Largest forest wildfire (mega-complex)

Wildfires come in several forms and can be measured in various ways. They are notoriously difficult to compare, particularly between those from different eras and those in remote regions where the accuracy of equipment and techniques vary drastically. Not only that, but the definition of different types of wildfire also varies. The most likely largest forest fire mega-complex (i.e., an outbreak of wildfires that occur concurrently in a single region) in recorded history is the series of forest fires that burned across Siberian Russia (then USSR) between April and October 1987 at the same time as the Daxing’anling Wildfire (aka Great Black Dragon Fire) in north-east China, which burned between 6 May and 2 June 1987. Satellite data suggests as much as 13–15 million hectares (32.1–37 million acres) of Siberian taiga were affected. If you combine that with the estimated burn area of the Chinese fire across the border, you get a total coverage of some 16–18 million hectares (39.5–44.5 million acres).

A fire "complex” is usually applied to fires that merge or are so close together that they are considered a single burn; we are taking "mega-complex" to mean a cluster of discrete conflagrations that occur simultaneously across a particular region (potentially across national borders).

In North America, the largest recorded forest fire complex is the Miramichi Fire, which burned some 1.7 million hectares (4.3 million acres) of forest in New Brunswick, Canada, and the bordering US state of Maine in autumn 1825.

Pre-1987, western Siberia is said to have experienced a similarly large fire mega-complex in 1915; the smoke cloud produced from the outbreak is reported in contemporary articles to have been roughly the same size as Western Europe. The fire is estimated to have covered some 14 million hectares (34.6 million acres) though given the political upheaval at the time, not to mention the impact of World War I, accurate scientific data to verify these claims is extremely limited.