by Howard V. Hendrix
“Paradise is burning.”
That’s the ubiquitous headline as I write this. The “Paradise” referred to in the media reports is Paradise, California, which is enduring the deadliest wildfire yet recorded in the state. The aforementioned headline, however, has broader applicability.
As a long-time volunteer fire fighter, I learned early on about the “fire triangle,” the three basic components needed for fire: Air (oxygen), heat (ignition source), fuel (substances amenable to rapidly oxidative exothermic reaction). To really understand the history of fire, however, we need to look at fire in deep time. So instead of thinking merely “air” or “oxygen,” think “Evolution of the Atmosphere.” Instead of thinking merely of “heat” or “ignition source,” think “Evolution of Climate.” Instead of thinking merely of “fuel,” think “Evolution of Vegetation.”
Compared to Venus and Mars—our two nearest neighbors and most analogous companion planets—Earth might indeed seem like a paradise. Venus is a hotspot, Mars is a coldspot, Earth is a garden spot (at least in geologically recent terms). The surface of Venus is plenty hot (900 degrees Fahrenheit, hot enough to melt lead), but there are no wildfires on Venus (also almost zero oxygen and no liquid water, although there are sulfuric acid clouds). Mars is plenty dry (liquid water is scarce to nonexistent at the surface), but there are no wildfires on Mars either (also very cold, at minus 80 Fahrenheit on average, and again almost zero oxygen).
Curiously, both the atmosphere of Mars and Venus are made of similar components—95-96 percent carbon dioxide, and around 3 percent nitrogen. The difference is that the atmosphere of Venus is extremely thick and dense (resulting in about 90 Earth atmospheres’ pressure at the surface), while the atmosphere of Mars is very thin (about one hundred times less dense than Earth’s). Carbon dioxide is a greenhouse gas, and the brutal high temperatures on thick-atmosphered Venus are generally attributed to a runaway greenhouse effect. The atmosphere on Mars, in contrast, is so thin that even its high percentage of carbon dioxide is not enough to maintain temperatures appropriate to a greenhouse.
The strength of the greenhouse effect on Venus makes things too hot. The weakness of the greenhouse effect on Mars makes things too cold. The greenhouse effect on Earth (with a relatively thick atmosphere, but carbon dioxide at only four one-hundredths of a per cent by volume) is just strong enough to make things just right, temperature wise. Earth is thus a so-called “Goldilocks planet,” a resident of the habitable zone, that range of orbits around a star where—along with appropriate gravity, a convecting planetary core and mantle, geodynamo, and magnetic field—a planetary surface can support the presence of liquid water.
Planetary formation (Planet “Earth”) and the first presence of water (Planet “Water”) are both abiotic (water in fact hails from terrestrial and extraterrestrial sources). Without life, Earth four billion years ago looked a lot like Venus and Mars. And it took 800 million years for life to arise on Earth (3.6 billion years ago).
What eventually made possible Planet “Air” was the capacity of later living things (first cyanobacteria and, still later, plants) to take carbon dioxide, water, and sunlight and, through the trick of photosynthesis, produce carbohydrates and release oxygen. All the other elemental “planets” (Earth, Water, Air) had to be in place before Planet Fire could exist.
So life is on Earth and Earth is on life, but it’s not that simple. Life is never easy. Climate is subject to many cycles involving celestial events—Milankovitch cycles, sunspot cycles, and more. The climate variation baseline is of geological age—much longer than the existence of human beings on this planet. That climate baseline features such events as, for instance, the shifts from icehouse to hothouse periods during the Permian Epoch (around 300 million years ago), and from “super-greenhouse” to icehouse during the Eocene (between 56 and 34 million years).
Numerous extinctions, too. Extinctions and shifts in climate run in tandem across time. In fact, the first five Great Extinction events—the ones that were not caused by human activities—all involve large shifts in climate. Within these larger time-frame changes, there are far more numerous smaller-scale shifts and oscillations in climate as well.
Despite these challenges, by about a half billion years ago, Life was thriving enough that, at last, the foundations for the Reign of Fire could be established. By about 400 million years ago Earth had transitioned from a world with no natural landscape fire to one featuring landscape fire.
So the reign of fire, then, began two billion years after what is known as the Great Oxidation Event, and after 90 percent of the Earth’s planetary history had already taken place. Why so long? An atmosphere with sufficient oxygen had been around a long time, and so had “heat” (namely lightning, the most frequent and persistent ignition source), and so had land (or at least rock) for an eventual “landscape.” For hundreds of millions of years, however, the vast majority of photosynthesizers (and sources of potential fuel) were aquatic.
Natural landscape fire had to await the evolution of land plants—terrestrial vascular plants—beginning about 450 million years ago, before the “natural” or non-anthropogenic fire regime could get underway. After such plants—combination solar panels, water pumps, and candy factories—had become sufficiently established and widespread enough to support fire across the landscape, the fire triangle in deep time was complete for natural landscape fire. However, this was only after changes in the atmosphere (chemical composition) and changes in the climate (temperature) had allowed for changes in vegetation (plant evolution).
How do we know that landscape fire began around 400 million years ago, or about fire in deep time more generally? An important way is through very recent technologies, particularly scanning electron micrographs of plant remains preserved in fossilized charcoal. From this and the fossil record overall, we know that a lot happens during the reign of natural or non-anthropogenic landscape fire, from the rise of the first forests in the Devonian period to the rise of hominins in the Quaternary period.
During natural landscape fire’s long rule, Life itself almost dies out completely from the Earth at the end of the Permian period (250 million years ago) and takes a number of major hits at the end of the Devonian (370 mya), the Triassic (200 mya) and the Cretaceous (65 mya). Importantly for any discussion of the fire in Paradise, California—located in the Sierra foothills—the Sierra Nevada mountain range itself arises only 40 million years ago, after 90 percent of the reign of natural landscape fire has already happened.
At 400,000 years ago, or after 99.9 percent of natural landscape fire’s existence on this planet, humans have at last made the transition from opportunistic “fire users” and “fire keepers” (beginning over a million years ago) to fire producers and fire managers (beginning at least half a million years later, at the earliest).
In that time between user and maker, however, fire had already shaped us. We say “humans discovered fire” but it’s almost as true to say “fire discovered humans.” Before we were making fire, fire was already making us. Yes, we domesticated fire to some degree, but to about an equal degree fire domesticated us.
James Boswell, chronicler of Dr. Samuel Johnson (author of the first dictionary), remarked that “no beast is a cook” and called Homo sapiens “the cooking animal.” The gastronome Brillat-Savarin and the anthropologist Levi-Strauss agreed that cooking is symbolic of how we are different from animals.
Domesticated fire altered the course of biological evolution by opening up to us a trove of more energy-dense and easily digestible food that was often unavailable to animals that did not have controlled fire—and therefore could not compete with us for that food source (starches in tubers, particularly). Fire also altered the course of cultural evolution: Raw food gatherers and foragers eat on the go, but coming together round the cooking fire sat us down to common meals with each other, giving us social focus and feeding our impulse toward civilization. Not to mention domestic fire’s importance for warmth, protection against large predators, and as a tool for making more tools.
To top it off, since we split off from the last common ancestor we shared with the Denisovans, the Neandertals, sometime in the last 800,000 years, we Homo sapiens evolved a unique mutation of the gene that makes the AHR (aryl hydrocarbon receptor) protein. That mutation allows us to cope much better with a smoky environment and the polycyclic aromatic hydrocarbons associated with such an environment, thereby allowing us to minimize many of fire’s deleterious health effects while also allowing us to more fully and efficiently harness the benefits of fire better than our fellow hominins ever could. Our long interaction with fire has literally shaped us at the genetic level, and has left in us a genetic marker of that shaping.
We took fire from the landscape and put it in the fire pit, but once we were familiar enough with it we reintroduced it to the landscape, first as a tool to drive animals in the hunt, and then to foster wild plant food and plant fiber availability. Later—in more controlled fashion beginning about 10,000-12,000 years ago or so—this reintroduction proved crucial to what became known as slash-and-burn agriculture, still an important food production process in much of the world.
Many cereal crops characteristic of agricultural production worldwide are also only edible after cooking. The preparation and cooking of starchy grains that could be planted, harvested, and stored eventually led to the shift from a more nomadic hunting-and-gathering existence to a more settled agricultural one. Before long, it was cities and empires.
The next great shift in fire use goes back importantly only about 300 years or so, and also involves cities. It involves not only a shift in spatial location but also a shift in time. Data from numerous sources indicate that, since the onset of the industrial revolution in the eighteenth century, combustion practices with carbon dioxide impacts have been shifting from open landscape burning to contained combustion for industrial purposes—from stubble fields to factory stacks, cornstalks to tailpipes.
Fire scientists Stephen Pyne and Andrew Scott have suggested that, with urbanization, there is yet another pyric transition underway. We harness fire for energy, heating, and transport but try to keep it away from our homes and businesses. As a percentage of total fire activity worldwide, agricultural fire use has been declining, natural fire has been suppressed in many environments, and fossil fuel use has increased. The temporal dimension of this transition is that we have moved from the use of real-time fuels (recently living biomass) as our fire’s source, to binging on fossil fuels (ancient fossil biomass, usually millions of years old) as our fire source.
The psychological dimension of this transition is that ideas of landscape fire management and use have been supplanted by ideas of fire suppression and even the eradication of fire. Since fire is something to be excluded from the cityscape, the prevailing attitude in many industrialized countries now extends that urban mindset to the idea that fire is bad everywhere, including everywhere in the landscape.
Yet fire has moved upon the landscape far longer than we have walked upon the Earth. The long history of fire shows us that it will not be eradicated. Our suppression of fires in the landscape causes the buildup of surface fuels, so that subsequent landscape fires, such as the one that swept through Paradise, become more intense and devastating. In the North American West, from Mexico to Alaska, we have taken ecosystems once sustained by fire and—through fire suppression—have turned them into ecosystems destroyed by fire. We have proven to be the victims of our own success.
This does not mean we can do nothing. Think again about those parallel tracks of extinctions and climate shifts, for there’s a deeper relevance here. For the vast majority of the history of life on Earth, extinctions have been nature’s business—none of our business. Over the last ten to twelve thousand years or so (initially unintentionally and almost unconsciously), and particularly over the last three hundred years, human beings have gotten into the extinction business. We’ve gotten into it in such a big way that our current epoch is increasingly referred to as the time of the Sixth Great Extinction, the Holocene or Anthropocene Extinction.
Similarly, for the vast majority of Earth’s climate history, climate variations have been nature’s business—none of our business. Over the last ten to twelve thousand years or so (again initially unintentionally and almost unconsciously), and particularly over the last three hundred years, human beings have gotten into the climate business.
If we are to return to balance our currently unbalanced relationship with fire, we must become consciously and intentionally reacquainted with the complexities of the fire system. We have become alienated from fire, our long-time intimate partner in the dance of life on this planet. As human population grows and becomes still more urbanized, this alienation from, and misunderstanding of, fire is also likely to grow, unless countered by educational efforts emphasizing that fire has its place—and both good and bad effects.
Even in the dreamed green city of the future, with its wind turbines and solar panels and geodesic rooftop greenhouses all plugging back into the Sun itself, room will always need to be made for fire. And for now it’s still a lot more difficult to make photovoltaic cells grow themselves, and store their energy, and reproduce themselves, than it is to plant and tend trees that do the same.
After an all-too-successful century of fire suppression, a more careful and nuanced re-involvement with fire in the landscape is what is needed—a shift from dominion to stewardship, in order to make our forests more resilient in the face of whatever climate variations may be forthcoming. Such an approach will require recognition of the reality of climate change, hand crews and mechanical thinning to reduce the fuel buildups in our landscape before we can reintroduce fire in a controlled fashion, and the hardening of structures against embers and brands for those of us who live or wish to live in the wildland urban interface. Such measures will depend on political will and personal wallet, but only through such an approach can we hope to rebuild Paradise.