# Increasing Ecosystem Fluxes Observed from Eddy Covariance and Solar-Induced Fluorescence Data
## 3 Results
### Spatiotemporal Variations in Global WUE
Meanwhile, ECSIF products showed positive trends of 0.0019 \(\pm\) 0.00048 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-2}\) in WUE, with regional hotspots over Eastern China, India, Europe, Sahel, and northwestern US (Figure 7d), where cropland is usually located [78]. However, the ensemble satellite-based products revealed positive trends close to 0 (0\(\pm\) 0.00206 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-2}\)) for WUE (Figure 7e), which differed from the trends of 0.0008 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-2}\) in PML-V2, \(-\)0.0028 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-2}\) in MODIS, and 0.002 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-2}\) in X-BASE. The trends in WUE for ECSIF and X-BASE demonstrate a high degree of spatial coherence, particularly in the Northern Hemisphere, South America, and Australia (Figure S4). Semi-mechanistic products showed larger differences globally, likely due to the varying models used in the two products. MODIS WUE displayed significant decreasing trends in Africa, Australia, and the Middle East, primarily because the positive trends in ET exceeded the positive trends in GPP in these regions. This imbalance resulted in a negative trend in global WUE (Figure S5a-c). In contrast, PML WUE showed a broader decline across the tropics, driven by higher ET trends relative to GPP at low latitudes, along with severe GPP declines in parts of Africa and South America. These declines were offset by significant increases in WUE in much of the Northern Hemisphere, including Europe, Central Asia, and parts of North America, ultimately resulting in a slight positive trend in global WUE for PML (Figure S5d-f). The most pronounced differences were observed in tropical regions, attributed to the strong positive ET trends derived from ensemble products (Figure 6e). Therefore, the accurate estimate of GPP and ET is of great importance to better understand ecosystem carbon and water fluxes and their coupling. For different PFTs, forests exhibited a larger WUE (2.73 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-1}\)) than non-forests (1.58 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-1}\)). The largest WUE of 3.14 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-1}\) was observed in DBF, while the lowest was 1.27 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-1}\) in GRA. Croplands showed an intermediate WUE of 2.19 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-1}\). Similarly, the trend for forests (0.0018 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-2}\)) was higher than that for non-forests (0.0008 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-2}\)). Within forests, DNF, ENF, and MF all showed significant positive trends ranging from 0.0017  
Figure 7: Long-term (**a**) mean and (**d**) trend in water use efficiency (WUE) derived with ECSIF and their comparisons with the (**b,e**) ensemble products during 2001–2020. Differences are shown in (**c,f**). to 0.0048 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-2}\). In contrast, DBF and EBF showed insignificant trends of 0.0002 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-2}\) and \(-\)0.0004 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-2}\), respectively. For non-forests, CRO and GRA showed positive trends of 0.0042 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-2}\) and 0.0037 g C kg\({}^{-1}\) H\({}_{2}\)O yr\({}^{-2}\), respectively, while the others showed no significant trends (Table S2).