The age of the megafire

Why the forest fires raging across Europe, North America and Australia are a sign of the world to come.

This may well be remembered as the year of the megafire. The Dixie fire in California, which is still raging, is the largest single wildfire in that fire-prone state’s history, while in Siberia, forest fires have broken all records for the amount of greenhouse gases they have released. The plume of smoke they generated has spread as far as the North Pole, scattering ash on the Arctic Sea ice as it goes, hastening its melting. In Canada, a place hardly known for its hot weather and fires, more than 4,900 blazes burn in British Columbia and Ontario alone, while in Europe 693 million hectares have burned – more than double the average by this time of year – and the number of fires in the continent has never been greater.

Australia, where I live, has a reputation as the land of fire. The continent has warmed by almost 1.5°C over the past century and the impact of this on fire offers a sort of window into the future for the Northern Hemisphere. Firefighting in Australia is often a family tradition, with knowledge being passed down the generations, and our firefighters have a long and detailed understanding of fire behaviour. Fifty years ago in New South Wales the fire season was well defined, occurring in the summer months. It has gradually got longer and longer, until today it is 11 months long and almost nowhere is safe. Even temperate rainforests that have never been known to burn are now vulnerable.

I speak from personal experience when I say that a forest fire is like an angry beast. I’ve lost one house near Sydney to the flames, and years later successfully defended another. Waiting for days or weeks for the attack in the stifling, smoke-filled air, your precious possessions stowed in your car, ready to evacuate at the approach of an unearthly roar and towering flames, leaves an indelible psychological scar.

This summer across the Northern Hemisphere, from the Greek island of Evia to south-western Turkey, California to Russia, large numbers of people are confronting the fire-beast close-up. Some have already lost their lives, and many, many more their homes and economic security. Sadly, those people are in the vanguard of a great global change, for while there have always been forest fires, the blazes are becoming larger, the fire season longer, and the burns more damaging almost everywhere. That’s because climate change has altered, in a fundamental way, the nature of wildfires.

That alteration has its origins in subtle shifts that have played out over decades, slowly building until thresholds are crossed and fire itself is transformed. We often miss seeing the subtle changes because we’re desperate to find someone to blame, and so search for an arsonist rather than the conditions that made the fire inevitable. But the sparks that light fires – whether they be dropped cigarette butts or lightning bolts – are regular occurrences. They only result in forest fires if the nearby vegetation is dried and cured into fire-fuel.

As they gauge the coming fire season, firefighters have learned to look not only at the weather forecasts, but at the forests themselves. Greater warmth means that the vegetation requires more water, and to get it trees suck moisture from the soil. When the soil is dry, the tree canopy wilts, and the shrubs and grass grow brittle. Even in mild conditions, such changes put firefighters on alert: they know that they are only one hot, windy day away from potential catastrophe.

Animal rescue: locals evacuate with their cattle as wildfires rage in Athens, Greece, on 7 August. Picture credit: Giorgos Moutafis / Reuters

As the fuel that feeds the fire becomes more abundant, fires are growing larger and hotter. Some become so big that they themselves alter the weather. Australia’s Black Summer fires of 2020 fed on unprecedented volumes of fuel created by the driest year on record (and one of the hottest) and grew to be like no fire previously experienced. Prior to 2000, in a bad year around 2 per cent of Australia’s temperate, broadleaf forests would burn. But in the Black Summer of 2020, 21 per cent went up in flames. That’s a tenfold increase – in a single year. Every impact of the fire was magnified by its scale. More than 400 people, some living many miles from the nearest fire, died of smoke inhalation. The damage to infrastructure, including homes, was unprecedented and will take many years to recover from. Some regional communities may never fully recover at all. And when the flames were finally doused by torrential rainfall and enormous floods, toxic ash washed into the ocean off eastern Australia in such volume that the marine environment was devastated, causing mass deaths on offshore reefs.

This paradoxical sequence of extreme drought followed by devastating flood seems set to spread beyond Australia’s shores. This summer Turkey suffered wildfires in its south-west and catastrophic flooding in its north. And taking a continent-wide view, the same thing can be said of Europe, with Belgium and parts of Germany overwhelmed by floods as Greece burned. Climate change has now gained such momentum that I fear Europeans will in coming years witness the tragic sequence so familiar in Australia, where megafires followed by megafloods sequentially devastate the same area.

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Forest fires are dynamic processes that are exquisitely sensitive to seemingly small changes in climate. Inherent in their development under warmer conditions are positive feedback loops that make them ever more menacing. Pyrocumulonimbus clouds occur when the heat from the fire creates convection currents that punch through to the stratosphere, lofting smoke and embers high into the air. Some fire-generated currents reach to 16 kilometres, and there the airmass cools, and in falling back to earth creates enormous thunderstorms.

Pyrocumulonimbus-generated storms spread fire in several ways. They can create fire tornadoes that implode buildings through low air pressure. They can generate an abundance of lightning strikes that spreads the fire front, and they scatter burning embers far and wide. Perhaps most damaging, however, are the extreme winds they generate, which fan the flames like bellows in a furnace.

According to firefighters, Australia’s 1939 Black Friday bushfires generated a pyrocumulonimbus storm. Another was not seen until 1978, and then one more in 2001. In the decade following, however, 60 were seen. Then came the Black Summer fires of 2020, which generated 35 – the greatest cluster ever seen anywhere on Earth.

Australia may be a long way from Europe, and its forests very different. But the same rules of physics apply to fires in both places. In 2017 an Australian scientist was remotely monitoring a forest fire in Portugal when he saw indications that a terrifying phenomenon that he was familiar with in Australia had formed. It would take months to confirm his hunch, but eventually it was announced that Europe had experienced its first recognised pyrocumulonimbus storm. It had resulted from the Pedrógão Grande fire in central Portugal, which burned 4,460 hectares and killed 64 people. Terrified eye-witnesses described the storm as being like “a sudden ‘bomb’ of fire spreading tongues of flames and sparks in all directions”.

As the Californians have learned through bitter experience, the vegetation that grows back after a megafire can itself feed future catastrophic fires. The first plants to sprout from the ashes are grasses, which are highly combustible. In the next fire season, grasses can feed fires that race through the country with terrifying speed, destroying houses, crops and livestock. For this reason, both Californians and Australians have learned to fear the abundant rain that can fall after a fire season, for it brings up a luxuriant crop of grass that dries and cures quickly.

Megafires can prepare the way for their successors in other ways as well. Because they burn vast areas, the vegetation that returns in their wake will be uniform in age over huge areas, and it will consist of the most fire-tolerant species. Such species, indeed, often need fire to complete their life cycle. The old mosaic of species that existed before the megafire, and which included fire-impeding species and areas with low fuel loads, is swept away, allowing the fires of the future to spread ever more swiftly and devastatingly.

The advice given to those facing fires in Australia has changed over the years. We used to be told to “stay and defend” where safe to do so. But nowadays the advice is to evacuate – sometimes at the first sign of smoke. As I watched the people of Evia heroically staying and defending their properties, often without the assistance of professional firefighters, I was filled with a mixture of admiration and foreboding. Europe’s fires have not yet, by and large, been transformed into the devouring monsters that Australia’s bushfires have become, but all signs are that in the near future they will be.

The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report, released this month, says that there’s a high probability that the extreme heat and loss of soil moisture that makes forest fires so deadly will increase globally in the future. We must do all we can to cut emissions, and in doing so reduce the scale of the damage. But the seeds of future megafires are clearly already sown, and Europe needs to be prepared for cataclysm.

Tim Flannery is an Australian zoologist and environmentalist. His books include “The Weather Makers: Our Changing Climate and What it Means for Life on Earth” (Penguin)

This article appears in the 18 August 2021 issue of the New Statesman, The Great Betrayal