Ecosystem restoration can lead to carbon recovery in semi-arid savanna grasslands in India

Semiarid savanna grasslands (SG) in India deliver enormous benefits to people and nature but are currently undergoing large-scale degradation. Soil carbon stocks in degraded SGs vary in response to land use and land management changes. Although there is increasing support for restoring grasslands by planting native grass species, its impact on soil carbon recovery is largely unknown. In this study, we undertake a plot-level investigation of soil and aboveground biomass carbon stocks to provide robust estimates of carbon densities across sites which have undergone restoration over the last 3 years. We compare these restored sites with a no-intervention control using a space-for-time substitution framework and two reference old-growth grassland sites. We find that SGs store significant amounts of carbon (11.57-26.76 tC/ha across 1- to 3-year restoration sites, respectively), with most of the carbon stored in soils (7.29-15.67 tC/ha across 1- to 3-year restoration sites, respectively). These estimates still remain well below the soil carbon stocks of the reference sites (range of 22.91-39.49 tC/ha). We demonstrate that soil organic carbon (SOC) stocks progressively increase with the age of grass plantings. The 3-year site shows an increase of 35% in SOC stocks compared to the no-intervention control and an increase of 30 and 21% in comparison to the 1- and 2-year sites, respectively. Our study demonstrates a robust approach to estimate soil carbon stocks in these ecosystems and highlights that effective conservation and restoration can enable SGs in India to act as natural carbon sinks at scale.