## 3 Results and Discussion  
Figure 2 shows the spatial distribution of the NDVI classes before and after the wildfires. Figure 3 summarizes these results by presenting the relative weight of each class of NDVI before and after the great wildfires of 1991, 2003, 2017, and 2019. Before the 1991 fires, the most represented NDVI classes in the study area were high and moderate. These areas correspond to agriculture and forestry (_Pinus pinaster_ Ait.). According to [PERSON] et al. (2016), they were the main land occupation in 1990, with 49% and 19% of the Macao municipality area, respectively. After the 1991 wildfires, the high class suffered an important decrease, and the remaining classes consequently increased, particularly the low and bare soil/water/urban (which was null before the fires) classes. Figure 2: Spatial distribution of NDVI classes before and after the 1991, 2003, 2017, and 2019 wildfires. A decade later, in 2002, the biomass had recovered. The high class increased to 49.1%, values nearly above the pre-1991 fires, while the remaining classes also recovered to pre-1991 values (with a decrease of approximately 15% in the low class). After the 2003 fires, a slight decrease in the moderate class (35.0%) and a sharp decrease in the high class (6.0%) were observed. The low class (25.1%) increased to an equivalent level to that of the post-1991 fires. The bare soil/water/urban class (33.9%) underwent a sharp increase, becoming almost equal to the moderate class in terms of area. After 14 years, in 2017, biomass had markedly increased with about 70% of the Macao municipality area within the high NDVI class. The remaining classes had decreased, particularly the bare soil/water/urban (0.2%) and low (2.5%) classes. After 2017, the moderate class (22.3%) continued to decline, and the high class suffered a sharp reduction, with a reduction of more than 50% of the total area of the municipality. The low (27.9%) and bare soil/water/urban (31.9%) classes increased to values very close to those of the post-2003 fires. In October 2017, the entire area of Macao presented an even distribution of NDVI classes. Two years after the wildfires of 2017, the high (33.3%) and moderate (52.8%) classes partially recovered, with a very strong increase in the latter. The low (11.8%) and bare soil/water/urban (2.1%) classes decreased to prewildfire values. In fact, before the fires, the latter class was always near null. After the 2019 wildfire, the moderate (42.8%) and high (18.3%) classes were decreased, but the moderate class continues to be the prevalent. The low (26.3%) and bare soil/water/urban (12.6%) classes consequently were increased. Figure 4 maps the severity of the wildfires using the dNBR index. In the 1991 fires, of the 131.03 km\({}^{2}\) of burnt area, 33.8% is classified as of low severity, and 16.7% as of moderate-low severity. The moderate-high severity class was the most representative, with 45.8% of the burnt area, while only 3.6% was classified as of high severity. In 2003, when 193.50 km\({}^{2}\) burnt, the low class was augmented to 5.3% of the Macao municipality area. The moderate-low class maintained similar values as those before, with 16.3%. The moderate-high and high severity classes increased considerably to 68.6% and 9.8%, respectively. In 2017, a year with a burnt area of 265.96 km\({}^{2}\), the high class showed the highest peak, with approximately 21.9%. The moderate-high and low classes dropped to 54.9% and 7.2%, respectively. The moderate-low class stayed almost unchanged with 16.0%. In 2019, with 56.31 km\({}^{2}\) of burnt area, the high class was of approximately 20.2%. The moderate-high class decreased to 33.5%, and the moderate-low and low classes increased to 22.3% and 23.4% of the Macao municipality area, respectively. Figure 3: Evolution of occupation of the NDVI classes before and after the wildfires of 1991, 2003, 2017, and 2019.