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Abstract

Humans profoundly alter fire regimes both directly, by introducing changes in fuel
dynamics and ignitions, and indirectly by increasing the release of greenhouse gases
and aerosols from fires, which can alter regional climate and, as a consequence,
modify fuel moisture and availability. Interactions between vegetation dynamics,
regional climate change, and anthropogenic pressure lead to high heterogeneity in
the spatio-temporal fire distribution. We use the new FireTracks Scientific Dataset
that tracks the spatio-temporal development of individual fires to analyse fire regimes
in the Brazilian Legal Amazon over the period 2002-2020. We analyse fire size,
duration, intensity, and rate of spread in six different land-cover classes. Particular combinations of fire features determine the dominant and characteristic fire regime in
each of them. We find that fires in savannas and evergreen forests burn the largest
areas and are the most long-lasting. Forest fires have the potential for burning at the
highest intensities, whereas higher rates of spread are found in savannas. Woody
savanna and grassland fires are usually affected by smaller, shorter, less-intense
fires compared with fires in evergreen forest and savanna. However, fires in
grasslands can burn at rates of spread as high as savanna fires as a result of the
easily flammable fuel. We observe that fires in deciduous forests and croplands are
generally small, short, and low-intense, although the latter can sustain high rates of
spread due to the dry post-harvest residuals. The reconstructed fire regimes for each
land cover can be used to improve the simulated fire characteristics by models, and
thus, future projections.