A new approach to quantify grazing pressure under mediterranean pastoral systems using GIS and remote sensing

Abstract

ABSTRACT Pastoral systems based on grazing itineraries are very common along the Mediterranean region and provide an opportunity to manage the fuel load and reduce fire risk in the ecosystem. Daily and seasonal movements of flocks bring on different grazing pressure (GP) (sheep ha−1) over the landscape. This study presents an approach to model sheep GP under a Mediterranean pastoral system in the Northeast of Portugal. The GP in a given location depends on the distance from the stable to the parish border, the distance to the stable, the heads of livestock and their preference for land use and cover (LUC). The geoprocessing we applied in this study integrated several spatial databases: the latest official Portuguese vector mapping of land use and cover (COS2015) and administrative boundaries (CAOP2018), the livestock stables location, and Sentinel-2 Multispectral Images. During the geoprocessing, the stocking density (SD) (sheep ha−1) were calculated and spatially interpolated. Homogeneous LUC units (permanent crops; annual crops; forest; shrubland; grassland; water bodies) were obtained by Random Forest supervised classification algorithm (kappa = 89.3%; global accuracy = 91.2%). Boolean overlapping of the LUC classes obtained by the supervised classifier with the mask created from COS2015 provides the potentially grazed LUC classes. Integrating LUC preferences with SD allows calculating and mapping the GP. The most common GP class is 0–0.25 sheep ha−1. Seeing the GP per LUC class, a value of 1.84 sheep ha−1 was found in permanent crops, 1.73 in annual crops, and 1.25 in grassland, 0.88 in grazed forests and 0.84 in shrublands. The GP modelling and mapping could assist in the implementation of herding programmes aimed at reducing fire hazards at a parish or at a regional scale.