As habitats degrade worldwide, there is an increasing need to protect and restore natural areas to safeguard benefits they provide for humans and biodiversity. Riparian vegetation buffers generate many essential ecosystem services, and often provide disproportionately high levels of services relative to their spatial extent. Riparian zones are therefore a key habitat to focus restoration efforts. Many countries have laws protecting riparian buffers, but they often are not well-enforced. Using Costa Rica as a case study, we explore the consequences of implementing an existing riparian protection law, Forest Law 7575, which specifies an amount of natural habitat to be preserved around rivers. We model changes in nutrient retention, sediment retention, and carbon sequestration in both a baseline scenario, using current land use, and a simulated reforestation scenario, where riparian forests are increased as per law. We do this using InVEST, an open source software produced by The Natural Capital Project that creates spatially explicit maps of ecosystem services based on different land use scenarios.
Results/Conclusions
Our results show that reforesting riparian buffers in Costa Rica would increase all three selected ecosystem services. With restoration of riparian habitats, the nationwide carbon stock is projected to increase by almost 2 million Mg, a 0.6% increase above current levels. Sediment, nitrogen, and phosphorous export to streams are all projected to decline, with decreases of 8.6 million tons/year (12% of current levels), 2.2 million kg/year (5% of current levels), and 500,000 kg/year (5% of current levels), respectively. Our modeling also identified hotspot regions where adding riparian buffers would provide high levels of benefits across multiple ecosystem services, including areas in the provinces of Alajuela, Cartago, and San Jose. We found that even with a relatively small increase in national forest cover of under 2%, targeted reforestation in riparian zones can have an outsize impact on ecosystem services. We hope that this study can provide guidance on prioritizing riparian reforestation in Costa Rica, and serve as a model for assessing the importance of riparian vegetation globally.