1. Introduction
Natural parks and protected areas are essential for promoting biodiversity, ecosystem services, and human well-being [
1]. In addition, they play a fundamental role in providing spaces for recreation and human connection with nature [
2]. However, as tourism activities intensify, reaching ever more remote and sensitive locations, the pressure on the environment and landscape becomes more evident [
3], and any changes in visitation patterns, whether spatially or temporally, have the potential to degrade the natural environment [
4]. Visitor overcrowding can have significant repercussions on landscape alteration and ecosystem degradation [
5], including organic contamination, damage to vegetation from trampling [
6,
7], soil compaction and erosion [
8], loss of biodiversity [
9], and excessive use of natural resources [
10]. The accumulation of waste [
11] or pollution from recreational boats contaminates surface and groundwater, having negative impacts on fauna and vegetation [
12,
13].
The extent and severity of damage are influenced by the resistance and resilience of vegetation [
14], abiotic site characteristics such as soil type, topography, and hydrology [
15], and additional factors including infrastructure quality, usage intensity, activity type, tourist behaviour, and seasonality [
16,
17]. Many impacts are highly localised due to variations in local resource availability, sociocultural structures, and the concentration of land uses and tourist activities near prime coastal and port areas [
18].
In island territories, the impact of visitors is even greater [
19]. In addition to the heavy dependence on the tourism industry for economic gains [
20], isolation, small spatial extent, limited resources, and fragile ecosystems are some of the main constraints that amplify the effects of tourism on islands and complicate the formulation of sustainable management and tourism development plans [
21]. Therefore, it is essential to monitor and control the flows and processes resulting from tourist activities, ensuring that visitors are not excessively invasive and that the socio-cultural and environmental impacts remain bearable [
22].
Understanding visitor experiences [
12,
23], and assessing the spatiotemporal patterns of their activities are fundamental strategies to avoid and minimise the negative impacts of tourism and ensure sustainable management of natural environments [
24,
25]. Visitor data can assist park managers in decision-making and policy formulation by identifying trends in tourist demand [
26], generating forecasts, determining facility locations [
27,
28], as well as identifying negative impacts [
29,
30], and vulnerable areas.
In the past decade, several researchers have used georeferenced data sourced from social networks to analyse the spatiotemporal behaviour of visitors in natural environments [
31,
32]. This data, voluntarily shared by tourists on online platforms (e.g., Wikiloc and Flickr), can be collected remotely, in a relatively simple way, and at a low cost [
5,
33], proving effective in the spatial and temporal analysis of visitors [
32]. Furthermore, it provides precise, real-time information on activities occurring in nature [
34] and enables assessments of how people observe and value the environment [
35]. Specifically, social media data has been used to determine visitation rates in parks and protected areas [
36,
37], usage patterns, and visitor characteristics [
5,
24,
28,
38,
39,
40], as well as visitor preferences [
33,
41,
42,
43,
44,
45]. Other authors have chosen to use these new data sources for landscape characterization [
46] or to explore cultural ecosystem services [
47]. Georeferenced trails and photographs not only allow the identification of the most traversed and photographed areas by visitors, but also make it possible to determine the most relevant landscape attributes [
48], identify critical points with high visitation [
24,
45,
49], and assess the impact of public use both on and off official trails [
50].
However, there are few studies that analyse the spatial distribution of visitors using trails and photographs with land use in protected areas [
51]. This data integration allows for the identification of the most frequented and affected land uses by tourist demand, as well as providing a more detailed insight into how visitation can impact different habitats and sensitive areas. This information can assist park managers in prioritising actions that ensure long-term conservation of affected natural resources and land uses under greater pressure and potential degradation.
To fill this knowledge gap, georeferenced data of trails and photographs shared by users of Wikiloc (
https://pt.wikiloc.com/) and Flickr (
https://www.flickr.com/) are used to analyse the spatial patterns of visitors according to land use in the Atlantic Islands of Galicia National Park (AINP) between the years 2008 and 2023. The analysis aims to address the following objectives:
Evaluate the distribution of the trails taken by visitors according to land use, and quantify the intensity of visitors along the trails;
Identify and analyse the most photographed areas and relate them to the park's land uses;
Determine the types of land use that are under the most tourist pressure using georeferenced data of trails and photographs.
Study Area
The Atlantic Islands of Galicia National Park (AINP), established in 2002 by Law 15/2002 [
52], is located on the southwest coast of Galicia, Spain. It comprises the archipelagos of the Cíes, Ons, Sálvora, and Cortegada Islands, extending from the Ria de Arousa to the Ria de Vigo (
Figure 1). The AINP is a protected natural heritage of extreme importance and an excellent example of the conservation status of Atlantic marine and coastal ecosystems, the associated fauna and flora species, and the cultural heritage of these areas [
10]. The oceanic waters have an enormous biological variety that is endemic and unique [
6]. The park's coastlines are notable for their fine sand dunes, beaches, and rugged terrain. The cliffs cut out the ocean's horizon, while shrubby vegetation such as gorse, heather, and eucalyptus groves mark the slopes [
53]. The park has a total area of 8,480 hectares, 87% of which is maritime space [
54].
In the Cíes Islands, the highest altitude is found in the northernmost sector, in Alto das Cíes (197 m). Similar to Ons island, the morphology presents a contrast, featuring a high cliff coast to the west and beaches to the east [
55]. The steep western cliffs feature small patches of acidic, nutrient-poor [
56], stony, and shallow soils [
57], reflecting the oceanic influence and the scarcity of vegetation. In contrast, the lower coast dominates the eastern part, which has lower slopes and prominent sandbanks. However, these sandbanks are non-existent on the slopes most exposed to the ocean [
58]. Sálvora and Cortegada are characterised by lower and more regular reliefs, with flatter contours and rounded shapes [
59]. The island of Cortegada is sheltered within the Ria de Arousa, opposite the village of Carril [
56], and avoids ocean waves. It has the lowest relief among the archipelagos, consisting mainly of flat areas occupied by forest cover.
Granites covered by acidic soils make up the majority of the park's geological substrate [
60]. In Cíes and Ons, the rocks are mostly highly fractured granitic alkaline feldspathic rocks that formed during the Hercynian orogeny [
6]. However, we can also have some metamorphic rocks [
61], such as mica schists, quartzites, and paragneisses. The flora is predominantly of the Mediterranean type, and native species dominate the archipelago's coverage, being seen both in cliff areas and on rocky slopes and vegetated cliffs [
6]. The vegetation is subject to extreme weather conditions and is therefore basically shrubby [
62]. Strong winds, high salinity, and shallow and sandy soils with low nutrient availability subject the plant species found on cliffs and dune systems to specific adaptations, arranging them in bands according to their tolerance to marine influence [
63,
64]. Due to human activity, species such as eucalyptus, acacia, and pine coexist with native species, which persist in dune and cliff environment’s [
65,
66].
Scrubland occupies a large part of the park's land surface, particularly on the islands of Ons and Sálvora (
Figure 1). On the Cíes Islands, they are especially visible on the Monteagudo and Faro Islands, interspersed with conifers. Evergreen trees, namely eucalyptus, acacias, cork oaks, and sloes (
Table S1), occupy the entire Alto do Príncipe sector on the Cíes islands and are found in a scattered manner and to a lesser extent on the islands of Ons and Sálvora. Ons is currently the only populated island in the national park. On its eastern side, which is more sheltered from the winds and adverse weather conditions, there are a few houses, accompanied by their characteristic granaries, as well as the corn and potato crops linked to them [
64]. Cortegada, the island with the highest tree density, closely links its vegetation establishment and dynamics patterns to the history and activities of human presence, with species such as oaks, pines, and laurels predominating [
67].
According to the official statistics from the Autonomous Agency of Spanish National Parks (OAPN), except for the years 2019 and 2020, the latter marked by isolation restrictions imposed by the COVID-19 pandemic, the number of visits to AINP has progressively increased since 2017 [
66]. The upward trend in the number of entries recorded between 2017 (440,661) and 2018 (489,953) was interrupted between 2019 (472,274) and 2020 (318,570). In 2021, corresponding to the post-pandemic period and the resumption of tourist activities, the national park received a total of 428,970 visitors [
66]. The increase in tourism on these islands has generated new concerns related to the likelihood of their carrying capacity being exceeded, as well as the negative repercussions resulting from the overuse of resources and consequent degradation of natural ecosystems [
10].
2. Materials and Methods
This research explores georeferenced data, specifically trails and photographs, shared by Wikiloc and Flickr users to analyse the spatial patterns of visitation according to land use in AINP.
Figure 2 shows the methodological procedures adopted to collect, process, and analyse the georeferenced data downloaded from both platforms. Additionally, we illustrate the processes applied to the geographic data collected on the land use and geology of AINP, enabling a detailed analysis of the islands that comprise it.
Wikiloc, founded in 2006, is a content-sharing social network with over 7.6 million users that allows free downloading of trails (including photographs) and coordinate points related to outdoor activities, which are voluntarily shared by users [
5]. More than 53.8 million outdoor trails and 98.3 million photographs shared on the platform demonstrate Wikiloc's popularity. Flickr, on the other hand, is a social network for sharing photos and videos available to the public since its launch in 2004. Their repository has over 60 million monthly active users, as well as more than 100 million photographers who upload and share photos of all types and places [
68].
Considering the period from 2008 to 2023, tracking points (GPS points along trails) and waypoints (points with photos and annotations) have been collected from Wikiloc for the islands using a Python script. Several authors [
5,
69,
70] have used this method to reduce processing time and manual labour required to obtain large amounts of data.
In total, 2936 trails and 13249 photographs were collected from Wikiloc by 964 users in GPX format. We chose this format because it enables the retrieval of all user-recorded points [
40]. We analysed the collected list of files, eliminating those with spatial or temporal errors, then imported the validated data into ArcGIS Pro and converted it into a shapefile. From Flickr, also using a Python script, 2206 photographs were collected from 731 users. The data was exported in .xls format, containing information such as the owner's identifier, coordinates, date and time, title, text labels associated with the photographs, as well as the address link.
Each set of data extracted from Wikiloc and Flickr was combined into a single file containing all the associated metadata. Subsequently, the waypoints collected on both platforms were analysed. The presence of some repeated photographs, as well as others with non-existent dates or dates before 2008, led to the exclusion of 97 waypoints from Wikiloc and 46 from Flickr. In total, 13152 photographs from Wikiloc and 2160 from Flickr were considered valid for analysis.
In terms of the trails, it was necessary to transform the data points captured by GPS (tracking points) into a linear format to enable spatial analyses of the trails. The tracking points contain information such as latitude/longitude, altitude, date and time of the trails, location, type of activity, etc. Since one of the objectives of spatial analysis is to identify the trails undertaken within the park, 100 meters buffers were created for the islands, and selections were made based on location, assuming only the trails that were included within the buffer areas. The new outputs were carefully examined, and some GPS errors were excluded to avoid influencing the interpretation of the results.
Subsequently, using high-quality orthophotos from Spain's National Aerial Orthophotography Plan (PNOA), available at [
https://centrodedescargas.cnig.es], the main paths on each of the islands were vectorized, resulting in the general trail network of AINP. Furthermore, the number of trails undertaken per month in each of the segments comprising the overall trail network of the park was counted. The sum of the data counted each month resulted in the maps depicting the intensity of trails undertaken by Wikiloc users. After completing this process, we also mapped the itineraries of AINP to facilitate the interpretation of the results (
figure 1).
The land use data (SIOSE AR_2017) for the provinces of A Coruña and Pontevedra were also collected from CNIG in GeoPackage format [
https://centrodedescargas.cnig.es]. The land use classes (
table S1) were reclassified into 14 new classes to individualise the main natural ecosystems within the park (
figure 1). To assess differences in visitor influx within each of the identified ecosystems, selections were made by location, and the trail segments and photographs captured in each of the established land use classes in the previous process were individualised.
Subsequently, we used the geological map (MAGNA_50/2nd Series) at a scale of 1/50000 available on the Geological and Mining Institute of Spain's website. The original data are openly available in [IGME] at [
https://info.igme.es/cartografiadigital/geologica].
The Terrestrial Reserve Zone (TRZ) of the Cíes Islands was further vectorized according to the cartography of conservation units from the AINP, established in the Management and Use Master Plan of the national park [
71] Wikiloc and Flickr photographs were overlaid onto the TRZ shapefile based on their respective land uses, enabling a more rigorous analysis of the impact of visitor activity on the ecosystems of the Cíes Islands that require the highest level of protection. Finally, based on results from maps detailing photograph distribution and trail intensity according to land use, we developed biogeographical profiles and geological cross-sections for the most popular tourist points.
Author Contributions
conceptualization, methodology, E.C., J.C. A.G. and A.P.-A; software and data curation, E.C., and J.C.; validation, A.G. and A.P.-A; formal analysis, E.C., J.C. A.G. and A.P.-A; investigation, E.C., J.C. A.G. and A.P.-A; writing—review and editing, E.C., J.C., A.G. and A.P.-A; funding acquisition, A.G. All authors have read and agreed to the published version of the manuscript.