# Mapping the Most Susceptible Regions to Fire in Portugal
## 3 Results
### Land Cover Distribution of Susceptible Areas  
The maps in Figure 6 show the distribution of land cover in Portugal (left panel) and the distribution of the signal of PC\({}_{\text{REC}}\).  
The map resulted from Equation (1) (with N = 6) and clarifies the regions where the fire susceptibility is higher, based on the weight of each PC. The areas with stronger signal (reddish spots) are mostly found in the centre and northern regions of the country whereas the southern regions are mainly characterized by negative PC\({}_{\text{REC}}\) signal (greyish spots). The amplification (reduction) of the signal can be strongly modulated by the landcover types of the region. Comparing the land cover distribution with the PC\({}_{\text{REC}}\) signal, upon first sight, the areas with high susceptibility are mainly covered by different types of tree or shrubland, while the croplands dominate the areas with less fire susceptibility.  
This result stresses the importance of analysing the role of different land cover types on the potential susceptibility of vegetation to fire. Observing the land cover distribution in Figure 6 (left panel), the plains from the south of Portugal are generally covered by croplands (_Agr_) and shrublands (_Shb_), whilst the centre and north of the country, including the most susceptible regions to burn, are covered by forests, such as eucalyptus (_Euc_) and pines (_Pi_).  
Figure 5: Loading factors of the chosen six PCs that reveal the contribution of each variable to each PC. The explained variance of each PC is described on the legend.  
As described before, we defined classes of fire susceptibility, considering different percentiles of PCREC, and the values are shown in Table 3.  
The land cover distribution (see Table S1) per susceptibility class is illustrated in Figure 7. For 'Low' and 'Moderate' classes, the distribution of croplands (_Agr_), forests (_CHO_, _Euc_, _HW_, _Pi_ and _Oth_), and shrublands (_Shb_ and _SV_) is quite similar, varying between 25% and 40%. However, for the 'High' and higher severity classes, the distribution of land-cover types becomes uneven. The frequency of Croplands (_Agr_) decreases in higher susceptibility classes, as only about 12% (7%) of _Agr_ is classified as 'Very High' ('Extreme'). In the opposite direction, an increasing percentage of shrubland (or forest) in the most susceptible classes is observed, as about 70% of the pixels classified as 'Extreme' are covered by shrublands and about 20% are covered by forest. Furthermore, an increase in the distribution of _Euc_ occurs in higher susceptibility classes ('Low': 8% and 'Extreme': 13%), as well as on the _Pi_ distribution from 'Low' (5%) to 'High' (8%). On the other hand, a decrease in the distribution of '_CHO_' and '_HW_' occurs in the highest susceptibility classes.  
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline  & **p20** & **p40** & **p60** & **p80** & **p95** \\ \hline PCREC signal & 0.94 & 2.37 & 4.40 & 7.12 & 11.71 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Values of PCREC percentiles that defined each susceptibility class. The 95 th percentile is only for observation of values within the ‘Extreme’ class.  
Figure 6: Distribution of land cover in Portugal, according to the categories previously defined (see Table S1 for classes classification) (left panel); distribution of the signal of the PCREC.