A 39-year analysis of fire incidence in a Chaco Serrano landscape using remote sensing

Abstract

In recent decades, there has been an observed increase in the frequency, intensity, and/or extent of fire events, attributable to the interaction between climate change and various anthropogenic activities. The Argentine Chaco ecoregion is characterized by a high incidence of fire across both space and time. However, there is a paucity of knowledge regarding wildfire dynamics, particularly in semi-arid areas with low population density. The Guasayán Mountains (ca. 233 000 ha) in Santiago del Estero Province are a good example of such knowledge gap. In this study, we classified Landsat and Sentinel 2 imagery acquired between 1986 and 2024 to build a long-term fire database and analyze the fire regime. Over the 39-year period, the Guasayán Mountains documented a total of 2954 fires, resulting in a cumulative burned area of approximately 302000 ha, with annual fire activity being highly variable. Large fires (≥ 1000 ha) represented only 2,5% of fire events, but they accounted for 49% of the total burned area. Thirty eight percent of the study area was affected by, at least, 1 fire event. Considering fire recurrence, the cumulative burned area over the 39-year study period represented 129% of the study area. Between 1986 and 2024, more than 1100 ha burned 15 to 22 times. Fires mostly occurred on flat land and on the western slopes. The areas of closed woodlands that transitioned to pastures and croplands experienced higher fire activity than woodlands that remained closed or transitioned to open woodlands. The generated fire database shows that fires were present in most farms, with varying frequency. It is likely that human activities have altered the natural fire regime, increasing its frequency by using fire as a management tool to promote forage regrowth and to clear lands. Based on the obtained results and under a climate change scenario, the Guasayán Mountains should be actively managed to mitigate fire risk and to enhance their capacity to provide valuable ecosystem services.