More and more fires these days are started by human beings, deliberately or inadvertently, although even when deliberate and for legitimate agricultural or conservational purposes, they sometimes get out of hand. But fires, commonly through not exclusively triggered by lightening, are part of nature. In the places where they naturally occur - virtually everywhere that has anything to burn and is not permanently wet - the local plants (and animals, to a greater or lesser extent) tend to be adapted to them. Grasses need to have their tops burned off if grazing animals do not do the job for them, or the tops become senescent and stifle the fresh growth beneath. Many trees are highly fireproof, like redwoods and eucalypts, and the seeds of many pines and other species will not germinate unless first effectively cooked, whereupon they "know" they can sprout in the nutrient-rich ash provided by their immediate predecessors.

But as every input - including water, general warmth, light, carbon dioxide, and many minerals that are in small doses essential - there can be too much of a good thing. Fire is lethal to the trees that are not adapted to it, of course - and even for those that need it, timing and intensity are all. If, for whatever reason, the fires come too frequently, or too rarely, or burn too intensely, then the best-adapted trees are overwhelmed. Human beings are altering the world in ways that are very much against the interests of wild trees, upsetting even those that seem well adapted. [...] Over the past few decades Brazilians and North Americans have introduced several grasses, which they feel make better fodder for cattle. Some of these grasses [...] spread into the surrounding land. These particular grasses, as it happens, burn more slowly than the native grasses; and this prolonged burning is far more damaging to other vegetation than quick, albeit hotter flames generated by native grasses.

Colin Tudge: The tree, A natural history of what trees are, how they live, and why they matter, Crown Pub., New York, 2006.