Demographic shrinkage promotes ecosystem services supply capacity in the karst desertification control

Although ecological services have been improved in karst desertification control areas, it is still unclear how population shrinkage affects ecosystem service supply capability through ecological assets. In this study, Theil-Sen median, regression analysis, and variance partitioning were applied to explore the linkages of population change (observed data and shared socioeconomic pathways 1-representative concentration pathways 2.6), ecological asset composition (land use), quality (Normalized difference vegetation index [NDVI] and tree height), and ecosystem services in different periods (population growth and decline periods). The results showed that the population change during the growth period (2000-2038) was dominated by migration patterns. In degraded ecoregions (karst desertification) dominated by population out-migration, the net expansion of forest was 15.88 % during 2000-2020, NDVI and tree height increased by 0.57 % and 54.96 %, and ecosystem service supply capability increased by 2.68 %. In contrast, in non-degraded ecoregions (non-karst and karst non-desertification) with population in-migration, change rates of forest (-5.40 % and - 23.68 %), NDVI (0.49 % and 0.53 %), tree height (-8.35 % and - 31.25 %), and ecosystem service supply capability (2.04 % and 2.18 %) were apparently lower than degraded ecoregions. During the population decline period (2039-2100), although the migration pattern between two regions during the growth period was replaced by a population drop within a single region, the positive correlation between population shrinkage with ecological assets and service supply capability was still followed. Overall, the study found that both ways of population shrinkage that involve out-migration and decline can alleviate the land pressure of degraded ecoregions, which enhances ecosystem service supply capability by regulating ecological assets.