The Olympics traditionally open with a fire ceremony. A torch kindled by natural sources (the sun reflects off a mirror onto the torch), and hence a pure fire, is passed from Olympia, the site of the ancient games, to wherever the modern games are to take place. Last year, nature seemed determined to return the gesture, as record-shattering blazes swept over Greece and even reached the ruins of Olympia itself.
These megafires came in three waves, each more savage than the last. The first outbreak commenced in late June and continued into July and most spectacularly burned two-thirds of Mount Parnis National Park, north of Athens. The second struck at the end of July with widespread points of ignition that overwhelmed the fire services and contributed the largest single fire in Greek history, a 74,100-acre burn near Aigialia in the northern Peloponnese. The third wave surged over the Peloponnese during the end of August; one, at Ilia, broke the new size record by reaching 99,000 acres, while another burned off the forest around Olympia. Altogether some 76 people died. The flames shook the political establishment and influenced a national election.
It is tempting to conclude that this outbreak, amid record temperatures and aridity, is another signature of global warming, that these are the sparks of a coming apocalypse. After all, similar types of fires forced evacuations in the American West, ripped through Portugal, invaded Brazil, and smothered Moscow in smoke. No valence other than global climate could possibly bond such disparate landscapes. So this, it would seem, is what the future holds: a rising sea of fire punctuated by ever more frequent tsunamis of flame.
But the Greek eruption was not a pure fire--not the simple expression of natural forces against which people can take preventative measures. As Gavril Xanthopoulos, Greece's premier fire scientist, has explained, the 2007 fires were the outcome of nature and people interacting in ways both deep and nuanced. The outbreak, and its cognates around the globe, resemble a stock market crash more than a tidal wave. In truth the global economy contributed as much to the happening as the global climate did.
The wildland fire community, meaning those who manage fires and those who study them, habitually thinks in terms of triangles. Combustion results from heat, fuel, and oxygen; fire behavior follows from weather, fuel, and terrain. And in like fashion, the global epidemic of fires can be broken down into three contributing causes.
The first is the most obvious: climate. If it rains, the fires die out, and if the winds quiet, the flames cannot spread. In this respect wildfire joins that pantheon of iconic images that have come to characterize the public awareness of global warming. Longer fire seasons, higher temperatures, more savage droughts--all of these give burning a boost. The real index, though, is not warming per se but the pattern of moisture and drought, for this is what sets aflame landscapes that are normally too empty to burn and sends flames racing through forests normally too damp to combust. In the summer of 2007, Greece suffered its worst drought in a century of keeping records.
For the past 20 years, the American West has endured a sustained period of aridity, best announced by the Siege of '87 in northern California and the 1988 Yellowstone conflagrations. Since then, the big fires have come with a roughly two-year rhythm. Nobody can say for sure how much of this agonizing bout of aridity is attributable to man-caused climate change and how much to the inevitable reappearance of dry spells in a region that has endured prolonged droughts for millennia. But certainly nature is not providing much relief. The relentless long drought has reduced options, shrunk room for maneuvers, and heightened the stakes. Its persistence could even allow landscape-sized conflagrations to catalyze a mass turnover of the biota, in which the organisms that presently inhabit the affected lands can no longer survive and will be replaced en masse. No one really knows.
Hot, dry conditions are only a necessary precondition for conflagration, however, not a sufficient one. Although they share heat as a causative factor, rising fires in Greece are not a simple complement to melting glaciers in Greenland. Ice melts from purely physical causes; melting can happen without a particle of life present. But fire cannot; it needs a biota in order to propagate. It feeds on that assembled biomass, and anything that shapes the biotic matrix will affect the kind of fire that results. Physical stresses must refract through a biotic prism, which has its own complex set of controls. Climate can only affect fire to the extent that its presence gets absorbed into the living world.
Moreover, the biota harbors a creature that can compete with lightning, climate's firestick, as a source of ignition, and this introduces yet another prism through which fire must be refracted. Put simply, people can start and stop fires. While in one sense this makes fire seem less "natural," it also brings combustion further within the realm of the living world.
The second cause of the global epidemic of fires is land use. Around the world, megafires cluster in nature preserves and on landscapes otherwise undergoing rapid change. Some instances of megafire, mostly in the developing world, involve forests forcibly converted to pasture or plantation. The clearing of rainforests and draining of peatlands in Borneo has sparked some of the largest, most noxious fires of the past 20 years. Other fires, vast in area rather than high in intensity, have helped transform Amazonian forest into ranches. In the developed world, public lands once managed for timber or pasture are being...