# Impact of Natural and Human Factors on Dryland Vegetation in Eurasia from 2003 to 2022
## 3 Results  
### Spatiotemporal Vegetation Activities in Eurasian Drylands  
Between 2003 and 2022, the growth rates of the normalized vegetation index (NDVI), gross primary productivity (GPP) and solar-induced chlorophyll fluorescence (SIF) in the Eurasian drylands were 1.00 \(\times\)\(10^{-3}\) yr\({}^{-1}\) (\(p<0.01\)), 1.30 g C m\({}^{-2}\) yr\({}^{-2}\) (\(p<0.01\)) and 1.00 \(\times\)\(10^{-3}\) Wm\({}^{-2}\)um\({}^{-1}\)sr\({}^{-1}\)yr\({}^{-1}\) (\(p<0.01\)), respectively (Figure 2). This suggests a significant increase in vegetation greenness, productivity and photosynthetic capacity in  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Vegetation Trend**} & \multicolumn{2}{c}{**Predicted and Residual**} & \multicolumn{2}{c}{**Relative Contributions (\%)**} & \multirow{2}{*}{**Explanation**} \\  & \(slope_{pre}\) & \(slope_{pre}\) & & **Natural** & **Human** \\ \hline Improvement & \(>\)0 & \(>\)0 & \(\frac{slope_{pre}}{slope_{pre}+slope_{pre}}\times 100\) & \(\frac{slope_{pre}}{slope_{pre}+slope_{pre}}\times 100\) & Double \\ \cline{2-6} (\(slope_{obs}>0\)) & \(>\)0 & \(<\)0 & 100 & 0 & Natural \\ \cline{2-6}  & \(<\)0 & \(>\)0 & 0 & 100 & Human \\ \hline Degradation & \(<\)0 & \(<\)0 & \(\frac{slope_{pre}}{slope_{obs}}\times 100\) & \(\frac{slope_{pre}}{slope_{obs}}\times 100\) & Double \\ \cline{2-6} (\(slope_{obs}<0\)) & \(<\)0 & \(>\)0 & 100 & 0 & Natural \\ \cline{2-6}  & \(>\)0 & \(<\)0 & 0 & 100 & Human \\ \hline \hline \end{tabular}
\end{table}
Table 2: The relative contributions of natural change and human activities.  
the Eurasian drylands. In other words, over the past two decades, the Eurasian drylands have exhibited an increasing trend in vegetation activity.  
At the pixel scale, over the past two decades, the proportions of significant increases in NDVI, GPP and SIF in the Eurasian drylands were 29.22%, 36.97% and 41.90%, respectively (Figure 3). Spatially, except for the EEU (E. Europe), the increase in vegetation activity in ten sub-regions was consistent (Table 3). For NDVI, GPP and SIF, the increasing trend was the highest mainly in agricultural areas (Figure 1b), such as South Asia (SAS: 0.36 \(\times\) 10\({}^{-2}\) yr\({}^{-1}\), 0.31 \(\times\) 10\({}^{-2}\) g C m\({}^{-2}\) yr\({}^{-2}\) and 0.17 \(\times\) 10\({}^{-2}\) Wm\({}^{-2}\)um\({}^{-1}\)sr\({}^{-1}\)yr\({}^{-1}\)) and East Asia (EAS: 0.29 \(\times\) 10\({}^{-2}\) yr\({}^{-1}\), 0. 29 \(\times\) 10\({}^{-2}\) g C m\({}^{-2}\) yr\({}^{-2}\) and 0.16 \(\times\) 10\({}^{-2}\) Wm\({}^{-2}\)um\({}^{-1}\)sr\({}^{-1}\)yr\({}^{-1}\)). In contrast, for NDVI, GPP and SIF, only 2.31%, 1.19% and 2.92% decreased significantly (\(p\) < 0.05); the trend in EEU was the lowest (\(-\)0.02 \(\times\) 10\({}^{-2}\) yr\({}^{-1}\), 0.01 \(\times\) 10\({}^{-2}\) g C m\({}^{-2}\) yr\({}^{-2}\) and 0.003 \(\times\) 10\({}^{-2}\) Wm\({}^{-2}\)um\({}^{-1}\)sr\({}^{-1}\)yr\({}^{-1}\)) (Table 3).  
Figure 3: Spatial distribution of the temporal trends in normalized difference vegetation index (NDVI, (**a**)), gross primary productivity (GPP, (**b**)) and solar-induced chlorophyll fluorescence (SIF, (**c**)) during 2003–2022.  
Figure 2: Interannual variation of normalized difference vegetation index (NDVI, (**a**)), gross primary productivity (GPP, (**b**)) and solar-induced chlorophyll fluorescence (SIF, (**c**)) in Eurasian drylands during 2003–2022. Shading denotes 95% prediction intervals. All regressions were significant (\(p\) < 0.05, the Student’s \(t\)-test).