Evaluation of Prioritized Natural Landscape Conservation Areas for National Park Planning in China

: Protecting representative natural ecosystems, rich biodiversity, and unique natural landscapes are the main considerations in China’s national park planning. Here, we mapped the distribution of China’s natural landscapes and evaluated their protection values for national park planning and construction. Grading evaluation methods combining standard comparison, inventory method, and expert consultation were used, and four levels of natural landscapes were identiﬁed. Furthermore, priority areas for national parks establishment were also proposed. Of all the landscapes evaluated, 76 were extremely important, 481 were important, 2070 were moderately important, and 1213 were slightly important. A total number of 67 priority areas for natural landscapes were identiﬁed with a total area of 1,218,000 km 2 . They comprised land and sea areas of 1,148,000 and 69,000 km 2 , respectively. We suggest strengthening natural landscape protection by establishing natural parks in priority areas. Our study will contribute to the e ﬀ ective protection of natural landscapes in China.


Introduction
"Establishment of protected area system with national parks as an essential part" is currently an important concept in the nature protection declaration in China [1]. National parks constitute the most important element in nature protection as they represent high-priority natural ecosystems, natural landscapes, natural heritage sites, and biodiversity [1,2]. The uniqueness and protection priority of natural landscapes are consequently important criteria for establishing national parks in China.
The International Union for Conservation of Nature (IUCN) defines national parks as "large natural or near natural areas set aside to protect large-scale ecological processes, along with the complement of species and ecosystems characteristic of the area, which also provide a foundation for environmentally and culturally compatible spiritual, scientific, educational, recreational and visitor opportunities" [3]. Consequently, according to the conditions of China's natural resources and the requirements for declaring national parks, China's national parks include strictly protected and managed areas designated to conserve the authenticity and integrity of natural ecosystems, landscapes, and habitats of rare and endangered animals and plants that are representative of the country [4]. They constitute the most important aspects of China's natural ecosystems, the most unique natural landscapes, and its natural heritage and rich biodiversity. National parks have global value and are recognizable national symbols [2]. feature. They included geological landforms, rivers, lakes, wetlands, wildlife, and other elements of scenic beauty with high aesthetic and scientific values. Under the premise of strict protection, such areas can be used for scientific research, education, tourism, and other activities. These landscapes have features of both authenticity and protected value. Considering that the majority of the natural landscapes were included in existing protected areas, the existing protected areas collected from different government departments were the major sources for landscape evaluation. They included world heritage areas, world geoparks, Ramsar wetlands of international importance, nature reserves, scenic areas, geoparks, forest parks, desert parks, wetland parks, and ocean parks. In addition, supplemental data outside the protected areas were obtained from China National Geography, China Heritage Sites, China Domestic Travel, China View and other books, magazines, and websites related to geography, tourism, and sceneries. These areas met two criteria: a large-scale natural area with aesthetic or scientific value, and unique landscape characteristics. A total of 3840 natural landscapes were selected, including 3758 from protected areas, and 82 from the literature. The data basically covered the major natural landscapes across the entire mainland of China, which was the scope of this research. For each item of landscape data, we collected basic attributes including names, protected targets, area, landscape features, locations, scopes, or boundaries to be used in further analysis.
Based on the collected information and related criteria we divided the natural landscapes into four types (i.e., terrestrial, hydrological, biological, and meteorological landscapes) and 17 contents (Table 1). These criteria are "Scenic Spot Planning Rules" [23], "Touristic Resources Classification, Investigation and Evaluation" [24], and "China Forest Park landscape resources grade evaluation" [25].

Natural Landscape Evaluation Criteria
We developed assessment criteria for natural landscapes with reference to guidelines and assessment criteria of different protected areas in China and other countries, such as "Guide to World Heritage Sites" [26], "World Geopark Network Guidelines and Standards" [27], and "China Recommended Appraisal Procedures and Standards of World Geoparks" [28]. More detailed guidelines can be found in the references [29][30][31][32][33][34]. Five indicators included typicality, aesthetics, authenticity, integrity, and historical and cultural values were considered in these criteria, and each indicator was divided into four classes (i.e., extremely important, important, moderately important, and slightly important) ( Table 2).

Grading of Natural Landscapes
Considering the large number of natural landscapes and the lack of detailed information for many non-famous natural landscapes, we adopted a grading evaluation method. Simple and objective methods were used in the evaluation of low-level landscapes, and complex and subjective expert consultation was used for high-level landscapes. The grading evaluation had three phases as shown in Figure 1. According to the evaluation criteria, natural landscapes were evaluated and selected from a low to a high level, using existing protected areas and literature data as the main landscape sources. Selected moderately important natural landscapes from slightly important natural landscapes according to the "standard comparison" method; selected important natural landscapes from moderately important natural landscapes according to the "inventory" method; and selected extremely important natural landscapes from important natural landscapes according to the "expert consultation" method.
In the first phase, we used the standard comparison method to select landscapes of a moderately important level or above. If natural landscapes were in an existing protected area, we compared its related protected area standard [23][24][25][26][27][28][29][30][31][32][33][34] with the requirements of the natural landscape standard ( Table 2). If the natural landscape area was not a protected area, we compared information from the literature with the natural landscape standards. In this phase, slightly important landscapes were eliminated and the others remained for the second phase.
In the second phase, we used the "inventory" method to select landscapes of an important level or above. All attributes including names, protection targets, protection levels, locations, types, and landscape characteristics were used. Moderately important landscapes were eliminated and the others remained for the third phase in accordance with the natural landscape evaluation criteria.
The third phase utilized the "expert consultation" method to select extremely important landscapes. An expert evaluation indexes system was established (Table 3), which contained national representativeness, authenticity, integrity, historical and cultural value, and other necessary conditions for national park constructions, the importance of ecological location, urgency, feasibility, and noninterference [4]. In this phase, important landscapes were eliminated and extremely important landscapes were selected. According to the evaluation criteria, natural landscapes were evaluated and selected from a low to a high level, using existing protected areas and literature data as the main landscape sources. We separated moderately important natural landscapes and level above from slightly important natural landscapes according to the standard comparison method, separated important natural landscapes and level above from moderately important natural landscapes according to the inventory method, and separated extremely important natural landscapes from important natural landscapes according to the expert consultation method.
In the first phase, we used the standard comparison method to select landscapes of a moderately important level or above. If natural landscapes were in an existing protected area, we compared its related protected area standard [23][24][25][26][27][28][29][30][31][32][33][34] with the requirements of the natural landscape standard ( Table 2). If the natural landscape area was not a protected area, we compared information from the literature with the natural landscape standards. In this phase, slightly important landscapes were eliminated and the others remained for the second phase.
In the second phase, we used the inventory method to select landscapes of an important level or above. All attributes including names, protection targets, protection levels, locations, types, and landscape characteristics were used. Moderately important landscapes were eliminated and the others remained for the third phase in accordance with the natural landscape evaluation criteria.
In the third phase, we utilized the expert consultation method to select extremely important landscapes. An expert evaluation indexes system was established (Table 3), which contained national representativeness, authenticity, integrity, historical and cultural value, and other necessary conditions for national park constructions, the importance of ecological location, urgency, feasibility, and noninterference [4]. In this phase, important landscapes were eliminated and extremely important landscapes were selected.

Boundary Determination of Priority Areas for Natural Landscape Protection
Three principles were considered in the determination of the boundaries of priority areas for natural landscape protection. First, priority areas should contain the extremely important natural landscapes, integrated with adjacent areas with the same type of natural landscape. This ensured the integrity of the natural landscapes. Second, the boundaries of protected areas containing natural landscapes can be used, especially those of nature reserves. Third, the boundaries were demarcated according to natural geographical boundaries, such as ecosystems, vegetation, landforms, and rivers.

Grading of Natural Landscapes
A total of 3840 natural landscapes were comprehensively evaluated. Of them, 76 were extremely important landscapes, 481 were important landscapes, 2070 were moderately important landscapes, and 1213 were slightly important landscapes ( Figure 2, Table 4). The extremely important natural landscapes were located in the great mountains, rivers, and lakes with high levels of representative, authenticity, and integrity. The slightly important natural landscapes were places for public leisure and recreation with aesthetics and tourist attraction, and strong accessibility with a relatively small area and moderate authenticity.
There were more natural landscapes in eastern and central China, and the majority were at moderately and slightly important levels with relatively low value, small area, and good accessibility. On the contrary, there were fewer natural landscapes in western China (including northwestern and southwestern regions) with high proportions of extremely important and important natural landscapes. Many landscape areas were large wilderness areas with high authenticity and integrity.

Natural Landscape Types and Distribution
Due to the relatively low representation of moderately and slightly natural landscape, extremely important and important natural landscapes were selected for classification. Of 254 terrestrial landscapes, 92 were hydrological landscapes, 211 were biological landscapes, and 66 were meteorological landscapes (note that meteorological and other landscape types overlapped) ( Figure  3).
Terrestrial landscapes mainly included mountains, deserts, canyons, Danxia landforms, karsts, volcanoes, natural relics, coasts, and islands. Of them, mountain landscapes were mainly distributed along China's main mountain ranges, desert landscapes were mainly in arid and semi-arid areas in northwestern China, and canyon landscapes were mainly along large mountains and rivers. Danxia landscapes were mainly distributed along the southeastern coast, central-southern China, parts of northwestern China, karst landscapes in Guangxi, Guizhou, Yunnan, and Chongqing in southwestern China, and volcanic landscapes mainly in Heilongjiang, Jilin, Yunnan, and Hainan. Besides, two types of natural relic landscapes (i.e., geological and paleontological relics) were relatively scattered, and coasts and islands were distributed along China's southeastern coastal areas.
Hydrological landscapes mainly included river, lake, and marsh wetlands, and waterfalls. Of them, river and lake wetland landscapes were distributed along China's main water systems, coastal shoal landscapes along the eastern coast, and forest swamp wetland landscapes were mainly within

Natural Landscape Types and Distribution
Due to the relatively low representation of moderately and slightly natural landscape, extremely important and important natural landscapes were selected for classification. Of 254 terrestrial landscapes, 92 were hydrological landscapes, 211 were biological landscapes, and 66 were meteorological landscapes (note that meteorological and the other landscape types overlapped) (Figure 3).
Terrestrial landscapes mainly included mountains, deserts, canyons, Danxia landforms, karsts, volcanoes, natural relics, coasts, and islands. Of them, mountain landscapes were mainly distributed along China's main mountain ranges, desert landscapes were mainly in arid and semi-arid areas in northwestern China, and canyon landscapes were mainly along large mountains and rivers. Danxia landscapes were mainly distributed along the southeastern coast, central-southern China, parts of northwestern China, karst landscapes in Guangxi, Guizhou, Yunnan, and Chongqing in southwestern China, and volcanic landscapes mainly in Heilongjiang, Jilin, Yunnan, and Hainan. Besides, two types of natural relic landscapes (i.e., geological and paleontological relics) were relatively scattered, and coasts and islands were distributed along China's southeastern coastal areas.
Hydrological landscapes mainly included river, lake, and marsh wetlands, and waterfalls. Of them, river and lake wetland landscapes were distributed along China's main water systems, coastal shoal landscapes along the eastern coast, and forest swamp wetland landscapes were mainly within the Greater and Lesser Khingan areas in northeastern China. In addition, volcanic lake landscapes were mainly distributed in Heilongjiang and Jilin in northeastern China, wetland desert oasis landscapes in northwestern China, alpine meadow wetland landscapes in southwestern China, salt lake landscapes mainly in the Qinghai-Tibet Plateau, and waterfall landscapes were distributed in the karst area in southwestern China.
Biological landscapes mainly included forests, grasslands, meadows, and rare animal and plant habitats. Among them, forest landscapes were mainly representative forest ecosystems in northeastern and southern China, and grassland and meadow landscapes were mainly distributed in Inner Mongolia, the Qinghai-Tibet Plateau, and the Tianshan hinterland, among other areas. In addition, rare animal and plant habitats were mainly distributed in the central Qinling Mountains, Qinghai-Tibet Plateau, plains along the central and lower reaches of the Yangtze River, and northeastern China.
Meteorological landscapes mainly included the sun, moon, stars, clouds, mist, ice, and snow. Of them, sun, moon, and star landscapes mainly included sunrise and sunset (in Tai Mountain), Buddha light (in Mount Emei), aurora (in Greater Khingan Mountains), and starlight (in Bosten Lake) landscapes. Besides, cloud, mist, ice, and snow landscapes mainly included cloud-mist and snow-ice landscapes, such as the Huangshan Sea of Clouds, Lushan Waterfall, and Great Khingan Mountains Arctic Village snow and ice landscape.

Priority Areas for Natural Landscape Conservation
A total of 67 prioritized areas for natural landscape conservation were identified. Prioritized areas covered a relatively large area in western China, and small areas in eastern and central China (Figure 4). The southwestern region was dominated by mountains, animal and plant habitats, plateau lakes, marsh wetlands, and canyons, including the Qomolangma, giant panda habitats, Qinghai Lake, Zoige Wetland, and Three Parallel Rivers Area. Northwestern China was dominated by mountains and deserts, including the Tianshan Mountain, Qilian Mountain, Kumutag Desert, and Alashan Desert. Northeastern China was mainly comprised of mountain, forest, grassland, and wetland

Priority Areas for Natural Landscape Conservation
A total of 67 prioritized areas for natural landscape conservation were identified. Prioritized areas covered a relatively large area in western China, and small areas in eastern and central China (Figure 4). The southwestern region was dominated by mountains, animal and plant habitats, plateau lakes, marsh wetlands, and canyons, including the Qomolangma, giant panda habitats, Qinghai Lake, Zoige Wetland, and Three Parallel Rivers Area. Northwestern China was dominated by mountains and deserts, including the Tianshan Mountain, Qilian Mountain, Kumutag Desert, and Alashan Desert. Northeastern China was mainly comprised of mountain, forest, grassland, and wetland landscapes, including the Changbai Mountain, Greater Khingan Mountain virgin forest, Hulun Buir Grassland, and Lesser Khingan Mountain swamp wetland. Central and eastern China were dominated by mountains, wetlands, karst, Danxia landform, and other unique landforms, including Shennongjia, Poyang Lake, northern Jiangsu coastal wetland, Lijiang River landscape in Guilin, and Wuyi Mountain.
landscapes, including the Changbai Mountain, Greater Khingan Mountain virgin forest, Hulun Buir Grassland, and Lesser Khingan Mountain swamp wetland. Central and eastern China were dominated by mountains, wetlands, karst, Danxia landform, and other unique landforms, including Shennongjia, Poyang Lake, northern Jiangsu coastal wetland, Lijiang River landscape in Guilin, and Wuyi Mountain.

Conservation Efficiency of Priority Areas for Natural Landscape Conservation
Priority areas for natural landscape conservation covered an area of 1,233,000 km 2 , with a land area of 1,162,000 km 2 , accounting for 12.1% of the total national land surface. The priority areas covered a sea area of 71,000 km 2 , accounting for 1.5% of the nation's territorial waters. These areas contained all of the extremely important landscapes and 94 (i.e., 20%) of the important natural landscapes. They also covered 178 moderately important and 48 slightly important natural landscapes. Generally, the priority areas achieved a high degree of protection of representative national natural landscapes.

Discussion
For the first time, we evaluated the status of natural landscapes in China and identified priority areas for conservation. We found that natural landscapes in western China had a lower density, covered a larger area, and had a higher proportion of extremely important landscapes compared to those in Central and eastern China (Table 5). Similarly, priority areas in Western China were also larger (on average 851,000 km 2 ) than in Central China (on average 112,000 km 2 ) or eastern China (on average 270,000 km 2 ). These might be an intergraded reason of natural condition and human disturbance. Western China is an ecologically fragile area, with very high elevation and arid areas. The region has large areas of wilderness and very low human population density. Natural landscapes in this region are large mountains, deserts, grassland or habitats for large mammals, with a very high level of integrity. Priority areas such as Hoh Xil and Qiangtang Plateau have large areas. On the contrary, the natural environments in central and eastern China were more suitable for human

Conservation Efficiency of Priority Areas for Natural Landscape Conservation
Priority areas for natural landscape conservation covered an area of 1,233,000 km 2 , with a land area of 1,162,000 km 2 , accounting for 12.1% of the total national land surface. The priority areas covered a sea area of 71,000 km 2 , accounting for 1.5% of the nation's territorial waters. These areas contained all of the extremely important landscapes and 94 (i.e., 20%) of the important natural landscapes. They also covered 178 moderately important and 48 slightly important natural landscapes. Generally, the priority areas achieved a high degree of protection of nationally representative natural landscapes in China.

Discussion
For the first time, we evaluated the status of natural landscapes in China and identified priority areas for conservation. We found that natural landscapes in western China had a lower density, covered a larger area, and had a higher proportion of extremely important landscapes compared to those in central and eastern China (Table 5). Similarly, priority areas in western China were also larger (on average 851,000 km 2 ) than in central China (on average 112,000 km 2 ) or eastern China (on average 270,000 km 2 ). These might be an intergraded reason of natural condition and human disturbance. Western China is an ecologically fragile area, with very high elevation and arid areas. The region has large areas of wilderness and very low human population density. Natural landscapes in this region are large mountains, deserts, grassland or habitats for large mammals, with a very high level of integrity. Priority areas such as Hoh Xil and Qiangtang Plateau have large areas. On the contrary, the natural environments in central and eastern China were more suitable for human habitation, with higher population density and larger scales of urbanization and transportation construction. After a long period of development, the remaining natural landscapes had a low level of integrity and a small area. Therefore, for the large surface area and fragile ecological environment in western China, large-scale human activities including illegal entering, tourism development, grazing, hunting, fishing, and logging should be restricted in the priority areas. Within the priority areas in central and eastern China, measures should be taken to protect the authenticity and integrity of natural landscapes, and strengthen regional comprehensive conservation and management. We used diversified methods to evaluate natural landscapes in China. Most existing evaluations of natural landscapes were for small-scale areas, and were used in urban or rural planning, landscape planning, and ecological planning [13][14][15]21,22]. Both perception and technical approaches have been used frequently. Perception approaches, like visual landscape assessment and the scenic beauty estimation method, were from a subjective perception to evaluate the aesthetic value and uniqueness of natural landscapes and scenery. Technical approaches such as remote sensing and GIS were from an objective perception to evaluate landscape integrity, authenticity, and quality. However, the aims of this study focused on natural landscape conservation by evaluating the aesthetics, integrity, uniqueness, and authenticity of natural landscapes on a national scale. It was difficult to meet these needs using these two methods. Therefore, based on previous standards and evaluations of protected natural landscapes, grading evaluation methods combining standards comparison, inventory, and expert consultation were adopted. This allowed for the final identification of priority areas for natural landscape conservation. The research methods improved on traditional evaluation methods and explored the values of natural landscapes based on existing research resources.
Our study will contribute to achieving effective protection of natural landscapes in the face of the new protected areas system [35]. In terms of the landscape construction requirements of the new protected area system, national parks mainly protect nationally representative natural landscapes, nature reserves mainly protect natural landscape areas of special significance, and nature parks mainly protect important natural landscapes with aesthetic value [1]. Based on the level classification of natural landscapes, we suggest that extremely important natural landscapes should be candidate areas for national parks. Important and some moderately important natural landscapes with high comprehensive values should be candidate areas for nature reserves. The remaining moderately important and slightly important landscapes should be candidate areas for natural parks.

Conclusions
From a macro perspective, natural landscapes on a national scale were evaluated for the first time in this study, by obtaining priority natural landscape characteristics, determining the spatial distribution of valuable natural landscapes, and proposing priority areas for national parks. Three main conclusions were reached. First, we graded natural landscapes into four levels depending on their typicality, aesthetics, authenticity, integrity, and historical and cultural values. Of the four levels of landscapes, 76 were extremely important, 481 were important, 2070 were moderately important, and 1213 were slightly important. Second, the numbers of natural landscapes in eastern and central China were higher than in western China, however, the average area was much lower in western China. Third, a total of 67 priority conservation areas were identified, which were mainly distributed in western China. They covered a total area of 1,233,000 km 2 which comprised land and sea areas of 1,162,000 km 2 and 71,000 km 2 , protecting a high degree of representative national natural landscapes.
The purpose of this research was to recognize the value and distribution of natural landscapes by evaluation, and propose candidate areas for national parks. However, several limitations might exist. Firstly, natural landscape data was incomplete, and some precious natural landscapes might not be covered in the existing protected areas and literature in this study. Secondly, the methods require improved accuracy and objectivity. Thirdly, the boundaries of priority areas should be adjusted for the establishment of natural parks or other types of protected areas. In the future, solutions to these problems need to be identified, and more efficient and reasonable protection measures of natural landscapes is required by the establishment of national parks, nature reserves, and nature parks.