1. Introduction
Forest parks incorporate tourism and leisure into nature, which promotes local development and improves employment and social welfare. However, due to the high opportunity cost associated with nature conservation and the pressure brought by economic benefits, many governments chose to reduce the regulations on nature conservation, leading to the weakening of the restriction on destructive human development activities [
1]. Especially in China, forest tourism has experienced a period of rapid growth since the policy of accelerating the development of forest tourism was issued in 2011. By 2019, the number of visitors to forest parks reached 740 million, and the tourism revenue was 9.527 billion US dollars, which was 2.56 times and 2.26 times that of 2011, respectively. After a long period of tourism development, ecological problems such as air pollution, soil erosion, ecological degradation, and vegetation damage arose because of the excessive pursuit of economic benefits [
2]. Thus, we need to re-examine the management of forest parks and continuously explore ways of sustainable development that can effectively coordinate forest resource protection and tourism development.
Ecological efficiency signifies how efficient economic activity is in consideration of the ecosystem’s resources and services, and environmental impact [
3], which effectively assesses whether the tourism business activities follow the principles of sustainable development [
4]. By comparing the differences in the ecological efficiency of forest parks, we can get an overall understanding of forest tourism development in a country or a region. The calculation of ecological efficiency involves the production process of multiple inputs and outputs, and the calculation methods mainly include Data Envelope Analysis (DEA) and Stochastic Frontier Analysis (SFA). DEA, as a non-parametric method that can avoid the influence of setting the function form subjectively, has become the most widely used method in the field of tourism research [
5,
6,
7,
8,
9]. However, this method fails to separate the efficiency value from the error term, which might overestimate the value of the inefficiency, making the research results more sensitive to outliers and sample size [
10,
11,
12]. SFA separates the efficiency value from the error term and makes up for the shortcomings of DEA to a certain extent; however, there may be problems related to the explanatory variable and the combined error term, and the distance function often does not meet the concave and quasi concave assumptions in economic theory, which affects the credibility of its results [
13]. To address these problems, Herrala and Goel established a new connection between the goal of minimizing pollutant emissions and the setting of random frontiers based on the stochastic frontier cost function (SFC) [
14], which has not yet been applied in tourism research. In addition, concerning the selection of pollution variables (undesirable outputs), it is difficult to accurately measure the actual impact of pollutant emissions on the environment or ecology. The common practice is to separately incorporate pollutants with different chemical components into the model [
15,
16]. However, the effects of pollutants with different chemical components on ecosystems may be the same, such as the superposition effect of SO
2 and NO
x in the atmosphere, which together form secondary pollution such as acid rain, haze, and PM2.5, directly affecting the local’s survival and vegetation growth. Therefore, the impact of economic activities on ecosystems can be reflected by assigning weights to emissions with the same pollution properties for normalization.
To improve the ecological efficiency of tourism, the influencing factors were further analyzed. Except for the regional economic level, the level of tourism development, the technical level of energy, the investment level, and environmental regulation on the eco-efficiency of tourism and other external business environments [
6,
8], and tourism investment, as the internal operation foundation of forest parks, are important factors. At present, there have been disagreements on the relationship between tourism investment and ecological efficiency. Some viewpoints believe that tourism investment can improve ecological efficiency [
8,
17] because greater investment in the tourism industry will stimulate long-term tourism revenue, innovation, and sustainable growth in the sector [
18]. Others argue that tourism investment reduces ecological efficiency [
19]. Peng et al. and Li et al. both found a negative correlation between tourism investment and ecological efficiency [
20,
21]. It can be seen that tourism investment plays a heterogeneous role in ecological efficiency, and the business category is a key factor in the relationship between the two. If the investment is in green tourism-related infrastructure, the negative impact of tourism development on ecology can be reduced [
22], and if the investment is in high energy consumption entertainment, the contradiction between tourism development and ecology will be exacerbated [
21].
The investment structure is essential to tourism operators to attract tourists with different traveling needs. From a practical perspective, there are diversified investment patterns including government investment, private investment, public-private partnerships (PPP), etc. In general, public investment mainly focuses on tourism-related infrastructure, while private investment is typically for commercial purposes and mostly driven by profit incentives, which are concentrated in such sectors as commercial accommodation and transportation services that generate high economic income, such as vacation homes, hotels, conference centers, airplanes, cruise ships, and tourist buses, etc. [
22]. Although private investment is more conducive to improving tourism efficiency compared to other sources of investment, these sectors are also pointed out as high energy-consuming industries [
23], especially in developing countries where the economic benefits brought by tourism are often more valued, while the excessive development of resources and the generation of environmental pollution are neglected [
24,
25]. Hence, the business category of tourism destinations is affected by the investment structure, which not only directly affects tourism revenue, but also has a close relationship with energy consumption types and pollution emissions [
8,
26]. That is, investment structure and business category do not independently affect ecological efficiency, but there is a mechanism instead. However, existing research has been limited to the overall effect of investment on ecological efficiency, which makes it impossible to determine and compare the heterogeneous effects of different tourism investment entities on ecological efficiency. It is necessary to clarify the relationship between tourism investment structure and ecological efficiency, in particular, to further verify how investment structures affect ecological efficiency through different business categories, which will help establish an environmentally friendly forest park management system.
In this context, we took 28 national forest parks in Liaoning Province as the research objects to identify the impact of different investment structures on ecological efficiency from 2008 to 2017. The marginal contributions of this article are: firstly, considering the superposition effect of pollutants in the environment, the environmental acidification substances generated in the process were calculated as ecological indicators, and a modified ecological efficiency model was constructed with a stochastic frontier cost function (SFC) to measure and analyze the ecological efficiency. Secondly, we divided the investment of forest parks into public investment and private investment and focused on analyzing the impact of different investment structures on ecological efficiency. Thirdly, we introduced business categories as mediating variables and constructed a mechanism analysis framework of “investment structure–business categories–ecological efficiency”. Through the horizontal comparison of forest parks, the reasons for and paths of the decline of ecological efficiency are revealed from the inside. This research is helpful for policymakers and park managers to adopt more environmentally friendly projects and accordingly achieve the goal of sustainable development of forest tourism.
The structure of this paper is as follows: the second part describes the research hypothesis, research methods, data sources, and data characteristics. The third is the empirical analysis. In the fourth part, the scientific nature of the calculation method and the research results and findings as well as the research deficiencies and prospects were discussed. The last part is the conclusion and policy enlightenment.
4. Discussions
4.1. Ecological Efficiency Characteristics of Forest Parks
It is indicated in this research that ecological efficiency could be more scientifically measured through the environmental cost stochastic frontier function and the new pollutant emission indicators based on environmental impact assessment. Due to the difficulty in obtaining data on environmental pollutants, previous studies included SO
2 or NO
x in ecological efficiency models [
16,
47] or only included SO
2 as an environmental acidifier [
21,
30], which cannot accurately reflect the actual impact of pollutant emissions generated by tourism operations on the environmental system. The weights provided by the environmental impact assessment were added in our study to normalize SO
2 and NO
x with different chemical compositions, but similar pollution properties on the total amount of real environmental acidification substances emitted by the forest park during its operation were re-estimated. In terms of measurement methods, we adopted the environmental cost stochastic frontier function proposed by [
14] to establish a revised ecological efficiency model, which avoids overestimating the ineffective rate value and the sensitivity of research results to outliers in the previous literature using DEA.
The mean value of the eco-efficiency of forest parks in Liaoning Province during the study period is 0.52, which means that the potential for improving the eco-efficiency of forest parks is 48%, and the forest parks with the lowest ecological efficiency can improve by 72% potentially compared with the optimal forest parks. This indicates that the gap in ecological efficiency was very large, but was gradually narrowing over time. Similarly, the ecological efficiency of Huangshan Forest Park from 1981–2014, measured by [
20], was 0.53; [
48] and [
21] calculated the ecological efficiency of inter-provincial forest parks in China as 0.773 and 0.502, respectively. These results confirm that the ecological efficiency gap of China’s forest parks is very large both vertically and horizontally. Our findings indicate that a higher proportion of clean energy, higher per capita GDP, and industrial agglomeration contribute to enhancing the ecological efficiency of forest parks. Regions with higher economic development levels and concentrations of the tourism industry can provide a better business environment for forest parks, attracting more visitors and enabling the adoption of more advanced management techniques [
49]. A high share of clean energy means that fewer pollutants are emitted while creating the same economic value. Conversely, higher park grades, larger local populations, and further distance from transportation hubs tend to lower the ecological efficiency of forest parks. These results suggest that forest parks often attract visitors through energy-intensive operational activities, especially those located at a considerable distance, which typically offer accommodation services. The hotel industry has been confirmed as a low ecological efficiency sector in tourism [
6,
8,
20,
21], corroborating our research findings.
In addition to these factors, the investment structure and operational categories of the forest park are worthy of scholarly exploration as influential factors in ecological efficiency. Although the 28 national forest parks in Liaoning Province are of the same class and are under the control of the same government department, there were obvious differences in their investment structure and business category. For example, from 2008 to 2017, the average private investment took up 100% in Shenyang forest parks, with skiing as the main operating project, and private investment took up 92.4% in Dalian Xijiao Forest Park, with hot springs and hotels as the main operating projects, while national investment accounted for 20% in Benxi Forest Park with natural landscapes as the main operating project. The business category not only affects the energy structure of forest parks but also is an important reason for deciding whether to carry out perennial operations. In northern China, where coal is a major heating source and source of air pollution, forest parks that run perennially consume more coal than those that run seasonally, all of which can lead to differences in the ecological efficiency of forest parks.
We also found that, over time, the ecological efficiency gap of forest parks gradually decreases, which is consistent with [
48]. Firstly, the Chinese government has been intensifying efforts in environmental governance. In 2009, the government issued the “Opinions of the State Council on Accelerating the Development of the Tourism Industry”, aiming to reduce electricity consumption by 20% in five years for star-rated hotels and A-grade scenic areas. In 2013, the State Council introduced the “Notice on Issuing the Action Plan for Air Pollution Prevention and Control”, targeting a more than 10% reduction in the concentration of inhalable particulate matter in national cities at or above the prefectural level by 2017 compared to 2012. In response to increasingly stringent environmental regulations, forest parks have implemented proactive measures, such as transitioning from coal to electric heating, as observed in Anshan National Forest Park. Secondly, technology exhibits a spillover effect, enabling mutual emulation and learning among park managers in terms of management experience and energy technologies, which led to a gradual improvement in the overall utilization of forest park resources, narrowing the gap in ecological efficiency.
4.2. The Relation between Investment Structure, Business Category, and Ecological Efficiency
The results above are new in that there has never been a study on the relationship between investment structure, business category, and ecological efficiency. The existing research has analyzed the impact of tourism investment on pollutant emissions in tourist destinations [
8,
19,
22] or ecological efficiency [
20,
21]. However, there is no agreement, as these studies overlooked the complexity of investment structures in tourist destinations or scenic spots. However, both forest parks and tourist destinations may be composed of multiple capital types. Distinguishing capital types and investigating their impact mechanisms on ecological efficiency can contribute to identifying the types of capital that have a negative impact on the environment and their degree of impact.
Our results indicate that investment structure significantly influences the ecological efficiency of forest parks, and business category plays a mediating role between the two. The results, consistent with Mascia et al. and Paramati et al. [
1,
22], demonstrate that the higher the proportion of private capital in the investment structure, the lower the ecological efficiency of forest parks, and vice versa. This can be explained by the fact that a significant portion of national capital is used for the ecological construction of forest parks, such as afforestation and forest transformation, as well as the construction of parking lots, signage systems, and restroom renovations for tourism-related facilities. However, these activities do not significantly contribute to increased tourism revenue or visitor numbers [
50]. In developing countries with low levels of urbanization, consumers prefer energy-intensive tourism products such as luxury hotels, spa resorts, and amusement parks to rustic and back-to-nature ones [
30]. Private capital aims to maximize profits as much as possible during the contract period, and in order to meet the market demand mostly focuses on developmental investment. Both energy-consuming amusement programs and accommodation programs will aggravate the conflict between tourism development and ecology [
21,
23]. As our empirical results indicate, an increase in the proportion of private capital corresponds to a higher share of forest park revenues coming from recreation and accommodation, both of which negatively affect eco-efficiency. As forest recreation gradually gains popularity, hotels and restaurants, spa treatment, and rural village accommodations are increasingly favored by large-scale private capital. The energy consumption intensity of lodging facilities located on the periphery is two to three times higher than that of urban centers [
51]. To maximize profits, private capital is unlikely to willingly embrace cleaner energy sources or invest in more energy-efficient equipment, as these would raise their costs, a finding in line with [
30]. Effective forest park management in many developing countries may be achieved by decentralizing the allocation and control of investment funds to relevant interest groups [
52,
53]. However, our results find that forest parks with a significant private capital share experience a decrease in eco-efficiency. This is because the profit-seeking nature of the investment body is different, leading to differences in the destination of capital investment, so investment structure is the direct cause of the differences in the ecological efficiency of forest parks, and its path is the operation category.
Finally, the negative effect of investment structure on the eco-efficiency of forest parks was 3.1% higher in high-level forest parks because of the heterogeneity effect of the operation category as a mediating effect in different levels of forest parks. High-level forest parks have the capacity to secure more substantial funds, enabling investments not only in amusement projects but also in the development of hotels, spas, accommodations, and other hospitality-related ventures. Conversely, low-scenic-level forest parks typically have access to fewer funds, leading to investments in lower-cost, faster-return amusement projects. For example, KUANDIAN Forest Park self-funded $900,000 for the construction of tourism projects such as children’s playgrounds, a skating rink, and a water park. Therefore, the high-leveled scenic area has a negative impact on eco-efficiency mainly through food and lodging operations; while low-leveled forest parks have a negative impact on eco-efficiency mainly through amusement operations. Since the negative impact of accommodation on eco-efficiency is higher than that of amusement, the negative impact of investment in forest parks is more pronounced in high-level forest parks. Specifically, it is more difficult to attract investment in rural areas of Liaoning Province, China, and this phenomenon is more prominent in forest parks with a high proportion of self-financing, and these findings can help the government and forest park operators to be more targeted in their environmental management and pollution control.
4.3. Limitation and Future Research
One of the shortcomings of this research is that we only consider the emissions of environmental acidification substances during the operation of forest parks. Coal, gasoline, diesel, gas, and other energy sources are consumed in tourist attractions, which emit not only environmental acidification substances but also greenhouse gases and PM2.5. For the reason that the forest system can absorb greenhouse gases and fine particles, we have ignored these problems. Another challenge is that obtaining data from non-listed companies is so difficult that we only obtained 10-year data for 28 forest parks in one province. Fortunately, these samples almost cover the number of local national forest parks and are representative of the region.
Considering the specific research content, future researchers can adopt the environmental impact assessment to give weight to more pollutants with different properties as an environmental indicator, accordingly including in the ecological economic model for relevant research on sustainable development. This method is not limited to the tourism field but can also be applied in other industries such as agriculture or industry. For forest parks or other tourism fields, future research can further reveal the impact mechanism of ecological efficiency, which is helpful in achieving the initial goal of sustainable tourism.
5. Conclusions and Implications
Based on the input and output data of 28 national forest parks in Liaoning province from 2008 to 2017, we measured the ecological efficiency with the atmospheric acidification index and the stochastic cost function, constructed the analysis framework of “investment structure, business category, ecological efficiency”, and analyzed the impact of investment structure on the ecological efficiency of forest park and its mechanism. The conclusions are as follows:
Firstly, the average improvement potential of the ecological efficiency of national forest parks in Liaoning province was 48%. There was a large gap in the ecological efficiency among forest parks, but these differences were decreasing over time. Secondly, the investment structure had a significant impact on the ecological efficiency of the forest parks. The increase in the proportion of private capital in the investment structure significantly decreased the ecological efficiency of the forest parks, and its overall impact on the ecological efficiency of the forest parks was more than 0.106. Thirdly, business categories played a mediating role between the investment structure and the ecological efficiency of the forest park. Investment structures negatively affected the ecological efficiency of the forest parks by increasing the proportion of accommodation and amusement activities. Finally, there is heterogeneity in the way that investment structures affect the ecological efficiency of forest parks, with high-class forest parks through accommodation and low-class forest parks through amusement.
Although our evidence and arguments are derived from a specific province in China, they bear relevance for other regions and countries, especially in developing nations. We proffer a quartet of strategic paradigms poised to augment the ecological efficiency of forest parks. Firstly, atmospheric pollution is primarily caused by using fossil fuels, so adjusting the fuel composition and improving energy efficiency can help improve eco-efficiency. Echoing the sentiments articulated by [
17], policymakers can incentivize forest park operators to replace antiquated machinery and facilities with more efficient alternatives and increase the proportion of clean energy through financial subsidy policies, such as installing solar streetlights and solar-powered buildings, promoting the use of new energy tour vehicles, and encouraging visitors to explore on foot. These devices not only align better with the ecological tourism philosophy of forest parks but also, from a long-term perspective, reduce fossil fuel consumption and economize tourism operation costs. Secondly, corporate innovation can contribute to improved energy efficiency and reduced environmental pollution [
54,
55]. The government can stimulate businesses to invest in research and development for low-energy engines in the tourism sector through policies such as tax reductions or subsidies as well as the development of building insulation materials to minimize heat loss from heating or air conditioning systems. Concurrently, public-private partnerships (PPPs) provide a strategic avenue to address government fiscal constraints, reducing business risks and alleviating project financing challenges. The government should supervise through meticulous investment selection mechanisms and contractual frameworks to mitigate investment risks and prevent disputes. Thirdly, forest park operators can enhance ecological efficiency through foreign direct investment (FDI) to introduce low-energy tourism products. An array of scholarly investigations indicates that FDI inflows play a significant role in reducing energy consumption across sectors [
22,
56,
57,
58]. Therefore, the infusion of foreign capital emerges as a potent lever for operators to elevate their ecological sustainability by assimilating advanced technologies into their operational environment. Fourthly, effective management of tourism product development is imperative [
59,
60]. Policymakers can guide private capital to develop the experiential value of forest parks through special appropriations or project subsidy policies. For instance, based on the unique resource advantages of each scenic area, developing and constructing creative hotels such as camping tents, crystal houses, and log cabins with lower energy consumption and construction costs, instead of constructing energy-intensive star-rated hotels commonly found in urban areas. Encouraging forest parks to increase the proportion of low-energy recreational products is essential. The government can engage in collaborative endeavors with forest parks to orchestrate forest tourism festivals, allowing visitors to experience joy in activities like forest yoga, fishing, bamboo rafting, nature education, forest picking, forest bathing, and jungle trekking, with an emphasis on experience, participation, health, and individual development, so as to achieve development and protection in tandem and to place equal emphasis on economy and ecology.