Post-Soviet Land-Use Change Affected Fire Regimes on the Eurasian Steppes

Abstract

Fire is an important disturbance in grassland ecosystems. Anthropogenic factors, especially land use, have drastically altered fire regimes in many regions, but how changing land-use intensity affects fire patterns remains weakly understood. Here, we reconstruct changes in fire regimes between 1989 and 2016 for the understudied Eurasian steppes, where major land-use changes happened after the dissolution of the Soviet Union in 1991. We mapped burned areas in a 540,000 km2 study region in northern Kazakhstan for 3-year periods centered on 1990, 2000, and 2015, based on all available Landsat imagery. We then used these maps to assess changes in the extent, number, and size of fires over time, and to explore links between changes in fire regimes and agriculture. We found a sevenfold increase in total burned area and an eightfold increase in fire numbers between 1990 and 2000. After 2000, burned area and fire numbers declined slightly, while fire size remained stable. Most of the observed increase in fires in the 1990s occurred on cropland, most likely due to the agricultural burning. The abandonment of cropland and pastures was also associated with intensified fire regimes, likely due to increased aboveground biomass and thus higher fuel loads. Overall, our results suggest that intensifying fire regimes on the Eurasian steppe are clearly linked to post-Soviet changes in agriculture. Given that fires on Eurasia’s steppes have wide-ranging consequences, affecting regions as far away as the Arctic, better regulation of agricultural practices, better fire monitoring, and more proactive fire management are needed.