A megafire is an exceptional

fire Fire is the rapid oxidation of a fuel in the exothermic chemical process of combustion, releasing heat, light, and various reaction Product (chemistry), products. Flames, the most visible portion of the fire, are produced in the combustion re ...

that devastates a large area. They are characterised by their intensity, size, duration and uncontrollable scale. There is no precise scientific definition. A megafire may or may not be a

firestorm A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires and wildfires. Although the term has been used ...

Definition

The concept may vary by region or country. In Europe, they are characterized as beginning at 1,000 hectares (10 km², 2,470 acres), in size, while in the United States and elsewhere, they may be classified beginning at 10,000 hectares (100 km², 24,710 acres). Another figure used in the United States is (400 km²). A recent

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

study expands the megafire definition to include a variety of factors: "Between

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

and almost a century of fire exclusion, forest fires have become more extreme in size, severity, complexity of behavior and resistance to extinction. These fires are commonly referred as megafires and are at the extremes of historical variations." Using one definition, only 3% of all fires reach "megafire" status, yet they are responsible for more than 50% of burned surfaces on the planet. In recent years, some fires have burned over a million acres, becoming what has been dubbed as gigafires. These include the Yellowstone Fire in

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

and

Idaho Idaho ( ) is a landlocked U.S. state, state in the Pacific Northwest and Mountain states, Mountain West subregions of the Western United States. It borders Montana and Wyoming to the east, Nevada and Utah to the south, and Washington (state), ...

that burned 1.58 million acres in 1988; the Taylor Complex in Alaska that burned 1.3 million acres in 2004; the fires that burned 1.5 million acres in

Victoria Victoria most commonly refers to: * Queen Victoria (1819–1901), Queen of the United Kingdom and Empress of India * Victoria (state), a state of Australia * Victoria, British Columbia, Canada, a provincial capital * Victoria, Seychelles, the capi ...

and

New South Wales New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

in 2020; and the August Complex in California in 2020. A 2022 United Nations report used the term "wildfire" to distinguish "an unusual or extraordinary free-burning vegetation fire which may be started maliciously, accidentally, or through natural means, that negatively influences social, economic, or environmental values". This term was used in contrast to "landscape fire" which describes a natural, more ordinary, less harmful occurrence.

Operation of a megafire

These fires form

pyrocumulus A flammagenitus cloud, also known as a flammagenitus, pyrocumulus cloud, or fire cloud, is a dense cumuliform cloud associated with fire or volcanic eruptions. A flammagenitus is similar dynamically in some ways to a firestorm, and the two phe ...

and pyro cumulonimbus, clouds which are also named "fire-breathing dragons". They cause giant thunderstorms, which often have little rain but with a strong potential for lightning, which can easily create and spread new fires. These huge fires are so intense that they generate their own weather. A merger of fires can create a megafire, such as multiple fires during the

2019–20 Australian bushfire season The 201920 Australian bushfire season commenced with serious uncontrolled fires in June 2019. , fires this season have burned an estimated , destroyed over 5,900 buildings (including 2,779 homes) and killed at least 34 people. An estimated o ...

in Australia, where multiple cases of many fires joining into a gigantic blaze were noted.

Causes

A megafire can be caused by various factors, such as high temperatures, drought, human activities, and poor health of forests. Almost all (96%) of the most disastrous 500 megafires in the past decade have occurred during periods of unusual heat and/or drought. The number of uncontrollable megafires is increasing.

Probability

A 2022 United Nations report said that, at the end of the 21st century, the probability of a major wildfire occurring somewhere in the world in any given year—an event "similar to Australia's 2019–2020 Black Summer or the huge Arctic fires in 2020"—will have increased by 31% to 57%.

Historic megafires

Megafires have affected multiple regions around the world, including

Amazonia The Amazon rainforest, also called the Amazon jungle or Amazonia, is a moist broadleaf tropical rainforest in the Amazon biome that covers most of the Amazon basin of South America. This basin encompasses , of which are covered by the rainf ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

, Australia,

Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...

, Greenland, Mediterranean Basin and the

Congo Basin The Congo Basin () is the sedimentary basin of the Congo River. The Congo Basin is located in Central Africa, in a region known as west equatorial Africa. The Congo Basin region is sometimes known simply as the Congo. It contains some of the larg ...

. They occur on all 6 continents that are permanently inhabited, including areas near the Arctic Circle. In November 2018, the

Camp Fire A campfire is a fire at a campsite. Campfire or Camp Fire may also refer to: Arts and entertainment * ''Campfire'' (James Blundell album) (2017) * ''Campfire'' (Kasey Chambers album) (2018) * ''Campfire'' (Rend Collective album) (2012) * "Camp ...

, a megafire in California, killed 85 people and ravaged . By early 2019, in the Mediterranean Basin, the countries affected by such fires included Spain, Portugal, Turkey, and Greece. At the end of 2019, Brazil, Congo, Russia, and the United States had suffered from megafires on a scale described as "unprecedented". In Australia, during the 2019–20's bushfire season, numerous megafires erupted. In all, an estimated 24.3 million

hectare The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), that is, square metres (), and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. ...

s (243,000

square kilometre The square kilometre (square kilometer in American spelling; symbol: km2) is a multiple of the square metre, the SI unit of area or surface area. In the SI unit of area (m2), 1 km2 is equal to 1M(m2). 1 km2 is equal to: * 1,000,000 squar ...

s) burned, with one consuming . The

August Complex Fire The August Complex fire was a massive wildfire complex that burned in the Coast Range of Northern California, in Glenn, Lake, Mendocino, Tehama, Trinity, and Shasta Counties. The complex originated as 38 separate fires started by lightni ...

in Northern California surpassed one million acres during the

2020 California wildfire season 2020 was a record-setting year for wildfires in California. Over the course of the year, 8,648 fires burned , more than four percent of the state's roughly 100 million acres of land, making 2020 the largest wildfire season recorded in Calif ...

. In July 2021, the

Bootleg Fire The Bootleg Fire, named after the nearby Bootleg Spring, was a large wildfire that started near Beatty, Oregon, Beatty, Oregon, on July 6, 2021. Before being fully contained on August 15, 2021, it had burned . It is the third-largest fire in the ...

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

overran chemical retardant firebreaks set by firefighters. It was so large and hot that it changed the local weather. In February 2024, the

Smokehouse Creek Fire The Smokehouse Creek Fire was a record-breaking wildfire affecting the northeastern Texas panhandle and western Oklahoma that started on February 26, 2024. The fire affected numerous communities in Hemphill and Roberts counties, including the ...

in Texas and Oklahoma burned over a million acres within three days.

References