The Potential Impact of Solar Geoengineering on Forest Productivity in Dryland Ecosystems

One of the leading ideas for reducing anthropogenic warming of the Earth is solar radiation management (SRM). An important concern is that SRM will have significant impacts on a wide range of ecosystems, most of which are not fully understood. Previous studies using data from volcanic eruptions and earth systems models suggest that increased diffuse radiation may result in an increase in forest gross primary production (GPP). These predictions are based primarily on understanding of temperate and tropical biomes; dryland vegetation may respond differently due to greater natural stress conditions and more narrow physiological safety margins. Climate change is predicted to expand dryland biomes, making it essential to understand how these ecosystems may respond to SRM. In this study we investigate the potential impact of SRM on dryland forest productivity, accounting for their high sensitivity to meteorological changes as a result of low water availability, high net radiation, and typically sparse canopy cover. We present data on how SRM may affect dryland forests using eddy covariance data in relation to variation in diffuse radiation resulting from suspended particulates (largely sand), greenhouse experiments to measure physiological and hydraulic effects of diffuse radiation, and global vegetation modeling. Because dryland forests are often an important resource for local communities, altering their functionality could have multiple adverse impacts. Our goal in combining leaf scale physiology and hydraulics, long-term data, and global modeling is to support the wise management of SRM in dryland regions.