Ecosystem-Based Adaptation in the Reventazón River Basin, Costa Rica

The Reventazón River Basin, to the east of the country’s Central Valley, is a critical nexus of water, food, and energy in Costa Rica. Home to 500,000 inhabitants, the basin supplies the region’s eight hydropower dams (generating 38% of national energy), and the capital city, San Jose, with 25% of its drinking water.

The Reventazón region is also a productive agricultural area, supplying 85% of the country’s vegetable crops. Nature also thrives in the 25 protected wilderness areas around the basin, including more than 250,000 hectares of forests (almost the size of Hong Kong), which play a fundamental role in protecting water resources.

Climate change and land degradation threaten this, with variable rainfall causing unreliability in the water supply and the risk of severe erosion. Restoring the ecosystem is crucial to stabilize hydrology and ensure a reliable water and energy supply.

The World Resources Institute is working with local stakeholders to identify nature-based interventions to provide the services required for a sustainable ecosystem, funded by the Global Ecosystem-based Adaptation Fund. We worked with them to assess the costs and benefits of a proposed pilot project:

• Nature-Based Infrastructure scenario, consisting of reforestation, agroforestry, and the development of contoured croplands, to help regulate water flow, reduce erosion, and increase agricultural production.

Our assessment found that this nature-based approach would generate a total net benefit of USD 3.17 million, with each dollar invested in NBI yielding USD 1.23 in returns for society.

In this study, we also explored a more ambitious scenario, scaling the NBI in the pilot site to a basin-wide approach representing nearly twice the number of NBI activities. Here, we find USD 6.31 million net benefit for society over 30 years.