A megafire is an extraordinary

fire Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction Product (chemistry), products. At a certain point in the combustion reaction, called the ignition ...

that devastates a large area. They are characterized by their intensity, size, duration, and uncontrollable dimension. There is no precise scientific definition.

Definition

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

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

study expands the megafire definition to include a variety of factors: "Between climate change 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 state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...

and

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...

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 and

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

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 phen ...

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 (Black Summer), was a period of bushfires in many parts of Australia, which, due to its unusual intensity, size, duration, and uncontrollable dimension, is considered a megafire. The Australian National ...

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, Amazon jungle or ; es, Selva amazónica, , or usually ; french: Forêt amazonienne; nl, Amazoneregenwoud. In English, the names are sometimes capitalized further, as Amazon Rainforest, Amazon Forest, or Amazon Jungle. ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

, Australia,

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part of ...

, Greenland,

Mediterranean Basin In biogeography, the Mediterranean Basin (; also known as the Mediterranean Region or sometimes Mediterranea) is the region of lands around the Mediterranean Sea that have mostly a Mediterranean climate, with mild to cool, rainy winters and w ...

and the

Congo Basin The Congo Basin (french: Bassin du Congo) 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 con ...

. 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 that provides light and warmth, and heat for cooking. It can also serve as a beacon, and an insect and predator deterrent. Established campgrounds often provide a stone or steel fire ring for safety. Campfires ...

, 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, with one consuming . The August Complex Fire in Northern California surpassed one million acres during the

2020 California wildfire season The 2020 California wildfire season, part of the 2020 Western United States wildfire season, was a record-setting year of wildfires in California. By the end of the year, 9,917 fires had burned , more than 4% of the state's roughly 100 mil ...

. In July 2021, the Bootleg Fire in

Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

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

References