Evaluation of an Ecological Network of Nature Reserves in Guangdong Province, and Suggestions for Ecological Restoration

The State Council of China has proposed the development and implementation of a 'land and space' ecological restoration plan, which is an essential component of ecological restoration, linking theoretical research to the application of land and space planning. Ecological network restoration is key to the systematic restoration of regional ecological functions. The fragmentation of regional habitats has blocked the exchange of species between island-like nature reserves, risking species degradation and weakening of ecological functions. This study uses the least cumulative resistance model to analyze potential ecological corridors. The nature reserves of Guangdong Province were used as the ecological source. Landscape types based on land-use categories, slope values based on a digital elevation model, and human interference based on land used for construction, were used as landscape, slope, human interference resistance surface correspondingly. The least-cost connectivity network was analyzed using a cost-connectivity tool in ArcGIS. The connections between the input nature reserves were considered as 1st level corridors and the connections between neighboring regions were considered as 2nd level corridors. By adding rivers and highway corridors to the 1st and 2nd level networks, we formed a Comprehensive Ecological Network (CEN). The CEN was evaluated using the α index, β index, γ index, and cost ratio. The results showed that: 1) In the Basic Ecological Network (BEN) composed of 1st and 2nd level potential ecological corridors, the α, β, and γ indices reached 0.54, 2.02 and 0.70, respectively, indicating that the BEN can enhance the structure of nature reserves in Guangdong Province and form effective linkages. 2) The river corridor of Guangdong Province, with its characteristic dendritic structure, improves the corridor structure and increases connectivity. By adding river corridors to the BEN we formed a River Ecological Network (REN), which has a more complete structure. However, because the river itself is a factor of greater resistance to the cross-strait matrix connectivity, the REN's α index (0.33), β index (1.64) and γ index (0.55) are lower than those of the basic ecological network. 3) By adding road corridors to the REN, we formed the CEN. The CEN's α, β, and γ indices reached 0.68, 2.34 and 0.79, respectively, indicating that the addition of road ecological corridors can compensate for the weakness of the REN, increase network closure, smoothen material and energy circulation, and increase the number of paths available for species diffusion, which plays an important role in stabilizing the ecological network. In the context of the current ecological restoration of territorial space, we suggest that 47 1st level ecological corridors and 52 ecological nodes should be constructed and restored. These corridors would connect to the Zhanjiang Mangrove National Nature Reserve in the west, Nanling National Nature Reserve in the north, Fengxi Provincial Nature Reserve in Dapu, Meizhou in the east, and Lianhua Mountain in the Huidong-Baipenzhu Water Source Forest Nature Reserve in the south, forming the primary ecological security network of Guangdong's nature reserves. The effects of this network would include: reducing the islanding effect of the nature reserves; promoting species exchanges between nature reserves; enhancing regional ecosystem service functions; and providing the core framework of ecological restoration and ecological security in Guangdong Province. This corridor analysis was performed at a regional scale, limiting its application when restoration work is on a small scale, such as a city or county. Therefore, more specific research is required.