# Desertification Mitigation in Northern China Was Promoted by Climate Drivers after 2000
## 3 Results
### Shift in Desertification after 2000 in NC  
Studies suggested that a reversal of desertification occurred around 2000 [72; 73; 74]. Additionally, climatic factors, such as the near-surface air temperature, precipitation, and wind speed, have exhibited dramatic interdecadal variability [75; 76; 77]. Therefore, it was necessary to further analyze whether the impacts of climate drivers and human activity on desertification in NC have changed over the past three decades. As illustrated by the empirical orthogonal function (EOF) decomposition of NPP (Figure 5A), the spatial mode of NPP variability showed an east-west reversal pattern, with the explained variance of the first leading mode of the EOF (EOF1) accounting for 34.65% of the total. The principal component (PC1) of EOF1 showed temporal turning around the year 2000 (Figure 5B). Such a decadal shift was consistent with previous studies [78; 42; 79]. To further analyze the desertification shift around the 2000s in NC, a comparison of the spatial patterns of the linear trends in NPP between the periods of 1984-2000 and 2001-2014 is shown in Figure 6. The NPP growth rate greatly increased after 2000 (Figure 6A,B). Similar changes appeared for ANPP except in the northeastern DPR, i.e., the Ordos, Horqin, and Hulunbuir regions (Figure 6C,D). This may have been due to missing data in the Hulunbuir region, uncertainties introduced by the methodology of directly extrapolating ANPP from the long-term NDVI, or the degradation of the AVHRR sensors assimilated by the GLASS [80; 81]. The changes in NPP and ANPP corresponded to an opposite change in PNPP, which exhibited noteworthy decreases in most regions before 2000 and remarkable increases thereafter (Figure 6E,F). Meanwhile, the consistent patterns of change in HNPP (Figure 6G,H) and PNPP suggest opposite contributions of climate drivers and human activity to desertification in the Ordos, Horqin, and Hulunbuir regions. Before 2000, ANPP increased while PNPP decreased, indicating that human activity supported the mitigation of desertification in these regions while climate drivers had a negative effect. After 2000, PNPP showed an increasing trend, reflecting a positive effect of climate drivers on the mitigation of desertification, as reported by [PERSON] et al. [82], [PERSON] et al. [83], and [PERSON] et al. [84]. Figure 4: Different factors (human activity, climate drivers, and both) affected the (**A**) mitigation and (**B**) exacerbation of desertification during the period from 1984 to 2014. The inset figures in (**A,B**) represent the total areas of desertification mitigation and exacerbation, respectively, and the pie charts represent the contributions of each factor. As shown in Figure 7, desertification-mitigated areas in the DPR of NC increased by 17.89% after 2000 (67.16%) compared to before 2000 (49.27%). The main driving factors were also different. From 1984 to 2000, human activity exhibited a 44.8% contribution to the mitigation of desertification, which decreased to 18.9% from 2001 to 2014 (Figure 7(top,middle bottom)). Conversely, after 2000, the contribution of human activity to the exacerbation of desertification increased to 81.7%, while climate drivers exhibited only a 12.3% contribution (Figure 7(middle top,bottom)). It should be noted that we used ANPP because its algorithms have a physical meaning and it could be compared with PNPP. We also compared the results with those calculated directly based on the GLASS NPP (Figures S4 and S5). The results of the GLASS-based NPP data analyses were generally  
Figure 5: First leading mode of EOF (EOF1) for NPP in NC. (**A**) Spatial pattern of loading vectors. (**B**) Principal component (PC1) of EOF1. Figure 6: The spatial pattern of the linear trends (slopes) for (**A**) NPP, (**B**) ANPP, (**C**) PNPP, and (**D**) HNPP during the periods of (**A**,**C**,**E**,**G**) 1984-2000 and (**B**,**D**,**F**,**H**) 2001–2014.