Shandong Provincial Key Laboratory of Water and Soil Conservation and Environmental Protection, College of Resources and Environment, Linyi University, Linyi 270600, China.
School of Geography and Tourism, Qufu Normal University, Rizhao 276826, China.
Int J Environ Res Public Health. 2022 Dec 1;19(23):16079. doi: 10.3390/ijerph192316079.
The accelerated urbanization process in China has led to land-cover changes, triggering a series of environmental issues as one of the major drivers of global change. We studied the land-cover changes in the built-up areas of 50 major cities in China from 1990 to 2015 with Landsat data combined with spectral unmixing methods and decision tree classification. The overall accuracy of urban land-cover type products with 30 m resolution was obtained as 84%, which includes impervious surfaces, bare soil, vegetation, and water bodies. Based on these land-cover type products, the results show that the urbanization of major cities in China manifests itself as a steep expansion of impervious surfaces (+32.91%) and vegetation (+36.93%), while the proportion of bare soil (-68.64%) and water bodies (-1.20%) decreases. The increase in vegetation indicates an increasing emphasis on greening during urbanization, which is especially vital for the sustainability of urban ecosystems. Increasing economic standards and population sizes are significantly correlated with impervious surface expansion and may be the main drivers of urbanization. Nationwide, there is a decreasing trend of shape complexity among different large cities, which indicates that landscape shapes will gradually become regular when cities grow to a certain level. Greenspace areas in the cities increased significantly during 1990-2015 and became more fragmented and tended to disperse across cities. These changes reflect the government's efforts to enhance urban ecosystem functions to serve the rapidly increasing urban population in China over the past three decades.
中国快速的城市化进程导致了土地覆盖变化，引发了一系列环境问题，成为全球变化的主要驱动因素之一。我们利用 Landsat 数据结合光谱分解方法和决策树分类，研究了 1990 年至 2015 年中国 50 个主要城市建成区的土地覆盖变化。30 米分辨率的城市土地覆盖类型产品的整体精度达到 84%，其中包括不透水面、裸土、植被和水体。基于这些土地覆盖类型产品，结果表明，中国主要城市的城市化表现为不透水面（+32.91%）和植被（+36.93%）的急剧扩张，而裸土（-68.64%）和水体（-1.20%）的比例减少。植被的增加表明，城市化过程中越来越重视绿化，这对于城市生态系统的可持续性尤为重要。经济水平和人口规模的提高与不透水面的扩张显著相关，可能是城市化的主要驱动因素。在全国范围内，不同大城市的形状复杂性呈下降趋势，这表明当城市发展到一定水平时，景观形状将逐渐变得规则。1990 年至 2015 年间，城市的绿地面积显著增加，变得更加破碎，并倾向于分散在城市之间。这些变化反映了政府为增强城市生态系统功能而做出的努力，以满足中国过去三十年来快速增长的城市人口的需求。
