias L.
Euphorbia peplis L.
Lotus creticus L.
Medicago marina L.
Polygonum maritimum L.
Achillea maritima (L.) Ehrend. et Y.P. Guo	2120: Shifting dunes along the shoreline with Ammophila arenaria (white dunes)
Ammophila arenaria LK.
Anthemis maritima L.
Cyperus capitatus Vand.
Echinophora spinosa L.
Eryngium maritimum L.
Lotus creticus L.
Pancratium maritimum L.
Sixalix atropurpurea (L.) Greuter and Burdet
Glaucium flavum Crantz	3250: Constantly flowing Mediterranean rivers with Glaucium flavum
Euphorbia terracina L.	2130 *: Fixed coastal dunes with herbaceous vegetation (grey dunes)
Verbascum niveum subsp. garganicum (Ten.) Murb.
Artemisia campestris L.	2230: Malcolmietalia dune grasslands
Erodium laciniatum (Cav.) Willd.
Lagurus ovatus L.
Malcolmia ramosissima (Desf.) Thell.
Matthiola incana (L.) R. Br.
Ononis variegata L.
Silene colorata Poir.
Verbascum niveum subsp. garganicum (Ten.) Murb.
Asparagus acutifolius L.	2250 *: Coastal dunes with Juniperus spp.
Juniperus macrocarpa Sm.
Myrtus communis L.
Phillyrea angustifolia L.
Pistacia lentiscus L.
Rhamnus alaternus L.
Smilax aspera L.
Asparagus acutifolius L.	2260: Cisto-Lavanduletalia dune sclerophyllous scrubs
Cistus creticus L.
Cistus salviifolius L.
Phillyrea angustifolia L.
Pistacia lentiscus L.
Rhamnus alaternus L.
Rosmarinus officinalis L.
Smilax aspera L.
Phillyrea angustifolia L.	2270 *: Wooded dunes with Pinus pinea and/or Pinus pinaster
Pinus halepensis Mill.
Pinus pinea L.
Pistacia lentiscus L.
Atriplex prostrata Boucher ex DC.	1410: Mediterranean salt meadows (Juncetalia maritimi)
Blackstonia perfoliata (L.) Huds.
Juncus acutus L.
Limbarda crithmoides (L.) Dumort.
Sarcocornia fruticosa (L.) A.J. Scott	1420: Mediterranean and thermo-Atlantic halophilous scrubs (Sarcocornietea fruticosi)
Schoenus nigricans L.	6420: Mediterranean tall humid herb grasslands of the Molinio-Holoschoenion
Scirpoides holoschoenus (L.) Soják
Tripidium ravennae (L.) H. Scholz

The coastal dunes with Juniperus spp. form a priority habitat characterised by a distinctive Juniperus scrub which is mainly threatened by urban expansion, tourist pressure [90], and invasive alien plants [91]. These dune juniper thickets, which reach the northern limit of their geographical range in Molise [86], are included in a Natura 2000 site, where they provide suitable habitats for several species of fauna of conservation concern, such as the Hermann tortoise [71].

The recorded salt meadows (Juncetalia maritimi) are characteristic of well-preserved back-dune depressions that are periodically flooded by brackish water. Unfortunately, as with most salt meadows, they are impinged by land reclamation, changes in water regimes, urbanization, invasive species, and coastal erosion [92]. The observed habitat, which represents one of the few remaining coastal wetlands in the Mediterranean [93], is encompassed within a Natura 2000 site. These meadows may play a pivotal role in biodiversity conservation, serving as essential habitats for both resident and migratory avian species, as well as various aquatic organisms, like fish and arthropods [94].

We also have detected the presence of Cymodocea nodosa (Ucria) Ascherson formations on the Central Adriatic coastal seabed. Cymodocea meadows may play a crucial role in supporting fish populations by offering refuge to schools, facilitating the establishment of trophic niches, and serving as nursery sites [95]. Additionally, these meadows have a significant function in safeguarding coastal areas from various environmental impacts [96]. The areas of occurrence, all identified outside the Natura 2000 network, warrant dedicated field campaigns to verify and map the presence of Cymodocea nodosa meadows.

The record of species that are diagnostic of habitats of European concern has enabled their identification on the Central Adriatic coast. Despite the partial degradation of coastal areas, these habitats remain valuable components, serving as important seed banks for the recolonization of degraded areas and providing the natural support for their recovery. Our findings highlight the potential of CS for vegetation monitoring, a task that, in line with the Habitat Directive, is typically scheduled every 5 years. However, this time interval may be inadequate for studying highly dynamic ecosystems like dunes [97]. Citizen Science could also help indirectly to monitor the anthropogenic pressures that most affect habitat and species of conservation concern, providing essential information for their proper management.

3.3. Alien Species

We registered 109 records of 44 non-native species (Table 4 and Table 5). We specifically reported the presence of 25 alien plants (57%) and 19 species of non-native fauna (43%). It is worth noting that six of the alien plants belong to the taxonomic family Asteraceae, which is distinguished by its mostly anemophilous dispersal mechanism, making them particularly effective in the processes of expansion and colonization. The substantial number of Asteraceae species aligns well with the overall composition of alien flora in Italy [54] and Europe [98]. Instead, the number of Poaceae records appears relatively low in comparison to Italy’s alien flora. This is likely due to the difficulty in identifying these species, which poses a challenge for both regular citizens in the field and professionals who rely solely on uploaded photos.

In terms of life forms, we found a significantly higher number of perennial plants, including herbs, shrubs, and trees, than the national average [99]. This is most likely due to their extensive and long-lasting vegetative structures, which allow them to be identified all year. In contrast, we have documented fewer annuals than the national list of non-native plants [54], which can be attributed to the limited season observational window of annuals.

Two of the alien plants, namely Acacia saligna and Ailanthus altissima, have been identified as invasive species of European Union concern [53]. For these two species, the Italian government is required to undertake monitoring, management, and control measures. Acacia saligna is among the most invasive taxa in Italy and Europe, and in the Central Adriatic coast, it mostly colonises back dune habitats, impinging several habitats of conservation concern (e.g., coastal dunes with Juniperus spp., dunes with sclerophyllous vegetation of Cisto-Lavanduletalia, and wooded dunes with Pinus pinea and/or Pinus pinaster). This information is supported by the studies conducted by Marzialetti et al. [100]. Ailanthus altissima, commonly known as the Tree of Heaven, is a highly invasive plant that is present on every continent except Antarctica. Its primary distribution in its invasive range includes urban areas, from where it has expanded into neighbouring natural and semi-natural environments [101]. Ailanthus altissima provides significant negative impacts on biodiversity by altering the vegetation structure, degrading soil properties, and threatening ecosystem stability [102]. The WCC has identified the existence of several invasive species of European Union concern within the Adriatic coast’s network of protected areas. These occurrence data can be used to lead future dedicated field investigations targeted at detecting and mapping alien plants, which are required for the implementation of control or eradication methods outlined in European legislation.

Table 4. List of non-native species, along with the number of reports, taxonomic family, and life form: “Tree” (phanerophytes); “Shrub” (nano-phanerophytes and woody climbers); “Dwarf” (chamaephytes); “Herb” (hemicryptophytes and geophytes); “Annual” (therophytes) (Sensu [103]) and geographic origin. Bold font highlights invasive alien species of European Union concern [53]. Superscript letters: NI, invasive neophytes; NC, casual neophytes; NN, naturalised neophytes; (Sensu [54]); TX, toxic.

Species	No.	Family	Life Form	Origin
Xanthium orientale subsp. italicum (Moretti) GreuterNI	11	Asteraceae	Annual	North America
Acacia saligna (Labill.) H.L. Wendl.NI	9	Fabaceae	Tree	Western Australia
Oxalis pes-caprae L.NI	7	Oxalidaceae	Herb	South Africa
Carpobrotus acinaciformis (L.) L. BolusNI	5	Aizoaceae	Dwarf	South Africa
Carpobrotus edulis (L.) N.E. Br.NI	5	Aizoaceae	Dwarf	South Africa
Erigeron bonariensis L.NI	3	Asteraceae	Annual	South America
Opuntia stricta (Haw.) Haw.NI	3	Cactaceae	Shrub	Central America
Robinia pseudoacacia L.NI	3	Fabaceae	Tree	North America
Symphyotrichum squamatum (Spreng.) G.L. NesomNI	3	Asteraceae	Annual	South America
Ailanthus altissima (Mill.) SwingleNI	2	Simaroubaceae	Tree	China
Datura stramonium L.NI-TX	2	Solanaceae	Annual	Central/North Am.
Euphorbia maculata L.NI	2	Euphorbiaceae	Annual	North America
Oxalis articulata SavignyNI	2	Oxalidaceae	Herb	South America
Agave americana L.NI	1	Asparagaceae	Shrub	Central/North Am.
Amorpha fruticosa L.NI	1	Fabaceae	Shrub	North America
Erigeron canadensis L.NI	1	Asteraceae	Annual	North America
Helianthus annuus L.NC	1	Asteraceae	Annual	North America
Mirabilis jalapa L.NI	1	Nyctaginaceae	Herb	South America
Nicotiana glauca GrahamNI-TX	1	Solanaceae	Shrub	South America
Oenothera glazioviana MicheliNI	1	Onagraceae	Herb	North America
Opuntia ficus-indica (L.) Mill.NI	1	Cactaceae	Shrub	Central America
Paspalum dilatatum Poir.NI	1	Poaceae	Herb	South America
Pittosporum tobira (Thunb.) W.T. AitonNN	1	Pittosporaceae	Shrub	Eastern Asia
Senecio inaequidens DCNI-TX	1	Asteraceae	Herb	South Africa
Yucca gloriosa L.NI	1	Asparagaceae	Shrub	North America

Table 4. List of non-native species, along with the number of reports, taxonomic family, and life form: “Tree” (phanerophytes); “Shrub” (nano-phanerophytes and woody climbers); “Dwarf” (chamaephytes); “Herb” (hemicryptophytes and geophytes); “Annual” (therophytes) (Sensu [103]) and geographic origin. Bold font highlights invasive alien species of European Union concern [53]. Superscript letters: NI, invasive neophytes; NC, casual neophytes; NN, naturalised neophytes; (Sensu [54]); TX, toxic.

Species	No.	Family	Life Form	Origin
Xanthium orientale subsp. italicum (Moretti) GreuterNI	11	Asteraceae	Annual	North America
Acacia saligna (Labill.) H.L. Wendl.NI	9	Fabaceae	Tree	Western Australia
Oxalis pes-caprae L.NI	7	Oxalidaceae	Herb	South Africa
Carpobrotus acinaciformis (L.) L. BolusNI	5	Aizoaceae	Dwarf	South Africa
Carpobrotus edulis (L.) N.E. Br.NI	5	Aizoaceae	Dwarf	South Africa
Erigeron bonariensis L.NI	3	Asteraceae	Annual	South America
Opuntia stricta (Haw.) Haw.NI	3	Cactaceae	Shrub	Central America
Robinia pseudoacacia L.NI	3	Fabaceae	Tree	North America
Symphyotrichum squamatum (Spreng.) G.L. NesomNI	3	Asteraceae	Annual	South America
Ailanthus altissima (Mill.) SwingleNI	2	Simaroubaceae	Tree	China
Datura stramonium L.NI-TX	2	Solanaceae	Annual	Central/North Am.
Euphorbia maculata L.NI	2	Euphorbiaceae	Annual	North America
Oxalis articulata SavignyNI	2	Oxalidaceae	Herb	South America
Agave americana L.NI	1	Asparagaceae	Shrub	Central/North Am.
Amorpha fruticosa L.NI	1	Fabaceae	Shrub	North America
Erigeron canadensis L.NI	1	Asteraceae	Annual	North America
Helianthus annuus L.NC	1	Asteraceae	Annual	North America
Mirabilis jalapa L.NI	1	Nyctaginaceae	Herb	South America
Nicotiana glauca GrahamNI-TX	1	Solanaceae	Shrub	South America
Oenothera glazioviana MicheliNI	1	Onagraceae	Herb	North America
Opuntia ficus-indica (L.) Mill.NI	1	Cactaceae	Shrub	Central America
Paspalum dilatatum Poir.NI	1	Poaceae	Herb	South America
Pittosporum tobira (Thunb.) W.T. AitonNN	1	Pittosporaceae	Shrub	Eastern Asia
Senecio inaequidens DCNI-TX	1	Asteraceae	Herb	South Africa
Yucca gloriosa L.NI	1	Asparagaceae	Shrub	North America

It is also worth noting the existence of some toxic alien plants (e.g., Datura stramonium, Senecio inaequidens, and Nicotiana glauca) [58] that pose an additional threat to human health. Following the CS approach, special campaigns for their identification might be organised, raising people’s knowledge of the risks connected with their ingestion, usage, or exposure.

The WCC recorded 40 observations of 19 alien species of fauna (Table 5). Myocastor coypus was the most recorded species, followed by Trachemys scripta. It is noteworthy that these two species, in addition to Gambusia holbrooki, are widely recognised as being highly invasive in Europe, thus warranting their inclusion in the European regulation [53].

Table 5. List of non-native species, along with the relative number of reports (40 for fauna), taxonomic category (taxon), and geographic origin (origin). Bold font highlights invasive alien species of European Union concern [53].

Species	No.	iNaturalist Taxon	Origin
Myocastor coypus (Molina, 1782)	13	Mammals	South America
Trachemys scripta (Schoepff, 1792)	4	Reptiles	North America
Hystrix cristata (Linnaeus, 1758)	2	Mammals	Africa
Magallana gigas (Thunberg, 1793)	2	Molluscs	Asia
Paysandisia archon (Burmeister, 1880)	2	Insects	South America
Rapana venosa (Valenciennes, 1846)	2	Molluscs	Asia
Sceliphron caementarium (Drury, 1773)	2	Insects	North America
Threskiornis aethiopicus (Latham, 1790)	2	Birds	Africa; Asia
Anadara transversa (Say, 1822)	1	Molluscs	North America
Blatta orientalis (Linnaeus, 1758)	1	Insects	Asia; Africa
Cairina moschata (Linnaeus, 1758)	1	Birds	South America
Complex Pelophylax ridibundus (Pallas, 1771)	1	Amphibians	Europe; Asia
Gambusia holbrooki (Girard, 1859)	1	Actinopterygii	North America
Harmonia axyridis (Pallas, 1773)	1	Insects	Asia
Isodontia mexicana (de Saussure, 1867)	1	Insects	North America
Leptoglossus occidentalis (Heidemann, 1910)	1	Insects	North America
Rhynchophorus ferrugineus (Olivier, 1790)	1	Insects	Asia
Steatoda nobilis (Thorell, 1875)	1	Arachnids	Macaronesia
Trichopoda pictipennis (Fabricius, 1781)	1	Insects	South America

Table 5. List of non-native species, along with the relative number of reports (40 for fauna), taxonomic category (taxon), and geographic origin (origin). Bold font highlights invasive alien species of European Union concern [53].

Species	No.	iNaturalist Taxon	Origin
Myocastor coypus (Molina, 1782)	13	Mammals	South America
Trachemys scripta (Schoepff, 1792)	4	Reptiles	North America
Hystrix cristata (Linnaeus, 1758)	2	Mammals	Africa
Magallana gigas (Thunberg, 1793)	2	Molluscs	Asia
Paysandisia archon (Burmeister, 1880)	2	Insects	South America
Rapana venosa (Valenciennes, 1846)	2	Molluscs	Asia
Sceliphron caementarium (Drury, 1773)	2	Insects	North America
Threskiornis aethiopicus (Latham, 1790)	2	Birds	Africa; Asia
Anadara transversa (Say, 1822)	1	Molluscs	North America
Blatta orientalis (Linnaeus, 1758)	1	Insects	Asia; Africa
Cairina moschata (Linnaeus, 1758)	1	Birds	South America
Complex Pelophylax ridibundus (Pallas, 1771)	1	Amphibians	Europe; Asia
Gambusia holbrooki (Girard, 1859)	1	Actinopterygii	North America
Harmonia axyridis (Pallas, 1773)	1	Insects	Asia
Isodontia mexicana (de Saussure, 1867)	1	Insects	North America
Leptoglossus occidentalis (Heidemann, 1910)	1	Insects	North America
Rhynchophorus ferrugineus (Olivier, 1790)	1	Insects	Asia
Steatoda nobilis (Thorell, 1875)	1	Arachnids	Macaronesia
Trichopoda pictipennis (Fabricius, 1781)	1	Insects	South America

The coypu (Myocastor coypus) is an aquatic rodent that is native to South America and was imported to Italy for fur farming [104]. The escaped individuals tend to establish themselves preferentially along riverbanks and in wetlands, leading to detrimental effects on biological diversity, ecosystems, crops, and irrigation systems. Given the severity of this invasion and the high ecological value of the studied coasts, our data underscore the urgent need to implement control and eradication measures. A management and restriction strategy for the coypu should be implemented following a thorough assessment of its current distribution along the Central Adriatic coast [104].

The pond slider (Trachemis scripta) is a tortoise native to North America that was introduced through the pet trade. Mostly sold as small hatchlings, they are often released by owners into natural systems during their adulthood. The pond slider can establish breeding populations and competes with native species for food resources and basking sites, also exerting strong predation pressure on the biodiversity of invaded water bodies [105]. Considering this, a deeper field evaluation aiming at better defining and comprehending the ongoing invasion became critical [106]. Such updated data could be utilised to identify the proper control mechanisms claimed by the European Union and the Italian management plan [106].

4. Conclusions

Citizen Science data from the WCC project showed the promise of this strategy, which directly engages citizens in biodiversity monitoring. Citizen research projects that are supported by the iNaturalist platform have shown that they can monitor habitats and species in complex and ever-changing landscapes, like coastal–marine transitions. Existing and archived data, as well as prospective data from the next phase of the project, may give biodiversity study and management opportunities. The WCC is a pioneering programme that collects multi-taxa and multi-domain data, which may be useful for integrated biodiversity monitoring, especially in long-term observation sites like the LTER network [23] in the examined area.

The WCC submitted new and amended spatial data on various IUCN red book or HD annex species. The simultaneous analysis of the spatial distribution and consistency of several conservation-important species across the coastal gradient can help determine comprehensive habitat restoration strategies and implement specific protective measures claimed by international agreements and policies like the Convention on Biological Diversity [9] and the HD. The high number of species on the WCC, indicating the presence of multiple European habitats of conservation concern (HD), showed a wide range of ecosystems along the Central Adriatic coast, some of which are new to the area. In line with previous research by Drius et al. [4], the WCC’s coastal transition mosaic is still largely intact.

The citizen research strategy using iNaturalist has also been helpful in catching alien species across large areas at a cheap expense. Our findings suggested that CS can help implement targeted monitoring and control actions against invasive alien species, as required by European law [53]. The WCC may help identify foreign plant and animal species, thus enabling early detection and eradication. Additionally, it may help monitor invasive taxa’s regional expansion and population dynamics to ensure effective control. Lozano et al. [107] and Di Febbraro et al. [108] emphasise that the data derived from CS can improve predictions of the spread of invasive alien species, especially when used in nationwide projects.