Collapse and recovery of livestock systems shape fire regimes on the Eurasian steppe: a review of ecosystem and biodiversity implications.

Shifts in fire regimes can trigger rapid changes in ecosystem functioning and biodiversity. We synthesize evidence for patterns, causes and consequences of recent change in fire regimes across the Eurasian steppes, a neglected global fire hotspot. Political and economic turmoil following the break-up of the Soviet Union in 1991 triggered abrupt land abandonment over millions of hectares and a collapse of livestock populations. The build-up of vegetation as fuel, rural depopulation and deteriorating fire control led to a rapid increase in fire size, area burned and fire frequency. Fire regimes were also driven by drought, but likely only after fuel had accumulated. Increased fire disturbance resulted in grass encroachment, vegetation homogenization and decreasing plant species diversity. Feedback loops due to the high grass flammability were likely. Direct and carry-on effects on birds, keystone small mammals and insects were largely negative. Nutrient cycling and carbon balance changed, but these changes have yet to be quantified. The regime of large and frequent fires persisted until 2010 but shifted back to a more grazing-controlled regime as livestock populations recovered, reinforced by increasing precipitation. Key future research topics include the effects of future climate change, changing pyrodiversity and pyric herbivory on ecosystem resilience. Ongoing steppe restoration and rewilding efforts, and integrated fire management will benefit from a better understanding of fire regimes.This article is part of the theme issue 'Novel fire regimes under climate changes and human influences: impacts, ecosystem responses and feedbacks'.