Multitemporal soil loss analysis in the Chirripó Pacífico watershed, Pérez Zeledón, Costa Rica (1986–2019)

Soil erosion is a major threat to tropical mountainous ecosystems, where intense rainfall, steep slopes, and land use changes accelerate land degradation, undermining ecosystem services and agricultural productivity. In Latin America, deforestation, agricultural expansion, and extractive practices have worsened land degradation. Climate change scenarios, such as the Shared Socioeconomic Pathways (SSPs), show that future erosion risks depend on both climate and land use governance. This study applied the Revised Universal Soil Loss Equation (RUSLE) within a Geographic Information System (GIS) framework to evaluate soil loss in the Chirripó Pacífico River watershed, southern Costa Rica, over a 33-year period (1986–2019). We analyzed four benchmark years (1986, 1998, 2008, 2019) using rainfall and land cover data to generate multitemporal soil loss maps. Results show a substantial decline in average soil loss, from 17.9 Ton ha⁻¹·year⁻¹ in 1986 classified as “high” erosion to 6.5 Ton ha⁻¹·year⁻¹ in 2019, with an overall mean of 11.55 Ton ha⁻¹·year⁻¹, classified as “moderate” by FAO thresholds. This reduction is mainly due to increased forest cover (from 62.8% to 68.9%) and conservation policies implemented in the 1990s that limited land use on steep slopes. High erosion rates persisted in agricultural and pasture lands in the western watershed, while forested and reforested zones stayed in low to moderate erosion classes. Our findings highlight the value of RUSLE-GIS modeling as a decision-support tool for identifying erosion hotspots and guiding sustainable land management in vulnerable tropical environments.