We owe Earth as we know it to fire. Fire-prone ecosystems cover 40 percent of the land surface today, and fires play a key role in maintaining many of the world’s major biomes, including grasslands, savannas, shrublands and boreal forests.
For hundreds of millions of years, wildfires have shaped the planet, from the plants, animals and ecosystems around us to the air we breathe.
The oldest evidenceof wildfire comes from a 420-million-year-old rhyniophytoid plant, a small leafless plant from the Silurian Period, whose charred remains were found in an English siltstone. Charcoal, soot, polyaromatic hydrocarbons and evidence of fire scars in tree rings are the typical evidence of fire, with charcoal, usually found in sedimentary rocks, being the most useful in studies of deep time. Scientists broadly correlate charcoal abundance with the frequency and extent of fire activity: the more charcoal present in the fossil record, the more fire is inferred to have been on the landscape. These records indicate that, while fire has been a presence throughout most of the past 420 million years, the extent of fire activity has varied considerably over this period.
To understand why some periods were more fiery than others and what this means for earth systems, it helps to look at what ignites and propagates wildfires. By definition, fire is an exothermic oxidation reaction dependent on the rapid combination of fuel and oxygen.
Volcanic activity, meteorite impacts, sparks from rock fall and arson can all provide the initial spark, but lightning is the most prevalent trigger. Terrestrial vegetation is the most common wildfire fuel. Vegetation characteristics — such as whether the fuel consists of tree trunks, leaves, duff or peat, and whether it’s wet or dry — determine if a spark will turn into a fire and exactly how it will propagate. And, of course, oxygen, which has been present in the atmosphere for at least a couple of billion years, but not always at today’s levels, is the third necessity.
The charcoal record shows that by 420 million years ago, these three ingredients — a spark, fuel and oxygen — were available in sufficient quantities such that fire became a presence on the landscape. The timing of Earth’s earliest flammability provides a key insight into the atmospheric oxygen content, a trait that Lenton calls one of the “master variables” of the earth system.
Sciencand tists colleagues continue to flesh out this relationship by further refining the limits of oxygen necessary to support natural fires, a range referred to as the “fire window.”
They have found that fires, even if ignited, will not propagate if the atmospheric oxygen concentration is below 16 percent. At our modern oxygen level of 20.9 percent, fires ignite and propagate readily.
Their work indicates that while there is not a firm upper limit to the fire window, 30 percent is a practical limit. Burn prevalence increases only slightly between 23 and 30 percent oxygen, and fuel moisture plays an important role too. It would only be possible to have periods with atmospheric oxygen concentrations approaching 30 percent (and preserve terrestrial vegetation) if Earth were much wetter than today.
Based on these fire window parameters, a model created, called FIREOX, which predicts burn probabilities as a function of atmospheric oxygen. The model indicates that burn probabilities remain low until atmospheric oxygen reaches 19 percent, then rapidly increase at 21 percent before plateauing at about 23 percent oxygen.
I believe changes to the climate have happened throughout earths history and we are currently in an interglacial period which began about 10,000 years ago. Data from the last interglacial, which occurred 125,000 to 118,000 years ago. Temperatures were up to 1℃ higher than today, like those projected for the near future. Scientists thought thought that todays sea levels were the highest in more than 100,000 years, but new evidence suggest oceans were higher during the Holocene period than they are today.
Human will not stop the changing climates that have ocured throughout time!!