Anna Júlia Lopes*
Repeated fires and fire intensity have caused forests in the southern Amazon to lose their resilience, resulting in a decrease in species diversity and an increase in tree mortality rates. The data is contained in the article “Resilience of the Amazon rainforest inferred from fire-induced changes in carbon stocks and tree diversity”, written by researchers from IPAM (Amazon Environmental Research Institute) and partners, and published in the scientific journal IOPscience.
For the study, the researchers considered four categories of experimental treatment applied to forest plots:
- Unburned control: no plots were burned during the experiment;
- B1: there was only one burn, in 2016. This represents a one-off, low-intensity fire;
- B2: the forest was burned twice, in 2013 and 2016. This represents a scenario of repeated fires; and
- B2 +: fires were also recorded twice, in 2013 and 2016, but with the addition of “fuel“to intensify the fire – in this case, dry branches and leaves. This is considered the most extreme scenario, as it combines repetition and increased intensity.
According to the research, in the cases where the fire was repeated (B2 and B2+), the changes in forest diversity began as early as 2014 – a year after the first burn – but intensified after 2016, with the second event. The article says that the long-term impacts of the fires were “even more pronounced” with increasing frequency.
The authors concluded that, in addition to species diversity, the composition and number of individuals underwent “gradual changes” from 2014 to 2024.
Furthermore, in the B2 + case, which brought in the intensity factor, there was an increase in tree mortality at the site. According to the article, in 2014, fires with the presence of dry leaves and branches increased the tree mortality rate by four to five times when compared to unburned areas.
“As for fires with high intensity, which is the case simulated in B2+, the impact is much greater, both for species diversity and mortality, which directly affects the carbon stock present in the aerial biomass of the species that are in this environment,” explains one of the authors, Leonardo Maracahipes-Santos, a researcher at IPAM.
The article shows that, with climate change, the scenarios in which there is “fuel” to intensify the flames are likely to increase, considering the rise in temperature in the forests of the southern Amazon. With projections indicating that up to 16% of the forests in the southeast of the biome could register fires in the coming decades, the study says it is uncertain whether the forest’s resilience will persist under more frequent and intense fire regimes.
“Climate change is likely to increase the frequency and duration of severe droughts in tropical forests, which could amplify fuel loads and potentially increase the intensity and severity of future fires,” says the document.
The research also highlights that, although the forest is resilient, this quality can be compromised under more extreme fire regimes and intensity. In conclusion, the authors stress that “urgent” fire protection and management strategies are needed to prevent the loss of ecosystem services in the Amazon.
The study was conducted at the Tanguro Research Station, in the municipality of Querência, Mato Grosso, located in an area of ecological transition between the Amazon and Cerrado biomes.
*IPAM journalist, anna.rodrigues@ipam.org.br