## 4 Discussion
Future work characterizing these preferences in detail, e.g., through the use of GPS collars, will be of key importance to adequately calculate stocking rates of the different herbivores, adjusting them to the type of vegetation exploited, and optimizing the design and operation of management (thus, foraging) units. The resilience of the vegetation to the combination of environmental stress (strong inter-annual fluctuations in rainfall and phenology) and grazing pressure will be further compounded by the expected impact of climate change. According to the model predictions, increasing livestock densities will decrease vegetation resilience to decreased rainfall levels or delayed phenological peaks, thus exacerbating the impact of medium-term changes (2041-2070) in the quantity and temporal distribution of rainfall predicted by the climate change scenarios. Based on the predictions of a moderate scenario of the MIROC model, we may conclude that the END's vegetation will face increasingly constraining conditions for its development. Vegetation will face a 16.5% decrease in annual rainfall. This shortage is not homogeneous over time; hence, its effect is compounded by its temporal interaction with vegetation phenology. If vegetation maintains its current patterns of phenological development, most types (all but the shrubland) will face a larger decrease (17.8-18.8%) during the growth period; and, if it adjusts its development to the changes in rainfall distribution, its phenological peak will have to be significantly delayed to achieve the levels of rainfall at which their production peaks (ca. 60 days for grassland vegetation, Figure 4). Else, they will not be able to achieve these levels because the potential growth season will end, prior to the commencement of the period of prolonged summer drought (saltmarsh and bulrush marsh vegetation, Figure 4). The latter trend is particularly concerning because the delay in phenology necessary to achieve optimal rainfall will play against the general trend resulting from the concomitant increase in temperatures, i.e., an acceleration in vegetation phenology. Indeed, the observed phenological shift of vegetation in the Northern Hemisphere during recent decades reflects an advance of 0-12 days [62; 63; 64], which would result in even lower levels of accumulated rainfall for the END's vegetation. The moderate reduction in primary production caused by these changes in rainfall amount and patterns, especially in marshland vegetation (9-20% for the two upper panels of Figure 4), will become significantly stronger under a scenario of moderate to high herbivore pressure, which can be expected under current densities of domestic herbivores (e.g., 11-28% for densities of 0.15 individuals/ha in the two upper panels of Figure 4). The effect of moderate herbivore density is smaller in grassland vegetation, but accelerates strongly at higher densities (lowest panel, Figure 4). The overall result is a strong decrease in the resilience of vegetation production to climate change in the presence of moderate to high domestic herbivore pressure. These effects will have, in turn, major consequences on the secondary production of livestock, whose profitability and sustainability will be thus compromised [65; 66]. These results highlight the importance of considering local stressors in combination with predicted climatic conditions in order to better understand the complex evolution of specific habitats.