Modeling multiple ecosystem services and beneficiaries of riparian reforestation in Costa Rica

Riparian buffers-forests along rivers-generate many essential ecosystem services, and their protection and restoration are the focus of many policy efforts. Costa Rica is a global leader in this regard, where legislative and executive frameworks work in concert to conserve forests that deliver public benefits such as water quality and carbon storage both locally and globally. Yet implementation and enforcement is an urgent challenge, and could benefit from high-resolution targeting with a quantitative understanding of expected benefits. Here, we under-take such an analysis, focusing on the benefits of implementing Forest Law 7575, which specifies the amount of forest to be preserved along rivers. We model changes in sediment retention, nutrient retention, and carbon sequestration from a baseline scenario based on current land use that is in partial compliance with the law. We contrast this with a simulated reforestation scenario, where riparian forest cover is increased to at least a minimum level of compliance (10 m buffers) everywhere. We find that targeted riparian refor-estation-increasing national forest cover by 1.9 %-would substantially increase ecosystem services. Water quality regulation would be improved via an increase of 3.9 % in sediment retention (1.4 Mt/year), 81.4 % in nitrogen retention (0.012 Mt/year), and 85.9 % in phosphorus retention (0.0022 Mt/year). Moreover, riparian reforestation would increase the national carbon stock 1.4 % above current levels (7.0 Mt). Our analysis shows where riparian buffers are most beneficial-generally in steep, erosion-prone, and intensively fertilized land-scapes. Through a canton-level analysis comparing potential increases in sediment and nutrient retention with demographic information, we find that these benefits would flow to communities that depend on rivers for drinking water and that are otherwise vulnerable. Small increases in riparian reforestation in Costa Rica, implemented via an existing law, could confer large benefits to rivers and all who depend on them.

Automated summary

Riparian buffers, such as forests along rivers, play a crucial role in providing essential ecosystem services. In Costa Rica, their protection and restoration efforts are supported by legislative and executive frameworks, aiming to conserve forests that deliver public benefits locally and globally. By conducting a detailed analysis, it was found that targeted riparian reforestation in Costa Rica can significantly improve water quality, increase carbon storage, and enhance other ecosystem services. These benefits are particularly important for vulnerable communities that rely on rivers for drinking water. Implementing riparian reforestation through existing laws could bring substantial benefits to rivers and those who depend on them.