1. Introduction
Minerals are indispensable materials that are used for the foundation of the development of modern economic societies. They play a crucial role in driving China’s modernization. Strategic exploitation and effective use of mineral resources are crucial measures in China’s modernization process and are fundamental methods for fostering long-lasting and robust economic and social progress [1,2,3]. As the intensity of mineral resource development and utilization in China continues to increase, serious ecological and environmental issues have been triggered. These issues have led to the destruction of regional ecosystems and natural landscapes, resulting in significant pollution and damage [4,5,6,7]. The United Nations declared the period from 2021 to 2030 as the “UN Decade on Ecosystem Restoration”, which has driven global efforts in ecological restoration and governance [8,9]. Both domestically and internationally, there has been increased focus on mine restoration projects and the promotion of ecological construction in mining areas, which has led to practical research in various fields [10,11,12]. Additionally, numerous ecological restoration policies have been enacted and implemented [13]. The Chinese government places high importance on the ecological restoration of mining areas [14]. In the 18th National Congress of the Communist Party of China, the construction of an ecologically sustainable civilization was incorporated into the Party Constitution, becoming a vital component of the cause of socialism with Chinese characteristics. The report of the 20th National Congress of the Communist Party of China emphasized that “promoting green development, fostering harmony between humanity and nature, and accelerating the implementation of major projects for the protection and restoration of important ecosystems” is essential.
The development of mine ecological restoration and assessment has been rapidly advancing [15]. Many countries have made significant contributions to the ecological restoration of mining areas, and efforts in this regard continue to progress [16,17]. As the scale of mine restoration and management expands, the quantitative evaluation of ecological restoration effectiveness becomes crucial for both the restoration of mining areas and the implementation of related measures [18,19,20]. An essential component of investigating the effect of open-pit mining on regional ecological environment is the dynamic monitoring of plant cover in mining regions and the analysis of vegetation change trends [21,22,23]. It can be used to evaluate the efficiency of ecological restoration and the structural integrity of the ecosystem, enabling prompt modifications to ecological restoration approaches. While traditional field surveys usually concentrate on small-scale sampling, they are expensive and ineffective when conducted in vast, isolated regions [3,24,25]. In recent times, satellite remote sensing has become a highly promising instrument for the surveillance of ecological rehabilitation in mining regions. Due to its extensive coverage, convenient accessibility, and quick data updates, satellite remote sensing is a very efficient method for promptly and thoroughly monitoring the dynamic process of ecological restoration in mining regions [26,27]. In some studies based on long-term Landsat remote sensing data, vegetation coverage in the study area is monitored by analyzing the dynamic changes in vegetation indices [3,24,28]. In these studies, the processes of ecological change under different conditions are examined. Zhang et al. [25] reconstructed the process of restoring spoil heaps on the basis of FVC and used predestruction vegetation coverage in the mining area as a reference to evaluate the effects of restoration. Zhao et al. [28] used the Tangshan Shougang Malanzhuang Iron Mine as the study area, and Landsat data and methods for analyzing differences were employed to explore the effects of vegetation coverage on ecological restoration in the mining area. Wang et al. [2] used Landsat 8 imagery and Zhuhai-1 data to calculate ecological quality indicators, such as the vegetation chlorophyll index and soil difference index, for the Pingshuo Coal Mine in Shanxi Province. A combined remote sensing ecological index was developed to assess the effects of ecological restoration in the Pingshuo Coal Mine area.
Owing to long-term illegal and unregulated mining, policy closures, and corporate bankruptcies, the issue of abandoned mines has become increasingly prominent, resulting in significant historical burdens and complex problems for mine ecology [29]. Currently, one of the key challenges and focuses of the work of spatial ecological protection and restoration for land is to understand the specific conditions of these historically abandoned mines and accelerate the pace of ecological restoration [9,30,31,32]. For mines of manganese, which is an important strategic resource, hosting a resource of about 4 billion metric tons, the Kalahari Manganese Field South Africa accounts for an estimated 80% of the world’s mineable manganese ore on land [33]. Due to the over-exploitation and utilization of mineral resources, land degradation and soil heavy metal contamination have become one of the most critical environmental issues [34]. Therefore, in the manganese mining areas of South Africa, local suitable plants and soil improvement techniques have been used for vegetation restoration [35,36]. Phytoremediation has significantly impacted plant diversity and achieved remarkable results. Yongzhou City of Hunan Province, as the main producing area of manganese ore in China, is known as the “manganese capital of southern Hunan” [37]. The historical legacy issues in the mining area are particularly urgent and require immediate action. The ecological restoration and monitoring of the manganese mining area in Yongzhou City are not only necessary but also crucial for effectively understanding the extent of vegetation destruction in the mining area and its surroundings. This is of great significance for strengthening mine management, supervision, and restoring the ecological environment of the mining area [19]. Therefore, it is particularly necessary to study vegetation coverage and its driving factors in depth [38]. Although existing research has focused mainly on natural factors, such as precipitation and temperature, limited attention has been given to the critical role of human ecological policies in vegetation restoration [39,40], Future research should place greater emphasis on the driving role of ecological policies in vegetation restoration, aiming for a more comprehensive understanding and promotion of the ecological restoration process in mining areas.
Therefore, the objectives of this study were: (1) To focus on Yongzhou City in Hunan Province as the study area and mining plots as the object of analysis, examining the extent of vegetation damage caused by manganese ore mining, and analyzing the vegetation cover changes from 2000 to 2023 to assess the degree of ecological restoration; (2) To analyze the driving factors of vegetation restoration in the study area and evaluate the impact of policy guidance on vegetation recovery, providing a basis for adjusting mine restoration policies; (3) To assess the effectiveness and existing issues in the ecological restoration and governance of manganese mining areas through the findings of this study.
2. Materials and Methods
2.1. Study Area
The study area is located northwest of Yongzhou City, Hunan Province (Figure 1), and includes the districts and counties of Lingling, Dong’an, Lengshuijiang, and Qiyang. Its geographical coordinates are 110°59′47″ E to 112°10′08″ E and 25°51′24″ N to 26°48′13″ N. The study area encompasses seven manganese mining areas: the Dicun Mining Area in Dong’an, the Jingmuchong Mining Area in Dong’an, the Lipichong Mining Area in Lingling, the Shuibuetou Mining Area in Lingling, the Xinzhaili Mining Area in Lingling, the Liziyuan Mining Area in Lengshuijiang, and the Shihuichong Mining Area in Qiyang. The total area of concentrated mining is approximately 11.2 km². The region has a subtropical continental humid monsoon climate with four distinct seasons. The annual average temperatures range from 17.6 °C to 18.6 °C, with the rainy season occurring from April to June, accounting for approximately 40% of the annual rainfall. The highest recorded yearly precipitation is 1937.6 mm. The area is dominated by low mountains and hilly landforms with erosion and denudation. The Quaternary period is well-developed, and the surface vegetation is primarily shrubland and tree. The strata in the area are well exposed, consisting primarily of Devonian to Triassic strata, followed by Cretaceous and Quaternary strata. The manganese-bearing strata are located in the upper section of the Permian Gufeng Formation, which is a set of carbonate rocks that are rich in silica and clay [41].
Manganese mining in Yongzhou City, Hunan Province has a long history. In the early years, mining operations were highly unregulated, with private mining sites operating independently [42,43]. The mining was mainly open-pit, and during the process, due to the uneven thickness of the ore layer and the occasional inclusion of small amounts of gravel, the overburden and waste rock were stripped and removed. The stripped soil and discarded waste rock were typically piled near the open-pit mining area without a designated waste disposal site [44]. Abandoned old pits, created by excessive and chaotic mining, are common, especially in some rich ore areas where illegal mining and ore washing were serious. The mining order was chaotic, with most operations being small-scale, informal, and using outdated equipment and methods. The practices of extracting high-grade ore while leaving lower-grade ore behind, and discarding fine ores while keeping larger blocks, were prevalent. This resulted in significant destruction and waste of manganese resources [45,46]. The mineral deposits in the mining area are generally located on hillsides and hilltops, with relatively high terrain. The waste materials from the mining area, aside from some backfill in adjacent pits, were often discarded down the slope without basic protective measures. Due to long-term disorganized mining and a lack of comprehensive development planning, land occupation and vegetation destruction were severe [47,48]. The mining areas far exceeded the ore deposit areas, and because the pits were not promptly rehabilitated, some of the pit edges experienced collapse and landslides, leading to the expansion of the damaged land.
2.2. Data Sources and Preprocessing
Historical legacy mines are mines that have been abandoned and for which the government takes it upon to restore and rehabilitate. These encompass mines that have been abandoned after early, non-standardized mining activities, mines where the parties responsible have vanished or cannot be identified, and mines that have been closed due to policy constraints such as withdrawal from protected areas or capacity reduction, with the government taking on the responsibility of restoration at the time of closure. The data on historical legacy mining locations in this study were acquired by conducting field surveys and integrating them with prior research findings and data from remote sensing dynamic interpretation analyses.
Yongzhou City experiences heavy rainfall and cloud cover in the spring and summer, often leading to Landsat imagery being obscured by clouds, making it challenging to extract ecological and environmental factors via remote sensing and significantly affecting subsequent analyses. In contrast, the autumn and winter seasons have less rain and cloud cover, providing good remote sensing images with minimal cloud coverage [49]. Therefore, in this study, Landsat imagery data from September to November were collected for ten years: 2000, 2003, 2006, 2008, 2012, 2013, 2015, 2018, 2022, and 2023 (Table 1). Remote sensing datasets with a spatial resolution of 30 m × 30 m were obtained from the United States Geological Survey (
2.3. Research Methods
2.3.1. Calculation of the Normalized Difference Vegetation Index (NDVI)
The NDVI is a significant measure that reflects the ecological conditions of vegetation development [54]. Reflectance ratios of the near-infrared band to those of the red band are occasionally employed when extracting vegetation information from multispectral photographs [55]. This method can eliminate some radiometric errors, and the range of values is −1 to 1 [56]. The NDVI model is employed to compute the vegetation indices within the designated research region for various years.
(1)
The equation NDVI denotes the Normalized Difference Vegetation Index, NIR represents the reflectance of the near-infrared band accepted by the sensor, and R indicates the reflectance of the red band. In general, there is a positive correlation between the NDVI value and the density of vegetation on the surface of green vegetation-covered regions.
2.3.2. Fractional Vegetation Cover (FVC)
The FVC is a complete quantitative measure that accurately represents the extent of vegetation and may be used to evaluate the biological environment of a specific location. Furthermore, alterations in vegetation cover can also serve as an indicator of the environmental development of mining regions [57]. This study used a pixel dichotomy model that relied on the NDVI to quantify the vegetation covering in the Yongzhou manganese mining region. This approach is appropriate for monitoring the dynamic changes in vegetation on a regional perspective [58,59]. Based on the principles of the pixel dichotomy model, the vegetation coverage is obtained, and the calculation is shown in Equation (2).
(2)
Meteorological conditions, distribution and types of ground objects, seasonal variations, and other variables contribute to the fluctuation shown in the NDVImin and NDVImax values. Prior to establishing the upper and lower NDVI thresholds, it is essential to define the confidence intervals for these values based on the real geographical conditions of the research region [60]. The present work focuses on the selection of NDVImin and NDVImax values at the 5% and 95% levels of the cumulative frequency of the camera pixels.
2.3.3. Methods for Classifying Trends in Vegetation Coverage Succession
The map illustrating the patterns of the succession of vegetation coverage can accurately depict the spatial and temporal changes in vegetation provision in mining regions. The present work involved the computation of vegetation coverage succession using the raster calculation module within the ArcGIS 10.0 software. The change in vegetation covering is represented by D in Equation (3), and the calculation yields the difference between the vegetation coverage values of the current year (year i) and the preceding year (year j).
(3)
Following the completion of raster computations, the reclassification module is employed to combine patches that have identical attribute values. This process helps to generate a map that visually represents the succession of vegetation covering in the research region. Based on the adjusted attribute values, the dynamic succession is further classified into seven distinct categories (Table 2).
3. Results
3.1. Statistics and Maps
The computed results displayed in Table 3 indicate the area and percentage of plant cover in the manganese mining region from 2000 to 2023. The numbers obtained are rounded to two decimal places. The vegetation cover values for the research area from 2000 to 2023 were analyzed using ArcGIS software. The calculated coverage was categorized into five types (Table 4). Figure 2 displays the map that categorizes the geographical variations in vegetation covering for the whole research region from 2000 to 2023.
3.2. Spatiotemporal Changes in Vegetation Coverage in the Yongzhou Manganese Mining Area
3.2.1. Mining-Induced Damage: 2000–2012
The FVC (Fractional Vegetation Cover) of the manganese mining areas in Yongzhou showed a significant decline from 2000 to 2012 (Figure 3 and Figure 4), with vegetation cover dropping from 0.58 in 2000 to 0.22 in 2012, and continuing to decrease until it reached its lowest value of 0.21 in 2013 (Figure 3). According to the statistics (as shown in Table 3), the land area with relatively low FVC (0–0.4) showed an increasing trend from 2000 to 2010 (Figure 3), rising from 297.81 hm2 (28.32%) in 2000 to 860.13 hm2 (81.64%) in 2012 (Table 3). The main reason for this was the intense mining activities in the manganese mining areas of Yongzhou during the 2000–2012 period, which led to severe environmental and vegetation destruction.
3.2.2. Pollution Control and Land Reclamation: 2013–2023
The vegetation cover in the manganese mining areas of Yongzhou showed an increasing trend from 2013 to 2023 (Figure 3), rising from 0.21 in 2013 to 0.40 in 2023. During this period, the area with extremely low vegetation cover decreased from 598.95 hm² to 278.82 hm2 (Table 3), with the proportion dropping from 56.85% to 26.47%. This change is reflected in the color shift of typical mining areas from deep purple to lighter shades between 2013 and 2023 (Figure 5). This trend reflects the efforts made by local governments and mining operations in pollution control and land reclamation between 2012 and 2023. The increase in vegetation cover is also a result of the growing global emphasis on green energy and sustainable resources [61]. During this period, China enacted and implemented a series of ecological and environmental protection policies, placing a strong emphasis on the construction of “green mines” as a key focus of mine restoration and governance. These policies have promoted the advancement of efforts in areas such as mine area greening, mine pollution control, and land reclamation. The emphasis on “green mining” has played a significant role in improving the ecological environment of mining regions, facilitating the restoration of vegetation and the overall rehabilitation of disturbed land [62,63,64]. Overall, the vegetation cover has improved significantly. This demonstrates the substantial success of ecological restoration measures, leading to further improvement in the vegetation cover of the manganese mining areas in Yongzhou.
3.3. The Impact of Different Restoration Methods on Changes in Vegetation Cover
To more intuitively reflect the changes in vegetation cover under different restoration methods, this study compares mining areas with artificial reclamation (Figure 6) and those without artificial reclamation (Figure 7). Historical imagery from Google Earth Pro v7.3.6.10155 (
Furthermore, we have chosen a specific location in the hilly part of Yongzhou City, measuring around 50 square kilometers, to serve as a control area. The control region remains unaffected by human activity, and the variations in vegetation coverage statistics indicate the effects of natural succession and environmental changes. In contrast to the intensively affected mining region, the control area has shown a significant percentage of medium and high vegetation coverage since 2000, suggesting favorable circumstances for plant cover. By 2012, the proportion of regions with high and very high vegetation coverage had notably risen, with comparatively high vegetation coverage making up 85.93% of the overall area. This phenomenon may indicate enhancements in the natural ecological landscape. In the year 2018, there was a notable rise in the percentage of high vegetation coverage, reaching 91.8%. Furthermore, the quality of the vegetation continued to enhance. From 2000 onwards, the control area has maintained a consistent level of high vegetation cover (Table 5, Figure 4 and Figure 5), suggesting that the vegetation has developed and achieved stability through long-term natural succession. In contrast to the shifting trends in the mining region, the control area exhibits a consistent vegetation cover, suggesting that vegetation coverage may be maintained at a steady level in the absence of mining activity.
3.4. The Spatial Evolution Trend of Vegetation Cover in the Yongzhou Manganese Mining Area
To better understand the spatial distribution of the overall vegetation cover evolution in the study area, the vegetation cover differences for the two periods (2000–2012 and 2012–2023) were calculated using Equation (3). Based on Table 6, the evolution trends were categorized, and the spatial distribution of vegetation cover evolution in the study area for the two periods (2000–2012 and 2012–2023) was obtained, as shown in Figure 8 and Figure 9. From 2000 to 2012, the vegetation in the Yongzhou manganese mining area showed a clear degradation trend. The area with significant degradation in vegetation cover reached 620.01 hm2 (Table 6), which was primarily related to the earlier disorderly mining practices in the Yongzhou manganese mining area and the national policies that encouraged mining at the time. From 2012 to 2023, the vegetation cover in the Yongzhou manganese mining area showed overall improvement, with areas of vegetation recovery reaching 591.12 hm2 (Table 6). This improvement was mainly driven by artificial reclamation activities under national policy guidance. Since 2012, with the promulgation and implementation of relevant national policies, Yongzhou has implemented a series of ecological restoration measures and engineering projects, effectively promoting the improvement of the mining area’s ecological environment. The increasing vegetation cover in the Yongzhou manganese mining area indicates that the ecological restoration efforts have achieved positive results. Accordingly, the areas with artificial reclamation showed the most significant increases in vegetation cover, especially in places where soil improvement and planting had taken place. These areas experienced a rapid increase in vegetation cover, reaching healthier levels. However, in areas without artificial intervention, the recovery remained slow and sporadic, mainly depending on natural processes, which were insufficient in heavily disturbed regions.
4. Discussion
4.1. The Impact of Natural Factors on Vegetation Coverage in Mining Areas
The temporal and spatial distribution and succession of plant cover are well-recognized to be determined by a dynamic interplay of natural and anthropogenic elements [65,66,67]. Within the realm of natural elements, the growth and dispersion of surface vegetation are significantly influenced by climate conditions, namely precipitation and temperature. Effects of climate change on regional temperature fluctuations and precipitation patterns have subsequently influenced the plant cover in mining regions [19,67,68]. Figure 10 displays the fluctuations in temperature and precipitation in Yongzhou City across the 22-year period spanning from 2000 to 2022. Between 2007 and 2012, the temperature in Yongzhou showed a dramatic decline, dropping from 20.7 °C in 2007 to 17.4 °C in 2012. The precipitation exhibited a declining pattern from 2002 to 2011, gradually decreasing from 2034 mm in 2002 to a minimum of 938 mm in 2011, after which it started to vary in an upward direction. Overall, precipitation and temperature in Yongzhou exhibited a pattern of initial decline followed by subsequent increase; however, the fluctuations were not very substantial. It should be emphasized that in 2011, during the period of minimum precipitation, the extent of vegetation was correspondingly limited, and it progressively grew as precipitation levels improved. Hence, it can be deduced that the extent of vegetation in the mining region normally aligns with the pattern of rainfall [69,70], which evidence suggests that the climatic circumstances have a crucial role in the dynamic fluctuations of vegetation in the research region.
Nevertheless, according to the examination of the control region, the extent of vegetation cover varied between 0.75 and 0.86 from 2000 to 2023, but remained consistent (Figure 11). A correlation analysis was conducted between the annual average precipitation, annual average temperature, and average FVC (Figure 12) for Yongzhou from 2000 to 2023. The results showed that the correlation between temperature, precipitation, and FVC was low, with FVC changing over time. Therefore, the main factors influencing the FVC in the mining area are still human activities. These findings suggest that although rainfall and temperature do exert some influence on vegetation covering in the research region, they are not the predominant determinants. Human activities, such as artificial reclamation driven by policy, are the leading factors promoting vegetation coverage.
4.2. The Impact of Human Factors on Vegetation Cover
Although natural factors influence the evolution of vegetation cover types under the broader environmental context, human activities are the primary drivers of vegetation cover changes in mining areas [71,72]. Human factors are the dominant forces affecting the regional vegetation area, the intensity of its evolution, and its diversity. The evolution of regional vegetation cover is influenced by multiple human factors simultaneously. Therefore, based on the characteristics of human activities in the Yongzhou manganese mining area, this study selects mining activities, artificial reclamation driven by policies, and ecological restoration projects as analytical factors to examine the impact of human activities on vegetation cover in mining areas.
4.2.1. The Impact of Mining Activities on Vegetation Cover
Mining activities have caused severe damage to the ecological environment of mining areas. Yongzhou City, as an important base for manganese resources in China, has been a key focus for the Hunan Institute of Geology and Mineral Resources since the 1960s. In January 2006, the State Council issued a decision to strengthen geological work, which further clarified relevant policies, including “encouraging various types of social capital to participate in mineral resource exploration, cultivating and expanding the commercial exploration market, and establishing the leading role of enterprises in commercial mineral resource exploration”. The policy also encouraged state-owned geological survey units to joint venture or cooperate with social capital to form commercial companies or geological service companies, and to promote the development of commercial mineral exploration companies with various ownership structures and flexible exploration mechanisms. In addition, early open-pit mining methods not only destroyed the vegetation cover but also exacerbated issues such as soil desertification, landslides, and water and soil erosion, which, in turn, affected biodiversity [73,74,75,76,77].The problem of heavy metal pollution in abandoned manganese mine sites was also severe, with surrounding soil, water bodies, and farmland facing contamination risks. It was not until 2008 that the Hunan Provincial Department of Land and Resources issued mining licenses for the mines, marking the beginning of standardized mining operations. As a result, during the period from 2000 to 2012, frequent mining and human activities led to a significant decrease in vegetation coverage in the Yongzhou manganese mining areas, with the Fractional Vegetation Cover (FVC) dropping from 0.58 in 2000 to 0.22 in 2012, severely impacting the ecological environment.
4.2.2. The Impact of Artificial Reclamation Driven by Policies on Vegetation Cover
National policies have a significant impact on the ecological environment of mining areas. After 2008, a series of policies and regulations were introduced to protect and restore historically impacted mining areas (Table 7). In 2011, the “Land Reclamation Regulations” were enacted to standardize land reclamation activities, strengthen land reclamation management, and ensure the implementation of reclamation projects for land damaged by production and construction activities. Land reclamation effectively restored arable land, improved the environment, and alleviated social conflicts caused by land use restrictions. Land reclamation has successfully rehabilitated cultivable landscape, enhanced the ecological conditions, and mitigated societal tensions arising from limitations on land usage [67]. In 2012, the “Measures for the Implementation of Land Reclamation Regulations” were issued to ensure the effective implementation of land reclamation, covering historical land damage reclamation and land reclamation acceptance. In the same year, the Hunan Provincial Government issued the “Notice on Standardizing and Promoting Land Reclamation Work” (Xiang Zheng Fa [2012] No. 15), emphasizing the implementation of land reclamation regulations and promoting land reclamation efforts in Hunan Province. As a result, vegetation coverage in the Yongzhou manganese mining area began to show an upward trend. In 2015, the State Council issued the “Opinions of the CPC Central Committee and the State Council on Accelerating the Construction of Ecological Civilization”, which proposed carrying out geological environmental restoration and comprehensive treatment of mining areas. In the same year, the State Council released the “Overall Plan for Ecological Civilization System Reform”, requiring improvements to the geological environmental protection and land reclamation systems for mining areas. In 2016, the State Council issued the “Soil Pollution Prevention and Control Action Plan” (the “Ten Measures”), aiming to establish and advance a government–enterprise–society collaborative soil pollution control system, strengthen soil pollution prevention, and improve soil environmental quality. The implementation of the “Ten Measures” laid a solid foundation for soil pollution control in China and significantly improved the capacity for soil pollution prevention. The plan set a goal to curb the worsening trend of soil pollution by 2020, stabilize the overall soil environmental quality, ensure the safety of agricultural and construction land, and control soil environmental risks. In the same year, the “Guiding Opinions on Strengthening Geological Environment Restoration and Comprehensive Management of Mining Areas” were issued, greatly advancing the effectiveness of ecological protection and restoration efforts in China. After 2016, vegetation coverage in the Yongzhou manganese mining area showed a significant upward trend, and the ecological environment improved steadily. In 2017, the Yongzhou Municipal People’s Government issued the “Measures for the Protection of Geological Environment and Land Reclamation in Mining Areas”, aiming to prioritize ecological protection and promote coordinated development of mineral resource exploitation and geological environmental protection, thereby further advancing ecological restoration in the Yongzhou manganese mining area. In 2019, the Ministry of Natural Resources and the Ministry of Ecology and Environment jointly issued the “Opinions on Accelerating the Comprehensive Management of Open-Pit Mines” (Natural Resource Office [2019] No. 819), calling for the exploration of new models of geological environmental restoration and comprehensive management for abandoned open-pit mines with lost responsibility entities, based on a “government-led, policy-supported, socially involved, development-oriented governance, and market-based operation” approach. In 2021, the State Council issued the “Management Measures for Key Ecological Protection and Restoration Funds” (Caizi Huan [2021] No. 100), aiming to regulate the supervision and management of joint rights transfers and special transfer payment projects between central and local governments in the natural resource system. The notice clarified departmental responsibilities, strengthened daily project supervision, and implemented performance management to achieve project goals. In the same year, the State Council issued the “Opinions on Encouraging and Supporting Social Capital to Participate in Ecological Protection and Restoration”, marking a further strengthening of the systematic and comprehensive restoration approach for historically impacted mines, accelerating integrated protection and restoration of mountains, waters, forests, farmlands, lakes, grasslands, and deserts. In 2022, the Ministry of Natural Resources issued the “14th Five-Year Plan for Ecological Restoration of Historical Mining Areas”, aiming to address ecological issues in historically impacted mining areas, improve the ecological environment, and effectively resolve ecological damage in key regions and important river basins. The plan aims to significantly improve the living environment around mining areas, enhance the comprehensive utilization of abandoned land, and gradually restore the ecosystem service functions. In the same year, the Yongzhou Municipal People’s Government in Liling District issued the “Interim Regulations on Ecological Protection and Restoration in the Liling Manganese Mining Area”, aiming to implement the ecological civilization development strategy, expand the achievements of green mine construction, and consolidate the restoration efforts of the manganese mining area. As a result, vegetation coverage increased from 0.21 in 2013 to 0.39 in 2022, demonstrating significant success in vegetation restoration in the Yongzhou manganese mining area. In 2024, the Hunan Provincial Department of Natural Resources promoted the implementation of the “Ecological Protection and Restoration Plan for Chengjia-Liujia Manganese Mine” in the Liling District of Yongzhou City. The plan aims to address long-term ecological environmental issues caused by mining activities, such as soil and water pollution, vegetation destruction, water quality deterioration, and soil erosion. The plan’s objectives include eliminating geological disaster risks, restoring natural landscapes, recovering soil fertility, increasing forest, agricultural, and grassland areas through reclamation, and safely disposing of hazardous waste to reduce pollution risks to the mining area and downstream water bodies. Due to decades of intensive mining, the manganese mineral resources of Yongzhou City have been severely depleted, resulting in a range of adverse effects such as land occupancy and destruction, environmental pollution, geological dangers, and ecological degradation. Thus, it is imperative to promptly implement the sustainable utilization of reclaimed mining land and industrial conversion. Effective implementation of ecological restoration of abandoned industrial and mining sites and the initiation of extensive ecological restoration projects are of utmost importance [6,78,79,80,81].Thus, through national policy-driven initiatives and government guidance, scientific evidence has been provided to support the feasibility of land reclamation, leading to effective ecological protection and restoration. As a result, the vegetation cover in the Yongzhou manganese mining areas has shown remarkable improvement.
4.2.3. The Impact of Ecological Projects on Vegetation Cover
By the end of 2024, Yongzhou has carried out ecological restoration of historical abandoned mining areas, implementing various key projects such as the Xiangnan Manganese Mine Ecological Protection and Restoration Pilot Project in the Zero Ling Manganese Mining Area, the Ecological Restoration of Abandoned Open-pit Mines in the Yangtze River Economic Belt, the Provincial Ecological Restoration of Historical Mining Areas (2022–2023), the Ecological Restoration Demonstration Project of Historical Abandoned Mines in the Key Source Areas of the Xiang River, the Water Ecological Environment Governance Project in the Urban Section of the Xiang River, and the Ecological Restoration Project of the Fu’er River Basin. The restoration efforts have yielded significant results. Through the implementation of numerous ecological engineering projects (Supplementary Table S1), Yongzhou has effectively increased forest coverage, enhanced the ecological function of the Nanling Mountains, reduced soil erosion, improved water conservation, and increased biodiversity. The restoration efforts have created additional farmland, forestland, and garden areas, achieving the comprehensive governance goal of “green mountains, clean water, restored forests, and protected fields.” These initiatives have eliminated mining-related geological hazards, restored the original topography of mining areas, repaired land damaged by mining activities, and mitigated soil pollution. As a result, the ecological environment quality of the Xiang River and the rivers and surrounding areas has improved significantly, strengthening the ecological function of the Yangtze River’s key ecological zones and the southern mountain ecological barrier, thus ensuring national ecological security. From the vegetation cover type map and evolution trend map of the Yongzhou manganese mining area, it is evident that between 2012 and 2023, forest and grass vegetation increased significantly, with the average vegetation cover in the mining area rising to 0.40. Areas of severe degradation rapidly decreased, and the ecosystem is moving toward a positive cycle.
5. Conclusions
This work assesses the efficacy of ecological restoration in the manganese mining region of Yongzhou City, Hunan Province, using remote sensing images and trends in vegetation coverage changes. It also investigates the natural and anthropogenic factors that influence vegetation coverage dynamics.
(1). Remote sensing images of the manganese mining areas in Yongzhou, Hunan Province show that from 2000 to 2012, vegetation cover in the study area exhibited a declining trend, while from 2012 to 2023, vegetation cover in the mining area showed an increasing trend.
(2). Frequent mining activities took place from 2000 to 2012, resulting in severe environmental damage and land degradation. The vegetation cover in the Yongzhou manganese mining area followed a trend of degradation from 2000 to 2012. Early unregulated mining was the anthropogenic driving force behind the decline in vegetation cover. After 2012, under the constraints of national policies and local regulations, and with the careful design and management of ecological restoration projects, mines were gradually closed. A series of artificial reclamation activities and ecological protection projects were implemented, leading to an improvement in vegetation cover from 2012 onwards. The implementation of artificial reclamation and ecological protection projects driven by policy is the anthropogenic driving force behind the increase in vegetation cover in the mining areas.
(3). In areas where artificial reclamation was carried out, the vegetation restoration was effective, while in areas without vegetation restoration, natural recovery alone struggled to reach the previous levels. Therefore, under the policy-driven approach, artificial reclamation and ecological protection projects urgently need to be carried out in areas that have not yet been restored.
J.L.: conceptualization, formal analysis, software, validation, writing—original draft, writing—review & editing; Z.H.: conceptualization, funding acquisition, methodology, resources, supervision; H.S.: resources; Y.Z.: data curation; J.W.: conceptualization, methodology, software; A.L.: methodology; L.L.: validation; R.Z.: software. All authors have read and agreed to the published version of the manuscript.
The raw data supporting the conclusions of this article will be made available by the authors on request.
The authors declare no conflict of interest.
Footnotes
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Enlarge this image.Figure 2. Map for classifying the vegetation coverage in the study area from 2000 to 2023.
Enlarge this image.Figure 3. Trend of changes in the vegetation coverage in manganese mining areas from 2000 to 2023.
Enlarge this image.Figure 4. Map for classifying the vegetation coverage changes in a typical manganese mining area from 2000 to 2012 (reference area (top); typical manganese mining area (middle and bottom)).
Enlarge this image.Figure 5. Map for classifying vegetation coverage changes in a typical manganese mining area from 2013 to 2023 (reference area (top); typical manganese mining area (middle and bottom).
Enlarge this image.Figure 7. Imagery of the untreated manganese mining area from 2012 (left) and 2022 (right).
Enlarge this image.Figure 8. The spatial evolution trend of vegetation cover in the manganese mining area from 2000 to 2012.
Enlarge this image.Figure 9. The spatial evolution trend of vegetation cover in the manganese mining area from 2012 to 2023.
Enlarge this image.Figure 10. Changes in temperature and precipitation in Yongzhou City from 2000–2022.
Enlarge this image.Figure 11. Curve showing the comparison of Fractional Vegetation Coverage (FVC) values between manganese mining areas and the reference area.
Key parameters of remote sensing imagery for different periods in the study area.
| Imaging Data | Satellite | Number of Bands | Wavelength | Spatial Resolution (m) |
|---|---|---|---|---|
| 2000/10/30 | Landsat7 | 7 | 0.45–2.35 | 30 |
| 2003/10/15 | Landsat4–5 | 7 | ||
| 2006/09/21 | Landsat4–5 | 7 | ||
| 2008/10/28 | Landsat4–5 | 7 | ||
| 2012/10/31 | Landsat7 | 7 | ||
| 2013/10/26 | Landsat8 | 8 | ||
| 2015/10/16 | Landsat8 | 8 | ||
| 2018/10/08 | Landsat8 | 8 | ||
| 2022/10/19 | Landsat8 | 8 | ||
| 2023/10/31 | Landsat8 | 8 |
Classification dynamic vegetation succession.
| Succession Type | D Scope (%) |
|---|---|
| Obvious degradation | D < −30 |
| General degradation | −30 < D < −15 |
| Slight degradation | −15 < D < −5 |
| Stable | −5 < D < 5 |
| Slight improvement | 5 < D < 15 |
| General improvement | 15 < D < 30 |
| Obvious improvement | D > 30 |
Note: D represents the difference between the vegetation cover assigned to the later year (year i) and the earlier year (year j). Succession types are used to categorize plant changes based on the D value into the following groups: substantial deterioration, overall deterioration, minor deterioration, stable, minor improvement, overall improvement, and substantial improvement.
Areas of different vegetation coverage categories in various periods in the mining area (unit: hm2).
| Year | 0–0.2 | 0.2–0.4 | 0–0.4 | 0.4–0.6 | 0.6–0.8 | 0.8–1 | 0.6–1 | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Areas | Percentage | Areas | Percentage | Areas | Percentage | Areas | Percentage | Areas | Percentage | Areas | Percentage | Areas | Percentage | |
| 2000 | 138.96 | 13.21 | 158.85 | 15.10 | 297.81 | 28.32 | 188.19 | 17.89 | 289.53 | 27.53 | 276.21 | 26.26 | 565.74 | 53.79 |
| 2003 | 199.35 | 18.92 | 175.59 | 16.67 | 374.94 | 35.59 | 256.05 | 24.30 | 304.20 | 28.87 | 118.44 | 11.24 | 422.64 | 40.11 |
| 2006 | 462.15 | 43.87 | 207.18 | 19.67 | 669.33 | 63.54 | 234.18 | 22.23 | 118.62 | 11.26 | 31.32 | 2.97 | 149.94 | 14.23 |
| 2008 | 573.30 | 54.42 | 181.98 | 17.27 | 755.28 | 71.69 | 142.38 | 13.51 | 108.18 | 10.27 | 47.70 | 4.53 | 155.88 | 14.80 |
| 2012 | 580.32 | 55.08 | 279.81 | 26.56 | 860.13 | 81.64 | 134.64 | 12.78 | 45.54 | 4.32 | 13.23 | 1.26 | 58.77 | 5.58 |
| 2013 | 598.95 | 56.85 | 256.95 | 24.39 | 855.90 | 81.24 | 128.88 | 12.23 | 51.12 | 4.85 | 17.64 | 1.67 | 68.76 | 6.53 |
| 2015 | 551.34 | 52.33 | 249.75 | 23.71 | 801.09 | 76.04 | 155.43 | 14.75 | 69.48 | 6.59 | 27.54 | 2.61 | 97.02 | 9.21 |
| 2018 | 494.37 | 46.92 | 264.24 | 25.08 | 758.61 | 72.01 | 193.59 | 18.38 | 83.79 | 7.95 | 17.55 | 1.67 | 101.34 | 9.62 |
| 2022 | 289.71 | 27.50 | 250.20 | 23.75 | 539.91 | 51.25 | 256.77 | 24.37 | 188.37 | 17.88 | 68.49 | 6.50 | 256.86 | 24.38 |
| 2023 | 278.82 | 26.47 | 148.94 | 23.63 | 527.76 | 50.09 | 264.33 | 25.09 | 191.88 | 18.21 | 69.57 | 6.60 | 261.45 | 14.82 |
Five classifications of vegetation coverage.
| Type | Vegetation Coverage Values |
|---|---|
| Very low | 0~0.2 |
| Low | 0.2~0.4 |
| Moderate | 0.4~0.6 |
| High | 0.6~0.8 |
| Very high | 0.8~1 |
Statistical table of graded Fractional Vegetation Coverage (FVC) in the reference area from 2000 to 2023.
| Year | 2000 | 2003 | 2006 | 2008 | 2012 | 2013 | 2015 | 2018 | 2022 | 2023 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Area (hm2) | ||||||||||||
| FVC Levels | ||||||||||||
| Very low | 39.15 | 119.79 | 17.64 | 117.99 | 10.89 | 59.76 | 87.75 | 8.1 | 125.91 | 113.67 | ||
| Low | 161.73 | 363.51 | 207.99 | 348.57 | 134.64 | 270.27 | 333.36 | 60.75 | 393.75 | 383.04 | ||
| Relatively low | 200.88 | 483.3 | 225.63 | 466.56 | 145.53 | 330.03 | 421.11 | 68.85 | 519.66 | 496.71 | ||
| Medium | 702.9 | 794.25 | 818.82 | 701.46 | 546.93 | 650.61 | 755.55 | 331.2 | 891.81 | 884.7 | ||
| High | 1337.04 | 1026.45 | 1404.09 | 991.08 | 1010.61 | 971.46 | 1119.24 | 1239.84 | 1381.32 | 1397.88 | ||
| Very high | 2689.47 | 2619.45 | 2474.91 | 2764.35 | 3220.38 | 2971.44 | 2627.55 | 32,836.32 | 2130.66 | 2144.16 | ||
| Relatively high | 4026.51 | 3645.9 | 3879 | 3755.43 | 4230.99 | 3942.9 | 3746.79 | 34,076.16 | 3511.98 | 3542.04 | ||
Classification data of dynamic vegetation succession.
| Succession Type | D Scope (%) | Area from 2000–2012 (hm²) | Area from 2012–2023 (hm²) |
|---|---|---|---|
| Obvious degradation | D < −30 | 620.01 | 43.74 |
| General degradation | −30 < D < −15 | 165.42 | 59.49 |
| Slight degradation | −15 < D < −5 | 90.27 | 74.61 |
| Stable | −5 < D < 5 | 80.28 | 162.27 |
| Slight improvement | 5 < D < 15 | 41.67 | 122.40 |
| General improvement | 15 < D < 30 | 35.01 | 236.43 |
| Obvious improvement | D > 30 | 20.16 | 354.69 |
Domestic policies.
| Issuance Date | Policy Document | Policy Sources |
|---|---|---|
| 2011 | Regulations on Land Reclamation | |
| 2012 | Implementation Measures for the Land Reclamation Regulations | |
| 2015 | Opinions of the Central Committee of the Communist Party of China and the State Council on Accelerating the Advancement of Ecological Civilization Construction | |
| 2015 | Overall Plan for Ecological Civilization System Reform | |
| 2016 | Soil Pollution Prevention and Control Action Plan | |
| 2016 | Guidance Opinions on Strengthening Geological Environmental Restoration and Comprehensive Management of Mines | |
| 2019 | Letter on Accelerating the Comprehensive Remediation of Open-pit Mines (Natural Resources Office Letter [2019] No. 819) | |
| 2021 | Opinions of the State Council Office on Encouraging and Supporting Social Capital Participation in Ecological Protection and Restoration | |
| 2021 | Management Measures for Key Ecological Protection and Restoration Funding (Financial and Ecological [2021] No. 100) | |
| 2022 | “14th Five-Year” Action Plan for Ecological Restoration of Historical Abandoned Mines | |
| 2021 | Hunan Province “14th Five-Year” Ecological Environment Protection Plan | |
| 2022 | Hunan Province Mining Ecological Restoration Fund Management Measures | |
| 2022 | Interim Regulations on Ecological Protection and Restoration in the Yongzhou Zeroing Manganese Mining Area |
Supplementary Materials
The following supporting information can be downloaded at:
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; Wang, Junke 1 ; Liu, Anfu 2 ; Li, Li 2 ; Zhu, Ruifeng 4 1 School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China;
2 Technical Centre for Soil, Agriculture and Rural Ecology and Environment, Ministry of Ecology and Environment, Beijing 100012, China;
3 School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China;
4 Technical Centre for Soil, Agriculture and Rural Ecology and Environment, Ministry of Ecology and Environment, Beijing 100012, China;