Impacts of forests and forestation on hydrological services in the Andes: A systematic review
Bonnesoeur et al (2019) Forest Ecology and Management
This paper is a synthesis of 155 studies on the effects of afforestation (tree-planting on naturally non-forested land) in the Andes on hydrology, erosion and landslide reduction. In contrast to public perception in the Andes, the review found that, overall, non-native tree plantations, and to a lesser extent natural forests (except cloud forest), reduce downstream water supply compared to natural grassland. In particular, replacing natural grassland with non-native trees was found to decrease water yield by 40%. In contrast, afforestation on degraded soils (with native or exotic species) was found to increase soil infiltration and soil organic matter content, and reduce soil erosion and surface runoff, at least in low intensity rainfall events. The review concludes that while afforestation is beneficial for hydrological services and reducing erosion when on degraded soil, it should be avoided on degraded grassland, where native grass species should be allowed to naturally regenerate instead. However, more work is needed, in particular on assessing the hydrological services provided through restoration with native tree species. Direct article link.