Analysis of how the spatial and temporal patterns of fire and their bioclimatic and anthropogenic drivers vary across the Amazon rainforest in El-Niño and non-El-Niño years

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Minerva Singh, Center for Environmental Policy, Imperial College London, London, United Kingdom and Xiao Xiang Zhu, Technical University Munich, Munich

Background/Question/Methods: Fire dynamics in the Amazon basin have changed considerably over the past few decades, a consequence of changes in land cover (deforestation) and climate (temperature and precipitation). Fire events have also increased as a result of droughts resulting from El-Niño events. Our research lays the groundwork for developing effective and location-specific strategies by identifying the variations in drivers of forest fire dynamics for countries within the Amazonian biome (Brazil, Bolivia, Colombia, Ecuador, Guyana, Peru, and Venezuela). The main aims of the research are to identify (1) If and how fire dynamics (fire size, fire speed, fire duration and expansion ) and their bioclimatic drivers (precipitation, maximum temperature, soil moisture and drought severity) varied between dry and wet seasons of the Amazon basin from 2003-16 (2) If variations in fire and bioclimatic driver dynamics were more pronounced in the El-Niño years (3) Identify the variation of these during the wet and dry seasons of the El-Niño and non-El-Niño years.
Materials and Methods: Data from publicly available databases on forest fires (Global Fire Atlas) and on climatic factors such as precipitation was obtained from TerraClimate was obtained. A general linear mixed-effect model was implemented to evaluate the impact of El-Niño years, seasonality, landcover and the interaction between these on fire dynamic variables across the different countries. Additionally, a machine learning model, Multivariate Adaptive Regression Spline (MARS) was utilized to determine the relative importance of the different drivers on fire dynamics across wet and dry seasons, both in El-Niño and non-El-Niño years.

Results/Conclusions: The findings make clear that El-Niño years also saw greater fire sizes and speeds as compared to non-El-Niño years. Declining precipitation and increased temperatures also have a strong impact on fire dynamics (size, duration, expansion and speed) for El-Niño years. The presence of grasslands and croplands also acted as a driver of fire in both El-Niño and non-El-Niño years while evergreen forests showed resistance. The importance of year type (El-Nino vs non-El-Nino), seasonality, landcover and their interactions (and subsequent impacts)varied across the Amazonian countries and landcover types. For e.g. El-Nino influenced fire duration in the grasslands of Brazil and Peru and the evergreen forests of Bolivia. As opposed to the majority of studies that only focus on the Brazilian Amazon, our study establishes the variability of bioclimatic variables and fire dynamics in the different countries that have the Amazon rainforest within their boundaries. Findings can help develop country-specific conservation strategies