Studying interactions of coupled human-natural system components provides better understanding of their influences on ecosystem health and improves effectiveness of managing such systems. To understand how human-nature interactions determine the sustainability of tourist destinations, using Jiuzhaigou Nature Reserve as an example, we analyzed how human-nature interactions influenced the reserve’s ecological services extraction, environmental conditions, and corresponding management actions through a historical lens. We first developed a model that represented the components and their interactions under coupled human and natural systems framework. We then summarized such interactions and their resulted environmental conditions in a time sequence. Human activities have changed Jiuzhaigou system from largely human-nature balanced to partially degraded, and then to recovered and intensively managed system during the past six decades. Such changes resulted from human-nature interactions predominantly driven by overuse of natural resources, responded to by natural components in loss of ecosystem functions, and then responded by management actions to restore the functions. The increased nutrient and sediment, modified benthic communities, and decreased travertine (crystal substrate formed by the precipitation of carbonate minerals) indicate that tourism pressure in Jiuzhaigou under the current intensive management strategy has exceeded its carrying capacity. Much more aggressive environmental friendly tourism policies are needed to sustain this valuable tourist destination. Our findings based on coupled human-natural system framework analysis have important implications for sustaining natural resources and ecological services, and the governance of both for the management of nature reserves.

Introduction

Understanding the structure, function, and process of natural systems is the central theme of ecological studies and science-based development of management policies and practices. Humans interact with the biophysical environment of natural systems and play key roles in the function of natural systems. Hence, humans have been considered as one of the critical components of ecosystems as the status of an ecosystem is the results of both the effects of humans on the environment and the effects of the environment on humans (Liu et al., 2007a).

In recognizing the importance of integrating the understanding of natural and human influences to sustain natural resources and the ecological services they supply, a conceptual framework for coupled human and natural systems (CHANS) has been developed (e.g. Liu et al., 2007a, 2007b; Alberti et al., 2011). This framework is also known as coupled human-environment systems (Turner et al., 2003) and coupled natural and human systems (Baerwald et al., 2016). The core concept of CHANS is that humans and nature are organized in interacting subsystems that make a cohesive whole at multiple spatial and temporal scales (Chen et al., 2015). Because CHANS pay particular attention to understanding of interactions in feedbacks, nonlinearities, thresholds, time lags, and legacy effects across multiple spatial, temporal and organizational scales (Liu et al., 2007a, 2007b), CHANS framework offers a clear way of studying interactions among human and natural system components and improves the understanding and management of protected areas.

The intensively managed Jiuzhaigou Nature Reserve represents CHANS of protected areas with unique linkages and interactions among human and natural components within the Jiuzhaigou system’s boundary that is spatially and politically defined by its watershed divide. The components of this system are also interactively influenced by factors outside of the system. Due to its natural scenic and societal importance, many studies have been carried out to evaluate the tourist influences on its biophysical environments (Li et al., 2005; Zhu et al., 2006; Gu et al., 2013) and water quality (Wang et al., 2006; Pan et al., 2016; Cao et al. 2016), define tourist capacity (Zhang and Zhu, 2007), and examine effects of tourism on local economy and culture (Li and Li, 2003). These studies focused on the characteristics of natural, human systems and societal benefits (e.g. economy and tourism), or the negative effects of human activities on the natural system individually. Such studies provide invaluable information about the structure of the natural system and about how humans have impacted on and benefited from the system. However, it is ineffective to study human and natural domains separately without considering system component interactions and feedbacks for developing strategies to sustain a balanced human-natural system (Liu et al., 2007a). Applying CHANS framework to Jiuzhaigou to integrate ecological components, human components, and factors linking ecological and human components provides insights on the interconnectedness and interdependence of social and ecological components of the system, which helps scientists to understand the system and policy makers and managers to make science-based decisions.

The natural and human characteristics of Jiuzhaigou at different periods of the past six decades represent a track of footprints of how humans and nature interacted. Such characteristics provide invaluable information for understanding the consequences of human-nature interactions and lessons learnt about how such interactions have directly affected both ecological services and sustainability of the system. Such information and lessons are especially important under the circumstances that China is experiencing unprecedented economic growth and tourist destination demands (Tang, 2015). This information is essential for local stakeholders and tourists to understand their roles in determining the structure and process of the systems, and for the central and local governments to develop adequate strategies and implement management actions.

The objectives of this study were to: (1) synthesize the characteristics of Jiuzhaigou human-natural system as results of interactions of system components using CHANS framework; (2) analyze the interactive relationships, and reciprocal effects and feedbacks among the system components; and (3) gain knowledge of unintended consequences resulted from the intensive management operations for the development of policy to sustain ecological services and protect ecosystem health. The findings from this example study reserve have broad implications for sustainable natural resource management, ecological services extraction, and the governance of both for protected areas in China and elsewhere.

Methods

Study area

Jiuzhaigou is located at the transitional belt of the high elevation Qingzang Plateau and the low elevation Sichuan Basin (Figure A1). This region has the steepest transition from a high-elevation plateau to a low-elevation basin in China (Liu et al., 2007c). Jiuzhaigou encompasses of a relatively small watershed area (643 km2), but has a large elevation variation from 4 764 m at its watershed ridge to 1 996 m at its confluence with the Baihe River (Deng et al., 2011).

The aquatic component of Jiuzhaigou consists of 114 alpine lakes, 17 groups of waterfalls, 5 shoals, and 11 sections of rapids (Deng, 2012), which is formed with valleys surrounded by steep-slope mountains and fed by groundwater and snowmelt from the mountains. Such water origins in this karst geology region are rich in calcium carbonate that settles on and covers the bottoms of lakes, rapids, and rivers to form crystallized substrates (travertine). Since nutrients are locked up in the bottom of waters, the lakes are extraordinarily clear and their crystallized bottom provides amazingly beautiful colors.

Coupled human and natural systems framework presentation, data sources, and analysis

We first developed a model using CHANS framework to represent the coupled human and natural system components and their interactions of Jiuzhaigou. The model components were identified by reviewing literature of other examples of CHANS framework, interviewing Jiuzhaigou mangers, and our own observations. The Jiuzhaigou system component grouping and their interactions were based on the principle of CHANS framework (Liu et al., 2007a; Alberti et al., 2011; Chen et al., 2015). We then summarized the characteristics of such interactions in the model and resulted environmental conditions in a time sequence of four periods for the past six decades according to the outcomes of human-nature interactions. We used the synthesized historical information to qualitatively describe human-nature interactions from 1960s to 1970s, and used tourism and reserve management data to quantitatively describe human-nature interactions from 1970s to 2010s (Figure A2). We used the quantitative data of environment, social, and reserve management measures obtained from the district and county governments, Jiuzhaigou Reserve, and our field sampling to present the outcomes of human-nature interactions (Figure A2). This time sequence analysis was used to illustrate the important roles that humans had played in determining both ecological services and environmental health under CHANS framework. We last presented the lessons learnt in the perspectives of human-nature interactions to provide important insights for sustainable natural resource management.

Results and Discussion

Structure of coupled human and natural Jiuzhaigou system

In our CHANS framework model, Jiuzhaigou system can be divided into a natural subsystem, a human subsystem, and their interactions (Figure 1). The natural subsystem consisting of climatic, terrestrial, and aquatic components supports the wildlife, vegetation, forests, rivers, lakes, and waterfalls for maintaining ecosystem function and providing resource for ecological services extraction. The human subsystem consists of human activity related land-use and landscape changes, tourism infrastructure and byproducts, and factors supporting societal wellbeing that have impacts to the natural subsystem components. Similar to findings elsewhere (Liu et al., 2007a; Chen and Liu, 2014), the health status of the natural and human subsystems of Jiuzhaigou is the results of interactions among the components of the two subsystems.

The Jiuzhaigou natural subsystem offers tourism enjoyment of natural scenery and experience of indigenous culture, and provides local and regional stakeholders with employment and economic growth. In turn, the tourism activities have direct physical impacts on soil, water, vegetation, and wildlife (Li et al., 2005; Zhu et al., 2006; Gu et al., 2013); generate food residual and waste (Pan et al., 2016); and require tourist transportation and restaurant services (Deng, 2009); which all potentially degrade the health of the natural subsystem. In order to sustain the ecological services, intensive management policy and practices have been implemented to minimize the impacts (Deng, 2012). As a result, building and maintaining tourism facilities and tourism management practices intended to protect the system also have unintended negative impacts to the ecosystem.

Coupled human and natural systems components interaction history

Current and future human and environmental conditions are influenced by the cumulative history of human and natural interactions (Goudie, 2013). Examining past system responses under CHANS framework reveals valuable insights that promote learning and adaptation in tourism and nature reserve protection policy and management (Kotchen and Young, 2007; Liu at al., 2007a). Based on how human-nature interactions determined the wellbeing of humans and health of environment, the history of Jiuzhaigou can be divided into four periods.

Period of approximately balanced human and natural components

Before mid-1960s, the only links between Jiuzhaigou and the outside world were horse trails and hillside paths, which were hardly known by the outside world. The indigenous Tibetans and Qiangs have inhabited in Jiuzhaigou for centuries with a population size less than 600, with a self-sustained life mainly through hunting and minor agricultural activities (Deng, 2009). The forests, wildlife, land, water, and ancient human-living style system was under dynamic equilibrium through self-adjustment of natural variation, which was similar to many natural systems before their development by human in many parts of the world (Goudie, 2013).

Period of increased human impacts on natural components

During the period of 1965-1978, Jiuzhaigou experienced extensive deforestation and impacts of human activities associated with logging (Deng, 2009; Deng et al., 2011; Deng, 2012). In 1966, the central government of China implemented the policy of exploitation of natural resources in remote areas for meeting regional economic needs. The central government invested about 70 million Renminbi (RMB) to establish two large logging operation centers in the Jiuzhaigou region. Since then, near one thousand logging workers were hired, many logging machineries were employed, hundreds of km of logging trails were built, and tens to hundred thousand large trees were removed from the pristine forests with a log production of over 100 000 m3 per year in the region (including Jiuzhaigou). Such activities lasted for more than ten years (Deng, 2009; Deng et al., 2012). As a result of the logging operation, many steep hills were eroded, groundwater levels were reduced, about one third of lakes were reportedly dried up (Deng, 2012; Han, Queensland University, unpublished 2006), and many of the natural components presented in the CHANS model were malfunctioned by the activities of human components (Deng, 2009; Deng, 2012).

Period of decreased human impacts on natural components

During the period of 1978-1997, Jiuzhaigou experienced changes from the worst human interrupted to an increasingly natural dominated process, entering a recovering stage as a result of a series of government policy implementation (Deng, 2009; Deng et al., 2011; Deng, 2012). The earliest formal measure taking place was the establishment of 200-m zone of waterfront where logging was prohibited. Since then, Jiuzhaigou was listed as the Provincial Nature Reserve in 1978 when logging activities were completely prohibited. Jiuzhaigou was listed as a National Key Place of Scenic Interest in 1984 with the establishment of the Nature Reserve Administration Agency and the reserve was officially open to visitors.

During this period, Jiuzhaigou became well known for its pristine forests and one of the most biologically diverse and threatened alpine systems in the world (Liu et al., 2007c). A large number of tourists were attracted by the snow-capped mountain peaks, unique forests, impressive waterfalls and lakes. Tourists arrived in Jiuzhaigou increased rapidly from hundreds in 1980s to over184 000 in 1997, and Jiuzhaigou faced new challenges of a different type of human components that could potentially imbalance and cause damage to the ecosystem.

Period of intensively managed human components to balance with natural components

During the period from 1997-present, Jiuzhaigou has been under continuous intensified management on human components intended to maximize tourism ecological services and minimize damage to the natural subsystem. The government has implemented a series management policies and practices (Deng, 2009; Deng et al., 2011; Deng, 2012) by removing more than 5 000 cattle, over 10 000 sheep, and hundreds of horses from the system; eliminating all farming activities; and relocating all hotels/restaurants and non-indigenous residents to outside of the reserve. The current 1,120 indigenous residents living in Jiuzhaigou are either working for the reserve tourism industry or turning their homes into visitor centers or gift shops.

In 1999, private tourist vehicles were replaced with shuttle buses for transporting visitors within the reserve. A completely controlled sewage disposal system was implemented to transport and treat all wastes outside of the reserve. Since then, about 57 km boardwalks and 67 km paved road were built. The intensively managed Jiuzhaigou human-natural system provides the outside world a new look and earned its reputation of one of the best managed tourism destination in China (Li et al., 2006; Zhuang et al., 2012).

Outcomes of interactions among Coupled human and natural systems components

Impacts of natural subsystem on human subsystem

The greatest ecological service provided by Jiuzhaigou is the tourism and its associated local economy. Since the tourism was initiated in 1981, the annual visitors had increased dramatically from less than 70 000 in 1985 to more than 5 090 000 in 2015 (Figure 2a). The growth of tourism has become the driver of economy in the immediate vicinity of Jiuzhaigou. The annual dollar amount from tourist admission and transportation inside the reserve increased from about $134 000 RMB in 1985 to 854 million in 2015 (Figure 2b). The development of tourism has boosted tourism related business, such as transportation, restaurants, hotels, and travel agencies in the region. As a result, the contribution of tourism revenue of Jiuzhaigou County increased from less than 2% in 1984 to 70% in 2005 (Yang and Liu, 2007; Gu et al., 2013). The development of tourism has improved economic condition of indiginous residents in Jiuzhaigou. Before tourism development, the residents had per capital income as low as 195 RMB in 1978 (Figure 2c). The resident per capital income reached 10 000 RMB in 2000 and 17 000 RMB in 2010 after tourism development.

Impacts of human subsystem on natural subsystem

Impacts of tourism related infrastructure and services

The most obvious disturbance to the natural subsystem is the building of pavement roads and boardwalk, construction of sanitation system, and employment of large number of tourist shuttle buses to meet the increased tourist demand. Although the intent of developing the infrastructure is to protect the natural subsystem, it has the consequence of altering the settings of natural subsystem.

The road system has changed dramatically from hardly any road before mid-1960s to nowadays approximately 67 km paved roads and 57 km boardwalk trails in such a small watershed of 49 km in south-north and 33 km in east-west dimensions. Building such a transportation system has resulted in increase in soil erosion (Gu et al., 2013), modified vegetation (Li et al., 2005), and other tourists’ disturbances on water and wildlife (Zhu et al., 2006).

The tourist vehicles and associated exhaust gas release increased remarkably from none in mid-1960s to over 12 850 tourist vehicles in 1998. Although the use of tourist shuttle buses and prohibition of private tourist vehicles have reduced number of vehicles to near 300 since late 1990s, the amount of exhaust released from tourist vehicles increased from less than 1 000 tons year−1 during 1990s to 10 000 tons year−1 in 2011. Such large amount of exhaust would be expected to have noticeable impacts on the terrestrial vegetation and aquatic system since excessive air deposition of sulfur and nitrogen was reported in the reserve (Qiao et al., 2015).

Extraordinarily high tourism pressure

In 2015, the number of tourists exceeded 5 million with an average rate of increase of 240 000 visitors year−1 since 1997 (Figure 2a). Such a tourism pressure is extremely high compared with other parks. For example, the annual number of visitors in 2014 for Jiuzhaigou was nearly twice as high as for the Yosemite National Park and three times as high as for the Yellowstone National Park per km−2 park areas in the United States (Figure A3a). The visitors in 2014 for Jiuzhaigou was nearly four times as high as for Yosemite National Park and eight times as high as for Yellowstone National Park km of roads and boardwalks (Figure A3b). Additionally, due to seasonality and national holidays, peak tourist seasons put much higher stress to the system. For example, the five-year peak season average exceeded 370 000 visitors month−1 (>62% annual visitors) during July-October (2010-2014 (Figure A4a). The maximum daily number of visitors in 2012 exceeded 52 000 day−1 (Figure A4b). This high density of tourists would unavoidably impact the system by leaving behind food residuals and litters, trampling travertine and vegetation, and leaking pollutants from sanitation and other service facilities (Pan et al., 2016).

Environmental impacts resulted from tourism development

Although Jiuzhaigou has been considered the best managed tourism destination in China (Zhuang et al., 2012), several lines of evidences indicated that major environmental changes have occurred. Increases in sediment and nutrient delivering to the aquatic system are evident from previous studies. Wang et al. (2006) found that runoff concentrations of TP and TN at areas with substantial tourist trampling near lakes were much higher than controls that were away from lakes. Li et al. (2014) found that the amounts of sediment and total organic carbon, TP, and TN in the sediment were linked to the aforementioned different periods of human activities in Jiuzhaigou. The relatively recent construction and maintenance of tourism service facilities and transportation systems also attributed to the increase in sediment and metals in lakes and terrestrial system (Xu et al., 2010; Gu et al., 2013).

Changes in benthic algal and macroinvertebrate communities as results of human activities are also evident. The data we collected indicated that percentages of sensitive benthic diatom and macroinvertebrate taxa were significantly lower for high than for lower tourism pressure lakes (Figure A5a and 5b). The travertine color change from 1985 to 2013 at Pearl Shoal, an iconic site with high tourist visiting rate, provided additional evidence of tourist impacts (Figure A6), which were also observed at many other scenery locations.

Management implications of human-natural system component interactions

Lessons learned from the human-natural component interactions

Using CHANS framework to examine Jiuzhaigou human-nature interactions through a historical lens provides insightful information for understanding the system function and process. Human activities have changed the Jiuzhaigou from a largely human-nature balanced to partially degraded, and then to recovered and heavily managed system. Such changes are results of human-nature interactions that were predominantly initiated and driven by extraction of ecological services, responded by nature in loss of system function, and then responded by management policies and actions to restore the function and sustain ecological services (Figures 1 and 3). A very important lesson learnt is that there are unintended consequences from human actions that are intended to protect ecosystem functions and services as emphasized in CHANS. As Figure 3 depicts, rich forest resource led to logging disturbance and resulted in partial malfunction of natural system (Figure 3a), and the logging activity discovered the natural beauty and resulted in the prohibition of logging (Figure 3b); the national and international Nature Reserve titles enhanced the protection of the system and resulted in the increased number of visitors and tourist services (Figure 3c); threats on sustainability from the ever increased tourism pressure and income from the tourism provided political wills and economic power to enable the reserve to be managed intensively as today, which has resulted in the present record high tourism pressure (Figure 3d). Such intensive management efforts no doubt have reduced the impact of human activities on natural system. However, such political wills and economic power also have direct threat to the natural system because the increased tourism demand and economic incomes it generates conflict with the effort of reducing tourism pressure for sustaining system function (Gu et al., 2013). Hence, only policies that promote a balanced human-natural system status can sustain the natural resources and the ecological services it provides (Xu and Sofield, 2016).

Challenges in balancing human and natural components

The aforementioned human-nature interaction cycle history and resulted environmental status indicate that the current tourism pressure of Jiuzhaigou has exceeded its capacity since it has shown clear early signs of degradation (Wang et al., 2018). The current continued increase in tourism pressure seems the major threat to the sustainability of Jiuzhaigou tourism and system health (Gu et al., 2013).

Several factors may have contributed to this current environmental status. First, legacy effects may continue to affect the system. These include the impacts of historical logging activities, unmanaged tourists and tourism service, and in-reserve residents’ farming and animal grazing. Second, inadequate operation or adequate operation but too much to handle of the current tourist management may have contributed accumulative degradation. Third, tourism pressure may have exceeded its capacity that the system can support and the unintended consequence of management actions. And last, global and local climate change may have gradual additive impacts on top of the other effects.

Among those potential contributing factors, legacy effect could be reduced by identifying hot legacy spots and implementing restoration measures. The impacts of facility operation could be improved by using most updated facilities and frequent updated training of operators. Prevention of overuse and unintended consequence of management requires thorough understanding how human-natural components interact, realistically estimate tourist capacity, and implement effective management policies. The climate change effect can be minimized by controlling factors that have additive effect with climate factors and applying adaptation strategies.

Applying CHANS framework to analyze human-nature connections and mutual influences during different tourism development stages of Jiuzhaigou reveals insights on the mechanisms of how human and nature have interacted. Our analysis of Jiuzhaigou, in conjunction with studies from other tourist destinations (Brown et al., 1997; Saveriades, 2000; Manning et al., 2002; Li, 2004), indicates that limiting tourism pressure to below the system’s capacity is utmost important. One of the challenges in implementing tourist capacity policy is associated with the local and regional economy (Gu et al., 2013). Because tourism is the most important economic source for Jiuzhaigou region (Gu et al., 2013) and other natural reserves (Salerno et al., 2013), limiting number of visitors to its capacity means reduction in revenue for local and regional governments. Therefore, the government officials must have an economy-sustainability balanced long-term vision and strategy. Without this, the continuously increased tourism pressure may eventually result in the collapse of not only the natural subsystem, but also human subsystem (Gu et al., 2013).

Another challenge of limiting number of visitors within its capacity in Jiuzhaigou and other overcrowded reserves is managing tourist flux. It would be extremely difficult to deny visitors from entering reserves once they have arrived during peak seasons. The reserve management needs to put in place mechanisms to regulate tourist flux and to limit tourist peak under its capacity. One potential mechanism is to establish multi-tourist destination networks using internet ticketing with location and time entrance fee adjustment to redistribute visitors among parks before their arrival at destinations. Mechanisms are also needed to redirect overflowed tourists to nearby scenery and entertainment spots. For example, Jiuzhaigou could establish such spots in its vicinities since several valleys nearby could potentially be developed as tourism attraction and entertainment spots, such as Zhongcha valley. Such vicinity tourism developments could also compensate the regional economic loss from the peak reduction of visitors at the reserve.

Conclusions

Increase in tourism pressure unavoidably intensifies human-nature interactions and results in environmental degradation for nature reserves (Chen et al., 2011; Cao, 2015; Wang et al., 2018). Applying CHANS framework, our study provides an example of how to holistically analyze such interactions and report on the resulted environmental and social-economic conditions through time. Although our study system is still largely in healthy condition, evidences in early signs of degradation suggest much aggressive environmental friendly tourism policies and management actions are needed to be in place before it becomes too late. One of the immediate important needs is to control the number of tourists below its capacity. Since the tourism pressure is oscillating within a year and among years, it is important to know how the system responds to such a ‘pulse’ stress, and if the system can and how long it will take to repair and recover from the stress. Such knowledge should be incorporated into the tourism capacity determination.

Although our study focuses on Jiuzhaigou, our approach and findings are applicable to other protected areas. For instance, the mutual adjustment and change between human and natural subsystems through time for Jiuzhaigou are common for CHANS (e.g. Turner et al., 2003; Chen et al., 2015; Baerwald et al., 2016). Jiuzhaigou presents the opportunity to learn the lessons and successful experience in integrating biological and cultural conservation, preserving geological and hydrological features, improving environmental practices, and sustaining ecological service. Understanding such dynamics and process of interactions provides insights on ecosystem behavior and human actions that are critical for informing the protection of natural systems for future generations. Because the increased tourism demand on the natural systems with unbalanced sustainability and ecological services are common problems for many CHANS, the lessons learnt here could be applied to the management of other similar tourist destinations in China and other parts of the world.

Acknowledgements

The authors are grateful to the leadership support of Jiuzhaigou Administrative Bureau, especially Directors Xiaoping Zhang and Ronglin Xu, the support from Jie Zhang at Nianjing Agriculture University, and field and laboratory supports of Qingxia Yang, Daijun Jian, and Weiyang Xiao at the Research Section of the Jiuzhaigou Nature Reserve. Dr. Kit Magellan and an anonymous reviewer provided comments that substantially improved the manuscript.

Supplemental Material

Supplemental data for this article can be accessed on the publisher's website.

Funding

This study was supported by a grant from International Science & Technology Cooperation Program of China (2013DFR90670) and in-kind supports from the Jiuzhaigou Administrative Bureau.

The text of this article is only available as a PDF.

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