## 5 Discussion  
Results of burn severity from Planet VIs were spatially compatible with ground survey burn severity classifications in both the WLD and UR domains. This demonstrates the potential use of high-spatial-resolution Planet images for burn severity assessment in the WUI. Previous studies using high and medium spatial resolution satellite images showed successful assessment of burn severity in WLD [23; 25; 63]. However, as far as the authors are aware, this study is the first to provide a burn severity assessment at the WUI. Planet Doves provide a limited number of four spectral bands, lacking the shortwave infrared (SWIR) band. The SWIR is the most frequently-used band for burn severity mapping, successfully tracking burn severity variability across the burnt area [13; 64]. Previous studies have shown that SWIR-based indices are usually preferable over NIR-based VIs [25], and in some cases, even essential  
Figure 8: Map of (**a**) burned trees and (**b**) woody biomass loss caused by the fire of 2016. Figure 9: Map of spatially distributed economic damage caused to the trees by the fire in the WUI area. Estimations are in US dollars per (3 m) pixel. when used for burn severity monitoring in Mediterranean ecosystems [19]. However, in this study, we found that simple NIR-based VIs, like GNDVI and NDVI, may provide satisfactory results in terms of burn severity assessment. We found that, in general, the NIR-based VIs (i.e., GNDVI and NDVI) performed better in terms of burn severity assessment than the RGB-based GCC index. This may be because of the higher sensitivity that GNDVI and NDVI have to vegetation due to their use of the NIR band [65]. Another reason may be shadow effects, which usually increase with spatial resolution, particularly in RGB-based indices [66]. Comparisons with the more reliable Sentinel-2A satellite revealed that Planet may provide high-quality images for fire monitoring and tree parameter assessments in the WUI. Moreover, the advantage of the temporal resolution of Planet--which has been improved since 2016--over that of Sentinel-2A was essential for tracking vegetation status immediately after the fire. The first available image from Sentinel-2A was 48 days after the fire (Table 3) when herbaceous vegetation had already started to grow, thereby affecting the VI signal [29] (see also Figure 2). This was probably the reason for the wider area classified by Sentinel-2A as medium instead of high burn severity in the WLD (where herbaceous vegetation is widely present) compared to Planet (a ratio of 2.86 compared to 1.42 of medium/high percentage area in WLD, respectively; see also Figure 7). Differences between the two satellite sensors for the same date (Table 4) were likely due to differences in the width of the spectral wavelength bands (see Table 1), and to the different spatial resolution. A recent study using Planet VIs showed that the high spatio-temporal resolution of Planet images may be used to track changes in stem water potential in Mediterranean vineyards [53]. This study also showed that simple Planet-derived vegetation indices can be used to derive important parameters of forest structure, such as stand tree density and DBH in a highly fragmented Mediterranean system composed of a variety of plant species (Table A1). The stand densities in our study area were within the range reported for similar Mediterranean systems [67]. Such results were also found in similar ecosystems in Greece [68] using Sentinel-2A images and with higher spatial resolution images acquired from the QuickBird satellite [69]. However, stand density was previously impossible to derive in urban areas with the coarser spatial resolution of Landsat (30 m) because of a mixed signal from features such as buildings, roads, and other impervious surfaces [70]. Finally, with regard to the economic evaluation of the fire damage to the urban forest in the WUI, our total estimated economic loss was of 41 \(\pm\) 10 M USD based on _i-Tree_ model, with some adaptations to the Israeli case.