## 3 Results and Discussion
Between 1991 and 2017, the municipality of Macao was plagued by wildfires that increased in terms of burnt area and severity, as is shown in Figure 4. This phenomenon occurs with an approximate periodicity of 10 years, which corresponds to the time of the year. Figure 4: Spatial distribution of dNBR classes before and after the 1991, 2003, 2017, and 2019 wildfires. vegetation recovery and biomass accumulation. The latter is caused by the lack of forestry and agricultural activities, derived from internal migrations from the inland rural areas to the cities near the coast of Portugal, as reported by [PERSON] et al. [PERSON] et al. (2016). These authors also stated that wildfires promote the homogeneity and continuity of vegetation coverage that could facilitate the occurrence of major fires. Many of the areas once occupied by agriculture and conifers were replaced by scrub and mixed forests ([PERSON] et al., 2017). This helps to explain the strong recovery of biomass before the fires of 2002, 2017, and 2019, evidenced by the high NDVI values. According to [PERSON] et al. [PERSON] et al. (2017), socioeconomic changes of the second half of last century were reflected in the abandonment of inland territories. Agricultural lands became landscapes prone to the occurrence of high-intensity fires due to the accumulation of biomass levels over the years. On the other hand, forestry was reshaped, and _Pinus pinaster_ Ait., with slow growth but with a high capacity for the colonization of burnt areas ([PERSON] et al., 2017), was largely replaced by other combustible species. The most common of these is _Eucalyptus globulus_ Labill., of easy planting and rapid growth, which give it great economic importance ([PERSON] et al., 2017; [PERSON] et al., 2017). The progressive increase in bare soil/water/urban areas (Figure 3) after the fires is explained by the fact that some of these areas are still in the bush stage. The regeneration of the forest is compromised by the inexistence of a seed bank, as plants may not reach reproductive maturity due to the short intervals between fires, especially in the case of coniferous forests ([PERSON] et al. (2017); [PERSON] et al. (2017)). In Portugal, the problem of biomass accumulation, particularly shrubs, has been addressed by different means. Portuguese laws and regulations ([PERSON] et al., 2017; [PERSON] et al., 2017; [PERSON] et al., 2017) are now more demanding regarding, e.g., the obligation of municipalities and landlords to remove accumulated biomass, with penalties when failing to comply. A large part of Portugal, including the centre of the country, is characterised by small land parcels of different landlords. This makes the proper management of the territory difficult. To overcome this issue, forest intervention areas (ZIF) were created by Decree-Law 127/2005 ([PERSON] et al., 2017) with the aim of promoting sustainable forest management, mitigating hindrances to forest intervention, and developing structural measures against wildfires ([PERSON] et al., 2017). In the specific case of Macao, five ZIFs were constituted ([PERSON] et al., 2017), towards promoting ecosystem services (e.g., hunting, tourism, and biomass valorisation), proper reforestation (by replacing softwood with hardwood species, and increasing cork oak areas), fostering pastoral areas to reduce herbaceous and shrubs, promoting traditional agriculture, and improving and maintaining forest defence infrastructures (e.g., firebreaks, water reservoirs). Figure 5 shows the relation between GPP and CO\({}_{2}\) flux before and after the 2003, 2017, and 2019 fires. The interval between wildfire events and satellite images was 10 (2003) and 12 (2017 and 2019) days, that is, within 1 month after the event. After the fires, the adjustment of the model was high, with R\({}^{2}\) ranging from 0.79 to 0.88. Before the fires, the adjustment was not so high, with R\({}^{2}\) between 0.49 and 0.69.