Changes in dryland areas and net primary productivity in China from 1980 to 2020

The drylands of China account for about 10.8% of the global dryland. They are severely affected by human activities and climate change. Dynamic changes in the drylands and within subtype (hyper-arid, arid, semi-arid, and dry sub-humid) areas, and the spatiotemporal characteristics in net primary productivity (NPP) of vegetation, are crucial for evaluating ecosystem functions and management strategies in China. This study defined drylands, and the area was determined based on the aridity index (AI). Our results demonstrated the drylands of China expanded from 5.8 million km 2 in 1980 to 6.6 million km 2 in 2020, with an average expansion rate of 0.019 × 10 6 km 2 (10 yr) −1 . These changes were driven mainly by the mean annual temperature (MAT) and solar radiation (Srad). Among the different subtypes of drylands, the arid and semi-arid areas expanded the fastest at 0.032 × 10 6 km 2 (10 yr) −1 , and the main driving factor was MAT. However, the hyper-arid area decreased in size at an average rate of 0.050 × 10 6 km 2 (10 yr) −1 , and the main driving factor was mean annual precipitation (MAP). Net primary productivity (NPP) of total vegetation and subtypes increased over 20 years. The NPP of the whole dryland increased at a rate of 10.78 g C m −2 yr −1 , which was dominated by the rapid growth of NPP (5.15 g C m −2 yr −1 ) in dry sub-humid areas. The NPP of four vegetation types (desert, grassland, forest, and cropland) increased (19.14 Tg C yr −1 ); the NPP in the forest and cropland increased considerably, while that in the grassland and desert increased slightly. The drylands in China might further expand with global warming because the MAT strongly affects the changes in dryland areas. With the development of eco-environmental protection projects (afforestation, construction of desert highway protection forest, etc.) and western region development and construction in China, the contribution of forest and cropland to the total NPP of all vegetation will increase. Research Highlights The drylands of China expanded from 5.8 million km 2 in 1980 to 6.6 million km 2 in 2020, with an average expansion rate of 0.019 × 10 6 km 2 (10 yr) −1 . These changes were mostly driven by the annual average temperature (MAT) and solar radiation (Srad). The NPP of the whole dryland increased at a rate of 10.78 g C m −2 yr −1 , which was dominated by the rapid growth of NPP (5.15 g C m −2 yr −1 ) in dry sub-humid areas. The NPP of four vegetation types (desert, grassland, forest, and cropland) increased (19.14 Tg C yr −1 ).