Identification, spatial distribution, and associated factors of urban protected areas in China.

The increasing proximity between protected areas (PAs) and urban areas, which can lead to urban protected areas (UPAs), is now commonplace. Use of Euclidean distance to measure the distance between PAs and cities has not correctly portrayed the spatial relationship between PAs and cities. We devised an isochronous circle model to accurately measure the distance between 2706 national PAs in 5 categories and 2844 cities in China based on human accessibility to identify urban human activity-influenced protected areas (UHAIPAs) and to quantitatively analyze their distribution patterns and relationships with China's economy, population distribution patterns, and urban development indicators. Most of the PAs in China were established near cities. Of 2746 PAs in China, 18.35% (n = 504) became UPAs, and 58.27% (n = 1600), 16.72% (n = 459), and 3.31% (n = 91) of PAs were within 0-30, 30-60, and 60-90 min, respectively. Both UPAs and UHAIPAs in China in general exhibited obvious spatial aggregation characteristics (e.g., wetland parks and scenic areas), and there was a significant spatial dependence effect among characteristics. The degree of spatial distribution and aggregation of UPAs was correlated with 16 indicators across urban economic development, urban natural substrate, and urban policy support factors. Based on the results of our study, we call for various governments and scholars to focus on areas where wetland parks and PAs overlap with urban boundaries. It is important to emphasize the potential link between the development of agriculture, forestry, livestock and fisheries industries, and UPAs. Overall, we believe that examining the accessibility of PAs can more accurately measure the distance between PAs and cities, and more realistically reflect the possible impacts of urban human activities on PAs, which is helpful for strengthening the conservation and management of PAs.