Figure 2
The map shows the outline of China divided into provincial regions, with each province filled using a specific color to represent intensity levels. A legend on the upper right explains the color coding, where “thin” is shown in light grey, “low” in light blue, “normal” in light green, “moderate” in green, “height” in saddle brown, “ultra-high” in red, and “nonedata” in white. Large areas of western and northern China appear in light grey, indicating “thin” levels. Several central and eastern provinces are shaded light blue and light green, representing “low” and “normal” levels. One eastern coastal province is shaded green, indicating a “moderate” level, while an adjacent coastal province is shaded saddle brown, indicating a “height” level. A small neighboring area is shaded red, indicating an “ultra-high” level. Provinces with no available data appear white. Blue boundary lines outline provincial borders, and island groups to the southeast are shown in the same boundary style, showing the geographic structure of China.The geographical distribution of population density across China. Note: Provincial-level population density is calculated by aligning the administrative regions from the 26th year of the Hongwu reign with current provincial boundaries. It is measured as the total population divided by land area (persons per square kilometer). The map illustrates the spatial distribution of population density across provinces, with colors representing different density levels as shown in the upper right corner