Tourist Loading Capacity – A Review of Methodologies and Applications in the Management of Tourist Resources

Over the years, the use of the Tourist Loading Capacity (TLC) as a planning and management tool has been in-tensifying, due to the large influx and overcrowding of tourist destinations, as well as the misuse of the resources found in them by visitors, which causes the degradation of natural or cultural resources, owing to lack of control and regulation of the number of visits. This study carries out a systematic review of the use that has been given to the Tourist Loading Capacity, to which specific destinations it has been applied and which methodologies have been used, in order to gather the existing information regarding this particular topic. The RS was carried out through a documentary analysis of academic literature related to the use and implementation of the Tourist Loading Capacity in different places and the adaptation and modification of the methodologies used. In general, the Tourist Load Capacity tool has become essential to efficiently plan and manage tourist destinations and has been widely used throughout the world, being the Cifuentes (1992) methodology the most widely used and adapted to different contexts.


INTRODUCTION
The great boom that the tourism sector has had, added to the tourist demand, mainly caused by the increase in the interest of tourists for the practice of recreational activities in open settings without altering the environment (Tudela Serrano and Giménez Alarte, 2009) has led to the fact that the nations interested parties, strengthen their actions in favor of taking advantage of the potential of rural natural areas, related to some protection or management scheme (Ibañez Pérez, 2016).
For this reason, a useful tool has been created that allows determining the maximum number of people that a given site can support, it is the tourist loading capacity (TLC), also considered as the type, quantity and distribution of the use that can be made of a site without leading to unacceptable impacts, on physical biological resources or on available recreational experience (García Hernández, 2001). Therefore, this indicator is very useful, in addition, it is associated with sustainability, since it not only tries to set a limit number of visitors, but at the same time allows generating alternatives to improve the understanding of the relationships between the number of visitors and the impact that they generate (Ibañez Pérez, 2016).
For the new world framework, being a responsible tourist destination and having sustainable Tourist Loading Capacity -A Review of Methodologies and Applications in the Management of Tourist Resources development is one of the preponderant objectives in accordance with the Millennium Goals, in its 2030 agenda (Naciones Unidas -Cepal, 2018). This is where the consideration of a tourist loading capacity arises, where it seeks to "rationalize the abusive use and deterioration of the resources that support the activity (...) the optimal use of existing natural resources and a distribution of tourist activity based on the physical and biological characteristics of the environment" (Matos and Pérez, 2018). Stands out the socio-economic importance of tourism in the communities surrounding to those tourist destinations and through the TLC methodology it is sought to find the limit that the tourist area can support, determining the number of visits that can be managed in a given time, without causing the loss or degradation of the resources present in the ecosystem, and provide a degree of satisfaction to the tourist. Humanity has made use of natural resources without returning anything that is extracted and this has made it unsustainable, there is no rational use of soil or water, this occurs especially in Latin America where these resources are misused (Gutiérrez-Fernández and Rodríguez Torres, 2019; Montalvo Vargas and Castillo Ramiro, 2018; Arancibia Arce, 2017).
For this reason, the systematic review of the use of Tourist Loading Capacity in tourist destinations is important because it allows finding the gaps in the analyzed information and the way in which this tool has been used as an element in planning and managing tourism resources where this instrument has been applied. Some authors have carried out different types of bibliographic reviews on this topic, addressing it in a different way or analyzing it from points of view different than those presented in this article (Baños Castiñeira, 2020; Castillo Galeano et al., 2019; Universidad Complutense de Madrid, 2015).
The present manuscript aims on determining what types of tourist destinations that has been applied Tourism Loading Capacity (TLC) and methodologies that have been used to set this indicator. Likewise, it is intended to verify whether in effect the places where this tool has been applied the most are tourist beaches and if the most applied methodology is the one proposed by Cifuentes.
The objective of this manuscript is to identify and analyze some factors and characteristics of the tourist loading capacity, in terms of the tourist system, the methodologies and the applications used for the optimal performance of a sustainable tourism according to the destination of host tourism, in the framework of balancing the supply, demand and conservation of the natural resources adjacent to it.

METHODOLOGY
The orderly procedure of the observation of the object of study and the facts of interest of this manuscript, considers that, from the field of synthesis and analysis, the deductive method is applied, because it establishes the abstractions of the significance of the phenomenon analyzed, from the general to the particular, based on the relationships of the empirical, logical reasoning and mental maps, consisting of a solid conceptualization according to elements of judgment and premises of the concrete and of the modification and decomposition in the parts of the event analyzed, being this, the climatic variability and sustainable tourism (Vergel Cabrales, 2010;Balestrini, 2001;Creswell, 2007).
According to the scope and analysis of the results obtained, the type of research considered, is of the descriptive order, since some causeeffect relationships are significantly described, as well as some characteristics of the homogeneous phenomenon studied. Based on the preestablished construct, the data collection is conceived, according to the level of abstraction of the operationalization of the variables analyzed in the object studied, that is, the climatic variability in sustainable tourism, according to the characteristics, situations and behavior of the empirical referent and the previous theories foreseen, consider a review of secondary, pertinent, current, exhaustive and adequate information to demonstrate the causal relationships in the order of the abstract and their corresponding analysis (Hurtado de Barrera, 2000; Vergel Cabrales, 2010; R. Hernández, 2010).
It was carried out through an analytical-documentary perspective, since it was done through the systematic review of academic literature and the analysis and comparison of antecedents on the use of methodologies to determine which is the most used, how the use of this tool and finally this indicator in which types of tourist settings it has been used, be they natural or cultural landscapes.
The development of the manuscript was carried out by means of a matrix in Excel where the information found in the different articles found in the databases was organized in order to be able to analyze the data in a better way, as well as with the help of the Mendeley platform.

The concept of loading capacity
The concept of Loading Capacity comes from the 70s. It was used to analyze the potential of use through direct development indexes, there are two very different fields; a) resource management, and b) development management. Two interpretations are distinguished; the one that refers to the optimal density of users for the enjoyment of the space, and according to the activity that generate a physical deterioration of the receiving space (Clark, 1990; Roig and Munar, 2003). Likewise, the load capacity refers to the maximum number of people that can be in a space, this has been commonly used from volume and density indicators (Anton, 1997; Roig and Munar, 2003).
The first references, from an environmental perspective, established that the reception capacity of an area of public use in a protected natural space was determined at the level of recreational use that would ensure the minimum environmental quality while ensuring an adequate quality of the lived experience (Wagar, 1964). But when the concept of loading capacity began to be applied to different tourist destinations (beaches, mountains, cities, etc.), some authors such as Butler (1991,2004) indicate that tourist loading capacity is determined both by market dynamics tourism, as well as the behavior of demand and potential users. Under this premise, the perception of visitors is fundamental in the concept of loading capacity (O'Reilly, 1986; Shelby, 1986; López Bonilla and López Bonilla, 2008).
For this reason, the load capacity, seen from a perceptual analysis, refers to the user's perception of the greater or lesser influx of other users in an area of public use, it also incorporates their perception of the lived experience, from several aspects: 1. From the enjoyment of the infrastructures, activities and services; 2. From the point of view of the environmental quality inherent to the protected area (Sowman, 1987).
Therefore, it is a subjective assessment that depends on the action-reaction of users to the characteristics of the public use area, generally those directly related to the perception of overcrowding (Leco Berrocal et al., 2013). The appreciation of overcrowding will be fickle since it is a function of personal factors linked to the user (search for tranquility, peace, silence, etc.), but also of other aspects related, for example, with the number of users with whom the participate in the experience. In short, the perceptual load capacity (social, psychological or behavioral), referring to the perception of the presence or absence of other visitors at the time of observation, implies the relationship of three objectives, such as the objectives of the management, the attitudes of the visitors and the impact of the recreational activity (Leco Berrocal et al., 2013).
The size of the ecosystem and the configuration of the space in relation to the fragmentation and connectivity of habitats are also interesting; the smaller the size, the greater the fragility of the ecosystem. Social constraints refer to visitors and are related to the quality of the recreational experience. Viñals et al. (2014) identify elements linked to physical and psychological comfort, a series of elements that determine the well-being of the visitor according to the physical and physiological requirements, with the environment, and with the equipment and services available. Among the limiting physical factors are bioclimatic and safety factors. Others such as natural hazards, the lack or poor state of equipment, the lack of information and signage or the lack of emergency plans can cause insecurity, although this depends on the perception of the risk of each individual (Viñals and Planelles, 2016).
Likewise, the level of attendance can affect the quality of the experience; for example, congestion produces dissatisfaction in those visitors' seeking solitude. In this case, the availability or not of equipment and services is not a determining factor, since visitors are aware of the limitations that these spaces may have and because they are in search of other experiences (Viñals and Planelles, 2016).
Likewise, other indicators of the quality of the experience have to do, according to Manning et al. (1996) and Manning (2011), with the number of visitors who frequent a place at the same time (PAOT) and the number of people present in a visual space. The studies by Stankey and McCool (1984) and Siles (2003) referring to the number of encounters with other groups or people along an itinerary have also been considered (Viñals and Planelles, 2016).
In recent years the demands and needs of visitors have change, because at present there is a greater purchasing power and therefore a greater number of visitors to protected natural spaces, which makes planning and management of public use urgent. For this reason, the person in charge of the administration of the protected area must necessarily evaluate the reception capacity or recreational load capacity that these areas can support in all aspects, such as equipment, services and physical-ecological conditions. All of this is due to the growing demand vs. pressure that protected natural spaces have had in recent times (Leco Berrocal et al., 2013).
If recreational use of a certain area is allowed to grow uncontrollably, the loading capacity threshold could cause severe damage to the environment, measurable both in visitor experience and environmentally. The problem resides in the definition of the threshold of use (Stankey and Cool, 1983), from which the tourist exploitation of a resource/area of public use is unsustainable because it is harmful (García Hernández, 2001).
It is well known that tourism constitutes a great source of wealth for a large number of places, but it does not at the same time produce harmful effects on the environment, affecting economic, social, cultural and environmental aspects. For this reason, those responsible for managing these areas must identify the inconveniences caused by tourist activity to correct and avoid them, as far as possible, based on adequate planning (López Bonilla & López Bonilla, 2008).
The growing increase in cultural tourism and the large influx of visitors highlights in the elements of the historical-cultural heritage the need to plan and manage tourism from sustainability, that is, it raises the responsible use of resources that are exploited for tourism, sustainable use being understood as that use that guarantees its conservation and transmission to future generations. Thus, it is necessary to know the limits of a resource for its tourist exploitation, that is to say, to know its reception capacity. For this reason, the load capacity or reception of a space with respect to its tourist use is one of the most important concepts in the management of the activity itself and the impacts that it can generate. It is not considered as an end in itself, but a useful means to improve the conditions of the visitor experience and to guide the decisions that have to be made in this regard (García Hernández, 2001)

The loading capacity in search of sustainable tourism
The literature dedicated to tourism provides a good part of the effort to forecast the future, due to the risk that this line represents in environmental management. In this activity the resources that are committed are many and reversibility is difficult and expensive. For this reason, the concern for the sustainability of tourism in the framework of global sustainability is decisive (M. González & León, 2010). The World Tourism Organization -WTO defines sustainable tourism as that "which takes into account the current and future economic, social and environmental repercussions to satisfy the needs of visitors from the industry, the environment and the host communities" (Organización Mundial del Turismo. Sustainable Development of Tourism. Definition). All tourism modalities, especially nature tourism, must embrace the principles of sustainability for the development and management of tourist destination areas, the socio-cultural authenticity of the host communities and the participation of all agents (Martínez Quintana, 2017).
Tourism is one of the most dynamic activities in the world. It occupies the third line of international trade, with 10.4% of gross domestic product (GDP) and is responsible for 313 million jobs worldwide, in addition, this sector has proven to be of great importance in the economy, in the social and environmental aspect, because its development is reflected in employment, income and opportunities for progress for the regions, for this reason, it is said that the tourism sector makes a great contribution to achieving the Sustainable Development Goals (SDG) (WTO & ITC, 2015). It is important to bear in mind that technological advances, the influence of the Internet and Information and Communication Technologies (ICT) in tourism is considerable. The intensity of the information conditions everything. And just as the past decade showed, in the future of hardware and software of Internet nothing is predictable, nor is it predictable in the influence of this tool on tourism events (González and León, 2010).
It is well known that tourism is not a harmless activity for the spaces where it takes place. Its rapid growth affects the natural environment, the local economy and the host society. It is the duty of today's society to ensure the transmission to future generations of a natural heritage and a level of responsibility to maintain harmony between tourism development and nature within the search for sustainability. This has progressed through the years, since it began with the identification and measurement of the impacts caused by tourist activity on different resources and destinations where an academic discussion is developed around the development of indicators of tourist pressure and the concept of " tourist loading capacity" (Universidad Complutense de Madrid, 2015).
Consequently, the ambivalent nature of tourism is evident, because it allows "to bring great advantages, especially in the economic sphere, but it can also be sociocultural corrosive, contribute to environmental degradation and the loss of local identity" (Serrano, 2011).

Tourist destinations where the load capacity methodology has been applied
The TLC has been applied in different types of ecosystems seeking sustainability, but it has been mainly concentrated in those tourist sites where there is a high concentration of tourists or overcrowding (García Hernández, 2001). According to the bibliographic review carried out, the tourist destination that has been the most object of the Load Capacity is the beaches, because tourism is its main economic activity. Including within its analysis two more components to the tourist carrying capacity, to ensure a holistic vision; one of them is the urban equipment that ensures a level of comfort and safety on the beaches in the development of tourist activity.
The second is the services related to sun and beach tourism, which allow the visitor to have the basic services for an adequate tourist experience (Botero Saltarén et  The TLC was applied to tourist -cultural destinations (museums, monuments, temples) and has been encouraged because the tourist influx to these sites has increased in recent years. This tool has become necessary since there is tourist overload in some of the area's most sought what cultural motivates managers to control high influx of visitors on these assets (García Hernández and De la Calle Vaquero, 2012; Gamero Huarcaya et al., 2021; Zhongbin, 2018). Finally, urban centers have been the object of TLC study due to the overcrowding of demand for these tourist destinations and the need to manage and plan resources and services to prevent them from being insufficient for both the local population and tourists

Some applied methodologies
According to the bibliographic review carried out, it was found that the most used methodology    to determine the Tourist Loading Capacity, for its simplicity is the one proposed by Cifuentes (1992) based on the physical loading capacity (PLC) of the place, understood as "the maximum limit of visits that can be made to a site with a defined space in a given time" (Cifuentes, 1992). Using a mathematical equation that considers other factors such as accessibility, precipitation, erodability, temporary closures and wildlife disturbances, it finally calculates the Effective or Permissible Loading Capacity (ELC) which is defined as "the maximum limit of visits that can be allowed given the ability to order and handle them" (Cifuentes, 1992).
Another of the methodologies used is the determination of the Perceptual Load Capacity, which is done through two approaches, the traditional narrative and numerical approach (Shelby and Heberlein, 1986), and the visual approach (Manning, Lime, Freimund and Pitt, 1996). Both approaches are carried out through surveys in which tourists and visitors are asked the acceptability of how many people they are willing to see at the same time in a given place (R . Blanco et al., 2019).
In other studies, it is possible to find methodologies that combine the Tourist Load Capacity and the perceptual approach where social participation and Recreation Opportunities (EOR) are promoted, which establishes differentiated experiences for users based on current uses and the conservation goals of the ANP (Segrado Pavón et al., 2017).
In some cases, measurements were used through photointerpretation and Geographic Information Systems to provide greater accuracy to the study.
It has also been found that there is a tendency to modify or combine existing methodologies, adapting them to different needs, involving different dimensions, such as physical, social, and perceptual to complement both qualitative and quantitative appraisals and each author proposing their own methodologies. in search of sustainability.

CONCLUSIONS
According to the findings of this bibliographic review, it can be concluded that the Tourist Load Capacity tool has become essential to efficiently plan and manage a tourist destination.
It was found that the methodology to find the TLC that has been used the most is the one proposed by Cifuentes in 1992 and has been modified and adapted to different contexts, as well as, enriched with modern techniques such as Geographic Information Systems and Photointerpretation to make it more precise, this has been used at different times and in different parts of the world, secondly, it is occupied by the perceptual methodology since the tourist's perception of the experience of a particular visit is very important to encourage tourism in said region. Other authors have adapted or combined the existing ones and have formulated their own methodologies for calculating the Load Capacity, according to the needs of the context and in search of sustainable tourism and integrating the three main aspects of sustainability: ecological, social and economic, which is considered a great contribution to enrichment in this area of knowledge.
Regarding the types of ecosystems to which marine ecosystems have been applied, they are the most studied with this tool, due to the high tourist interest they represent, secondly, there are natural ecosystems due to the boom that tourism has acquired of nature and despite the effort to conserve them, the destruction of habitats, overexploitation and the consequent loss of resources have become evident. Among the freshwater aquatic ecosystems, lakes, reservoirs, cenotes and the economic aspect of a river were found, but it is important to note and arouses special interest the fact that the Loading Capacity has not been applied to tourism in Rivers, according to the bibliographic review carried out.