# Vegetation Health in China Is Severely Compromised by Drought, Wet and Heat Stress Events
## 3 Results
### Characteristics of Stress Events  
China is experiencing a trend of warming and increased humidity, particularly in the western regions where the climate has become more humid over the past decade [42]. Drought stress has shifted from widespread and stable to more extreme. The average impact area of SPEI CD stress is significantly smaller than that of SM CD, occurring only in parts of Tibet, Qinghai, and Shaanxi (Figure 6a). In 2019, the SPEI CD in the three northeastern provinces reached a peak drought intensity of \(-8.2965\). SM CD reached its peak in 2001, impacting all regions except the Tarim Basin in Xinjiang, southwestern Tibet, parts of Qinghai, and western Inner Mongolia, and persisted throughout 2000 to 2020. In the three northeastern provinces, western Qinghai, Yunnan, western Sichuan, Guangxi, Hunan, and parts of Fujian, SM CD values exceeded \(-4\). In 2008, the maximum intensity of SM CD reached \(-41.8675\) (Figure 6b) with the most severe drought years concentrated before 2010. Notably, the Yunnan-Guizhou Plateau experienced severe drought stress in 2010 with Z values surpassing \(-20\). However, in parts of Xinjiang, Tibet, Gansu, and Yunnan, the most intense drought stress occurred after 2010 (Figure 6f).  
Figure 5: Trend and future persistence of VHI changes. (**a–c**) represent the spatial distribution of Sen’s slope, MK test, and Hurst exponent, respectively. (**d**) shows the changes in VHI for different vegetation types from 2000 to 2020.  
In the northern arid and semi-arid regions, influenced by a temperate continental climate, CPA is extremely low. As latitude decreases, CPA significantly increases in southern regions. The highest CPA was recorded in Guangxi in 2001 at 17.4597 m, while the lowest was in 2003 at 7.24901 m. After 2010, CPA decreased by an average of at least 61.02% compared to levels before 2010. Most parts of China experienced the strongest CPA post-2010, especially in the northern regions and the Northeast Plain (Figure 6c). Meanwhile,  
Figure 6: Characteristics of stress events from 2000 to 2020. (**a–d**) show the climatology of SPEI CD, SM CD, CPA (units: m), and CH (units: \({}^{\circ}\)C), respectively. (**e–h**) depict the years when the maximum values of SPEI CD, SM CD, CPA, and CH occurred. (**i–l**) present the normal distribution of SPEI CD, SM CD, CPA, and CH.  
the average CH is relatively strong in central and eastern Xinjiang, most of Qinghai, Inner Mongolia, parts of Sichuan, Guangdong, and Yunnan. In 2020, the strongest CH was observed in Tibet, Yunnan, and south China, reaching 5.48 \({}^{\circ}\)C, exceeding the annual average CH (0.7 \({}^{\circ}\)C) by 4.78 \({}^{\circ}\)C (Figure 6d).  
In 2020, CPA increased by 0.36 m to 2.21 m compared to the annual average of 1.85 m (Figure 6k), and it showed increases of 0.11 m and 0.48 m compared to 2010 (2.10 m) and 2000 (1.73 m), respectively. Correspondingly, drought stress as indicated by SPEI CD has generally declined over the past few decades, reaching its lowest average value of 0.07 in 2020 (Figure 6i). SM CD exhibited a similar downward trend, decreasing by 22% in 2020 compared to 2000 and by 20.67% relative to the annual average. Conversely, CH has continually increased over these decades, rising from 0.29 \({}^{\circ}\)C in 2000 to 0.86 \({}^{\circ}\)C in 2020, which is 22.85% higher than the annual average (Figure 6l).  
Simultaneously, in 2020, the probability of CH occurring in SM CD was 36.75%, which was an increase of 27.09% from 2000 (9.66%) and 13.03% higher than the annual average (23.72%). From 2000 to 2020, stress events have gradually shifted toward a warm and humid trend with a higher frequency of occurrence near latitude 30-40\({}^{\circ}\) (Figure S7). This change is characterized by increased CPA and decreased SPEI CD and SM CD, which is consistent with the increase in atmospheric moisture and more intense water cycle processes induced by global warming.