3.1 Land use change status
Table 1 sets out the descriptive statistics of land use type areas and changes from 1990 to 2020. The dominant land use types in the study area are cropland, forest land and grassland, with the areas of 79346.29 km2, 74836.64 km2 and 45670.23 km2 in 2020, accounting for 36.95, 34.85 and 21.27 percentage of the study area, respectively. The area of forest land increased from 57142.74 km2 to 74836.64 km2 at a rate of 655.33 km2year-1, with the percentage increasing from 26.61 to 34.85%. The area of grassland decreased from 69226.26 km2 to 45670.23 km2 at a rate of 872.45 km2 year-1, with the percentage decreasing from 32.23 to 21.27%. Under the influence of human activities, the expansion of built-up areas was evident with the percentage increasing from 3.07 to 5.87%, and the area increasing from 6596.23 km2 to 12605.26 km2 at a rate of 222.56 km2 year-1.
Table 1 Descriptive statistics of land use type areas and changes from 1990 to 2020