How changes in ignition sources influence fire probability in the Amazon and Cerrado biomes: a perspective based on frontier age

<p>Agricultural expansion and ongoing climate change are rapidly altering the fire regime of natural ecosystems along the Cerrado-Amazon biome boundary. While agricultural intensification has driven a decrease in fire ignitions in some regions, agricultural expansion has increased fire usage in other landscapes for deforestation and managing pasturelands. These contrasting patterns of fire activity across different land-use frontiers limits our ability to accurately predict where and when fires may occur, particularly under the context of climate change.</p> <p>To predict fire activity with land-use transitions, we modelled fire probability as a function of the age of different land-use transitions across the Amazon and Cerrado. We investigated annual land-use and associated burned areas based on the MapBiomas Collection 6.0 and MapBiomas Fire Collection 1.0 data, respectively, from 1986 to 2020. This allowed us to quantify how the time-since conversion of native vegetation (forest, savanna, and grassland) to pasture and farming influence fire occurrence. Additionally, we explored the joint impact of land-use change and climate extremes in fire activity in terms of estimated vapor pressure deficit (VPD) and maximum cumulative water deficit (MCWD), two common measures of flammability and drought impact.&#160;</p> <p>Our results confirm that transition age is a strong predictor of fire probability. They also suggest that fire probability increases (decreases) at different rates before (after) clearing in Amazon and Cerrado. The role of climate extremes in modulating burning activity associated with land-use transitions varied by biome, post-fire land use, and the size of the burned area associated with the conversion. These findings provide insight into incorporating the effect of land-use transition age on ignition probability for fire modelling in combination with climate drivers. From an operational point of view, our results aim to contribute to environmental policies capable of sustaining ecosystem integrity at the ecotone between the Amazon and Cerrado biomes.</p>