In March 2020, a group of Asian elephants in China's Yunnan Province traveled north from their original habitat in Xishuangbanna Dai Autonomous Prefecture, passing through Pu'er City, Yuxi City, Honghe Hani and Yi Autonomous Prefecture, and Kunming City, and returned safely after a long journey of more than 500 days and more than 1 300 kilometers. This event shows the world China's determination and actions for biodiversity conservation, and also puts forward new requirements for the conservation of Asian elephants, such as the construction of ecological corridors. On October 12, 2021, President Xi Jinping mentioned in his keynote speech at the Leaders' Summit of the 15th Conference of the Parties to the Convention on Biological Diversity: "The journey of Yunnan elephants to the north and back shows us the achievements of China's wildlife conservation. China will continue to promote the construction of ecological civilization, unswervingly implement the new development concept of innovation, coordination, green, openness and sharing, and build a beautiful China. ”
Asian elephant conservation status and human-elephant conflict
Population and distribution of Asian elephants
The Asian elephant (Elephas maximus) is the largest and most representative terrestrial vertebrate in Asia, and is the "engineer" of maintaining the forest ecosystem, with about 45 671-49 028 Asian elephants in the wild, distributed in 13 countries including India, Sri Lanka, Myanmar, Thailand and China. It is an Appendix I species of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), and is also a national first-class key protected wild animal in China.
The number and distribution of Asian elephants in China
Asian elephants are found in southern Yunnan Province and southern Tibet (Figure 1), and their populations continue to increase under strong protection from the mainland. In 2018, a background survey of wild Asian elephant resources in Yunnan, China, showed that there were at least 293 wild Asian elephants in Yunnan Province, a nearly threefold increase from 101 recorded in the first systematic survey of Asian elephants in 1976. In recent years, monitoring has shown that there are no unnatural deaths of wild Asian elephants in Yunnan Province, and there are constantly newborn baby elephants, and the current Asian elephant population is estimated to be well over 300. The survival of the largest (189) and smallest (12) Asian elephant populations in Yunnan Province was analyzed, and the results showed that there was no bottleneck in their survival in the near future.
The main protective measures that have been taken
In order to protect Asian elephants, China has established the Xishuangbanna National Nature Reserve and the Yunnan Nanrollhe National Nature Reserve, which are the main protection objects of Asian elephants, established the Xishuangbanna Asian Elephant Rescue and Breeding Center, built a number of Asian elephant food sources, artificial nitrate ponds, and Asian elephant monitoring towers, and used a large number of viaducts and tunnels in the construction of highways and the China-Laos-Kunwan Railway to avoid blocking the Asian elephant population and habitat. In addition, in order to protect Asian elephants, China also issued the Notice of the General Office of the State Council on the Orderly Cessation of Commercial Processing and Sales of Elephant Ivory and Ivory Products on December 30, 2016, which clearly requires the closure of ivory processing and sales sites, and the complete cessation of processing and sales of ivory and products by December 31, 2017.
Human-elephant conflict due to population growth
With the increase of the Asian elephant population, the original habitat environment has changed, and it is difficult to accommodate the growing Asian elephant population, resulting in the outward spread of the Asian elephant, and gradually approaching or even entering the human-dominated area, and the spatiotemporal overlap of human-elephant activities. According to the 2018 Asian Elephant Background Survey, only 22.9% of Asian elephants live in protected areas, 14.7% live on the edge of protected areas, and as many as 62.4% of Asian elephants live outside protected areas.
At present, human-elephant conflict has become the biggest challenge to the conservation and management of Asian elephants in mainland China. From 2013 to 2017, Asian elephants killed 24 people and injured 26 people in Yunnan Province, resulting in economic losses of 93.6603 million yuan. From 2011 to 2020, the Lancang-Menghai population (19 individuals) caused 31 deaths, more than 50 injuries, and economic losses of nearly 20 million yuan. In 2021, a total of 1 501 cases of losses caused by the northward migration herd were declared, and the damage was assessed at 5.1252 million yuan. After Asian elephants enter the human production and living areas, their living habits have changed significantly, eating a large number of crops, and entering villages to steal grain and salt. Eighty-three percent of residents in the vicinity of the Asian elephant area said they had suffered damage to their crops. At the same time, due to the frequent activities of Asian elephants around the village, the local residents are unable to carry out production activities such as tea picking and rubber harvesting in time, resulting in huge indirect losses and heavy psychological pressure. Despite this, there has never been an incident on the mainland in which an Asian elephant was retaliated for causing an accident that resulted in the death or injury of an Asian elephant. However, Asian elephant accidents still occur frequently, the threat to the safety of local residents' lives and property still exists, and the local economic development is also affected and delayed. In order to better protect Asian elephants, alleviating human-elephant conflict will be an important measure to achieve human-elephant coexistence.
The main current response to human-elephant conflict
Some studies believe that the number of accidents caused by Asian elephants is at the core of the relationship between the consequences of human-elephant conflict, so the work of mitigating human-elephant conflict should be carried out to reduce the number of accidents. At present, the mainland has carried out a lot of work to alleviate human-elephant conflicts, including monitoring measures based on drones, infrared cameras and Asian elephant early warning systems, protective measures such as electric pulse fencing and elephant prevention ditches, compensation measures such as public liability insurance for wildlife accidents, and protection measures such as the construction of food sources and nitrate ponds and habitat restoration. However, except for monitoring measures such as early warning systems, other measures have problems such as insufficient coverage, large investment but ineffective results, and unsustainability. Some foreign studies have evaluated the effects of some mitigation measures, and the results are similar. In Sri Lanka, for example, elephants often return to their places of origin after being returned to protected areas and further conflict erupts, while in India, Asian elephants have adapted over time to avoid warnings such as campfires and loud noises.
The necessity of building ecological corridors
Among the many ecological processes of species conservation, landscape connectivity is often crucial. With the development of economy and society, the large-scale rise of planting, the construction of linear transportation facilities such as highways and railways, and water conservancy facilities such as reservoirs, the destruction of natural vegetation has formed a large number of artificial isolation belts, resulting in the islandization and fragmentation of the habitat of Asian elephant populations in China, isolating Asian elephant populations in different "isolated islands", seriously hindering inter-population communication, and threatening the survival and development of Asian elephants. For example, the Banna-Pu'er population area is divided into two parts, east and west, the Lancang-Menghai population is stranded due to the inundation of the migration channel of the Jinghong Power Station built on the Lancang River, and the Mengla-Shangyong population is only active in the protected area near Laos due to the blockage of villages, towns, reservoirs and scenic spots. The overlapping space of human-elephant activities brings fierce human-elephant conflicts and contradictions, and threatens the life and property safety of residents in the surrounding communities of Asian elephant distribution areas and the protection of Asian elephant populations. For species such as the Asian elephant, which live in fragmented human-dominated habitats, the key to the long-term survival of the population depends on its ability to move freely through large landscapes.
The construction of ecological corridors between habitat patches can increase landscape connectivity, provide a larger habitat range, improve habitat structure and function, effectively alleviate population isolation, and ensure population communication, thereby reducing the intensity of agricultural land use by Asian elephants, reducing the impact on cropping industry, and alleviating human-elephant conflict. Ecological corridors can also increase species viability by mitigating landscape fragmentation caused by the conversion of natural habitats to human-dominated habitats. Ecological corridors connect habitat patches into an overall ecological protection network, which tends to be more resilient in the face of climate change, and species can be transferred to new habitats as climate refuge and increase access to resources. The use of natural and artificial Asian elephant ecological corridors to maintain and achieve landscape connectivity can also play a positive role in the migration of other wildlife plants. The reports of the 19th and 20th National Congresses of the Communist Party of China respectively pointed out that "the implementation of major projects for the protection and restoration of important ecosystems, the optimization of the ecological security barrier system, the construction of ecological corridors and biodiversity conservation networks" and "improve the diversity, stability and sustainability of ecosystems." Focusing on national key ecological function zones, ecological protection redlines, and nature reserves, we will accelerate the implementation of major projects for the protection and restoration of important ecosystems", and the construction of ecological corridors and biodiversity conservation networks has become one of the important measures to build a beautiful China.
The construction of the Asian elephant ecological corridor
Design Principles of the Asian Elephant Ecological Corridor
Existing research has demonstrated that the prerequisite for the conservation of species, habitats and ecosystems is to maintain the functional connections between patches. As one of the important measures for Asian elephant conservation, the ecological corridor aims to connect fragmented Asian elephant habitat patches, improve the connectivity of the entire landscape, help Asian elephants adapt to climate change, and enhance the survival capacity of Asian elephant populations. At the same time, climate change, such as rising temperature and decreasing precipitation, has led to changes in natural vegetation and land use, reducing the availability of food and water, and further affecting the suitability and distribution of Asian elephant habitats. Therefore, in the process of designing and planning the Asian elephant ecological corridor, it is necessary to clarify the range of Asian elephants, and fully consider that the movement and distribution of Asian elephants are affected by climate change, natural environment and human activities when they move long distances between habitat patches in search of food and shelter. As researchers pay more and more attention to ecological corridors, more and more methodological theories are applied to the identification of ecological corridors, and the least-cost path identification (LCP) identification method based on the minimum cumulative resistance model and the connectivity model based on circuit theory (hereinafter referred to as the "current model") are the two most commonly used methods. The minimum cumulative drag model can transform the influence of distance and landscape characteristics of species in habitat patches into spatial movement resistance that needs to be overcome to identify LCP, while the current model treats the movement process of species in the landscape as the movement of electric charges on the conductive plane to simulate their movement route and occurrence probability, and then evaluate the connectivity of habitat patches. The combination of the two models can complement each other's advantages and effectively identify the ecological corridors between habitat patches and the landscape elements that affect landscape connectivity.
Asian elephant ecological corridor design scheme
In the past 20 years, scholars have put forward many plans and suggestions for the planning of Asian elephant ecological corridors in China, but some of them are large in area, long distance, difficult to renovate, and costly (Fig. 2). At the same time, as the range of Asian elephants gradually moves northward, some of the corridors in the plan have either become Asian elephant activity areas, or are no longer suitable for Asian elephants due to environmental changes. Therefore, there is an urgent need to re-plan the feasible ecological corridor based on the current range of Asian elephants.
In view of the outstanding problems faced in the conservation of Asian elephants, such as natural habitat degradation, population isolation, and frequent human-elephant conflicts caused by climate change and land use change, this study summarized the technical process of ecological corridor planning as follows: "obtaining species distribution, identifying source patches and resistance surfaces, constructing corridors based on the least cost path model, analyzing corridor centrality through current model, Ecological pinch points and obstacle points—field investigation—adjustment and optimization of ecological corridor design—recommendation of corridor construction design scheme—long-term monitoring of wildlife use of ecological corridors", and based on several activity area patches of Pu'er-Banna Asian elephant population in 2020-2022 as the starting and ending points of the corridor, the difference between the habitat suitability index and the theoretical maximum value was used as the movement cost to reflect the relatively real movement resistance, and eight main ecological corridors were identified through the integrated circuit theory (Fig. 3).
The corridors identified by the model were investigated on the spot, and the ground features with large resistance values such as residential areas, roads, cultivated land, and fish ponds were marked, and the model parameters were adjusted to obtain the optimized corridors. The results of the optimized current model show that as the core of the landscape and the hub connecting the east and west, the source has a very high centrality, which is crucial for the connectivity of the whole landscape. The corridors connecting Dadugang Township, Mengwang Township, and Kangping Township to the east and west from the Puwen Corridor are all highly centralized corridors, which play an important role in the connectivity and integrity of the entire landscape and habitat and corridor network (Fig. 3), and should have a higher conservation priority. The resistance values of the two long-distance corridors, Mengwang-Jiangcheng Ecological Corridor (A) and Puwen-Nanping Ecological Corridor (B), are 37.71 and 26.64, which are relatively high, and it is difficult for Asian elephants to pass through the corridor, but their unit distance resistance is at a low level, and the passage of Asian elephant populations in the corridor is small, so the corridor needs to reserve a short-term stay area for Asian elephants. The resistance value of Mengwang Ecological Corridor (F) is between 8.85 and 5.39, which is relatively low, and the obstacle to the passage of Asian elephants is small, and the four corridors are located in the key area of landscape connectivity (high current density area) (Fig. 4), and Asian elephants are easier to pass through in the corridor.
Based on big data from long-term monitoring of Asian elephants and systematic field investigations, this study identified key ecological corridors connecting the current Asian elephant population. At present, the range of Asian elephants has expanded significantly, and the northward migration of the elephant herd has made the corridor area II (Fig. 2) proposed by Zhang et al. in 2015 now the main activity area, and it has good connectivity with the surrounding activity area, and there is no need for additional corridor planning. In addition, corridors 2 and 3 proposed by Huang et al. in 2019 (Fig. 2) have too high resistance values and low connectivity in the optimized current model, and these two corridors are not used in this scheme.
The technical process proposed in this project takes relevant influencing factors as variables, including the natural environment and human disturbance factors that directly affect the activities of Asian elephants, and the land use and vegetation changes indirectly affected by climate change, and water availability factors, which can more comprehensively reflect the migration resistance of Asian elephants. In addition, in the process of optimizing the Asian elephant ecological corridor, the effectiveness of the corridor function, the feasibility of specific implementation and the impact on the production and life of local residents were also considered, and the regional environment of the corridor was investigated and adjusted on the spot, so as to avoid difficult areas such as cultivated land, residential settlements and roads under the premise of ensuring the smooth passage of the Asian elephant population, connect and isolate the elephant herd, and alleviate the human-elephant conflict. The corridor planning scheme based on empirical research will also provide strong support for the construction of Asian elephant national park.
Recommendations to advance the conservation of Asian elephants
In 2010, the Fifth Plenary Session of the 17th Central Committee of the Communist Party of China emphasized the need to accelerate the construction of a resource-saving and environment-friendly society, improve the level of ecological civilization, actively respond to global climate change, vigorously develop circular economy, strengthen resource conservation and management, increase environmental protection, strengthen the construction of ecological protection and disaster prevention and mitigation system, and enhance the capacity for sustainable development. The Communist Party of China (CPC) has put forward the idea of ecological civilization construction, adhered to the overall planning of the management of mountains, rivers, forests, fields, lakes, grasslands and sands, maintained ecological balance, promoted green development, and realized the organic unity of economic development and ecological civilization construction. In order to better protect the Asian elephant, the "engineer" of the forest ecosystem, the following four protection measures are proposed according to the population, distribution status and protection needs of the Asian elephant in mainland China.
Construct an Asian elephant conservation engineering system with national parks as the carrier. Guided by the concept of "mountains, rivers, forests, fields, lakes, grasslands and sands are the community of life", we should strengthen the ecological restoration and construction of damaged ecosystems in the region, promote the conservation of regional biodiversity of natural and artificial ecosystems, and maintain the comprehensive ecological service functions of regional ecological balance. The construction of the Asian elephant conservation engineering system can achieve full coverage of the Asian elephant conservation work in the mainland, enhance the natural exchange of Asian elephant populations and genes, promote the recovery of the Asian elephant population, alleviate human-elephant conflicts, provide a scientific basis for the protection of Asian elephants and the layout of nature reserves such as national parks, and provide scientific and technological support for promoting the harmony between man and nature and the sustainable development of regional economy and society.
Construct an ecological corridor network of Asian elephants to connect isolated Asian elephant populations. Taking national parks and nature reserves as key nodes, the "habitat-ecological corridor" network system should be scientifically constructed, the spatial structure of ecological corridors should be optimized, the environmental quality of ecological corridors should be improved, landscape connectivity should be enhanced, and the isolated populations of Asian elephants should be connected through the ecological corridor network. In the design process of Asian elephant ecological corridors, it is necessary to fully consider the dispersal capacity of Asian elephant populations and their habitat needs for food, water and shelter, and avoid large areas of farmland, villages and other densely populated areas and linear infrastructure of roads and railways. Carry out overall planning for Asian elephant habitats, carry out zoning management, and continue to improve the Asian elephant habitat protection system. Based on the trend of Asian elephant population dispersal, adjust and optimize the planting structure of Asian elephants in the distribution area, supplement food resources and build artificial nitrate ponds in the core activity areas of Asian elephants, supplemented by protective measures such as fencing and elephant ditches, and actively guide Asian elephants to return to nature reserves and promote harmonious coexistence between Asian elephants and humans. Through the design and demonstration of the Asian elephant ecological corridor, the integrity and connectivity of the ecosystem can be effectively enhanced, the construction and protection of "ecological islands" can be prevented, and the concept of "lucid waters and lush mountains are invaluable assets" can be practiced.
Create a new model of broad social participation in Asian elephant conservation. Establish and improve a government-led, multi-participatory mechanism for the long-term conservation of Asian elephants, improve laws and regulations related to biodiversity and wildlife conservation, improve the regulatory capacity of national parks and nature reserves, and strive to promote the harmonious coexistence of man and nature. The government and all sectors of society should actively carry out publicity and education on the conservation of Asian elephants and other rare and endangered species, make full use of mobile phones, television and other online channels to publicize the achievements and contributions of Asian elephant conservation, and raise public awareness of biodiversity and ecological protection. At the same time, we should give full play to the advantages of scientific research institutions, strengthen technical support and personnel training, and continue to promote the construction of ecological civilization. In the field of Asian elephant conservation, cross-border cooperation among Asian elephant range countries can promote technical exchanges, jointly formulate conservation strategies, work together to build transnational ecological corridors, and work together to combat illegal poaching, so as to create a good living environment for Asian elephants. In addition, it is necessary to carry out long-term monitoring of Asian elephants, continue to improve the monitoring and early warning system of Asian elephants, collect genetic information of Asian elephants and individuals, and establish corresponding archives, and actively promote the shelter, treatment and wild release of Asian elephants and other rare and endangered species. Actively carry out compensation for wildlife accidents, compensate for the losses caused by Asian elephants to local residents through public liability insurance for wildlife accidents, and build a modern ecological system in which humans and elephants coexist in harmony.
Strengthen basic research on Asian elephants and guide the scientific conservation of Asian elephants. Focusing on the scientific frontiers and key technical problems of Asian elephant conservation, we will carry out in-depth research on Asian elephant behavior, ecology, physiology, habitat, population structure, population genetics, etc., so as to provide theoretical basis and technical support for the scientific protection and effective management of Asian elephant population, and provide scientific guidance for better resolving human-elephant conflicts and even dealing with the relationship between humans and nature. Through the exploration of the feeding habits and suitable habitat characteristics of Asian elephants, it can be applied to the habitat transformation and food source construction of Asian elephants, so as to enhance the attractiveness of native habitats to Asian elephants. To analyze the movement patterns and dispersal trends of Asian elephants among various patches, to grasp the factors driving the spread of Asian elephants, and to guide the movement and return of Asian elephant populations to nature reserves. Try a variety of monitoring methods such as global positioning system (GPS) positioning collars, infrared camera arrays, unmanned aerial vehicle patrols, and community joint monitoring, train Asian elephant monitors in professional skills, strengthen the efficiency of Asian elephant monitoring, and release early warning information in a timely and efficient manner, so as to ensure the safety of humans and elephants and reduce conflict losses.
(Authors: Jacky Li, Qiupeng Yu, Zhechang Hu, Xuelong Jiang, Key Laboratory of Biodiversity and Ecological Security in Gaoligong Mountain, Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences.) Contributed by Bulletin of the Chinese Academy of Sciences)