Mapping conservation status and land use change drivers in Chilean espinal agroforestry systems using CORONA KH‑4B and Sentinel‑2 data (1972–2023)

Abstract

Abstract Over the past five decades, land-use change driven by government subsidies for tree planting—particularly of exotic species such as Pinus radiata and Eucalyptus spp.—together with irrigated agricultural expansion, has caused substantial declines in Chile’s ‘espinal’, an agroforestry system dominated by Vachellia caven . This study maps the conservation status of ‘espinal’ systems and assesses the main drivers of land-use change affecting ‘espinal’ in Mediterranean central Chile. We analyzed recent and historical satellite imagery covering approximately 38,000 km 2 to map ‘espinal’ extent and conservation status in 2023 and to reconstruct land-use changes between 1972 and 2023, with a detailed assessment of a 500,000 ha focus area in the Cauquenes region. ‘Espinal’ and other land uses were mapped using Sentinel-2 imagery and declassified CORONA KH-4B data. For 2023, ground-truth data from field surveys and drone imagery were used to train a random forest classifier on Sentinel-2 data and vegetation indices were used to stratify ‘espinal’ systems into conservation classes based on tree cover density. For 1972, ‘espinal’ and other land-use samples were visually interpreted from CORONA KH-4B imagery and used to train a comparable classifier, followed by post-classification change detection. In 2023, ‘espinal’ covered over 12,000 km 2 , comprising 5609.8 ± 1,056.9 km 2 of low-density, 5151.2 ± 727.8 km 2 of medium-density, and 1,786.0 ± 571.6 km 2 of high-density ‘espinal’. In the Cauquenes region, ‘espinal’ declined by more than 40% over five decades, mainly due to conversion to agricultural and forested land (83%), although localized re-establishment was observed. Greater distance from irrigation infrastructure and steeper terrain increased the likelihood of ‘espinal’ persistence and recovery. Despite its dramatic decline, ‘espinal’ remains the dominant land-use system in central Chile.