Modelling gross primary productivity in tropical savanna pasturelands for livestock intensification in Brazil

Abstract

In the grass-fed cattle ranching sector, precise and accurate information on the available dry biomass for consumption is of fundamental importance for the economically and environmentally sustainable meat production. In extensive pasture areas, as those found in Brazil, the use of orbital remote sensing data can be instrumental for the fast retrieval of biophysical parameters related to biomass production, based on which the livestock intensification potential can be determined. Within this context, in this study we estimated the dry biomass production of the State of Goiás (located in the Cerrado biome) pasturelands based on the use of a new highly precise and accurate pasture map and MODIS MOD13Q1 NDVI images (normalized difference vegetation index). Gross primary productivity (GPP) estimates, at 250m spatial resolution, were derived based on the light use efficiency of Brachiaria brizantha (dominant pasture species in the Cerrado), which determines the amount of Absorbed Photosynthetically Active Radiation (APAR) that is utilized in carbon fixation. Considering the current Animal Unit (AU) per hectare and the estimated forage production, the cattle herd in Goiás could double (reaching about 40 million heads) without the need of expanding the existing pasture areas; i.e., with the appropriate information (as the one derived in this study), proper management practices, and adequate public policies, cattle ranching in Goiás (and in Brazil) can be substantially improved (regarding productivity gains), while preventing new deforestations and increases in GHG emissions.