## 4 Discussion
### Spatial Distribution of the Burnt Areas  
In reviewing the spatial distribution of the fires in the forest domain, it is clear that the fires occurred mainly in open forests, more specifically in the very open Marantaceae forests. From the density of roads, it is deducted that while mainly located inside a logging concession, fires occurred in old logged areas and in areas that were never exploited.  
Around 80% of the burnt areas detected with S1 and S2 data occur in the core of the very open Marantaceae forest. Another 13% is observed in the open forests situated at the border of the very open forests formations. According to the analysis, the dense forest was only slightly affected, with less than 2% of this class mapped as burnt. However, this low percentage is only indicative as the vegetation map has a coarser spatial resolution compared to the burnt area maps.  
Only a certain proportion of Marantaceae forests were affected by fires. According to [PERSON] et al., [26], Marantaceae formations in the study area occupy more than 300,000 ha. To understand the distribution of the fire, we looked at the logging roads network and the accessibility in general. For the burnt areas observed in historically logged areas in the north (Figure 8A), the origin of the fires is adjacent to old logging roads. The roads were identified by [PERSON] et al., [31] as not yet entirely recolonized by vegetation in 2015. Although these roads have been closed and are no more used for active logging exploitation, they may have remained partly accessible for people on foot. In Amazonian and Indonesian tropical forests, the presence of recent logging roads has been reported as a potential facilitator for fire in forests [8; 10; 61].  
For the burnt areas observed in areas not previously logged, some are located along the main road (visible as a black thick line in Figure 8A), where there are a number of small to large villages. Some areas are located up to a distance of 8 km from the road. The areas accessed by local communities and indigenous people for hunting and gathering is thought to reach up to 30 km into the forest. Another extent of burnt area is situated in the south of the study area (Figure 8B), close to savannas.  
From the analysis of a the VHR image together with the timing of the fire derived from S2 burnt area maps and MODIS active fire data (see Figure 9), the hypothesis can be made that fires started close to roads, both in logged and non-logged forests, or close to a savanna, but all fires started in very open forests, then propagated to the border of the ecosystem and into denser canopy cover forests.  
From the S2 and MODIS data, it is clear that fire started at the same time in different locations. Wind and dry vegetation may well have facilitated the spread of the fire to such a widespread extent. There is, as yet, no firm explanation for the origin of these fires, however, they are unlikely to be of natural origin (i.e., lightning) [10] and more likely to be related to the presence of local communities and indigenous people in the forest. Human activities have probably initiated fire in an environment more prone to fire after the drought of the beginning of the year. The fires observed along the main road could be related to shifting cultivation activities by the villagers living there. Poaching activities are known to occur in the area, given that fauna such as gorillas and elephants are present in the open forests. However, to confirm the origin of the fires, a more detailed accessibility study and surveys with local people are needed.