1. Introduction
Sustainability, which can be expressed as “the capacity to endure” [
1], has become a worldwide goal of environmental development. Sustainability is crutial for a region’s policy-making. All human activities depend on the planet’s natural capital, which can be defined as a stock of materials including ecosystem, minerals, forests, biodiversity, and so on, to provide ecological services and natural resources [
2]. Humans have had significant effects on the earth, associated with population growth and economic development. Currently, many conflicts have become more notable among natural resources, environment, and economy, and there are increasing risks of ecosystem quality degradation and tipping the biosphere into a state where it would be very difficult or even impossible to support the human civilization [
3]. Therefore, studies should focus on the coordination between environmental protection and economic development. In addition, the conflict between short-term development and long-term welfare must be taken into account [
4]. Since the early 1970s, many reports such as “The Limits to Growth”, “Our Common Future”, and “State of the World” have warned that the unlimited growth of the human population and consumption would lead to unsustainability [
5,
6]. In recent years, environmental deterioration has still been getting worse. The detrimental effect of human behavior on the biosphere is also coming to the surface [
7,
8]. To achieve long-term sustainability, the human consumption of resources cannot exceed the environmental carrying capacity to maintain sustainability. It is necessary to measure the consumption of human needs and the region’s carrying capacity to estimate how much further we can go.
Ecological footprint (EF) was initiated as a policy and planning tool for sustainability [
9], and has become an emerging ecological economics method to evaluate sustainable development quantitatively. EF of any defined population (from an individual to the population of a city or country) is the area of biologically productive land and water appropriated exclusively to produce the resources used and the waste generated by the population. Carrying capacity is the number of individuals of a given species that a given habitat can support without being permanently damaged [
10]. As the ecological footprint and carrying capacity are measured in the same unit, they can be compared in order to assess the state of regional sustainable development. If the ecological footprint of a region is larger than the carrying capacity, the region experiences an ecological deficit; if the carrying capacity is larger than the ecological footprint, the region is an ecological reminder.
Currently, EF has been widely adopted to evaluate the sustainability of different scales, for instance national [
11,
12], regional [
13,
14,
15], city [
16,
17], and campus [
18], and of different systems (e.g., agricultural [
19], grassland [
20], tourism [
21], industry [
22,
23], and biogas systems [
24]. However, there are some obvious, inherent flaws in EF [
25,
26]. First, the ‘equivalence factor’ and ‘yield factor’ are based on the global productivity and international standard, failing to reflect the complexity of the ecological functions and the temporal differences of the natural environment. Second, the conventional method does not distinguish the renewable and nonrenewable land uses. In addition, it does not consider the land with low biological productivity. To remedy these deficiencies, many scholars have combined EF with other methods, such as the input–output analysis [
27,
28], the thermodynamic method [
29], emergy accounting [
4,
30], and embodied exergy [
31]. In these studies, emergy accounting was proven to complement the EF and overcome some limitations of the EF.
Emergy (spelled with an “m”), originated by Odum in the late 1980s, is defined as available energy previously used up directly or indirectly in the process of producing a product or service [
32,
33]. It is measured in solar equivalent joules and its unit is sej (solar equivalent joules). More detailed information about emergy analysis can be found in [
34,
35,
36].
Zhao et al. (2005) [
37] proposed an emergy ecological footprint method (EEF) by integrating emergy analysis into the conventional ecological footprint model. This method provided insight to evaluate the resource consumption and the impact on the environment through the method of tracking emergy flows in ecosystems. In recent years, many researchers have introduced this new method to evaluate the sustainable development [
24,
30,
38,
39,
40].
The Qinghai–Tibet Plateau (QTP), known as the world’s third pole, holds the largest typical alpine meadow ecosystem and provides a unique environment for a wide variety of alpine species. However, due to climate change and increasing grazing pressures, the QTP is faced with severe problems on sustainable development. For example, nearly 40% of the QTP’s grassland has experienced fragmentation and decreased in grassland coverage [
41], or degraded to desert or “black soil beach” [
42]. This degradation could further affect the ecosystems of surrounding areas and threaten the livelihood of nearly 40% of the population of China. As the QTP covers wide areas, different regions are significantly different in economy and environment, so it is not reasonable to evaluate the overall sustainability of the QTP. The objective of this article is to evaluate the long-term sustainability of the QTP through a modified emergy ecological footprint model. Qinghai Province and the Tibet Autonomous Region are taken as the study areass because they are two main regions in the QTP. Moreover, three evaluation indicators were proposed to analyze the sustainability of Qinghai and Tibet. Finally, the future sustainable status was predicted with the grey model. Several suggestions considering the local realities were proposed to protect local environment and restore ecological functions. Results of this study are expected to contribute to the sustainable development of the QTP.
4. Discussion
In this study, the model of emergy ecological footprint was modified by using region emergy density to calculate emergy carrying capacity and emergy ecological footprint. This method not only can reflect the true supply capacity of the ecosystem and human resource consumption situation in the study area, but also make the results of carrying capacity and ecological footprint comparable. As a result, the assessment of regional sustainability is more reasonable. In addition, we used the 30 m resolution of the digital elevation model (DEM) to estimate solar radiation emergy. Compared with the method of using the average solar radiation, solar radiation emergy that is calculated by the above method will better reflect the real situation of the study area. Actually, when calculating regional renewable resources, this part of emergy was too small to be included. Instead of using consumption data, we used regional biological resource productivity and emergy to estimate the ecological footprint of human population growth and economic development, because only the sum of economic activities and resources extracted within the area can reflect the real ecological footprint produced by humans. The eco-economic system is complex, so we simplify the complex system to assess sustainability of the study area. However, this approach does not include data which are difficult to obtain (such as topsoil loss, soil erosion, waste material, and so on), and some data of consumption are not available in each county’s statistical yearbooks, which can cause a small amount of deviation between study results and actual conditions. The modified method can increase the reliability of the study results to some extent, but still needs further improvement.
Table 2 and
Table 3 show that among six land-use categories, built-up land contributed more than half of the total
eef of Qinghai in 2014; while in Tibet, the contribution of grassland was the largest, with a value greater than 40%. This result indicates that the growth of Qinghai’s
eef is primarily caused by the rapid urbanization, particularly industrialization, because Qinghai is abundant in many resources that provide great convenience for industry development. However, Qinghai’s resource utilization efficiency is low due to the backward technology, so a lot of wastes, including waste water, waste gas, and solid waste, which are main proportions of the built-up land category, are produced in the processing of production. Moreover, the proportion of land-use categories reflects that the distribution of the
eef is far from balanced. As for Tibet, animal husbandry is the main industry and many residents make a living by grazing. Therefore, grassland produced the most emergy ecological footprint. The urbanization in Tibet has developed fast in recent years, but not as fast as that in Qinghai, so the contribution of built-up land to the total
eef of Tibet is lower than that of Qinghai.
Figure 2 and
Figure 3 indicate that the sustainability of Qinghai and Tibet decreased from 1995 to 2014. Qinghai’s
ecc exceeded its
eef in 2005 and since then EFI of Qinghai has been less than zero. This result is consistent with Wang and Ding (2011) [
67] and Liu et al. (2011) [
68], both of which indicated that Qinghai’s ecological carrying capacity decreased but the ecological footprint increased and Qinghai is already unsustainable (Liu et al., 2011; Wang and Ding, 2011) [
67,
68]. Tibet’s
ecc was always high enough to cover local
eef and its EFI was more than 60% in the investigated period. The results are in accordance with An and Chen (2014) [
69] and Li et al. (2015) [
70], who proved that Tibet’s sustainability showed a downward trend, but its carrying capacity was still larger than local ecological footprint. Qinghai is abundant in petroleum, nonferrous metal, natural gas, and so on. More than 72.71% of local industrial enterprises are heavy industrial enterprises, which are highly dependent on local resources and cause serious damage to the environment (Pan and Gai, 2016) [
71]. Qinghai is less developed in terms of science and technology, so the resource utilization efficiency was low, resulting in a large amount of resource waste. Many factors, including population growth, urbanization acceleration, economic, social, and industrial development, have resulted in the growing demand and consumption of resources. These are the main factors which led to the increase of
eef in Qinghai province. Qinghai features a plateau continental climate, the rainfall is about 300 mm a year and varies a lot among different areas [
43], so the
ecc of Qinghai was impossible to support the increasing
eef. Tibet is one of the most important biological reserves in China. Environmental protection is the primary goal of local economic development. The modern industry in Tibet is backward—up to 2014, there were only 763 industrial enterprises, more than 54.91% of which were light industrial enterprises. Most Tibetans make a living by grazing—the output of animal husbandry accounts for 49.98% of the gross output of farming, forestry, animal husbandry, and fishing. The economic development pattern in Tibet is relatively primitive so the environment was less disturbed. After the implement of “Western Development”, the economy of Tibet began to develop gradually, but Tibet still puts the most effort into protecting the environment because of its momentous ecological status. As a result, the
eef of Tibet increased at a low speed. Tibet is abundant in rainfall and solar radiation due to its unique location and climate (Zhao et al., 2005) [
37], plus with the ecosystem integrity, vast territory areas, and low population density, the local environment shows the features of primeval ecology, so the
ecc is high enough to maintain local economic activities.
From
Figure 4 and
Figure 5, we can see that the resource utilization efficiency and economy of the study area were improved from 1995 to 2014. The resource utilization efficiency of Qinghai was lower than that of the Tibet, but Qinghai’s economy developed faster. Equation (11) shows that EFG has a positive relationship with EEF but a negative relationship with GDP. Despite the fact that Qinghai’s GDP was more than that of Tibet, Qinghai’s EEF was almost three times as much as that of Tibet, thus EFG of Qinghai was lower than that of Tibet. However, compared with other developed areas, both Qinghai and Tibet should be improved in further development (Weng et al., 2006; Wei and Wu, 2011; Qin, 2013) [
72,
73,
74].
Based on the current economic development pattern and growth rate of population, the future sustainability of the study area was forecast by GM (1,1). The prediction results showed that the unsustainability of Qinghai would intensify, and the sustainability of Tibet would continue to decrease from 2015 to 2024. This is probably because the ten-year time frame is too short for Qinghai to reform local development pattern, and the economic growth still depends on the consumption of natural resources. The gap between Qinghai’s EEF and ECC becomes larger, and the environment is more unsustainable. As for Tibet, the increase of local population leads to the increase of livestock, which in turn leads to the excessive exploitation of grassland resources (Zhang et al., 2007) [
75], so as local grassland vegetation coverage and grass yield will decrease, the grazing capacity will also decline. Moreover, because of the lack of scientific and effective management, Tibet’s grassland experiences different degrees of degradation and grassland pests and diseases are getting more serious. Although Tibet is still sustainable at present, the annual reduction rate of ecological surplus will reache 2.70%, which indicates that Tibet is surely to be unsustainable in the near future if the development pattern is not changed.
Policy Implication
In order to achieve sustainable development of the Qinghai–Tibet Plateau, different regions should adopt appropriate policies and measures to develop the local economy.
Resource-based industries have made great contributions to Qinghai’s economic growth, but also lead to severe environmental degradation. Since Qinghai plays an important ecological service role to China and the rest of the world (Wang et al., 2015) [
76], efforts to promote sustainable development with the balance of economic growth and ecological protection should be made. First, Qinghai should be actively engaged in developing a circular economy that aims to improve resource efficiency by exchanging byproducts and reusing wastes (Geng et al., 2016) [
77]. Second, Qinghai can optimize its industrial structure by developing more service-oriented businesses because such businesses consume less materials and produce less impact on the local environment. Qinghai has become one of the most famous tourism destinations because of its abundant landscapes, rare species, and minority culture. The tourism income accounted for 8.77% of Qinghai’s GDP in 2014, but there is great potential to further expand it. Besides, it is urgent for Qinghai to make the best use of national policies and regional advantages to import advanced technologies and attract talents. Qinghai can also build up ecological compensation mechanisms to reduce environmentally damaging behaviors and recover the local ecosystem. However, Qinghai is one of the less developed regions in China, which lacks money to further protect local environment. Ecological compensation seems to be an effective method to balance ecological protection and economic growth. Thus, how to determine an appropriate compensation rate is of great importance. In this regard, more research should be made to identify the best compensation rate.
Tibet is an important ecological reserve in China. Protecting the environment should be on its priority list. Considering the decreasing trend of sustainability, Tibet should first continue to carry out the policy of giving rewards and subsidies (GRS) for grassland ecological conservation, which has been implemented by the Chinese government since 2009. The GRS policy encourages herdsmen to determine the number of grazing animals by the size of pasture. If herdsmen cut down the number of livestock, they can get rewards and subsidies from the government. Then the problem of overgrazing can be solved, the grassland vegetation coverage and grass yield will be increased, and carrying capacity of grassland will be improved (Yang, 2014) [
78]. Second, Tibet should make full use of local renewable energy resources, such as hydroenergy, water resources, and geothermal power, to develop the economy because renewable energy can not only help reduce pollution caused by fossil fuel, but also bring more economic and sustainable benefits. Tibet is also well-known for its primary environment, rare species, and Tibetan Buddhism, so developing tourism is a good choice to develop the local economy. Tourism income accounted for 22.15% of the Tibet’s GDP in 2014, but there is still a great potential to further expand it. Last but not least, Tibet should increase the resource utilization rate through technological innovation to reduce the waste of resources.