**6. Conclusions**

Although the concept of sustainability, the idea that the current generation has responsibility for future generations, originated at least as far back as the 17th century, according to the UN-GSDR 2019, the world is not on track for achieving most of the targets that comprise the SDGs by the target date of 2030. Meanwhile, through the EO4SDG initiative of the GEO, the full potential of RS for SDG monitoring is now being explored at a global scale. As of April 2020, 21 (70%) of the RS-based SDG indicators already have at least some preliminary statistical data according to the Global SDG Indicators Database, and 10 (33%) of the RS-based SDG indicators are included in the SDR-ID 2019. These statistics, however, do not necessarily reflect the actual status and availability of raw and processed geospatial data for the RS-based indicators, which remains an important issue. Nevertheless, various initiatives have also been started to address the need for open access data. RS data can also help in the development of potentially relevant complementary indicators or sub-indicators, which will help address one of the current challenges in SDG monitoring, which is how to operationalize the SDG indicators.

**Author Contributions:** R.C.E. conceptualized this review. He performed the review, prepared all the tables and figures, and wrote the paper. The author has read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Japan Society for the Promotion of Science (JSPS), through Grant-in-Aid for Young Scientists (B): 20K13262 (PI: Ronald C. Estoque).

**Acknowledgments:** This work was also supported by the Climate Change Adaptation Program of the National Institute for Environmental Studies, Japan. The author also acknowledges the four anonymous reviewers whose comments and suggestions helped improve this manuscript.

**Conflicts of Interest:** The author declares no conflict of interest.
