Safeguarding future water supplies by restoring fire-dependent longleaf pine savannas

Urbanization and agricultural expansion has increased the pressure on water resources in the Apalachicola-Chattahoochee-Flint (ACF) Basin over the past decades, revealing the need to integrate long term water planning with primary land management objectives for restoring fire-dependent longleaf pine savanna landscapes. The basin covers 51,200 km² in Georgia, Alabama, and Florida, and supplies water to 3 million people living in the greater Atlanta Metropolitan Area. Drought returns every 1 to 4 years and has the most significant impact during the summer when water demand for residential use and crop irrigation is highest. The gradual replacement of the natural longleaf pine savanna with loblolly pine plantations changes not only the forest structure, biodiversity and appearance of the landscape, but also the water balance---annual evapotranspiration in dense loblolly pine plantations is much higher than for open canopy longleaf pine savanna. Our simulations with the Soil & Water Assessment Tool (SWAT) suggest that the restoration of fire-dependent longleaf pine savanna can increase annual water production by up to 7% (1981-2010), and in the future possibly up to 12% (2041-2070). In view of growing water demand and competing water interests, longleaf pine savanna restoration can be especially beneficial for water supplies in the summer when water demand is highest.