From the Arctic to the Amazon, from California to Gran Canaria, from Borneo to India to Angola to Australia – the fires seem everywhere. Their smoke obscures subcontinents by day; their lights dapple continents at night, like a Milky Way of flame-stars. Rather than catalogue what is burning, one might more aptly ask: what isn’t? Where flames are not visible, the lights of cities and of gas flares are: combustion via the transubstantiation of coal and oil into electricity. To many observers, they appear as the pilot flames of an advancing apocalypse. Even Greenland is burning.

But the fires we see are only part of our disturbed pyrogeography. Of perhaps equal magnitude is a parallel world of lost, missing and sublimated fires. The landscapes that should have fire and don’t. The marinating of the atmosphere by greenhouse gases. The sites where traditional flame has been replaced by combustion in machines. The Earth’s biota is disintegrating as much by tame fire’s absence as by feral fire’s outbreaks. The scene is not just about the bad burns that trash countrysides and crash into towns; it’s equally about the good fires that have vanished because they are suppressed or no longer lit. Looming over it all is a planetary warming from fossil-fuel combustion that acts as a performance enhancer on all aspects of fire on Earth.

So dire is the picture that some observers argue that the past is irrelevant. We are headed into a no-narrative, no-analogue future. So immense and unimaginable are the coming upheavals that the arc of inherited knowledge that joins us to the past has broken. There is no precedent for what we are about to experience, no means by which to triangulate from accumulated human wisdom into a future unlike anything we have known before.

Yet a narrative is possible. Where once there was one kind of fire on Earth, then two, there are now three. That’s the narrative. Between them, they are sculpting a Fire Age equivalent in stature to the Ice Ages of the Pleistocene. That’s the analogue. Call it the Pyrocene.

The Pleistocene began 2.58 million years ago. Unusually among geologic periods, it is characterised by climate. The Earth cooled and, atop that trend, it repeatedly toggled between frost and thaw, as 40-50 cycles switched between glacial ice and interglacial warmth. Some 90 per cent of the past 900,000 years have been icy. Our current epoch, the Holocene, is one of the interglacial warm spells, and most calculations reckon that the Earth is due – maybe overdue – to swing back to ice. The Little Ice Age (starting somewhere between 1350 and 1550, and ending in 1850) suggests what that transition might look like. The world chilled, winters lengthened, glaciers and ice packs spread, crops failed and famines flourished. The Pleistocene is also the age of humans. Homo appeared near its onset, brachiated into a clad of hominins, and by the end of the last glacial shrank to only one, H sapiens.

The term Ice Age (Eiszeit) was popularised by Louis Agassiz in 1837. The Little Ice Age had expanded Alpine glaciers, and Agassiz realised that he could explain much of what the newly invented science of geology was discovering by extrapolating the realm of ice beyond its mountain niches. Ice sheets had once covered much of North America and northern Eurasia, Greenland and Antarctica; glaciers had spilled down mountains from the Sierra Nevada Mountains of California to the Karakoram Range to Mount Kilimanjaro in Kenya; and Arctic and Antarctic oceans were frozen. Vast outwash plains filled with sand and loess. And everything around the ice felt its presence. The mounding ice sucked enough water out of the world ocean to drop sea levels by 100 metres on four occasions, exposing vast swathes of the continental shelves, and so joining Siberia to Alaska, Britain to France, and Australia to Indonesia. Under the crosscut of climate, one of the five great extinctions in geologic history occurred, as alternating bouts of frost and thaw shrank habitats, isolated ecological sanctuaries, and compelled forced-march migrations over and again. Only a handful of megafauna have survived; among the hominins, only one.

How to characterise the interglacial during which we sapients stormed across the globe, pitched cities on Antarctic ice, guided vessels to the bottom of the Marianas Trench, and went off-world? Geologists first named it the Recent, then morphed it into the Holocene, and now debate whether to spin it off as an Anthropocene. Other than the fact that it’s our time, and we are sufficiently special in our own eyes to merit our own era, there is little cause to have split it off from the Pleistocene. The grand conditions that set into motion an Ice Age – the arrangement of mountains, interior seas, continents and oceans, and the suturing of Panama that shut off ocean currents between Atlantic and Pacific – remain unchanged. Above all, the Milankovitch cycles that describe the wobbles, stretches and swings in the Earth’s rotation and orbit around the Sun, and that cause perturbations in the amount of sunlight received, endure unaltered. By the metrics that established the Pleistocene, the Pleistocene persists. Only humanity’s vanity insists on a secessional epoch. The ice will return.

Or not. Something seems to have broken the rhythms. That something is us. Or more usefully, among all the assorted ecological wobbles and biotic swerves that humans affect, the sapients negotiated a pact with fire. We created conditions that favoured more fire, and together we have so reworked the planet that we now have remade biotas, begun melting most of the relic ice, turned the atmosphere into a crock pot and the oceans into acid vats, and are sparking a sixth great extinction. If this sounds familiar, as though having passed through a looking glass, it’s because fire has become as much a cause and consequence as ice was before. We’re entering a Fire Age.

The firestick morphed into an Archimedean lever by which to move the planet

All analogies fail, and some become silly, but consider, as a thought experiment, how a Fire Age might compare with an Ice Age. The big difference is that ice is a substance easily seen and fire is a reaction quickly passed. Ice exists in masses; an ice sheet is a plateau of frozen water, glaciers are slow-moving rivers of ice, and outwash plains are swathes of sand and silt from meltwater and wind. By contrast, flame is ephemeral; its evidence lies primarily in its effects on the living landscape. Instead of ice sheets, glaciers and periglacial environments adjacent to the ice, a Pyrocene manifests itself with fire-informed biotas, fire-starved biotas, hot spots where fire is the dominant energy source, peripyric landscapes where humans equipped with pyrotechnologies have reshaped the scene, and of course a warming atmosphere and unhinged climate that passes over the planet. Nothing on Earth would be unaffected – certainly not the planet’s keystone species for fire, ourselves.

Let’s put details to the analogues. The Pleistocene had its hemispheric ice sheets, its pluvial lakes, its glaciers, its periglacial terrains that constituted second-order ice effects. What would be the equivalent for the Pyrocene? The great steppes, savannas and prairies that, stripped of fires, soon overgrow with trees; boreal forests routinely overturned and renewed by flame; fynbos heathland and Mediterranean shrublands – these are analogues of ice sheets. Montane forests and grassy woodlands no longer subject to regular fire and so transfiguring into woody jungles could be the echo of pluvial lakes. Cities and biotic patches such as pitch pine-oak resemble ice caps and glaciers. And for peripyric landscapes, think Cerrado, moor, rainforest, temperate forest converted to fire-catalysed agriculture, or the outwash plains of smoke or even electrical blackouts.

And then consider the ways in which the rhythms of fire engines are replacing the Milankovitch pacemaker. The Milankovitch rhythms acted as a rheostat that modulated the swings into and out of ice. The wholesale combustion of fossil biomass is similarly recalibrating the Earth’s climate and redefining how people in the developed world live on the land. By burning fuels from deep time, we are redefining the options available for generations to come. We are taking carbon from lithic landscapes of coal and petroleum buried in the geologic past, passing it through today’s living landscapes, and releasing it into the geologic future. Little of the planet is unaffected.

It’s not that Earth will go up in flames – it won’t, any more than Pleistocene ice plated the entire planet. Most of the effects will be indirect; a good deal of what fire does is catalyse other processes; it’s the ultimate interactive technology. It’s that the pact between humanity and fire is reshaping the planet as thoroughly as ice had before. Our combustion habits are driving out the last surface expressions of Pleistocene ice, save in refugia such as Antarctica, and even opening up buried reservoirs such as organic-rich permafrost. In the process, the oceans are rising, the climatic frames for life are rapidly deforming, and a wave of extinction is rippling over the planet. An ice-informed Pleistocene is yielding to a fire-informed Pyrocene.

Really? As an idea, the Pyrocene gives us a usable narrative, a crisp analogy, and a new way to imagine our fast-morphing world. It furnishes the historical continuity that Cassandras of a climate-addled Anthropocene prophesise the future will lack. Our fire habits are the weld that binds past with future.

The process by which the Pyrocene has been created didn’t begin with coal-fired engines. It began with aboriginal peoples burning to keep grasslands, shrublands and woodlands open, which stalled carbon-sequestering forests from overrunning them. Through successive iterations, the firestick morphed into an Archimedean lever by which to move the planet. It ratcheted up with agriculture, especially where forests were cleared and peatlands slashed and burned, and where wet-rice paddies and livestock pumped out new volumes of methane. The spread of agriculture aligned roughly with the stabilisation of the global climate.

Curiously, the onset of the Little Ice Age might have responded to the mass die-offs of Indigenous peoples in the Americas and to the plagues that emptied much of Eurasia, which allowed forests to spread widely, partly resetting the historic cycle in which global refreezing would follow a thaw. The Little Ice Age receded when forests were recleared and fossil fuels began to measurably boost greenhouse gases. With the shift to coal, the engines of the Pyrocene got afterburners. This time, however, there was no check on the process.

The ice ages obeyed grand geophysical forces. As ice retreated, biotas advanced, storing carbon, interacting with the wobbles and swaying of sunlight, and thus encouraging the next round of ice. Fire-wielding humans seem to have disrupted the process, keeping global temperatures higher than the historic rhythms would have predicted. Still, there were limits to human-enabled burning. Burn too much, too quickly, and living landscape cannot recover, and the fires ebb.

Once humans started burning fire’s lithic landscapes – fossil fuels – there seemed to be no such limits. Fuels were essentially unbounded, and they can be fired without regard to such ancient ecological barriers and baffles as seasons and sunshine, wet and dry spells, winds and terrain, the combustion character of grasses and woods. The ancient quest for fire had been a search for new stuff to burn. Today’s crisis is what to do with all the effluent. The sources have overwhelmed the sinks. There is nothing to stop the burning except human will. But while we have rewired the Earth’s energy system, we have not rewritten the operating manual. Instead, fire sparks more fire.

All fires take apart what photosynthesis puts together. But not all fires behave the same way. Three fires now exist, and they interact in a kind of three-body dynamic. The first fire is nature’s. It has existed since plants first colonised continents. It can be lumpy in space and time; it depends on lightning’s lottery to kindle suitable fuels. The second fire is humanity’s. It’s what humans have done as they moved from cooking food to cooking landscapes, and because it feeds on the same grasses, shrubs and woods as first-fire, the two fires compete for fuels: what one burns the other can’t, and neither can break beyond the ecological boundaries set by their biotic matrix. Second-fire can extend the domain and timing of burning – can recode the patches and pulses of fire on living landscapes. Third-fire transcends the others. It burns fossil biomass, a fuel which is outside the biotic box of the living world. Where third-fire flourishes, the others don’t, or can burn only in special preserves or as genuinely wild breakouts. After a period of transition, third-fire erases the others, leaving ecological messes behind. Because it doesn’t burn living landscapes, those combustibles grow and pile up and create conditions for more damaging burns; because it isn’t in a biotic box, its smoke can overwhelm local airsheds and its emissions can clog the global atmosphere.

Third-fire doesn’t play well with the others. Wherever it and second-fire meet, it substitutes for or suppresses flame. This is especially so in the built environment. Electric lights replace candles; heat pumps, propane heaters and fuel-oil furnaces substitute for open hearths; electric or propane stoves supplant fires and wood-burning stoves. Except for ceremonial purposes such as birthday candles or candle-lit dinners, open flame disappears. The same occurs in factories and offices.

Landscapes can burn with a savagery beyond their natural order

The substitution of third-fire for second-fire spread to agriculture. Tractors fed by diesel shove aside oxen and mules fed on grains grown on fire-renewed fallow; herbicides, pesticides and artificial fertilisers replace the fertilising and fumigating effects of fire. Contrary to European agronomic thinking, fallow is not a superstitious practice worsened by then burning the rested fields; the ecological jolt of fire is the purpose. Since fire needs fuel, in an agricultural system that means growing it, which is the function of fallowing. Now, fossil fallow serves that role. It supplies a stored surplus that we can burn to enrich fields indirectly and avoid setting part of the agricultural landscape temporarily aside.

The mosaic created by fallowing held most of a rural landscape’s biodiversity. Fallowed fields, hedgerows, woodlots – such sites dappled agricultural lands with a kaleidoscope of habitats. In abolishing the practice, third-fire demanded that people invent an alternative place for biodiversity in the form of nature reserves. Initially, this meant eliminating open flame in the preserves as well. Yet suppressing fire, or even attempting to remove it, from places accustomed to it can profoundly disrupt ecosystems. Eventually fire will return; the issue is whether it happens deliberately through controlled burns or through wildfires. But fire there will be.

Paradoxically, ours has become a great era for first-fire and for second-fire gone feral. The loser is traditional second-fire, the primary means by which humans have over tens of millennia crafted a working habitat. Wildfire, machined fire – these dominate the developed world. The developing world is transitioning to third-fire as speedily as possible. Even without climate change, third-fire has scrambled the Earth’s pyrogeography. It has created a damaging deficit of fire in living landscapes and a corrosive surplus of combustion from lithic ones.

The three fires we see today – nature’s; those fires that people set in living landscapes; and those burning lithic landscapes – are competing and colluding in weird ways. The polar bear on a shrinking ice floe has become an iconic image of climate change stoked by fossil-fuel combustion. But the bears spend part of their lives on land for denning and birthing. On the western shores of Hudson Bay, wildfires are thawing the permafrost that overlies the dens, causing them to collapse. On land and sea, the bears are caught between three fires.

So are we. The 2016 fire that burned Fort McMurray in Alberta roared out of the wildlands to slam into a city maintained by fossil fuels – in fact, created to mine tar sands. The prevailing images are of refugees fleeing by car, and of cars melted on their driveways. The fires that burned into Gatlinburg in Tennessee (2016) and that incinerated almost all of Paradise in California (2018) started from powerlines. So did most of the bushfires that savaged the Australian state of Victoria on Black Saturday (2009); of the 173 people killed, 162 died from fires set by powerlines traversing the landscape from the Hazelwood powerplant which burned brown coal that made it, until it was finally decommissioned, the greatest single source of Australia’s greenhouse gases. Eventually, the open mine itself caught fire.

It is not just that town and countryside meet like matter and antimatter. It’s that the source of ignition often comes when lines of power cross both worlds and when the landscapes can burn with a savagery beyond their natural order because third-fire has changed how people interact with them. It isn’t just that third-fire has unmoored the climate, it’s that it fundamentally shapes how we live on the land – how we get around, how and where we grow food, what kinds of housing we prefer, whether the countryside is rural or wild, how we get and use power. Those melted cars in the driveways of Fort Mac and Paradise are the pyric doubles of the bears at the burning garbage dump at Churchill. The bears are not alone.

There is a tendency in Western thought to identify a single grand cause or theory for whatever catches the imagination. It is an inclination so recurrent that it seems to emanate from cultural DNA, perhaps a secularisation of Judeo-Christian theology. We like to prune and push and probe until we have identified a sole, jealous motive that binds all and will have no other purpose before it. So, while fire seems to appear everywhere as a cause for our unsettled future, a consequence of our past habits, and a catalyst for our present condition, it is not everything, nor does everything point to it. But granting it an organising role in history can allow many of humanity’s actions to come together thematically. We hold over fire a species monopoly, after all. Our fires uniquely trace our ecological agency. Fire is not all, but not much that humanity touches is untouched by it.

What do we get by the notion of a Pyrocene? We can track a chronicle of fire that traces back to the earliest plants on land. We get a narrative that stretches back to our origins as a species. We can see how a recourse to fossil-fuel combustion evolved – the initial steam engines, after all, burned wood. We can shift away from the clotted discourse over climate change since climate history has now become a subtheme of fire history. We can understand better how the three fires interact, and where we can intervene usefully to prevent bad fires and promote good ones. We get a vivid mental image of how and why our world looks as it does. We can even appreciate the paradoxes of our fire power.

Between ice and fire, ice is the more terrible. It obliterates what it mounds over; it crushes and drives off life. By contrast, fire is a creation of the living world: life gave it oxygen and fuel and, with people, ignition. Its fundamental chemistry is a biochemistry that takes apart what photosynthesis puts together. It cannot exist without life. We can manipulate fire, directly and indirectly. We can’t ice. We survive ice by leaving. We survive fire by living with it. If at times it seems our worst enemy, it is also our best friend. We can’t thrive without it.

Cold will remain camped outside the gates, waiting for a crack that it can wedge into another ice age

Left to itself, it seems the Earth would slowly spin into another glacial epoch. It might be that only our fire habits, however inadvertently, however much entangled in the unsavoury bond that joins us to fossil-fuel combustion, are preventing a planetary winter from returning. That imperative has passed. We need to shut down as quickly as possible our binge-burning of fossil biomass and clean up as much of the mess as we can. A full-blown Fire Age will not be a pretty picture. If we want to survive it, we’ll have to renegotiate the Faustian bargain with fire that gave us big heads and small guts, and then took us to the top of the food chain.

But that is not the end of our role as the Earth’s keystone species for fire. We had a fire crisis before climate segued clearly out of past norms. In the 1960s and ’70s, the United States, for example, underwent a revolution in fire policy to reinstate flame, not just to prevent bad fires but to promote good ones. We needed to renegotiate the balance between first-fire and second-fire, and that meant a lot more burning in living landscapes. It might mean perhaps an order of magnitude more fire on the land than we have now. It means letting more of nature’s fires burn. It means setting lots of fires to tweak biotas into more habitable forms. It means getting passably good fires now to help buffer against the worst fires sure to come. It means widespread burning. Endless burning. Burning in perpetuity.

Third-fire upsets the choreography between natural and anthropogenic fire directly by competing with second-fire and indirectly by altering the climate. Even if fossil-fuel burning and its legacy vanished overnight, we would still have deep obligations to get fire right in living landscapes. The consequences of our effluent-gagged atmosphere will linger for decades, perhaps centuries into a deep future. But as we ratchet third-fire down, we need to ratchet second-fire up. Third-fire adds to Earth’s carbon load. First-fire and second-fire recycle what exists.

Still, fire’s three-body problem will persist. Unless the Milankovitch cycles dim and the oceans and continents abruptly rearrange themselves, the cold will remain camped outside the gates, waiting for a crack that it can wedge into another ice age. At some point in the future, we will have to rekindle third-fire. For a few generations, it needs to remain in the ground as fossil fallow. Then we will see if our fire powers will destroy or save us.

Our history has been a story of how we and fire have co-evolved. The same holds for our future.