Climate change mitigation through afforestation/reforestation: A global analysis of hydrologic impacts with four case studies

Background

While much attention is being given internationally to the opportunities for carbon sequestration to mitigate climate change, little attention is being paid to the environmental tradeoffs that are associated with these types of schemes. This study examines the implicit hydrologic dimensions of international efforts to mitigate climate change, specifically potential impacts of the Clean Development Mechanism-Afforestation/Reforestation (CDM-AR) provisions of the Kyoto Protocol (KP) on global, regional and local water cycles.

Research & methods

Modeling predicts significant impacts on local hydrologic cycles on runoff and surface water flows. However, large impacts are not predicted at regional or global scale due primarily to the current limit on carbon offset projects under the Kyoto Protocol. Predicted decreases in runoff range from 54% in drier areas to less than 15% in more humid areas. Almost 20% (144 Mha) of all land affected by CDM-AR show little or no impact on runoff and another 28% (210 Mha) show only moderate impact. About 27% (200 Mha), primarily in more arid areas, is in the highest impact class, exhibiting an 80–100% decrease in runoff.

Conclusions & takeaways

Factors other than climate, e.g. upstream/ downstream position, are found to be important in evaluating impacts. This study demonstrates that it will become increasingly important to consider implications on local to regional water resources, and how the hydrologic dimension of CDM-AR impacts issues of sustainability, local communities, and food security.