**1. Introduction**

Rapid globalization has strengthened the political and economic ties between countries [1], which has largely changed the previous disadvantage experienced by border areas of a country [2]. For example, the border areas of the European Union (EU) account for 40% of EU territory, 30% of the EU population, and 30% of the EU gross domestic product (GDP) [3]. The resources and environmental factors of border areas have a more important impact on national security and international economic cooperation than in the past [4–7], and ecologists also pay more attention to the resource management in these regions [8]. Although natural ecosystems are often spatially continuous, the boundary lines indicating the boundaries between the territories of different sovereign states will objectively lead to competition between countries for resources and environmental conditions in border areas [9,10]. As a result, the ecological security (ES) of border areas not only becomes an important part of a country's comprehensive national security system but also becomes the most sensitive part of that system. Because border areas involve political boundaries where environmental changes are complex and uncertain, the ES of border areas not only includes the security of development and the environment but also includes the rational use of resources, border management, ecological maintenance of the area, and geographical cooperation between countries [11]. In this context, studying the ES of border areas is

**Citation:** Hu, Z.; Qian, M.; Teng, X.; Zhang, Z.; Zhong, F.; Cheng, Q.; Wen, C. The Spatiotemporal Evolution of Ecological Security in Border Areas: A Case Study of Southwest China. *Land* **2022**, *11*, 892. https://doi.org/ 10.3390/land11060892

Academic Editors: Li Ma, Yingnan Zhang, Muye Gan and Zhengying Shan

Received: 17 May 2022 Accepted: 9 June 2022 Published: 11 June 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

of great significance to promote the cooperation between neighboring countries in the ecological field and maintain the stability of border areas.

The idea of ES first appeared in the land function and land health evaluation in the 1940s. Its concept is based on the theory of environmental security [12]. In 1989, the International Institute for Applied Systems Analysis first proposed the concept of ES when explaining global ecological and environmental problems. With the maturity of the theoretical framework of ES, the concept of ES has better clarity, that is, ES refers to maintaining the health and integrity of an ecosystem, ensuring that the human living environment does not change with the changes in external conditions and states, and keeping the environment in a stable and sustainable state [13]. In recent years, with the continuous and increasing change in the global environment and climate [14,15], regional ES has attracted significant attention and has become an important scientific problem that countries urgently need to solve [16]. Researchers have carried out much research on ES assessment in multiple scale areas and achieved many valuable results. By using a Pressure–State–Response model [17,18], the gray comprehensive evaluation method [19], and an ecological footprint model [20], researchers have evaluated ES at the national [21], provincial [22,23], urban agglomeration [24,25], watershed [18,26], and urban scales [27].

Although these studies provide a theoretical basis for ES analysis, some problems remain. First, existing studies have paid more attention to the ES of inland areas, but little attention has been paid to the field of ES in international border areas. Moreover, scholars often study large-scale administrative units such as countries and provinces, while these studies may not meet the needs of more detailed actual environmental management. Second, these existing studies have mainly focused on the retrospective evaluation of ES, which enriches the current situation and phenomena of ES but lacks the ability to predict the future of ES. Third, most of the existing studies ignore the analysis of the mechanisms that promote ES and lack a discussion of measures designed to improve the level of ES.

Since the 1990s, China has promoted a series of "geo-cooperation initiatives," namely transboundary infrastructure projects such as highways, railways, and oil and gas pipelines [10], which has effectively promoted the sustainable development of border areas. However, these projects can also lead to ecological problems such as land use-cover change [28], landscape fragmentation, and a loss of biodiversity [29] in border areas. To this end, the Chinese government has adopted a series of ecological restoration projects, such as a natural forest protection plan [30], designated ecological red lines [31], and mandated transboundary water resource management [32] and biodiversity conservation [33] to protect the environment of border areas. There are 110 international rivers and lakes in the southwest, northwest, and northeast borders of China. These regions are the birthplace of most Asian rivers, making China the most important upstream country for ES in Asia [34]. In 2015, the United Nations adopted the 2030 Agenda for Sustainable Development and formulated 17 Sustainable Development Goals (SDGs) [15], in which SDG 6 calls for sustainable management of water resources and SDG 15 calls for curbing the loss of biodiversity. Yunnan Province, located in the southwest border of China, is the upstream of Nujiang, Lancang, Honghe, and Daying rivers [35]. It is also one of the hotspots of biodiversity in the world [36]. Studying the ES of border areas in Yunnan Province can promote international cooperation on ES and the sustainable management of water resources, so as to effectively reduce border conflicts and ensure the safety and stability of border areas. However, the existing literature has paid little attention to this field. Considering that counties are the basic administrative unit in China [37] and that they can fully reflect the characteristics of border areas, this study selected the 25 counties in Yunnan Province as the case study area.

The security of international borders is becoming more and more complicated. Therefore, how to reposition the functions of the border areas needs more attention from the academic community. Based on the above literature review and an analysis of existing research gaps, the purpose of this study is as follows: (1) Analyze the temporal and spatial change characteristics of ES in the border areas of Yunnan Province under the background

of increasingly close international cooperation. (2) Probe into the main obstacles and factors and factors affecting the ES in border areas. (3) Predict the status of ES in border areas in 2025 and 2030. In addition, policy suggestions on improving the level of ES in border areas are also put forward. **2. Study Area and Data Sources**  *2.1. Study Area*  The border areas analyzed in this paper are located in Yunnan, China (21°08′–29°15′

change characteristics of ES in the border areas of Yunnan Province under the background of increasingly close international cooperation. (2) Probe into the main obstacles and factors and factors affecting the ES in border areas. (3) Predict the status of ES in border areas in 2025 and 2030. In addition, policy suggestions on improving the level of ES in border

*Land* **2022**, *11*, 892 3 of 21

#### **2. Study Area and Data Sources** N, 97°31′–106°11′ E) (Figure 1), with a total area of 9.03 × 104 km2. This region borders

areas are also put forward.

#### *2.1. Study Area* Myanmar, Laos, and Vietnam and includes the upstream regions of the Nujiang, Lancang,

The border areas analyzed in this paper are located in Yunnan, China (21◦080–29◦150 N, <sup>97</sup>◦310–106◦11<sup>0</sup> E) (Figure 1), with a total area of 9.03 <sup>×</sup> 104 km<sup>2</sup> . This region borders Myanmar, Laos, and Vietnam and includes the upstream regions of the Nujiang, Lancang, Honghe, and Daying rivers [35], as well as plateau wetland and tropical forest ecosystems. This area has a complex terrain as part of the Qinghai–Tibet Plateau, Hengduan Mountains, and the Yunnan–Guizhou Plateau where the elevation gradually decreases from northwest to southeast; the maximum relative elevational difference is approximately 4751 m across the region. The climate is dominated by plateau mountain climate, subtropical monsoon climate, and tropical monsoon climate conditions. The average temperature is 15–23.7 ◦C, and the annual precipitation falls between 1020 and 3388 mm. The combination of climate and complex terrain makes the border areas one of the global biodiversity hotspots [36,38]. Honghe, and Daying rivers [35], as well as plateau wetland and tropical forest ecosystems. This area has a complex terrain as part of the Qinghai–Tibet Plateau, Hengduan Mountains, and the Yunnan–Guizhou Plateau where the elevation gradually decreases from northwest to southeast; the maximum relative elevational difference is approximately 4751 m across the region. The climate is dominated by plateau mountain climate, subtropical monsoon climate, and tropical monsoon climate conditions. The average temperature is 15–23.7 °C, and the annual precipitation falls between 1020 and 3388 mm. The combination of climate and complex terrain makes the border areas one of the global biodiversity hotspots [36,38].

**Figure 1.** Map of the study area location along the southern and western borders of Yunnan Province. An inset map shows the study area location within the provinces and other administrative areas of China. Note: Map was created by authors using ArcGIS 10.7 based on the digital elevation model (DEM) data from the Resources and Environment Data Center of the Chinese Academy of Sciences (https://www.resdc.cn/, accessed on 4 January 2022). **Figure 1.** Map of the study area location along the southern and western borders of Yunnan Province. An inset map shows the study area location within the provinces and other administrative areas of China. Note: Map was created by authors using ArcGIS 10.7 based on the digital elevation model (DEM) data from the Resources and Environment Data Center of the Chinese Academy of Sciences (https://www.resdc.cn/, accessed on 4 January 2022).

The study area included the following 25 counties (cities): Cangyuan, Fugong, Funing, Gengma, Gongshan, Hekou, Jiangcheng, Jinping, Jinghong, Lancang, Longling,

The study area included the following 25 counties (cities): Cangyuan, Fugong, Funing, Gengma, Gongshan, Hekou, Jiangcheng, Jinping, Jinghong, Lancang, Longling, Longchuan, Lushui, Lvchun, Malipo, Maguan, Mangshi, Menghai, Mengla, Menglian, Ruili, Tengchong, Ximeng, Yingjiang, and Zhenkang. This part of China is relatively less developed than other areas of China and includes areas inhabited by people of various ethnic minorities. The traditional culture of ethnic minorities and rich tourism resources make tourism the main industry in border areas [39]. By 2016, the study area had a permanent population of 6.92 million, and a GDP of 158.48 billion yuan, of which income from tourism comprised 85.99 billion, accounting for 54% of the total GDP. In a word, as the border areas of Yunnan Province are rich in biodiversity and located in the upstream of many international rivers, it is representative to select these regions to study ES.
