Storylines of climatic impact-drivers relevant for forests: La Plata Basin, a hotspot for land-based mitigation

Abstract To limit global warming to 1.5 or 2° by 2100, carbon dioxide removal is essential. Currently, re- and afforestation are the main implemented carbon dioxide removal practices and will be key to mitigate climate change. La Plata Basin, located in South America, has been suggested in the literature as one of the most strategic regions in the world to implement these techniques, but the prosperity of forests and their capacity to act as a carbon sink under increasing climate change is not well studied in general, and even less so in the La Plata Basin. In this work, we study changes in climatic impact-drivers that are relevant for risk and impacts for tropical forests. We apply the dynamical storyline methodology to construct seasonal storylines, conditional on the response of large-scale circulation to global warming, of change in five climatic impact-drivers : mean near-surface air temperature, agricultural/ecological drought, fire weather, mean precipitation, and aridity. We construct two final storylines, by selecting self-consistent combinations of changes in large-scale circulation throughout the seasonal cycle. In this way we can assess the plausible simultaneous response of the five climatic impact-drivers as a function of global warming on both seasonal and annual timescales. We find that the northeastern La Plata Basin, a key region for re- and afforestation, has the most challenging climatic conditions for forests. Meanwhile, the southern La Plata Basin, a region where the natural vegetation cover is mostly grassland and has been suggested as a region for afforestation, has a more suitable future climate for forests. We highlight the importance of these kinds of regional studies because forest plantations remaining stable carbon sinks in a warming world is crucial to halt global warming. Furthermore, understanding whether the La Plata Basin can sustainably support large-scale forest expansion is crucial given its importance for water availability, agriculture, and energy production in the densely populated region.