Nature-based solutions (NbS) is an approach to solving climate change and social issues based on nature. Despite NbS being widely studied as an effective method to solve social problems, the trends in NbS research have hardly been analyzed. Therefore, this study examined change patterns in NbS-related research topics over time and analyzed the interactions of NbS research and relevant activities in various fields. After reviewing research papers based on the search term ‘nature-based solutions’ on Scopus, and collecting 1567 research papers, we conducted dynamic topic modeling (DTM) and network analysis. The papers were classified into 19 topics via DTM. Water, forest, and urban topics made up the greatest portion of NbS research, while NbS topics in the forest sector showed a steady increase over time. This study also found close connections between NbS studies on forests and other sectors and confirmed that the forest sector can become an integrated means of contributing to climate change responses and other resultant social issues. This study demonstrates that DTM and network analysis are useful tools for understanding the trends in NbS research and finding the linkages between various fields.

Climate change mitigation Official Development Assistance (ODA) primarily aims to reduce greenhouse gas (GHG) emissions in developing countries while also seeking to enhance human welfare as a fundamental goal of development aid. This study investigates whether climate mitigation ODA contributes to achieving the principles of the doughnut framework—staying within the ecological ceiling (mitigating GHG emissions) while meeting the social foundation (enhancing human development index, HDI). We analyzed data from 77 developing countries between 2010 and 2020, including subgroup analyses by income level (high-, middle-, and low-income groups), using an instrumental variable–fixed effect approach. The results show that climate change mitigation ODA significantly improved the HDI but had no impact on reducing overall GHG emissions, including fossil fuel-based and land use change and forestry-based mitigations. When disaggregated by income level, ODA was found to improve the HDI and reduce fossil fuel-based GHG emission in low-income countries; however, these effects weakened as income levels increased. Across all income groups, there was no significant reduction in GHG emissions resulting from land use change or forestry. These findings suggest that climate change mitigation ODA can yield a greater impact when prioritized for low-income countries and that current ODA strategies for addressing GHG emissions related to land use change and forestry should be reconsidered.

The Sustainable Development Goals (SDGs) are global objectives adopted by countries worldwide to achieve sustainable development by 2030 and consist of 17 goals and 169 specific targets. Among them, SDG 15 (Life on Land) aims to conserve terrestrial ecosystems and promote their sustainable use. Successful implementation of SDG 15 requires continuous management of terrestrial ecosystems and positive forest transitions. However, systematic analyses examining the role of green official development assistance (ODA), which supports environmental improvement in developing countries, remain limited. Accordingly, this study investigates the role that green ODA can play in forest transitions. Focusing on green ODA provided to developing countries between 2010 and 2023, this study employed shapley additive explanations (SHAP), an explainable artificial intelligence (XAI) technique, to predict its influence on SDG 15 implementation scores and to analyze the contributions of economic, environmental, and social indicators. In addition, a SHAP value-based decomposition and a gap index were calculated to examine the contribution of green ODA relative to its input. The results indicate that the overall contribution of green ODA to SDG 15 implementation in developing countries is relatively limited. However, statistically significant effects were observed in country groups with higher levels of SDG 15 implementation performance. In contrast, the effects were weakened or constrained in some country groups with lower levels of SDG 15 implementation. These findings suggest that green ODA may function as a transition accelerator that facilitates positive forest transitions in countries with stronger capacities for implementing SDG 15. Strengthening and improving the existing limitations of green ODA could enhance its role and enable it to contribute more effectively to sustainable development and the conservation of terrestrial ecosystems in developing countries.