Assessing the pasturelands and livestock dynamics in Brazil, from 1985 to 2017: A novel approach based on high spatial resolution imagery and Google Earth Engine cloud computing

Abstract

The livestock activity accounts for a large part of the transformations in land cover in the world, with pasture areas being the main land use in Brazil and the main livelihood of the largest commercial herd in the world. In this sense, a better understanding of the spatial-temporal dynamics of pasture areas is of fundamental importance for a better occupation and territorial governance. Moreover, because they provide different ecosystem services, pastures play a key role in mitigating climate change and in meeting GHG emission reduction targets. Within this context, and based on Landsat image processing via machine learning methods in a cloud computing platform (Google Earth Engine), this work has mapped, annually and in an unprecedented way, the totality of the Brazilian pastures, from 1985 to 2017. With an overall accuracy of about 90%, the 33 maps produced indicated the pasture area varying from ~118 Mha ±3.41% (1985) to ~178 Mha ±2.53% (2017), with this expansion occurring mostly in the northern region of the country and to a lesser extent in the midwest. Temporarily, most of this expansion occurred in the first half of the period evaluated (i.e. between 1985 and 2002), with an increase in Brazilian pasture areas of ~57 mha in just 17 years. After 2002, this area remained relatively stable, varying between ~175 mha ±2.48% and ~178 mha ±2.53% by 2017. In 33 years, about 87% of the mapped areas experienced zero, one, two, or three land-cover / land-use transitions; overall, of the ~178 mha ±2.53% of existing pastures in 2017, ~52 mha are at least 33 years old, ~66 mha were formed after 1985, and ~33 mha may have undergone some reform action in the period under consideration. The dynamics revealed in this study reinforce the thesis of pasture utilization as a land reserve, and demonstrate the importance of these areas in the economic, social, and environmental aspects of Brazil.