Managing the forest-water nexus for climate change adaptation

Climate change can directly affect forest hydrology by altering precipitation, evapotranspiration, and streamflow generation, or indirectly by changing disturbance regimes and forest structures at multiple scales. Climate change impacts on the forest-water nexus across biomes are pervasive characterized by a great complexity and uncertainty, significantly impeding the design of adaptive forest watershed management to mitigate climate change risks. This paper reviews our current knowledge on the interactions between climate change and the forest-water nexus at the scales of individual tree, stand, and watershed. We found that climate change dramatically altered watershed hydrology in many parts of the world, with varying hydrological responses at multiple scales of tree species, forest types, climate types, and hydrological regimes. The streamflow response was often more pronounced in snow-dominated or water-limited watersheds, especially in watersheds with increasing droughts due to climate change and intensively managed plantations of either non-native tree species (e.g., Eucalyptus plantations in Brazil, Chile, Uruguay, and Australia) or young coniferous species. Climate change impacts can be compounded or offset by forest changes (i.e., deforestation, and forestation) through forest-climate interactions and feedbacks. Forest management can mitigate or aggravate the negative hydrologic impacts of climate change. Adaptive forest management is a prerequisite for managing the forest-water nexus in the face of climate change. Various forest management strategies aiming at maintaining optimal forest structure and high species diversity are recommended to enhance forest resistance and resilience to climate change and sustain water provision services from forests and other beneficial ecosystem services while minimizing negative impacts and risks of climate change.