Carrying Capacity and Assessment of the Tourism Sector in the South Aegean Region, Greece

Abstract

Since the early 1950s, Greece has been a popular travel destination providing high-quality tourism services. This was amplified by its diverse landscape, extended sandy beaches, scattered archaeological sites, people’s mentality, and adequate infrastructure. In particular, the south Aegean Archipelago attracts more than six million (6,000,000) visitors annually, approximately 27% of tourist arrivals in Greece. The carrying capacity assessment of the South Aegean region aims to improve the already high standards of the offered tourist services. Seventeen appropriate variables were analyzed to assess and increase tourism attractiveness by alternative products for long-term and sustainable management. Furthermore, the outcomes of the carrying capacity indicators application provide specialized solutions to control the over-tourism impact, mitigate the natural environmental degradation, and establish a roadmap for sustainable development in the study area. The required data were interpreted based on the PAP/RAC 1997 and WTO, enriched with more suitable variables from national and international literature to determine the carrying capacity. Therefore, the selection of seventeen (17) most representative indicators was unavoidable. Finally, the calculation of the different indexes showed that Mykonos and Thira are far above the indicator scale limits and are facing over-tourism issues. Additionally, the numbers of tourists concentrated in the abovementioned islands may accelerate the environmental degradation and, as a result, the tourist product will be downgraded. The set of these seventeen indicators works best since low, obfuscated, or no environmental data are available for the South Aegean region from the official state agency. Alternative tourist development and the extension of the tourist season based on local climatic conditions must be applied to ease the over-concentration and, consequently, the degradation of the tourist product. The large islands do not seem to face significant problems. However, the calculation of CCA will contribute to the decongestion of tourism concentration together with environmental decompression, leading to sustainable development in the South Aegean region.

1. Introduction

The concept of sustainable tourism development is considered of great importance in decision-making strategies. Consequently, it requires the calculation of the carrying capacity of an area based on specially selected indicators. Such quantification constitutes a valuable tool for assessing the potential negative or positive effects on Greek destinations, which should be studied physically, socially, and economically. So, they must be defined as a totality of such variables by considering the different regional characteristics [1]. Greece depends mainly on the tourism economic sector; consequently, much research has been conducted to maintain one of the most valuable products, since the main occupation in this specific region is related to the tourist industry (29.5% of the working force in South Aegean is employed in this sector) [2]. Additionally, tourism contribution is 30% of the total tourist income in the study area, 3% of the country’s total GDP [2], and at the same time 63% of the South Aegean’s GDP [2]. Based on the aforementioned, the main goal is the viability of the tourist sector in a long-term perspective, as it has contributed significantly to national income over time [3]. The process of calculating the tourist sector value includes quantitative and qualitative variables. Greek territory has a diverse landscape with 9835 islands and more than 15,000 km of shoreline, providing numerous options for tourists at their destination. The latest gross national product (GNP) surveys point out that the offered tourism services will soon need to be more catching and environmentally friendly in order to attract more investments and, thus, maintain their leading position in the Greek economy [4,5].

In the last few decades, researchers have been trying to develop, test, and implement tools for maintaining sustainability by measuring tourism carrying capacity [6,7]. According to the World Tourism Organization, carrying capacity is defined as “the maximum number of tourists who may visit a destination at the same time without affecting the economic, physical, and social environment, and not to limit the satisfaction of tourists” [8,9,10,11,12]. For this reason, the researchers soon realized that tourism has many aspects, so they changed their studies from an economic-based to a multivariable perspective. Consequently, these studies consider the economic, environmental, and social impacts. As a result, the estimation of carrying capacity is of great importance since the benefits of tourism without proper planning can be harmful, affecting the attractiveness and competitiveness of the destination. Hence, the destination will be overloaded, tourism quality will be weakened, and any benefit from tourism flow will be diminished [7].

Consequently, in the last 20 years, tourism standards have been trying to match the social requirements for better environmental quality by using innovative environmental practices and taking advantage of the cultural specificities for the benefit of the region’s tourist development. In order to determine the optimum tourist load for a particular area, the World Tourism Organization [13] published a guidebook with a large number of indicators of sustainable growth for tourism destinations. Similarly, UNEP-WTO (2005) [14] recommended a guide with policies and indicator tools based on real cases collected worldwide. The European Commission (2006) [15] also published a methodological manual for the assessment of the sustainable development of tourism [5,7].

In the present paper, a set of the seventeen most representative indicators was proposed, based on the national–international literature in the quantification process of carrying capacity, and tailored to this particular study area’s characteristics and the availability of data. Since there are no or too few environmental data, the numbers of tourists concentrated in a specific area (solid waste production, wastewater production, drinkable water consumption, and CO₂ emissions can lead to environmental stress) are used as a logic indirect indicator for embedding the environmental impact of tourism in the results/discussion/conclusions. The main objective is to cover all the physical–ecological, social–demographic and political–financial aspects, delineating and describing the present state of the carrying capacity for tourism in the South Aegean region (Figure 1). Aiming toward the best practices for sustainable development, the results of this study can contribute to recommendations for local administrators, decision-makers, and stakeholders.

2. Area of Concern

Generally, Greece is one of the most popular tourist destinations worldwide because of its extensive coastline, numerous islands, natural beauty, and Mediterranean climate. Consequently, it was ranked 13th on the WTO list of top destinations worldwide in 2018.

The Southern Aegean region is one of Greece’s thirteen administrative regions. It comprises the Cyclades and Dodecanese Island complexes. The region covers a total area of 5286 km² (Cyclades: 2572 km², Dodecanese: 2714 km²), approximately 4% of the total area of Greece. The study area (Figure 1) has a diverse landscape, including extended sandy, tourist-orientated beaches, numerous archaeological sites, and adequate infrastructures. It consists of two island complexes, namely the Cyclades and Dodecanese. The Cyclades are situated in the central part of the Aegean Sea on a shallow plateau (or platform) with water depths of less than 200 m [16,17,18]. The Cyclades complex consists of approximately 220 islands. Naxos is the largest island; Syros is the city of Ermoupoli, the administrative center, and Andros has the longest coastline. Due to the lithology, the sediment load on the shore and the very shallow marine areas is limited [19,20,21,22,23]. The unique landscape with sandy beaches and crystal waters, the traditional architecture, tasty food, and the hospitality of local people make the Cyclades a “must-visit” destination. Famous islands with a global reputation, like Mykonos and Santorini, attract annually millions of tourists.

In addition, the Dodecanese islands are also significant tourist areas. They are primarily extended islands with many kilometers of coastline, attracting more than two million tourists annually. Rhodes is the largest among the Dodecanese islands in terms of land, area, and population. Many travelers visit this region in Greece not only because of the natural environment but also for the cultural, historical, and archaeological particularities. Since the 1950s, the tourism industry has flourished; thus, it is the central pillar of development in the Dodecanese. This can be highlighted by the presence of high numbers of businesses and tourist beds of different types (hotel, rooms to let, villas, etc.) are concentrated in Dodecanese islands.

Dodecanese islands are located in the southeastern Aegean Sea, near the Hellenic Trench. A complicated system of fault-controlled relief dominates the area and leads the natural processes, forming deep submarine troughs and high terrestrial ridges [24,25,26,27,28,29,30]. In some islands, e.g., Rhodes, Karpathos, and Kassos, active tectonics have uplifted shorelines up to 3.8 m since the mid-Holocene [26,31,32]. The Dodecanese Archipelago is mainly formed by metamorphic and sedimentary rocks belonging to various geotectonic units [23,33], which supply the coastal zones with noncohesive sediments (mainly sands).

3. Literature Review

Carrying capacity is considered a multidisciplinary approach to tourism sustainability as part of the planning process. Furthermore, it is a crucial aspect of sustainable tourism development and is often used to specify limitations for tourist use and measure the impacts at each destination. Tourism carrying capacity (TCC) refers not only to the number of tourists but also to the capability of the local community to manage tourism flows. [5,7]. Buttler (1980) [34] demonstrated the cycle of a tourist destination and described the distinctive stages that follow its development process, aiming to plan and manage tourism assets. O’Reilly (1986) [35] recommended that tourism carrying capacity applies not only to the maximum limit of visitors but also to the maximum rate of growth, above which it is harmful. Martin and Uysal (1990) [36] described the link between carrying capacity and tourism lifecycle and suggested policy implications. McElroy and de Albuquerque (1998) [37] proposed a five-fold system: to construct a simple index of tourism penetration and to apply this index to a sample of twenty (20) small Caribbean islands in order to group them into subsets based on levels of tourism penetration; to present four case studies that describe the different characteristics of each island at various levels of tourism penetration; and to highlight the policy implications of such an indicator. Blancas et al. (2010) [38] introduced a new synthetic indicator to simplify the measurement of sustainability and facilitate the comparative analysis of the ranking. This measurement was obtained by applying a procedure to minimize the number of subjective decisions made by the analyst, using an innovative two-stage aggregation methodology based on principal component analysis. The indicator, as mentioned earlier, was applied to Spanish coastal destinations, and the results serve as a guideline for tourism planning. Zacarias et al. (2011) [39], based on tourism carrying capacity assessment combined with the PAOT (People At One Time) approach, explore the area of Praia de Faro, attempting to assess the optimum number of people that should be allowed without degrading the surrounding ecological, social, and cultural environment. Jurando et al. (2012) [40] established a methodology to assess the growth limits of tourist destinations, and this method was applied to the management and planning of an open tourist resort. The limits to growth are established using mathematical formulation (i.e., multicriteria analyses based on the reference point methodology) based on synthetic indicators applied to two scenarios: weak and strong sustainability. De Lucia et al. (2019) [41] consider one of Italy’s most visited tourist destinations (Puglia) and use quantitative (i.e., inferential and text mining) and qualitative (i.e., survey) approaches. The main results reveal that socioeconomic and environmental factors positively affect residents’ perception of tourism as a driver of sustainable development. Furthermore, the spatial dimensions of the territories of Puglia, perceived by local indigenous knowledge, are key elements for the tourist attractiveness of its destinations. Also, Coccosis and Koutsopoulou (2020) [42] present a framework that measures and monitors sustainability at the local level by introducing a three-tier system of indicators. The framework manages to incorporate the different types of tourism activities and the unique characteristics of coastal tourist destinations in the Mediterranean while simultaneously allowing for comparisons among them.

International organizations such as WTO, OECD, UN, and UNESCO EC have increased their awareness of the sustainability of the tourism sector and its major impact on communities. The Secretary-General of the WTO, Zurab Pololikashvili, addressed the European Committee on the 19th of February 2020 and stated: “Making the tourism sector as a key part in the EU Agenda and as we face up to the biggest challenge of our lifetimes in the climate emergency, we must make sure tourism’s potential to contribute to the European Green Deal is fully realized. The tourism sector should use its unique dynamic to lead the response to the climate emergency and ensure responsible growth” [7].

In Greece, recent studies aim to calculate the carrying capacity for various destinations using various indicators based on the framework proposed by national and international literature. Tselentis et al. (2006) [9] used, for the cases of Kos and Rhodes islands, a set of selected parameters/indicators such as tourist arrivals related to the local population during high and low season, seasonal population, airport and port arrivals, beach impact factor, natural environment, and garbage and waste management, based upon the availability of the data. Tselentis et al. (2012) [43] applied the principles of coastal environmental management for the islands in the central Aegean Sea islands via the carrying capacity assessment methodology to develop environmental performance indicators necessary for formulating a novel sustainable development policy proposal for Greek tourism. Prokopiou et al. (2018) [3] applied three axes of carrying capacity calculation: tourist development, economic and social assessments, and environmental assessment. Varelas and Belias (2019) [44] calculated and analyzed the limits and prospects of tourism development as they are approached and evaluated through the methodological tool of the carrying capacity assessment on a local scale.

Moreover, Vagiona and Palloglou (2021) [45] developed and implemented an integrated indicator-based system covering different tourism carrying capacity (TCC) components. The indicator-based method was applied to the island of Milos (Greece). Twenty indicators were selected to contribute to the final system for TCC calculation. The study was focused on an island (Milos) with a tourism-based economy. The abovementioned technique was used to assess TCC and can be adapted to other coastal tourist destinations.

4. Materials and Methods

Carrying capacity assessment (CCA) is the most common technique used for the estimation of tourism assessment and management [5,46]. The analysis of CCA in the field of tourism globally has included, during recent years, measurable physical and ecological–environmental parameters as well as demographic and sociocultural factors that are difficult to quantify [9,10,12,40,43,47]. This can be achieved mainly through increasing or restricting the economic measures (tax policy, construction of large-scale public infrastructure systems, etc.) and the handling and utilization of the CCA, especially in developed countries of the Mediterranean, mainly to which these guidelines are addressed. The general context for quantifying the CCA for the Mediterranean tourism sector is also based on these three sets of parameters. In addition, the relationship among the parameters is crucial for the overall framework of the CCA through an integrated coastal area management (ICAM) program for each administrative area. For the South Aegean region, the research approach is based on the quantification, analysis, and evaluation of [12,13], enriched and customized according to various researchers. Precisely, the methodology (indicators) proposed by [1,3,5,7,9,42,43,44,48] is thought to be the most indicative methodology based on the conceptualization of CCA, the Greek reality, and the availability of information concerning regional characteristics.

Relevant carrying capacity indicators have been selected and categorized according to global and regional context: 1. physical–ecological, 2. social–demographic, and 3. political–financial. It is highly topical to develop and integrate such indicators into the planning process for the Greek tourist business, specifically the island tourist trade, on which the Greek economy depends so heavily. It is believed that, via this process, realistic, sustainable scenarios for tourist development can be proposed for such areas [9,49,50,51]. Therefore, the carrying capacity of tourism for the South Aegean region has been calculated through seventeen (17) indicators, as demonstrated in

Table 1. Selected variables used to calculate the carrying capacity in the South Aegean region based on the implementation in Greek territory and available data.

Indexes/Variables
Physical–Ecological Indexes	Tourist Operation Index-(TOI) (V1)	$\frac{\mathbf{T}\mathbf{o}\mathbf{t}\mathbf{a}\mathbf{l}\mathbf{b}\mathbf{e}\mathbf{d}\mathbf{s}\times 100}{\mathbf{R}\mathbf{e}\mathbf{s}\mathbf{i}\mathbf{d}\mathbf{e}\mathbf{n}\mathbf{t}\mathbf{p}\mathbf{o}\mathbf{p}\mathbf{u}\mathbf{l}\mathbf{a}\mathbf{t}\mathbf{i}\mathbf{o}\mathbf{n}}$	[5,12,13,15,44,52,53,54]	Offers useful conclusions regarding the degree to which the tourism industry is developed
	Tourism Density Index (TDI) (V2)	$\frac{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{b}\mathrm{e}\mathrm{d}\mathrm{s}\times 100}{\mathrm{R}\mathrm{e}\mathrm{s}\mathrm{i}\mathrm{d}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{p}\mathrm{o}\mathrm{p}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\times \mathrm{t}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{A}\mathrm{r}\mathrm{e}\mathrm{a}}$	[44,52,55]	If this number is higher than others, phenomena of “over-tourism” are present, while in the opposite case, phenomena of “under tourism”
	Tourism Intensity Index (TII) (V3)	$\frac{\mathrm{B}\mathrm{e}\mathrm{d}\mathrm{s}}{\mathrm{P}\mathrm{o}\mathrm{p}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}$	[3,5,38,44,55]	This index determines the true capability of the main regional market
	Tourists per m of beach (V4)	$\frac{\mathrm{B}\mathrm{e}\mathrm{d}\mathrm{s}\left(\mathrm{T}\mathrm{o}\mathrm{u}\mathrm{r}\mathrm{i}\mathrm{s}\mathrm{t}\mathrm{s}\right)\mathrm{p}\mathrm{e}\mathrm{r}\mathrm{d}\mathrm{a}\mathrm{y}}{\mathrm{m}\mathrm{o}\mathrm{f}\mathrm{b}\mathrm{e}\mathrm{a}\mathrm{c}\mathrm{h}}$	[5,9,48]	Demonstrates the concentration of tourists on the beach in a single day
	Tourism Pressure Index (TPrI) (V5)	$\frac{\begin{array}{c}\mathrm{T}\mathrm{o}\mathrm{u}\mathrm{r}\mathrm{i}\mathrm{s}\mathrm{t}\mathrm{s}\\ \mathrm{p}\mathrm{e}\mathrm{r}\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}\mathrm{d}\mathrm{a}\mathrm{y}\end{array}}{\mathrm{A}\mathrm{r}\mathrm{e}\mathrm{a}}$	[48,55,56]	Indicates whether the number of tourists fluctuates in such levels so as not to exceed the limits of each tourist destination’s carrying capacity concerning a specific area
	Tourism Tolerance Population Index (TTPI) (V6)	$\frac{\mathrm{N}\mathrm{u}\mathrm{m}\mathrm{b}\mathrm{e}\mathrm{r}\mathrm{o}\mathrm{f}\mathrm{t}\mathrm{o}\mathrm{u}\mathrm{r}\mathrm{i}\mathrm{s}\mathrm{t}\mathrm{s}\mathrm{p}\mathrm{e}\mathrm{r}\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}\mathrm{d}\mathrm{a}\mathrm{y}}{\mathrm{P}\mathrm{o}\mathrm{p}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}$	[5,52,55]	Indicates whether the number of tourists fluctuates in such levels so as not to exceed the limits of its carrying capacity for each tourist destination concerning the resident population
	People-users per m of beach (V7)	$\frac{\mathrm{R}\mathrm{e}\mathrm{s}\mathrm{i}\mathrm{d}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{p}\mathrm{o}\mathrm{p}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}+\mathrm{b}\mathrm{e}\mathrm{d}\mathrm{s}}{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{g}\mathrm{t}\mathrm{h}\mathrm{o}\mathrm{f}\mathrm{b}\mathrm{e}\mathrm{a}\mathrm{c}\mathrm{h}\mathrm{e}\mathrm{s}\left(\mathrm{m}\right)}$	[9]	Demonstrates the general burden of the users on the beach
	Tourists/Beds per km of beach (V8)	$\frac{\mathrm{B}\mathrm{e}\mathrm{d}\mathrm{s}}{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{g}\mathrm{t}\mathrm{h}\mathrm{o}\mathrm{f}\mathrm{b}\mathrm{e}\mathrm{a}\mathrm{c}\mathrm{h}\mathrm{e}\mathrm{s}\left(\mathrm{k}\mathrm{m}\right)}$	[3]	Demonstrates the tourist burden of the users on the beach
	People-users of beach in peak day per m of beach (V9)	$\frac{\mathrm{R}\mathrm{e}\mathrm{s}\mathrm{i}\mathrm{d}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{s}+\mathrm{b}\mathrm{e}\mathrm{d}\mathrm{s}+\mathrm{c}\mathrm{r}\mathrm{u}\mathrm{i}\mathrm{s}\mathrm{e}\mathrm{s}}{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{g}\mathrm{t}\mathrm{h}\mathrm{o}\mathrm{f}\mathrm{b}\mathrm{e}\mathrm{a}\mathrm{c}\mathrm{h}\mathrm{e}\mathrm{s}}$	[9,12,13,52]	Demonstrates the total number of people/users on the beach
	Tourism Concentration Index (TConI) (Ha) (V10)	$\frac{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{O}\mathrm{v}\mathrm{e}\mathrm{r}\mathrm{n}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{y}\mathrm{s}}{\mathrm{A}\mathrm{r}\mathrm{e}\mathrm{a}}$	[53]	Demonstrates the will of the visitors to stay in a specific area
Social–Demographic Indexes	Tourism Penetration Index (TPenI) (V11)	$\frac{\mathrm{O}\mathrm{v}\mathrm{e}\mathrm{r}\mathrm{n}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{y}\mathrm{s}\mathrm{n}\mathrm{o}\mathrm{n}-\mathrm{G}\mathrm{r}\mathrm{e}\mathrm{e}\mathrm{k}\times 100}{\mathrm{R}\mathrm{e}\mathrm{s}\mathrm{i}\mathrm{d}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{P}\mathrm{o}\mathrm{p}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\times 360}$	[37,44]	Expresses the level of development as a tourist destination
	Tourism Attractiveness Index (TAI) (V12)	$\frac{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{I}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{n}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{a}\mathrm{l}\mathrm{A}\mathrm{r}\mathrm{r}\mathrm{i}\mathrm{v}\mathrm{a}\mathrm{l}\mathrm{s}}{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{D}\mathrm{o}\mathrm{m}\mathrm{e}\mathrm{s}\mathrm{t}\mathrm{i}\mathrm{c}\mathrm{A}\mathrm{r}\mathrm{r}\mathrm{i}\mathrm{v}\mathrm{a}\mathrm{l}\mathrm{s}}$	[40,42,57]	Presents the ratio of the number of arrivals of foreign tourists at a destination to the domestic equivalent
	Total Arrivals to a Specific Area (km2) Index (V13)	$\frac{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{A}\mathrm{r}\mathrm{r}\mathrm{i}\mathrm{v}\mathrm{a}\mathrm{l}\mathrm{s}}{\mathrm{A}\mathrm{r}\mathrm{e}\mathrm{a}}$	[53]	Demonstrates the will of the visitors to visit a specific area
	Tourism Overnight Stays Index (TOSI) (V14)	$\frac{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{O}\mathrm{v}\mathrm{e}\mathrm{r}\mathrm{n}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{S}\mathrm{t}\mathrm{a}\mathrm{y}\mathrm{s}}{\mathrm{R}\mathrm{e}\mathrm{s}\mathrm{i}\mathrm{d}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{p}\mathrm{o}\mathrm{p}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}$	[7,58]	Demonstrates the total time of tourist stays in a specific area and the possible pressure on the local population
Political–Financial Indexes	Contribution of tourism to the region’s GDP (V15)	Single value (2019)	[2,41,42,59,60]	Demonstrates the contribution to the tourist industry in this specific region
	Total beds per Area (km2) (V16)	$\frac{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{B}\mathrm{e}\mathrm{d}\mathrm{s}}{\mathrm{A}\mathrm{r}\mathrm{e}\mathrm{a}}$	[9,42]	Demonstrates the tourist development/economic revenues in a specific area
	Employment per beds (single value for the whole region) (V17)	$\frac{\mathrm{E}\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{o}\mathrm{m}\mathrm{i}\mathrm{c}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{e}\mathrm{p}\mathrm{o}\mathrm{p}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}{\mathrm{B}\mathrm{e}\mathrm{d}\mathrm{s}}$	[52,60]	Demonstrates the ratio of the economically active population to the tourists visiting each destination

, and their thresholds (

Table 2. Thresholds of CCA indicators, provided by national and international literature of relevant research.

Thresholds of CCA Indicators
TOI (V1)	>500	Excessive/intensive tourism development
	100–500	Almost exclusive tourism development
	40–100	Main growth relative to other sectors
	10–40	Important but not main growth
	4–10	Small or very small tourism growth
TII (V3)	3	High level of tourist services, exceeding tourist carrying capacity
	1–3	Satisfactory level of tourism services, growth potential
	<1	Low level of tourism services, significant growth potential
TTPI (V6)	>2	Exceeding tourist carrying capacity, control of tourist arrivals
	2	Significant point of exceeding carrying capacity, control of tourist arrivals
	1.5	Satisfactory level of tourism, need of control of tourist arrivals
	1	Low number of tourists, greater number of tourists can be received
People-users/m of beach (V7) and (V9)	0	No danger for environmental degradation
	1	Existence of pressure
	2	Existence of significant pressure
Tourism Concentration Indicator (V10)	>9.58	Highest risk
	=6.31–9.58	High risk
	=4.50–6.30	Medium risk
	=3.18–4.49	Low risk
	<3.18	Lowest risk
Tourism Attractiveness Indicator (V12)	0–1	Preferable to domestic tourists
	>1	Preferable to international tourists
Overnight to residents indicator (V14)	>9	High level of tourist services
	=6–9	Satisfactory level of tourist services
	6<	Low level of tourist services

).

The data collected in the present study/paper are mainly related to the population structure (permanent residents, nonresidents, overnight stays, domestic/international arrivals, seasonal population, etc.), to the physical characteristics (geomorphology of the area, the total length of the coastal area, environmental quality, infrastructures, etc.), and to the economic/financial situation (contribution of tourism to the region’s GDP, available beds, and the number of tourists arrived in the region per peak day, etc.).

The available data were quantified by applying the appropriate equations proposed by national and international researchers in this field. They are provided and explained thoroughly in Table 1, along with their thresholds in Table 2. After the statistical analysis of the data, possible scenarios for sustainable development for the South Aegean region were proposed.

5. Results

5.1. Sociodemographic and Physical Data for the Calculation of CCA in the South Aegean Region

Based on the investigation of the data acquired from [2,61,62], it is easily detected that the island with the highest values for tourism presence is Rhodes (with the islands of Simi, Tilos, Megisti, and Halki). It is also the largest island with an area of 1404.1 km² and a coastal length of 298,603.78 m. The resident population inhabiting Rhodes is 129,151. It has the highest number of beds; thus, it can accommodate 108,138 tourists per day (hotels, rooms to let, and villas). Rhodes also received large numbers of tourists, 1,400,557 from international arrivals, 255,411 from domestic arrivals, and 131,090 persons from cruises. Rhodes had the maximum overnight stays from Greek (473,309) and non-Greek (8,392,603) tourists. Finally, the load of tourists per peak day was also the highest in the South Aegean region (239,228) (Appendix A,

Table A1. Sociodemographic and physical data for the calculation of CCA, such as coastal length, area, total beds/tourists/beds, cruise traffic, tourists per peak day, overnight stays for Greek and non-Greek tourists, total overnight stays, domestic arrivals (by airplane), international arrivals (by airplane), and total resident population of the islands of the South Aegean region. The color palette is selected from the lowest (green) to the highest (red) value. The colors in between yellow and orange show an average value for the study area (sources: [2,59,62]). All values are annual counts.

Island	Coastal Length (m)	Area (km2)	Total Beds (2021)	Cruise traffic	Tourists per peak day	Overnight stays non-Greek (2021)	Overnight stays Greek (2021)	Total Overnight stays (2021)	Domestic Arrivals	International arrivals	Resident Population (2021)
Thira	76,525	76	50,216	104,074	154,290	1,597,022	235,919	1,832,941	272,723	472,224	19,013
Mykonos	127,868	86	32,006	201,821	233,827	1,272,664	183,230	1,455,894	137,823	362,452	9802
Naxos	177,748	429	23,592	0	23,592	437,034	151,649	588,683	44,894	0	21,777
Paros	152,479	196	27,120	2,579	29,699	525,116	199,134	724,250	97,278	911	15,554
Milos	176,838	157	24,166	7909	32,075	106,447	126,689	233,136	32,118	0	10,023
Syros	119,433	84	8299	3833	12,132	99,104	161,856	260,960	4208	0	20,791
Tinos	159,984	195	7408	0	7408	32,817	140,564	173,381	0	0	8611
Andros	254,945	379	5703	0	5703	30,615	64,253	94,868	0	0	8883
Kea-Kythnos	248,188	231	4669	0	4669	20,801	62,351	83,152	0	0	3886
Rhodes	298,604	1404	108,138	131,090	239,228	8,392,603	473,309	8,865,912	255,411	1,400,557	129,151
Kos	141,694	287	63,105	5150	68,255	4,632,990	174,696	4,807,686	83,053	680,384	38,029
Karpathos	237,706	300	8249	0	8249	178,254	23,996	202,250	26,901	42,769	7640
Kalymnos	133,103	110	10,831	21,804	32,635	184,962	106,714	291,676	18,351	0	31,382

).

On the contrary, a smaller island in the Cyclades also presents a very intense tourism presence. This island is Mykonos. The area of Mykonos is 86.33 km², and the total length of the coast is 127,868.38 m. The resident population is 9802. Mykonos also receives large flows of tourists, 362,452 from international arrivals, 137,823 domestic arrivals, and 201,821 persons from cruises. It can accommodate 32,006 tourists per day (hotels, rooms to let, and villas). Mykonos had a large number of overnight stays by Greek (183,230) and non-Greek (1,272,664). Additionally, the tourists per peak day were also high throughout the South Aegean region (233,827) (Appendix A, Table A1).

Thira has an area of 75.94 km² and total length of 76,524.85 m. The resident population inhabiting Thira is 19,013. Thira also receives large numbers of tourists, 472,224 from international arrivals, 272,723 from domestic arrivals, and 104,074 persons from cruises. It has a high number of beds; thus, it can accommodate 50,216 tourists per day (hotels, rooms to let, and villas). Thira had also many overnight stays from Greek (1,597,022) and non-Greek (235,919) tourists. Particularly, the number of tourists per peak day also present high numbers for the South Aegean region (154,290) (Appendix A, Table A1).

Naxos has an area of 428.66 km² and a coastal length of 177,748.19 m. The resident population inhabiting Naxos is 21,777. Naxos did not receive international flights; it received about 44,894 people from domestic flights and 0 persons from cruises. It has a moderate number of beds compared with the other destinations; thus, it can accommodate 23,592 tourists per day (hotels, rooms to let, and villas). The number of overnight stays from Greek tourists was 235,919 and overnight stays from non-Greek tourists was 1,832,941, and the number of visitors per peak day was 23,592 because it has no tourists from cruises (Appendix A, Table A1).

Paros has an area of 195.55 km² and a coastal length of 152,478.71 m. The resident population inhabiting Paros is 15,554. It has 27,120 beds (hotels, rooms to let, and villas). Paros received 911 tourists from international flights, 97,278 people from domestic flights, and 2579 persons from cruises. The number of overnight stays from Greek tourists was 19,9134 and the number of non-Greek was 525,116. The visitors per peak day were 29,699, adding the visitors from cruises to the total beds-tourists (Appendix A, Table A1).

Milos has an area of 157.39 km² and a coastal length of 176,838.15 m. The resident population inhabiting Milos is 10,023. Milos did not receive tourists from international flights in 2021, but it received 32,118 people from domestic flights and 7909 persons from cruises. Milos has 24,166 beds (hotels, rooms to let, and villas). The number of overnight stays from Greek tourists was 126,689 and non-Greek was 106,447. The visitors per peak day were 32,075 (Appendix A, Table A1).

Syros has an area of 84.06 km² and a coastal length of 119,433.45 m. The resident population inhabiting Syros is 20,791. Syros did not receive tourists from international flights in 2021, but it received 4208 people from domestic flights and 3833 persons from cruises. Syros has 8299 beds (hotels, rooms to let, and villas). The number of overnight stays from Greek tourists was 161,856 and non-Greek was 99,104, and the visitors per peak day were 12,132 (Appendix A, Table A1). Tinos has an area of 194.77 km² and a coastal length of 159,983.52 m. The resident population inhabiting Tinos is 8611 people. Tinos did not receive tourists from international or domestic flights or cruises in 2021. Tinos has 7408 beds (hotels, rooms to let, and villas). The number of overnight stays from Greek tourists was 140,564 and non-Greek was 32,817. The number of visitors per peak day was 7408 since there were no visitors from cruises (Appendix A, Table A1).

Andros has an area of 378.98 km² and a coastal length of 254,945.03 m. The resident population inhabiting Andros is 8883. Andros did not receive tourists from international or domestic flights or cruises in 2021. Andros has a capacity of 5703 beds (hotels, rooms to let, and villas). The number of overnight stays from Greek tourists was 64,253 and non-Greek was 30,615. The number of visitors per peak day was 5703 since there were no visitors from cruises (Appendix A, Table A1).

Kea and Kythnos appear as an ensemble in Hellenic Statistical Authority [61]; as a result, the total area of the islands is 230.50 km² and the coastal length is about 300 km. The resident inhabitants are 3886 people. Kea–Kythnos did not receive tourists from international or domestic flights or from cruises in 2021. They both have a capacity of 4669 beds (hotels, rooms to let, and villas). The number of overnight stays from Greek tourists was 62,351 and non-Greek was 83,152. Also, the number of visitors per peak day was 4669 since there were no visitors from cruises (Appendix A, Table A1).

The islands of Kos (along with Nisyros island), Karpathos (and Kasos), and Kalymnos (with Astypalaia, Leros, Patmos, Lipsi, and Agathonisi), complete the South Aegean region. Specifically, Kos extends in 287.23 km² and its coastal length is about 141,693.99 m. The resident inhabitants are 38,029 people. The accommodation capacity is 63,105 beds (hotels, rooms to let, and villas). Kos received 680,384 tourists from international flights, 83,053 from domestic flights, and 5150 tourists from cruises in 2021. The number of overnight stays from Greek tourists was 174,696 and non-Greek was 4,632,990, and the visitors per peak day were 68,255 (Appendix A, Table A1).

Karpathos extends in 300.19 km² and its coastal length is about 237,705.92 m. The resident inhabitants are 7640 people. The accommodation capacity is 8249 beds (hotels, rooms to let, and villas). Karpathos received 42,769 tourists from international flights, 26,901 from domestic flights, and 0 tourists from cruises in 2021. The number of overnight stays from Greek tourists was 23,996 and non-Greek was 178,254, and the visitors per peak day were 8249 since no tourists from cruises have been received (Appendix A, Table A1).

Kalymnos extends in 110.43 km² and its coastal length is about 133,102.70 m. The resident inhabitants are 31,382 people. The accommodation capacity is 10,831 beds (hotels, rooms to let, and villas). Kalymnos did not receive tourists from international flights, but it received 18,351 from domestic flights and 21,804 tourists from cruises in 2021. The number of overnight stays from Greek tourists was 106,714 and non-Greek was 184,962, and the number of visitors per peak day were 32,635 (Appendix A, Table A1).

5.2. Results from the Calculation of the Appropriate Indicators for the Estimation of the Tourist Impact on the South Aegean Region

The results derived by calculating the selected indicators/variables describe the current status of tourism in South Aegean region (Appendix A, Table A1 and

Table A2. Results of the calculated indicators/variables estimating the carrying capacity for the South Aegean region. The classification of variables V1, V3, V6, V7–9, V10, V12, and V14 are scaled according to national and international thresholds. The remaining variables are classified from low (green) to high (red). The colors in between yellow and orange show an average value for the study area.

Island	Tourism Operational Index	Tourism Density Index	Tourism Intensity Index	Tourists per m of beach	Tourism Pressure Index	Tourism Tolerance Population Index	Indicator of beach environmental impact (people/m of beach)	Beds per km of beach	People-users per m of beach peak day	Tourism Concentration Index- Total overnights/Ha	Tourism Penetration Index	Tourism Attractiveness Index	Total Arrivals/km2	Total overnights/residents	Contribution of Tourism to Region’s GDP	Beds per Area km2	Economically active Population divided by total beds
	TOI (V1)	TDI (V2)	TΙI (V3)	(V4)	TPrI (V5)	TTPI (V6)	(V7)	(V8)	(V9)	TCI (V10)	TPenI Non-Greek (V11)	TAI (V12)	TArI (V13)	TNRI (V14)	(V15)	(V16)	(V17)
Thira	264.11	3.48	2.64	0.66	2.03	8.11	0.90	3.64	2.92	241.36	23.33	1.73	9809.25	96.40	63%	661.23	0.31
Mykonos	326.53	3.78	3.27	0.25	2.71	23.86	0.33	4.27	2.16	168.65	36.07	2.63	5795.11	148.53		370.75
Naxos	108.33	0.25	1.08	0.13	0.06	1.08	0.26	2.08	0.39	13.73	5.57	0.00	104.73	27.03		55.04
Paros	174.36	0.89	1.74	0.18	0.15	1.91	0.28	2.74	0.47	37.04	9.38	0.01	502.12	46.56		138.69
Milos	241.11	1.53	2.41	0.14	0.20	3.20	0.19	3.41	0.37	14.81	2.95	0.00	204.07	23.26		153.54
Syros	39.92	0.47	0.40	0.07	0.14	0.58	0.24	1.40	0.35	31.04	1.32	0.00	50.06	12.55		98.73
Tinos	86.03	0.44	0.86	0.05	0.04	0.86	0.10	1.86	0.15	8.90	1.06	0.00	0.00	20.13		38.03
Andros	64.20	0.17	0.64	0.02	0.02	0.64	0.06	1.64	0.08	2.50	0.96	0.00	0.00	10.68		15.05
Kea-Kythnos	120.15	0.52	1.20	0.02	0.02	1.20	0.03	2.20	0.05	3.61	1.49	0.00	0.00	21.40		20.26
Rhodes	83.73	0.06	0.84	0.36	0.17	1.85	0.79	1.84	1.60	63.15	18.05	5.48	1179.46	68.65		77.02
Kos	165.94	0.58	1.66	0.45	0.24	1.79	0.71	2.66	1.20	167.38	33.84	8.19	2657.96	126.42		219.70
Karpathos	107.97	0.36	1.08	0.03	0.03	1.08	0.07	2.08	0.10	6.74	6.48	1.59	232.09	26.47		27.48
Kalymnos	34.51	0.31	0.35	0.08	0.30	1.04	0.32	1.35	0.56	26.41	1.64	0.00	166.17	9.29		98.08

), according to the thresholds provided by the national–international literature and the international organizations. Specifically, considering all the variables, the islands leading the tourism sector in the South Aegean region in 2021 are Mykonos, Thira, Milos, Paros, Rhodes, and Kos (Appendix A, Table A2). The highest scores of TOI (V1) (between 100 and 500) present the islands of Mykonos (326.53), Thira (264.11), Milos (241.11), Paros (174.36), Kos (165.94), Kea–Kythnos (120.15), Naxos (108.33), and Karpathos (107.97). These islands show almost exclusive tourism development, accepting thousands of tourists (Greek and non-Greek) (Appendix A, Table A1). In the next class of TOI (important but not main growth) are the islands of Tinos (86.03), Rhodes (83.73), and Andros (64.20). Finally, Syros (39.92) and Kalymnos (34.51) present important but not main growth (Appendix A, Table A2, Figure 2a). The next variable corresponds to TDI (V2). The most significant scores are presented by Mykonos (3.27) and Thira (2.64), followed by Milos (1.53) and Paros (0.89). The other islands studied show scores far below “1”. Specifically, the calculated scores are as follows: Kos (0.58), Kea–Kythnos (0.52), Syros (0.47), Tinos (0.44), Karpathos (0.36), Kalymnos (0.31), Naxos (0.25), Andros (0.17), and finally Rhodes (0.06) (Appendix A, Table A2, Figure 2b). As for TII (V3), the island with the highest score is Mykonos (3.27) corresponding to “high level of tourist services exceeding tourist carrying capacity”. The next class (satisfactory level of tourism services, growth potential) includes the islands of Thira (2.64), Milos (2.41), Paros (1.74), Kos (1.66), Kea–Kythnos (1.20), Karpathos (1.08), and Naxos (1.08). In the last class are Tinos (0.86), Rhodes (0.84), Andros (0.64), Syros (0.40), and Kalymnos (0.35) (Appendix A, Table A2, Figure 2c). In addition, for the tourists per m of beach variable (V4), the highest scores encountered are at Thira (0.66), Kos (0.45), and Rhodes (0.36). The islands with lower scores are Mykonos (0.25), Paros (0.18), Milos (0.14), Naxos (0.13), Kalymnos (0.08), Syros (0.07), Tinos (0.05), Karpathos (0.03), Andros (0.02), and Kea–Kythnos (0.02) (Appendix A, Table A2, Figure 2d). According to the V5 (tourism pressure index), the islands with the highest scores are Mykonos (2.71) and Thira (2.03). The islands that present medium scores are Kalymnos (0.30), Kos (0.24), Milos (0.20), Rhodes (0.17), Paros (0.15), and Syros (0.14). The lowest scores are found for Naxos (0.06), Tinos (0.04), Karpathos (0.03), Andros (0.02), and Kea–Kythnos (0.02) (Appendix A, Table A2, Figure 2e). The TTPI (V6) is one of the most significant variables [38], describing a region’s carrying capacity. The highest scores, according to the thresholds, are those of Mykonos (23.86), Thira (8.11), and Milos (3.20), which exceed the limits. In the next class are found the islands of Paros (1.91), Rhodes (1.85), Kos (1.79), Kea–Kythnos (1.20), Karpathos (1.08), and Kalymnos (1.04). The final class includes Tinos (0.86), Andros (0.64), and Syros (0.58) (Appendix A, Table A2, Figure 2f). Concerning the indicator of beach environmental impact (V7), Thira (0.90), Rhodes (0.79), and Kos (0.71) present the highest values, followed by Mykonos (0.33), Kalymnos (0.32), Paros (0.28), Naxos (0.26), Syros (0.24), Milos (0.19), Tinos (0.10), Karpathos (0.07), Andros (0.06), and Kea–Kythnos (0.03) (Appendix A, Table A2, Figure 2g). Observing the next variable, “beds per kilometer of beach” (V8), the islands with the highest scores are Mykonos (4.27), Thira (3.64), Milos (3.41), Paros (2.74), Kos (2.66), Kea–Kythnos (2.20), Karpathos (2.08), Naxos (2.08), Tinos (1.86), Rhodes (1.84), Andros (1.64), Syros (1.40), and Kalymnos (1.35) (Appendix A, Table A2, Figure 2h). The islands with the highest value for ”people users per m of beach peak day” (V9) are Thira (2.92), and Mykonos (2.16) exceed the defined limitations, followed by Rhodes (1.60) and Kos (1.20). The other studied islands present values under “1”, such as Kalymnos (0.56), Paros (0.47), Naxos (0.39), Milos (0.37), Syros (0.35), Tinos (0.15), Andros (0.08), and Kea–Kythnos (0.05) (Appendix A, Table A2, Figure 2j). The highest values for “tourism concentration index” (V10) are found in Thira (241.36), Mykonos (168.65), Kos (167.38), Rhodes (63.15), Paros (37.04), Syros (31.04), Kalymnos (26.41), Milos (14.81), and Naxos (13.73), which appear in highest risk than the other islands according to the thresholds. Tinos (8.90) is in high-risk, Kea–Kythnos (3.61) is in low risk, and Andros (2.50) is at lowest risk (Appendix A, Table A2, Figure 2i). For the “tourism penetration index” (V11), the highest scores are presented by Mykonos (36.07), Kos (33.84), and Thira (23.33), and they are followed by Rhodes (18.05), Paros (9.38), Naxos (5.57), Milos (2.95), Kalymnos (1.64), Kea–Kythnos (1.49), Syros (1.32), Tinos (1.06), and finally Andros (0.96) (Appendix A, Table A2, Figure 2k). The “tourism attractiveness index” (V12) concerns the attractiveness of each destination, values between 0 and 1 demonstrate that the area is preferable to domestic tourists, and for values above 1 (>1), the area is attractive to international tourists. Following the condition mentioned above, Mykonos, Thira, Rhodes, Kos, and Karpathos are attracting international tourists. On the contrary, Naxos, Paros, Milos, Syros, Tinos, Andros, Kea–Kythnos, and Kalymnos attract domestic (Greek) tourists (Appendix A, Table A2, Figure 2l). Investigating the “total arrivals per km²” (V13), the highest values are encountered in islands such as Thira (9809.25), Mykonos (5795.11), Rhodes (1179.46), and Kos (2657.96). The other destinations present medium to low values, such as Paros (502.12), Karpathos (232.09), Milos (204.07), Kalymnos (166.17), Naxos (104.73), and Syros (50.06). Tinos, Andros, and Kea–Kythnos do not have any value because they do not have airports; thus, the arrivals cannot be counted (Appendix A, Table A2, Figure 2m). The next variable, “total overnight stays to residents” (V14), separately concerns the total overnights per resident in every destination. The limits of V14 throughout the South Aegean region widely overcome the thresholds, according to Appendix A, Table A2. Specifically, Mykonos (148.53) presents the highest score for this variable (V14), Kos (126.42) follows, and Thira (96.40) is in third place. The other islands, from high to low values, are Rhodes (68.65), Paros (46.56), Naxos (27.03), Karpathos (26.47), Milos (23.26), Kea–Kythnos (21.40), Tinos (20.13), Syros (12.55), Andros (10.68), and Kalymnos (9.29) (Appendix A, Table A2, Figure 2n). The variable “contribution of tourism to region’s GDP”(V15) refers to the percentage of the contribution of tourism to the region’s GDP, which is 63% (for the year 2019), and is a single value according to the latest data available [2,61] (Appendix A, Table A2, Figure 2o). Another variable calculating the CCA of the study area is ”beds per area” (V16). The island with the highest score is Thira (661.23), then Mykonos (370.75) follows, along with Kos (219.70), Milos (153.54), Paros (138.69), Syros (98.73), Rhodes (77.02), Naxos (55.04), Tinos (38.03), Karpathos (27.48), Kea–Kythnos (20.26) and finally Andros (15.05) (Appendix A, Table A2, Figure 2p). The last variable, “economically active population divided by total beds” (V17), is also single-valued and refers to the economically active population per total beds; consequently, the value of the variable is 0.31 for the South Aegean region (Appendix A, Table A2, Figure 2q).

6. Discussion

Estimating carrying capacity is a practical and internationally tested tool to indicate the potential endangered areas from uncontrollable tourist growth. Its main goal is to contribute to the decision-makers, stakeholders, and local administration by selecting suitable variables according to data availability and area characteristics. The analysis of the physical, social–demographic, and economic characteristics of the South Aegean region demonstrates that the Cyclades insular receives the most significant number of tourists in terms of total tourist accommodation and food service [2,59,61]. The seventeen selected indicators describe and delineate in the best possible way the present situation in the tourism industry and its pros and cons for the South Aegean region.

At this point, the authors must highlight the lack of direct environmental information from state agencies or certified resources. Although indirect environmental assumptions based on the concentration of tourists in a specific area (drinkable water consumption, solid waste production, wastewater production, and management) must be taken into account by researchers, stakeholders, and local administrators, given a time step of at least five years for wastewater management (for a plant to be constructed) and yearly ratio for the solid waste production, the drinkable water consumption, and CO₂ emissions (fuel demand and consumption). The local administrations can easily quantify these indicators by comparing their values in nontouristic and highly touristic periods (peak of arrivals). It must be highlighted that these values may vary significantly whether the destinations attract wealthy travelers or not [63]. Additionally, it is also essential, concerning the management of the pollutants, to indicate the exact method of treatment in order to diminish the negative environmental footprint in each study area. Therefore, certified bodies must establish a database to concentrate and assess all this valuable information about each tourist destination separately. The researchers and the stakeholders will then have more accurate and diverse data to assess the CCA from different points of view, as accurately as possible. Therefore, the selected indicators can be implemented in similar areas with many islands, a significantly augmented tourism sector, and millions of visitors per year, especially in the eastern Mediterranean region.

This study provides valuable insight into the causes and consequences of over-tourism in a host destination since it highlights the proper strategies that policy-makers and stakeholders should adopt for environmentally friendly/sustainable growth.

Nevertheless, the unregulated growth of tourism (tourists per peak day/area) can contribute to significant environmental degradation. This risk is higher during periods of intense tourist concentration in the coastal areas, particularly at the top destinations in the South Aegean region. However, all these factors are rapidly spreading and irrevocably changing tourism destinations, as well as the rate at which the realization of this transformation has been growing. Meanwhile, it is increasingly necessitating appropriate and effective tourism planning and management.

Incorporating carrying capacity assessment (CCA) based on these specific indicators into the tourism and management planning process proved to be necessary. The carrying capacity assessment for South Aegean region contained a set of specific indicators to determine the best scenarios and management practices for tourism development in this area according to its distinctive characteristics. It should be used as a guideline for designing tourism development and management plans at all levels.

Furthermore, the results of calculating the appropriate indicators, with the most accurate data possible concerning the characteristics of each region, can lead to various conclusions. Specifically, the tourist load is not equally distributed throughout the study area since some islands attract more travelers than others. These islands are Rhodes, Thira, Mykonos, and Paros. According to TOI (V1), the economy of most islands in the study area is based exclusively on the tourism industry (almost exclusive tourism development and main growth relative to other sectors). The islands presenting the highest values in most indicators due to the massive tourist exploitation are the two famous Cyclades islands of Mykonos and Thira. For instance, the island of Thira faces multivariable dangers, social and space privatization, and a decline in purchasing power parity for residents vs. visitors. According to CCA indicators, these islands (Mykonos and Thira) are already facing significant pressures due to over-tourism and the massive number of visitors, making them no longer comfortable, despite that they continue to receive millions of tourists annually due to their global reputation (Appendix A, Table A1). TDI (V2) and TTPI (V6) also highlight this fact. The islands of Kos and Rhodes are the top destinations in the Dodecanese area, which receive vast numbers of tourists (Appendix A, Table A1). They present the highest scores among the other Dodecanese islands, although they do not reach the top levels of the indicator thresholds. The fact is that the population and the extent of each destination play a significant role in diminishing the indicators’ upper limits. Thus, many top priority islands, especially in Dodecanese, present “medium” tourism development, such as Rhodes, which indeed has many opportunities for its tourism sector to be further augmented [5]. For example, Kos and Rhodes present medium to low values of indicators that are directly dependent on the population. Consequently, all the large, highly populated islands, especially in the Dodecanese, present low scores concerning indicators, which their calculation is based on population or area; thus, the results demonstrate that the region can serve a larger number of tourists. On the contrary, for indicators as “people-users per meter of beach”, the highly populated islands present scores above the thresholds when the visitors from cruises are added to the people and tourists per day. The indicator that presents high numbers in all the islands of the South Aegean region is that of overnight stays per local residents. This is observed in the concentration and attractiveness indicators, mainly due to the great appeal to foreign tourists and the unique natural environment. In parallel, the exceptional tourist services offered in the South Aegean region multiply the demand for overnight stays and visits per day through cruises, which has, as a result, additional pressure mainly in the already endangered islands from over-tourism. Nevertheless, the TTPI (V6) index indicates that the study area’s three islands (Mykonos, Thira, Milos) exceed CCA limits and need immediate action. Three of them are close to the highest limits of CCA (Paros, Rhodes, Kos). Obviously, the set of the selected indicators work more effectively by combining their results based on each island individually, according to its specific characteristics. These results defend the necessity of CCA in such regions and the direct-action plans to mitigate the consequences of tourism. The lack of sufficient resources, such as drinkable water, and the absence of wastewater plants [61] continue to exist. Environmental degradation will be swift in that case, jeopardizing renowned tourist destinations.

7. Conclusions

The spread of the tourist arrivals aims to ease the studied islands from over-exploitation, mainly in areas that have already overcome their carrying capacity. In such areas, the primary environmental pressure is applied on the littoral area of the islands, where millions of tourists are concentrated daily. Consequently, the coastal areas must be protected since they are used intensively in the South Aegean region. At the same time, the exploitation of the coast brings enormous revenue to the local community, around EUR 784,432 per km of beach per year [2], and to the state through taxation. Therefore, designing and implementing a tourism development plan based on local particularities and data availability is necessary. Following the path of sustainability, modern strategies for the promotion and growth of tourism should be applied in ecological, social, and financial multidimensional axes in order to not only protect the natural wealth of a region, but also to achieve different types of tourism throughout the year. This solution will be facilitated by extending the tourist period since high temperatures are present even during early November (Hellenic National Meteorological Service) due to the local climatic regime following global climate change.

Apart from the natural environment, tourism development should follow axes such as culture, sports, diving, sportfishing, medical, luxury, sea tourism (yachting), conference, etc. Moreover, communities must monitor the number of tourists during specific periods or, in some geographic regions, to compare and note patterns of change. In addition, further studies in the area must be implemented in order to measure through subjective indicators the residents’ attitudes, satisfaction, and perception of tourism development. Evaluating implementation using both objective and subjective indicators will help to create a robust monitoring system. Following the UN directives for tourism development until 2030, this study contributes to 17 development goals. Since tourism is one of the fastest augmented economic sectors, this region especially can play a significant role in all of these 17 UN goals represented also by Capocchi et al. (2019) [60,64]. Based on these directives, the seventeen (17) indicators for this specific area were selected as the most representative. The calculation of CCA has numerous choices following various aspects of carrying capacity due to physical–ecological–demographic differences in the study area and data availability. The interested parties can use direct or indirect indicators with limited or no data, without the accuracy of their results to be negotiable. For this reason, the researchers should collect their information from official authorities in order, at least, to be as close to the abovementioned directives as possible. Nevertheless, a database for at least wastewater production and management plans (5 year ratio), solid waste production and management per year, and drinkable water consumption per year must be published regularly by state agencies to calculate the data in CCA estimations. Thus, in this study, these particular indicators (set of seventeen proposed indicators) perfectly describe the current situation of the carrying capacity in the mutli-islandic South Aegean region.

Finally, a new tourism model must be based on respect for tourist resources while limiting the one-sided “sun and sea” model to achieve good sustainability policies in tourism activities. Additionally, the determination of protection zones for cultural heritage and natural resources (based on the Natura 2000) is necessary to limit or prohibit the possibility of construction and, consequently, potential landscape degradation. The high quality of the services provided (in terms of human resources and infrastructures) to the environmental and natural advantages of the South Aegean region gives the area a major lead over its competitors, according to statistical evidence [2]. Therefore, it is necessary to have a concerted effort by the state and local administration to adopt alternative tourist models that aim at sustainability.