Improving the estimation of grazing pressure in tropical rangelands

Abstract

Livestock grazing is a key land use globally, with major environmental impacts, yet the spatial footprint of grazing remains elusive, particularly at broad scales. Here, we combine livestock system indicators based on remote sensing and livestock vaccination data with a biophysical grass growth model to assess forage production, livestock carrying capacity, and grazing pressure on rangelands in the South American Dry Chaco. Specifically, we assess how considering different livestock systems (e.g. fattening in confinement, grazing with supplementary feeding, woodland grazing) changes estimations of grazing pressure. Our results highlight an average carrying capacity of 0.48 animal units equivalents (AUEs) per hectare for the Chaco (0.72 for pastures, 0.43 for natural grasslands, 0.37 for woodlands). Regional livestock requirements ranged between 0.02–6.43 AUE ha−1, with cattle dominating livestock requirements (91.6% of total AUE). Considering livestock systems with different production intensities markedly altered the rangeland carrying capacity and degradation estimations. For example, considering confinements and supplementary feeding drastically reduced the pasture area with potential overgrazing, from about 58 000 km2 to <19 000 km2 (i.e. 13.5% vs 5.7% of the total rangeland area). Conversely, considering the typically unaccounted-for cattle of woodland smallholders markedly increased the potentially degraded woodland area, from 3.2% (∼1000 km2) to 12.1% (3700 km2) of the total woodland area. Our work shows how ignoring production intensity can bias grazing pressure estimations and, therefore, conclusions about rangeland degradation connected to livestock production. Mapping indicators characterizing the intensity of livestock systems thus provide opportunities to understand better grazing impacts and guide efforts towards more sustainable livestock production.