Smartphone-based photogrammetry for biomass assessment in North African highland rangelands

Source Agritrop Cirad (agritrop.cirad.fr) International audience Moroccan pastoralism, sustaining millions across 70% of agricultural lands, faces desertification, overgrazing, and climate variability in semi-arid steppes, threatening grassland resilience. This study develops a cost-effective protocol to estimate pasture biomass, enhancing sustainable grazing management. In a field mission in Ifrane-Timahdite, 60 vegetation circles (66 cm diameter, 0.33 m2) across three pastoral farms, selected for species diversity (33–63 species), were filmed using iPhone 11 Pro smartphones with hemispherical scanning for high-density 3D reconstruction (4.81 points/m2). Photogrammetry via Pix4Dmapper generated digital surface models to derive vegetation volumes, and an RGB index was calculated to characterize vegetation cover. Dry biomass, measured through destruc-tive sampling (oven-dried at 70°C for 48 h), was correlated with volumes using a linear regression (80% training, 20% test), achieving a robust correlation. This non-destructive, scalable approach, leveraging accessible smartphones, enables precise pasture monitoring despite spatial heterogeneity. By supporting adaptive grazing, it strengthens resilience in pastoral systems, balancing pastoral livelihoods and biodiversity conservation. Future integration with drone and satellite data will enhance national-scale predictions, offering a replicable framework for sustainable pastoralism in vulnerable semi-arid regions.