Population concentration and built-up land expansion are two prominent features of contemporary urbanization. Existing literature on the population aspect of urbanization has mostly focused on national and regional aggregates, and literature on the land development aspect has often relied on spatial case studies of individual cities or their meta-analyses. Using newly-available data, here we conduct the first global-coverage, spatial analysis of the relationship between (changes in) population and built-up land at multiple spatial scales, and compare to existing common beliefs about urbanization based on individual city studies. We find that population and built-up land show distinctly different spatial and temporal patterns (with a global correlation coefficient around 0.6). Contrary to common impressions, our results show that during recent decades, developed and developing regions across the world experienced comparable amounts of built-up land expansion. While meta-analyses have reported that built-up land in urban areas expands globally on average twice as fast as population grows, our results show the global change rates of built-up land and population are similar. Also, most global population, including what national statistics agencies call urban population, reside in areas with low land development levels (which are frequently less than 5% built up). These changes in perspective suggest that urbanization's potential large-scale impacts may need to be re-evaluated, and lead to best-practice recommendations for urbanization modeling and analysis. Especially, the common practice in large-scale earth system modeling of assuming demographically-defined urban population resides in areas with medium to high built-up land development levels should change.

中文翻译：

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全球人口和建设用地的不同时空格局

人口集中和建设用地扩张是当代城市化的两个突出特征。现有关于城市化人口方面的文献主要集中在国家和区域的总体上，而关于土地开发方面的文献往往依赖于个别城市的空间案例研究或其元分析。使用新获得的数据，我们在多个空间尺度上对人口（变化）与建成用地之间的关系进行了首次全球覆盖、空间分析，并与基于个别城市研究的关于城市化的现有共同信念进行了比较。我们发现人口和建成区显示出明显不同的时空模式（全球相关系数约为 0.6）。与一般印象相反，我们的结果表明，近几十年来，世界各地的发达和发展中地区都经历了相当数量的建设用地扩张。虽然荟萃分析报告称，全球城市地区建成用地的扩张速度平均是人口增长的两倍，但我们的结果表明，全球建成用地和人口的变化率相似。此外，大多数全球人口，包括国家统计机构所说的城市人口，居住在土地开发水平较低的地区（通常不到 5%）。这些观点的变化表明，可能需要重新评估城市化的潜在大规模影响，并为城市化建模和分析提出最佳实践建议。尤其，