Jennifer Balch considers herself a "tropical fire ecologist," a term that would have been an oxymoron a half-century ago. The tropics are, by popular definition, sweaty places with lots of water dripping everywhere and things going squish with every footstep. Sure they're hot, but that's only one part of the three needed for fire.

Balch, a postdoctoral fellow of the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara, does her fieldwork in the Brazilian state of Mato Grosso, at the southern end of the Amazon rain forest. Such rain forest, she explained, might see a wildfire every couple of centuries, and then only when the predominant environmental variable was severe drought.

But times are different now, and the combination of climate change and intentional fires set to peel back the jungle to create pastures or cropland has made the study of "tropic fire" genuinely timely.

"It was almost a misnomer to say that fire occurred in a tropical forest just a few decades ago," mused Balch, who's worked in the Amazon since 2004. Now, she said, fires in many tropical forests occur every couple of decades — which isn't all that different from areas commonly associated with wildfires, like the Western United States or Australia.

Fires in the jungle are more likely at the edges of the tropical forest — hence her work on the Amazon's arc of deforestation, where the savannah meets the humid forests (a zone known as the transitional forest). Fire is more common too when forests are diced into pieces — more edge, after all — or when the canopy of leaves and branches is broken, allowing sunlight and breezes to dry out the accumulated vegetable matter on the forest floor or the detritus of earlier incomplete burns.

Balch was the lead co-author, with David Bowman, of a recent paper in Science magazine headlined "Fire in the Earth System." That ambitious paper, among other things, suggested that intentionally set fires used to peel back the world's forests for cultivation have generated a fifth of the human-generated carbon dioxide pumped into the atmosphere in the 250 years since the dawn of the Industrial Revolution.

Her work is on the burning edge, literally, of wildfire and human-caused — or anthropogenic — fires. When people meet forest, the story is ultimately predictable — expect fire.

Down Under
David Bowman has studied the history of fire in a very different environment, the world's most arid inhabited continent, Australia. And after years of watching indigenous Australians wrangle fire to craft their own habitat, he feels most people are at best imperfect users of fire and at worst serial bunglers.

An ecologist based at the University of Tasmania, he only has to let his mind wander north, across the Bass Straight to the state of Victoria, to see the consequences of that bungling. In February, a series of wildfires — some apparent arsons — broke out in the forested areas northeast of Melbourne, ultimately killing more than 200 people.

To Bowman, the best way to look at the Victorian fires is to go back, 45,000 years back, to be exact, when Australia's indigenous people brought fire to the continent. "It's a deeply important question," he said, "what do indigenous people do with fire? Were they skillful with fire?"

In the aborigines' case, Bowman finds the answer is yes. He found their use pragmatic, to bend the natural habitat to do things like create a surplus of kangaroo to hunt, protect their own resources from wildfires or clear land for planting or transit. They left behind a patchwork of burnt and untouched areas, a "habitat mosaic." And, Bowman said, "They had effectively tamed fire to create a benign habitat — for them." He's further argued that their stewardship, for such it was, even resulted in greater biodiversity for the continent.

Skip forward several dozen millennia, and enter the European settlers with a different take on fire. Rather than tame fire, they felt it was better to subdue it, to ensure that nothing burned.

"It was a rational response," Bowman argues, "but uninformed historically." And after World War II, with plenty of military hardware lying around that could be used to fight fires, "They said, 'We will now wage total war with fire.'

"We are now looking at defeat in that war," he concluded. "I call it Smokey the Bear blowback. After each wildfire, fire had a nasty habit of coming back bigger and harder."