What do we know about the albedo effect of afforestation and reforestation? A systematic synthesis of the scientific literature

Abstract Carbon dioxide removal (CDR) will play a crucial role in mitigating climate change and achieving net zero CO 2 emissions. As one technique of the CDR portfolio, afforestation and reforestation (A/R) is heavily relied on in both climate change mitigation scenarios and policy strategies. However, beyond CO 2 sequestration, A/R can have side effects that may affect its effectiveness in drawing global temperatures down, which is the ultimate aim of CDR. In our study, we focus on A/R’s impact on the Earth’s albedo. Here, we provide the first systematic overview of the albedo effect. We review and synthesize the existing evidence in the scientific literature and analyze patterns of the albedo effect. The results show a heterogeneous literature landscape with large areas of underrepresentation. Our collected data shows a reduced albedo in almost all cases, and different temperature responses on different scales. Considering the data heterogeneity and availability, our research findings show that more detailed research is needed to comprehensively assess the albedo impact of A/R and consider fine-grained site-specific factors such as topography.