Composite index for soil-related ecosystem services assessment: Insights from rainforest-pasture transitions in the Colombian Amazon

Land use change is one of the major drivers of soil degradation, affecting the ability of soils to supply multiple ecosystem services (ES). Despite the growing importance of soil-related ES, there is a lack of comprehensive methodologies to systematize how land use change affects the ability of soil to supply them. Here, by using primary information on soil properties, we develop a series of indices to assess the impact of land use change on the ability of soil to supply five soil-related ES: support for plant growth (SES1), C storage (SES2), nutrient cycling (SES3), erosion control (SES4), and water regulation and aeration (SES5). We focus our analysis on the rainforest-pasture transition for extensive ranching in the Colombian Amazon. Despite the global importance of the Amazon Forest biome, the existing methodological and knowledge gaps restrict our understanding of the impacts of land use change in the region’s soil-related ES. The results revealed that the extensive conversion of forest to pasture degraded the soil’s ability to supply all measured soil-related ES, with a higher impact for SES2 (47% of soil C storage reduction), SES1, and SES4 (40% and 31% decline of related indices, respectively). According to the average scores for the three sites, the capacity of the soil to supply related ES is severely threatened by extensive ranching, causing a decline in the index from 99% in forest sites to 73% in pasture sites. A significant correlation among most indices revealed that the supply of the five soil-related ES is interdependent, with the indices of soil C storage and erosion control services being the major drivers of synergies and trade-offs. Our study highlights the importance of re-adjusting management practices to mitigate the negative historical impacts of pasture conversion on soil properties linked to soil-related ES.