Projected vegetation changes are amplified by the combination of climate change, socio-economic changes and hydrological climate adaptation measures

Climate change is projected to strongly affect the hydrological cycle, altering water availability and causing successive shifts in vegetation composition and distribution. To reduce potential negative effects on vegetation, policymakers may implement hydrological climate adaptation measures, which may -in turn- require land use changes to be successful. Policy driven land use changes should therefore be taken into account when evaluating climate change and adaptation effects on the water-vegetation system, but this is rarely done. To support such policy interventions, we applied a coupled land use – hydrology – vegetation model to simulate effects of (i) climate change, (ii) socio-economic change, (iii) hydrological measures and (iv) policy driven land use change, alone and in interaction, on vegetation communities in the Netherlands. We simulated two climate scenarios for 2050 that differed in predicted temperature (+0.9 °C and +2.8 °C) and precipitation changes (groundwater recharge +4% or −14%). The associated socio-economic scenarios differed in the increase of gross margins per agricultural class. The land use changes concerned agricultural changes and development of new nature areas from agricultural land. Individually, land use changes had the biggest effect on vegetation distribution and composition, followed by the hydrological measures and climate change itself. Our results also indicate that the combination of all four factors triggered the biggest response in the extent of newly created nature areas (+6.5%) and the highest diversity in vegetation types, compared to other combinations (max. +5.4%) and separate factors. This study shows that an interdisciplinary, coupled modelling approach is essential when evaluating climate adaptation measures.