Restoring Brazil’s savannas: new techniques to quantify the carbon sequestration potential and water use of restoration projects

Abstract

The Brazilian Cerrado is a seasonally dry tropical savanna dominated region. Vegetation cover is highly heterogenous and spans a gradient of physiognomies ranging from fully open grasslands to closed canopy forests. Native vegetation is highly biodiverse and plays an important role in regional carbon and water cycling. Despite this, land-use-changes in the Cerrado have been extensive and, as a result, the potential to restore degraded or underutilized pastures in the region is high. However, relative to other tropical ecoregions, our understanding of the drivers of vegetation occurrence and distribution across these complex landscapes is limited and there have been few attempts to quantify the potential climate change mitigation payback and other benefits that may might be gained through restoration in the region. This thesis aims to quantify potential carbon, water and biodiversity paybacks from restoration and conservation in the Cerrado and to produce tools that facilitate restoration planning at a range of spatial scales. In the first empirical chapter a map of ‘hotspot’ areas for grassland, savanna and forest restoration is produced across the extent of the Brazilian Cerrado. Several areas are identified where restoration implementation may be easier, and potential carbon sequestration into biomass and flora biodiversity gains might be maximized. The second applied chapter assesses a methodology for producing detailed maps of cerrado vegetation using freely available satellite products. Physiognomy level maps of native vegetation are produced across a large case study region using a combination of surface reflectance and radar products, accounting for vegetation phenology, and burn events. In the final experimental chapter, the ecosystem level water and carbon balance of three functionally different cerrado grasslands (campo sujo, campo úmido and an exotic pastureland) is compared. Whilst each site displayed different phenological patterns, cumulative evapotranspiration was lower than precipitation at all sites, and each site was a net carbon sink over a 16-month monitoring period. Restoration and conservation of native vegetation in the Brazilian Cerrado, across arrange of vegetation types within the landscape, is likely to have a substantial climate change mitigation potential and be valuable in terms biodiversity protection and hydrological services.