Nature‐based solutions (NbS) to climate change currently have considerable political traction. However, national intentions to deploy NbS have yet to be fully translated into evidence‐based targets and action on the ground. To enable NbS policy and practice to be better informed by science, we produced the first global systematic map of evidence on the effectiveness of nature‐based interventions for addressing the impacts of climate change and hydrometeorological hazards on people. Most of the interventions in natural or semi‐natural ecosystems were reported to have ameliorated adverse climate impacts. Conversely, interventions involving created ecosystems (e.g., afforestation) were associated with trade‐offs; such studies primarily reported reduced soil erosion or increased vegetation cover but lower water availability, although this evidence was geographically restricted. Overall, studies reported more synergies than trade‐offs between reduced climate impacts and broader ecological, social, and climate change mitigation outcomes. In addition, nature‐based interventions were most often shown to be as effective or more so than alternative interventions for addressing climate impacts. However, there were substantial gaps in the evidence base. Notably, there were few studies of the cost‐effectiveness of interventions compared to alternatives and few integrated assessments considering broader social and ecological outcomes. There was also a bias in evidence toward the Global North, despite communities in the Global South being generally more vulnerable to climate impacts. To build resilience to climate change worldwide, it is imperative that we protect and harness the benefits that nature can provide, which can only be done effectively if informed by a strengthened evidence base.

This is the first global, systematic map of studies reporting the effectiveness of nature‐based interventions to address the adverse impacts of climate change on people. The mapping exercise revealed a high volume of potentially relevant studies, with an upsurge in research effort since 2012. The dispersion of this knowledge across multiple disciplines and journals, representing a range of timeframes and research objectives, presents a significant challenge to policymakers and practitioners in need of clear evidence to inform target setting and action on the ground. Responding to calls for more innovative ways to visualize evidence bases (James et al., 2016), we present the results of our systematic map as an open‐source, user‐friendly online platform that will be updated over time (www.naturebasedsolutionsevidence.info). This provides a tool to support evidence‐based decision‐making, allowing users to efficiently explore 376 peer‐reviewed studies, and to rapidly identify articles that report effects of nature‐based interventions on climate impacts across a range of ecosystem types and geographies. Interactive heatmaps reveal the extent and distribution of existing evidence, highlight well‐studied linkages between interventions and social and ecological outcomes, and pinpoint major knowledge gaps (for a snapshot of this heatmap, see Figure 2a).

Here, we discuss the main findings of the evidence map and its limitations, including important evidence gaps and related opportunities for future synthesis and research.

Nature‐based solutions currently have considerable political traction, with the greatest emphasis on the role of ecosystems as sinks of GHGs. However, there is a large and growing body of evidence that protected, restored, or well‐managed natural or semi‐natural ecosystems are essential to help people and economic sectors adjust to and manage the negative impacts of climate change. On this basis, many organizations are advocating for national and subnational policies to raise ambition for the use of NbS as a means of climate change mitigation and adaptation. In 2020, this is highly relevant for the revision of NDCs to the Paris Agreement (Seddon, Daniels, et al., 2020). However, this ambition is unlikely to be met unless the process is informed by robust evidence from science, practice, and local and indigenous knowledges.

To help increase the impact of science on the design and implementation of NbS for climate change adaptation, our systematic map helps guide policymakers to the information they need. However, the map also reveals that the evidence base has substantial gaps. First, there is a marked imbalance in the geographic distribution of evidence, with most studies concentrated in the Global North. Yet, it is communities in the Global South which overall are more vulnerable to climate impacts and could potentially gain most from the multiple benefits of NbS. Second, there is a lack of robust, site‐specific investigations of the effectiveness of interventions compared to alternatives and of more holistic appraisals that take broader social and ecological outcomes into account. To build the resilience of communities globally to our rapidly warming world, it is imperative that we protect and harness the benefits that nature can provide, and for that, a strengthened evidence base is key.