# Fires Drive Long-Term Environmental Degradation in the Amazon Basin
## 4 Discussion  
The analysis of GPP results indicate that the average C absorption of the forest is neutral, and the C absorption/pixel was 0.0751 kg C m\({}^{-2}\) year\({}^{-1}\) during the study period. However, the occurrence of fires has seriously compromised the C balance. Specifically, during the study period, the forest absorbed 1,092,037 Mg of C, but emitted 2908 Tg of C, which is 2.66 times greater than the C absorbed, thereby compromising the role of the forest in acting as a C sink (Figure S1 and Table S5). Deforestation and forest fires are primarily responsible for the high CO\({}_{2}\) emission rates in the Amazon [14]. However, climate variability has also contributed to changes in C balance [81]. During the severe droughts of 2005, 2010, and 2015 (due to El Nino or warm Atlantic SST conditions), C absorption tended to decrease as a result of a water deficit, thereby reducing the photosynthetic rate [55; 82; 83]. Severe droughts lead to increased tree mortality, biomass losses, and a temporary cessation to the C sink in the Amazon [45; 84; 85]. The Amazon contains vast reserves of C but can experience major changes in rainfall patterns, mainly because of the influence of large-scale phenomena (ENSO, SST anomalies, and moisture transport anomalies; e.g., [PERSON] and [PERSON] [38], [PERSON] et al. [29], [PERSON] et al. [36], [PERSON] et al. [86]) which affect C dynamics [81]. Herein, the results obtained for the El Nino drought period, such as in 2009 when the annual absorption rate of \begin{table}
\begin{tabular}{c c c} \hline \hline
**Variable** & **Pettitt’s Test** & **Man–Kendall Test** \\ \hline Fire foci & 0.2342 & 0.1773 \\ Rainfall & 0.2078 & 0.5291 \\ SPI & 0.0588 & 0.1476 \\ Emissions & 0.5756 & 0.4002 \\ GPP & 0.0688 & 0.2948 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Trend analysis (\(p\)-value) applied to annual time series fire foci, rainfall, standardized precipitation index (SPI), emissions, and gross primary production (GPP). Figure 7: General representation of the Amazon Basin during the period 2001–2019, including (**a**) the study period average gross primary productivity (GPP, kg C m\({}^{-2}\)); **(b**) the sum of each year’s standardized precipitation index (SPI); and (**c**) the sum of the burned areas (quarters, Q1–Q4). Exact values of the variables mentioned for the Amazon Basin are listed in Table S1. C/pixel was 0.050 kg C m\({}^{-2}\) year\({}^{-1}\), showed no significant differences with those obtained for the La Nina drought period (cold phase of ENSO). Therefore, the results of the GPP analysis revealed that the performance of C uptake by the Amazon Basin during the study period was neutral, meaning that the sequestration of C through the forest was zero as the mean C uptake/pixel matched 0.0751 kg C m\({}^{-2}\) year\({}^{-1}\). Nevertheless, as this study period is short, we cannot claim, based on our data, that the Amazon Basin is entering a drought period and is moving rapidly toward its \"tipping point\". However, we can state that this forest is no longer acting as a C sink and that it is currently a net source of GHG emissions, which contribute to global warming, as a result of anthropic actions, for example, the replacement of original land cover for crops and livestock, and opening highways [87]. According to [PERSON] et al. [88], the death of trees in the eastern and southern Amazon implies that C absorption is neutral. Our results are consistent with these findings, but also highlight a key difference. As GPP decreases with seasonal decrease in water availability, this causes negative impacts on C absorption [2; 89]. Meanwhile, fires impact the global and local ecosystems via vegetation effects (loss of biomass), contributing to the release of accumulated C stocks [90; 91]. Although natural variability explains forest burning, this study found that burning occurred in quarters where vegetation was green and humid during the rainy season (especially in quarters Q1 and Q2), indicating the strong presence of anthropic action in the Amazon region.