Introduction

Mount Tláloc, located in Texcoco, State of Mexico, was recognized in 2010 by UNESCO like a Los Volcanes Biosphere Reserve, based on the benefits on biodiversity, specifically because it is the habitat of some birds in danger of extinction; for its importance in the water balance of the place; and by the landscape value of the area, which is reflected in a tourist asset (^{Conanp, 2018}).

It is an old volcano formed around 5 million years ago and was completed two million years ago. It has an altitude of 4 125 m and together with the El Telapón hill (4 065 masl), the Papagayo hill (3 640 masl) and the Tlamacas hill (3 170 masl) make up the Sierra de Río Frío, which is part of the Transversal Neovolcanic Axis that crosses the Mexican country from west to east over two primordial fractures and divides North America and South America (^{Montero, 2004}) (Figure 1).

Source: ^{Conanp, 2018}.

Figure 1 Geographical location of Mount Tláloc. 

The economic valuation of environmental goods and services is a guide for public policies that lead to a better management of resources, their efficient allocation, decrease the deterioration of the environment and increase the conservation of natural resources so that their use is sustainable (^{Aoun, 2015}). However, the environmental services of natural systems do not have a market in which a price can be established for what they offer, that is. They are non-marketable goods (^{Vásquez et al., 2007}). Environmental services are treated as pure public goods, which constitutes a market failure that leads to their inefficient allocation (^{Stiglitz, 2000}).

The ways of providing society with these goods have become unsustainable and the loss of well-being of society that causes pollution, deterioration and the lack of natural resources has increased, sufficient reasons to use valuation methods for environmental services (^{Glover, 2010}), that guide the search for solutions that directly include their users.

Mount Tláloc is the most important in the Texcoco de Mora municipality; it has forests that offer tourist attractions such as camping areas, cabins, zip lines among others, in addition to allowing the use of ATVs, mountain bikes and mountain biking. It has various archaeological sites and an ancient sacred space in the form of a causeway, located in the highest part of the mountain, where the ancient inhabitants of Mexico performed ceremonies dedicated to their deity Tláloc, which is classified as one of the worship sites of highest elevation in the world (^{Neyra, 2012}).

^{Soto and Sosa (2014)} assessed the different attributes of forest areas expressed in the values of option, inheritance and existence, since they constitute spaces that can be used for the preservation of a significant number of plant and animal species that, on many occasions, are considered in danger of extinction.

Only from a visual perspective, on Mount Tláloc the problems of overloading of visitors in various areas are identified: the large amount of garbage that is thrown in the place without regard for its consequences, the recent forest fire that occurred in April 2017, the increasingly high erosion due to the continuous passage of motor vehicles, for example. It was also observed that some ejidatarios of the place have opted for the change of land use by transforming their lands into agricultural fields to cultivate corn, potatoes, broad beans and oats, mainly due to the richness of the forest floor. However, this change in land use contributes to the generation of CO₂ and reduces the forest cover in the area; in the same way, the fire-wood and resins are used, without taking into account that these practices make the trees more prone to infection and fire; in the same way, immoderate logging for construction and firewood for the production of charcoal are one of the most common uses that are given to the natural resources of Mount Tláloc, resulting in erosion and a decrease in the groundwater level the main consequences (^{Montero, 2004}).

Mount Tláloc is a pure public good, and therefore it is not exclusive. So, no, an individual should not be separated from his enjoyment. Nor does it present rivalry in consumption, since a good is not rival in consumption, if the consumption of additional units has a marginal cost of zero (^{Stiglitz, 2000}; ^{Nicholson, 2008}). That is why he is mistreated so much and no one has incentives to take care of him; even governments can make policy failures by encouraging traditional cultivation rather than sustainable forestry (^{Panayotou, 1994}). An assessment can contribute to correcting these failures and contribute to caring for the environment, even with economic growth (^{Glover, 2010}).

This research seeks to know the economic valuation that visitors make of this natural resource. In order to create a sense of conservation and recovery of Mount Tláloc, currently a fee of MEX$ 10.00 is charged to visitors to the Mount, which is administered by the Union of Ejidos de la Montaña “La Joya Monte Tláloc”; however, many of the attendees avoid paying, in addition to the fact that it is unknown if this is an optimal fee according to their Willingness to Pay (DAP, for its acronym in Spanish), and how much they value Mount Tláloc and what general and environmental services could be improved.

With the study described here, the resolution of these doubts was intended, since to date there has not been an environmental economic assessment of the place as proposed here. The objective was to estimate the economic value of the environmental services of Mount Tláloc according to the perception of its visitors from their Willingness to Pay (DAP). The application of the Contingent Valuation Method (CVM) allows to analyze the influence of socioeconomic variables and the environmental perception of users. In addition, with it you can identify and evaluate the improvements in environmental and tourist services that should be made, as well as suggest an access fee.

The hypothesis raised is that there is willingness to pay by most of the users of Mount Tláloc to maintain and improve the environmental and tourist services that the park offers.

Materials and Methods

In this study, the Contingent Valuation Method (CVM) was applied. This method allows valuing goods and services without a market and helps to grant people a certain environmental resource, for which a structured questionnaire is used that the selected individuals answer (^{Azqueta, 2007}). This methodology has been used to calculate the DAP for protected natural areas (^{Almendarez et al., 2016}; ^{Gandini and Millones, 2019}).

In this type of methodology, a market for a good or a set of goods for which there is no market is simulated by means of surveys and hypothetical scenarios, because there are no explicit prices (^{Mendieta, 2005}). The analysis of data obtained through the survey allows us to infer the value of the environmental asset (^{Labandeira et al., 2007}).

The economic value is obtained from asking the DAP, for an improvement in the quality or quantity of the ecosystem good or service, in a hypothetical scenario. The selected format for data collection was a structured questionnaire divided into three parts: 1) Socio-demographic information: in this part of the observation instrument, information on the socioeconomic characteristics of the interviewees is obtained; 2) Environmental perception: the interviewee is provided with information about the property that is intended to be valued, in this way they can better understand the surrounding scenario, in addition to their own perception; and 3) Economic valuation: here closed questions are asked aimed at how much the visitor values the mountain and its environmental attributes.

Finally, the open format question is formulated to know the DAP and the dichotomous format.

For the design of the contingent assessment question, a mixed format was used. In a dichotomous way, a scenario was presented in the first instance in which an initial utility function of the original state of the ecosystem good or service is proposed, and a final utility function that represents the hypothetical scenario. The representation a = 0 would be the ecosystemic good or service in its current state and a = 1 would be the final situation; in it, the responses (with value 1 or 0) denote the state with and without the proposed scenario, respectively. Second, if the interviewee answered affirmatively, he (she) was asked, in an open format, the amount of money he (she) would be willing to pay to improve the conditions of the mountain; if the interviewee answered the dichotomous answer negatively, the reason for his answer was asked.

Since the Union of Ejidos de la Montaña or other institution has not an accounting record of the annual tourist visitors to Tláloc Mount, for the purposes of this research, statistical sampling was used and, starting from the great variability in attendance, it was considered an unknown target population. According to the statistical methods to define the sample size by which the population mean is estimated and the N (target population) is infinite or unknown, simple random sampling was used, better known as "MAS" (^{Cochran, 1984}) which is obtained by the following equation:

Where:

n = Sample size

α

Z = Confidence index

∂ = Variance

ε = Sampling error

A pilot sampling of 30 randomly selected participants was carried out to statistically deduce the variance of the sample and substitute it in the formula for obtaining the sample size. A significance level of 95 % was chosen, which gives a Z value of 1.96 determined from the accumulated probability tables; the variance of the pilot sample was ∂ = 0.19 and a sampling error of 2.5 % (0.025). By substituting the data from the pilot sample, a sample size of n = 230 surveys was calculated, with an error of 5 % and a significance level of 95%. For the present research we worked with a sample of 251 surveys.

An econometric model of logistic distribution was applied to determine what factors explain the DAP of each visitor to Tláloc Mount and analyze the influence of socioeconomic variables and the environmental perception of users. The empirical model of the proposed logistic regression is the following:

Where:

DAP = Willingness to pay for conserving Tláloc Mount: “1” = DAP to improve it and “0” = No willingness to pay to improve it

α = Intercept of the function

β ₁ ,…, β _12b = Coefficients of the respective explanatory variables:

ESTU = Education

YFAM = Family income

PA = Environmental concern

PERD = Perception of environmental degradation on Tláloc Mount

SSUF = The services you receive from Tláloc Monte are enough

PERQ =Perception of environmental quality in Tláloc Mount

e = Error

The model was estimated in the software "N logit" version 4.0.

Results and Discussion

In the sample of respondents, 55 % have university studies, 23 % finished high school and 9 % have a technical career, some even with postgraduate degrees. None of the respondents lacks studies, so it is considered that the level of education of the visitors to Mount Tláloc is generally high (Figure 2).

Sin estudios = Lack of studies; Doctorado = Doctorade; Maestría = Mater´s degree; Universidad = University; Carrera técnica = Technical career; Preparatoria = High school; Secundaria = Secondary School; Primaria = Elementary school.

Figure 2 Level of studies. 

In regard to the occupation of the visitors (Figure 3), most of them are students (39 %), followed by professionals or technicians (30 %) and in the third place, merchants (12 %). If the main percentage of individuals are economic dependents, it is expected that the relationship with the DAP will be lower in monetary terms.

Otro = Other; Sin trabajo = Without job; Artesano = Artisan; Estudiante = Student; Obrero = Laborer; Acts. Agropecuarias o forestales = Agriculture and livestock or forestry activities; Jubilado y/o Pensionado = Retired and/or Retiree; Comerciante = Merchant; Profesionista y/o técnico = Professionals and/or technicians; Funcionario y/ o Jefe = Civil servant and/or Chief.

Figure 3 Employment. 

The environmental perception of all the visitors to Mount Tláloc was of concern; however, 70 % of those interviewed stated that they were highly concerned and 30 % considered that they were regular or little concerned.

Within the context of global environmental problems that are experienced today, 31 % of those surveyed expressed concern mainly about overpopulation in the world; the second is pollution in general (23 %) and third, the loss of biodiversity (20 %). All three are present on Mount Tláloc, which undoubtedly affects the DAP.

The way in which the interviewee notices environmental degradation is important, as it influences their DAP, and by not doing so, they will not see the need to pay to improve the natural environment. Thus, 90 % of those surveyed did perceive this situation, 57 % conceived it as medium degradation, 27 % as high degradation, 15 % as low degradation, and only 1 % without any deterioration in the place.

According to the environmental problems that affect the mountain, the interviewees considered that the main environmental problem is that of contamination by the waste left by visitors (43 %); the second cause for concern is the intense erosion (21 %) and 16 % considered deforestation on Mount Tláloc. This information is crucial for the resolution of the conflict situations most evident to visitors to the mount.

The main recreational activities carried out on Mount Tláloc are: walking, with a frequency of 29 %, enjoying the scenic beauty with 25 %, doing sports with 20 %, and camping with 14 %. According to this information, it is possible to discern which activities affect the environmental resource in question to a greater extent. Likewise, it can also be observed that visitors value the mountain as the theory establishes, since they assign it a value of direct and indirect use and of non-use of existence (^{Vásquez et al., 2007}).

Of the 20 % of those interviewed who mentioned sport as their main incentive, athletics was the most popular (37 %), the second was enduro (15 %) and the third was cycling (14 %). Special attention should be paid to these preferences to provide the appropriate conditions to practice them and simultaneously avoid environmental deterioration (Figure 4).

Ciclismo = Cycling; Atletismo = Athletics; Futbol = Soccer; Montaña fantasma = Ghost mountain; Tradiciones = Tradition; Espiritualismo = Spiritualism; Compartir experiencias = Share experiences; Senderismo = Hiking; Alpinismo = Mountain climbing; Rapel = Rapelling; Visita de zonas arqueológicas = Visit of archeological sites; Montañismo = Mountaineering; Investigación = Research.

Figure 4 Activities associated with the site . 

Visitors suggested improvements in general services within Mount Tláloc (Figure 5). The first is related to security, as 28 % indicated that it should increase; 21 % were concerned about the cleanliness of the area. The third improvement is related to the signs, directions and information of the place, to avoid getting lost, getting to know it better and becoming more aware of its value. This information would be useful for the administrative authorities of Mount Tláloc and the governmental institutions related to it, when carrying out actions that increase the coexistence, order, safety and ecological conservation of the site.

Señalamientos = Signs; Mantenimiento de caminos = Road maintenance; Emergencias = Emergencies; Seguridad = Security; Servicios turísticos = Tourist services; Limpieza de la zona = Cleanliness of the area; Sanitarios = Rest rooms; Transporte = Transport; Mejorar la administración = Improve management; Prohibir puestos de alimentos = Ban food stalls; Información sobre la zona = Directions and information of the place; Iluminación =Lighting; Mejorar infraestructura = Improve infrastructure; Registro de los visitantes = Visitors registration; Tienda = Store; Depósitos de basura = Garbage dumps; Cobertura telefónica = Telephone coverage; Servicios médicos = Medical services.

Figure 5 Opportunity areas. 

The interviewee's appreciation of the environmental quality of Mount Tláloc (Figure 6) is not entirely unfavorable, since 55 % of them believe that it is good, 27 % that it is fair and 16 % that it is very good, and only 1% that it is bad and very bad. These levels of perception are a good incentive to respond positively in the DAP for conserving this recreational place.

Reforestación = Reforestation; Prevención de incendios = Fire prevention; Disminuir la deforestación = Decrease deforestation; Disminuir la erosión = Decrease erosion; Campañas de concientización = Awareness campaigns; Limpieza de la zona = Cleaning the area; Cuidado y conservación del agua = Water care and conservation; Cuidado y conservación de la fauna = Fauna care and conservation; Control de incendios = Fire control; Cuidado y conservación de la flora = Flora care and conservation; Regular el número de visitantes = Regulate the number of visitors; Cuidado y conservación del suelo = Soil care and conservation; Seguridad = Security.

Figure 6 Environmental improvements. 

The environmental needs demanded by the visitors are also important to carry out environmental care and conservation actions by the ejidal and governmental authorities. The average visitor agrees on the main environmental services that should be improved, because, according to the results obtained in the survey, 40 % suggest that reforestation should increase, 22 % mentioned that deforestation should decrease and 21 % were concerned by garbage and its effects on the mountain, as seen in Figure 6.

Finally, according to the willingness to pay to care for and conserve Mount Tláloc, most visitors expressed interest, since 82 % accepted the DAP and only 18 % gave a negative answer, a result that coincides with other cases (^{Amiri et al. , 2015}).

Such a high level of positive response was to be expected, since it was observed that the average visitor is concerned about the environmental problems that affect the place, a high perception of its quality and its degradation, as well as direct, indirect and non-use values present. It should also be noted that there are biases related to negative responses known as protest responses, which means that the interviewee disagrees with the approach to solving the problem and does not mean that they do not value the environmental resource in question, as stated by ^{Azqueta (1994)}.

In the six strata that were defined to classify the different levels of visitor income (Figure 7) it was determined that the individual income level is low, since 38 % is located in an interval between the absence of perceptions and the MX $ 3 000.00 per month; Stratum 2 followed with 22 % of those interviewed whose income ranges from MX $ 3 000.00 to MX $ 6 000.00 per month and in third place, 17 % have an individual income between MX $ 6 000.00 to MX $ 9 000.00 per month.

Número de encuestados = Survey respondents ; Estrato = Stratum.

Figure 7 Income level by stratum. 

Conclusions

Based on the sample of visitors studied, 82 % are willing to pay to conserve Mount Tláloc; the average DAP is MX$ 9.00 per visitor. The variables that positively influence the DAP are the level of studies, family income, environmental concern and the perception of environmental degradation in the area, while those that decrease the probabilities of the DAP are the perception of the level of environmental services and that of the environmental quality of the area.

Just over half (55 %) of the consulted population perceive the quality of Mount Tláloc as good, however, 90 % consider that there is environmental degradation in the area, mainly due to contamination by garbage produced by visitors and the level of erosion noted as the most worrying factors for the average visitor. They also indicated a low level of security in the mountains, the lack of cleanliness in the area and the lack of signage on routes and sidewalks.