**5. Conclusions**

A total of 63 environmental fire danger rating systems from across the globe were analyzed and compared. The most important parameters were associated with weather and hydrology although the most accurate indices required only two to five inputs. Some of the most-used systems—also reported in the present review—require complex calculations. However, the top-rated indices and the most accurate as well were those with simpler

formulas and procedures. In addition, indices developed in a specific region have been proven to be more accurate in different environments—as most of the Mediterranean indices included in the current study underperformed in Greece. Additionally, the most complete systems—such as the CFFDRS and the NFDRS—had a fine performance, while the FFDI5 reached near the top, leading to the conclusion that if these systems adapt better to the local conditions, their performance will be greater than the respective one of the simpler indices. Finally, this review corroborated the inadequacy of the existing environmental fire danger rating systems in predicting modern day incidents, as the top-performing systems had an accuracy of 60–66% and a total score of 59–68%, indicating the need for an integrated approach including social and other factors.

**Supplementary Materials:** The following supporting information can be downloaded at: https:// www.mdpi.com/article/10.3390/land12010194/s1, Paragraphs S2.1–S2.18; Tables S1–S42. The SM file presents the calculation procedure and value range for each system and index. Also, the SM includes the nomenclature.

**Author Contributions:** Conceptualization, I.Z. and V.A.T.; methodology, I.Z. and V.A.T.; software, I.Z.; validation, I.Z. and V.A.T.; formal analysis, I.Z.; investigation, I.Z. and V.A.T.; resources, V.A.T.; data curation, I.Z.; writing—original draft preparation, I.Z.; writing—review and editing, V.A.T.; visualization, I.Z.; supervision, V.A.T.; project administration, V.A.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Data Availability Statement:** Meteorological open data were downloaded from the National Observatory of Athens, https://www.meteo.gr/Gmap.cfm (accessed on 1 September 2022). Fire incidents data were downloaded from the National Fire Service of Greece, https://www.fireservice.gr/en\_ US/stoicheia-symbanton (accessed on 1 September 2022). Spatial open data were downloaded from https://geodata.gov.gr/en/ (accessed on 1 September 2022). For meteorological data processing, the Python open-source programming language was used, and for spatial analysis and mapping, the open-source Quantum GIS was deployed. All data are included in the paper.

**Conflicts of Interest:** The authors declare no conflict of interest.
