FIRE is bad, right? In the modern world, flames are closely controlled even on those odd ritual occasions when we are allowed to strike a light. Under no circumstances must fire be allowed to escape.
That attitude is widely held, says Andrew C. Scott in Burning Planet. He blames it on the “pyric transition”, one that took place as ever more people moved from rural areas, where fire was an important tool, into urban centres. Here it was needed for energy, heating and transport, but only in contained settings, out of view. Natural fire today, such as the wildfires that have swept parts of California and Australia, is seen as a universal bad, something to be eradicated.
But there’s the rub, says Scott. Fire is crucial to the health of many types of vegetation, from the eucalypts of Australia to the proteaceous plants of South Africa. If we want to conserve those ecosystems, fire is essential. In many other places, such as the ponderosa pine forests of the western US, suppressing fire leads to a build-up of dead wood and therefore to more intense and dangerous fires.
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Scott’s argument is that to make sense of wildfire today, we must understand its 400-million-year history as a force of nature. Much of Burning Planet is an exploration of that history and how we know about it.
Scott is emeritus professor of geology at Royal Holloway, University of London, a palaeobotanist and an expert in fossil charcoal, which turns out to be the hero of the book. A residue of ancient fires, it forms layers in sediments, rocks and coal, ones that tell tales scientists can interpret. Scott was one of the first to stress charcoal’s importance, as he learned the lessons it had to teach – for example, that the temperature at which charcoal is made dictates the amount of light it reflects and how far it can travel across water before it absorbs so much moisture that it sinks.
In Scott’s hands, charcoal reveals how common fire was over geological time, which plants existed, what the climate was like, and even the oxygen and carbon dioxide content of air. He walks us through the past, starting 420 million years ago when plants provided the very first kindling. Then, as now, lightning was by far the most common fire starter.
We discover that the first forest fires did not coincide with the first forests, 360 million years ago, because atmospheric oxygen levels were low. It’s not until they rose 10 million years later that extensive wildfires appeared. We watch fires burn through the Carboniferous period and rage through the Permian, when oxygen was abundant enough to coax all but the wettest vegetation to ignite. Then, 250 million years ago, even plants that were adapted to this high-fire world died off as Earth headed for its largest mass extinction.
“Should people with homes in flammable ecosystems expect firefighters to risk their lives?”
By the Cretaceous, the time of the dinosaurs, fire was again a constant danger. But not, it seems, for the first flowering plants, which appear in charcoal 70 million years ago. Fire has driven the evolution of many species, says Scott, and there is good evidence that it did the same for flowering plants.
This is a thought-provoking book. What begins with arcane science broadens out to give an intriguing view of Earth’s history, wildfire’s potential role in human evolution and the mess we find ourselves in today over how to deal with it. Should people be allowed to build homes in flammable ecosystems, for example? If so, should they expect firefighters to risk their lives when the inevitable happens?
Then again, what can we do about invasive grasses which burn readily and threaten treasured plants? Scott believes that unless we stop the spread of these grasses, the iconic saguaro cactus ecosystem may disappear within 30 years.
The tragedies fire might cause are numerous, especially in a warming world where access to water may become a challenge. And fire has a habit of breaking out even when we have done our best to prevent it. What we need, says Scott, is a transformation in our attitude to this essential cog in Earth’s workings.
Consider the alarm raised.
Oxford University Press
This article appeared in print under the headline “Why fire is a hot potato”
