Society's rapid economic development creates major challenges to the creation of nature reserves, especially in a region with high levels of ecosystem fragmentation. The reserves of the Pearl River Delta have different ecological functions and face different threats. At the same time, these nature reserves have different levels of protection and serve different purposes, such as the protection of local species and providing society with regionally protected areas. A comprehensive evaluation of nature reserves would lay a solid foundation for their management and for related policies and decision making. Three types of indicators were selected to facilitate acquiring comprehensive protection status for the nature reserves in Pearl River delta region: the size of the reserve, the level of threat from human activities, and the current level of management. An entropy method was used to make a comprehensive evaluation of the reserves. Each reserve was given a ranking from high to poor, based on a comprehensive look at all these factors. The results indicate:
(1) Seven of a total 48 nature reserves studied ranked high. Thirty ranked moderately high, 10 are moderately well protected, and only one is poorly protected. In general, although some of the nature reserves were ranked high, obvious differences in their layout and design exist, especially those in the cities of Shenzhen, Zhongshan, and Foshan, where new nature reserves should be added.
(2) Because the cities of Zhuhai and Huizhou have a relatively large number of nature reserves, these reserves have major differences. The design and geographic layout of nature reserves in Huizhou are relatively uniform, but in Zhuhai significant differences exist between them since some of the nature reserves are on oceanic islands. We conclude the protection level can be ranked as: Zhaoqing and Jiangmen > Shenzhen > Guangzhou and Huizhou > Foshan and Zhongshan > Zhuhai.
(3) Current research in nature reserve protection focuses on determining the appropriate size for nature reserves. Governments departments administering these areas are attempting to solve this important problem. In theory, increasing the size of a nature reserve may benefit the reproduction, growth, and survival of the living creatures there, but increasing the size has a limit to its benefits, especially when human-caused pressures and management goals are considered. So the appropriate size of each area should be determined. Our research indicates the overall quality of these nature reserves is closely related to their physical size. We used a regression model to select the most suitable sizes for them.
(4) Our results show an increase in the overall protection level of regional reserves is positively related to the geographic size of these areas. By constructing some high quality reserves with large geographic areas, the region can create core ecological reserves that preserve some ecological aspects of the original landscape. These reserves can also support the development of other reserves through an exchange of species and its influence on the local environment, but the size differences of these regional reserves should be small. The cooperation and coordination among nature reserves of various sizes, the level of protection each reserve provides, and species resources present should also be considered when designating a reserve.
(5) The influence of natural disturbances on the comprehensive protection of reserves is larger in coastal areas or in man-made ecological islands than it is in other types of reserves.