## 3 Results
### Model Predictions  
Plots of model predictions (Figure 5) show the combined effect of either rainfall or phenology, and the grazing pressure exerted by domestic ungulate species, including only those with significant effects on each vegetation type: horses for saltmarsh, cattle for bulrush marsh, cattle and horses (combined as \"livestock\") for grassland. (Shrubland is not included because there were no significant effects of domestic herbivores on it, and the effects of fallow deer were weak and dependent on 2-3 values of unusually high density). All plots show similar patterns: the decreases in primary production at lower rainfall levels or later phenological peaks are strongly accelerated at higher ungulate densities, reaching very low levels of plant production (<50% of the maximum), where they flatten out. Resilience to domestic ungulate grazing (showing as a vertical \"crest\" in the six panels) is relatively high at optimal rainfall and phenology. However, a displacement away from these conditions (both towards the left or the right part of the plots) causes production to drop as soon as moderate (0.1 cattle/ha for bulrush marsh, 0.2 livestock/ha for grassland) or even low (0.2 horses/ha for saltmarsh) densities of domestic ungulates are reached.  
Figure 5: _Cont_.  
The prediction plots also show that the medium-term changes (2041-2070) in the quantity and temporal distribution of rainfall predicted by the MIROC RCP4.5 climate change scenarios (REDIAM, 2014) [52] will probably cause a strong decrease in plant production, whose impact would be exacerbated at medium to high levels of livestock density. The effects of decreased rainfall levels are relatively moderate for the Donana vegetation, albeit particularly strong for saltmarsh type. However, they will be compounded by the prolonged period required to achieve comparable levels of accumulated rainfall,  
Figure 5: Model prediction plots describing the combined effect of climatology (either rainfall, left panels, or phenology, right panels) and grazing pressure exerted by domestic ungulate species, including only those with significant effects on each vegetation type. Note that the color palette varies among graphs, i.e., the same color does not indicate the same range of production values (as indicated at the contour plots) in all graphs. Vertical dashed lines indicate the observed (green color; 1961–2000) and predicted (red color; 2041–2070, using the MIROC RCP4.5 scenario) values of accumulated rainfall and phenological peak (calculated, respectively, for the mean day of occurrence of the phenological peak or the corresponding value of accumulated rainfall in our 2000–2014 data series), obtained from REDIAM’s ADVECRA (available at: [[https://kerdoc.cica.es/cc?tr=lang_es](https://kerdoc.cica.es/cc?tr=lang_es)]([https://kerdoc.cica.es/cc?tr=lang_es](https://kerdoc.cica.es/cc?tr=lang_es)) accessed on 20 October 2020). For simplicity, we pooled the (significant) effects of cattle and horse in a single factor named ‘livestock’, using a HGAM model with these variables pooled (which showed a 99% correlation with the predictions of the model with separate variables discussed above: see Figure A4, Appendix A).  
i.e., by the strong delays in phenology required to attain them, whose strong impact on plant production will cause severe drops in plant productivity (NDVI \(<\) 0.15, i.e., \(<\)50% of maximum values) at intermediate levels of livestock density. Overall, the results indicate that the vegetation will face a combination of lower productivity and shorter phenological cycles, in turn causing lower biomass yields and shorter growth periods, and thus a strong decrease in food quantity and quality for herbivores.