Burning Bush. Stephen J. Pyne
that flamed across nearly the whole spectrum of Australian biotas, one that exhibited a special relationship, a positive feedback, with scleromorphs, grasses, and ephemerals—the most characteristic and unique of Australian floras. As fire spread, it became something more than a process; it assumed the character of a defining presence—or more, of an informing principle. The second upheaval, the internal revolution within the scleroforest, is unintelligible without reference to it. Bushfire became an inextricable part of Australian geography, history, and consciousness.
The history of Australia is not synonymous with the history of fire, but the history of neither can be told without reference to the other. Even as fire proliferated, the resistance to its spread was terrific; rainforest gave way grudgingly. But of all the environmental levers by which the landscape could be moved, fire was the most sensitive, subtle, and, in short spells, the most powerful. It was, more tellingly, the lever most accessible to humans. It thrived on instability, and humans destabilized. With each transformation, the pressures argued for more fire, not less.
WHEN GONDWANA BROKE UP, its rafting fragments had to search out new identities. They could no longer derive their meaning from the collective commonwealth of the supercontinent. With each passing eon their Gondwanic heritage faded, the imperative for a separate future became larger, and the possibility of new alliances among the continents and subcontinents more likely. India hurried to a violent union with Asia, massively deforming each in the process. South America rafted eastward toward an eventual, tenuous linkage with North America, part of a brave if wary New World. Africa reunited with Europe and Asia, suturing microplates in Asia Minor, warping borders into mountains and huge basins that filled to become separating seas. Along its great rift valley it nearly split, then halted—a place of origins, and a crossroads for the Old World. Madagascar, New Zealand, the Seychelles—all fragmented so badly that they became outright islands, too insular to share in continental history. That left Antarctica and Australia.
Antarctica drifted only slightly poleward. Its deteriorating climate, which culminated in its colossal ice field, was the product of its singular isolation around the South Pole. As the other Gondwanic plates deserted it, as its connections to other continental masses were removed, Antarctica acquired new patterns of circulation that made it not only cold, but wet. Precipitation fell in what had been a continental desert. Snow became ice, ice created more ice, and the entire continent evolved into a slab of glacial ice so immense that it deformed the shape of the planet. Its ice was ruthless, final, deathly. The ancestral biota it once shared with much of Gondwana failed, without replacement. In the ice of Antarctica, life all but vanished. Its ice, too, repelled humans.
Its Gondwanic twin, Australia, took an antithetical direction. Australia became steadily isolated because of its own positive plate motion, not merely the relative movement of the plates around it. Those travels, however, took Australia into the Pacific, away from the other continents; only to the north, where its edges ground against a submerged Asian plate, did it reestablish contact, and then with the upheaved islands of the Sunda arc; and as often as not even that land linkage was lost to deep channels and rising sea levels. As Australia entered the tropics, new circulation patterns not only raised its overall temperature but introduced aridity—seasonal, secular, selective. Aridity promoted the scleromorphs, and the scleromorphs brought fire. Where Antarctica was progressively informed by ice, Australia was increasingly shaped by fire. Rock had turned to dust, and dust to ash.
The Australian biota might have evolved in several directions. Sclerophylly encompassed a suite of traits that adapted organisms to a suite of environmental conditions; not every trait was specific to fire, and fire could hardly subsume the whole spectrum of adaptations. But among the dominant environmental pressures fire was the most active, and like Antarctic ice, Australian fire had self-reinforcing tendencies. It was as though the landscape had been gently tilted and its streams accorded a particular channel. Each subsequent event tilted the land further and the stream of fire history entrenched itself more deeply. The fire-proneness of the island continent ratcheted steadily upward, each event so tipping the balance that correction became impossible. Even before the arrival of humans, Old Australia had probably crossed a biotic threshold that bound it irreversibly to fire. The advent of humans, however, inexpungably committed Australia to the Pacific’s ring of fire.
Like Antarctic ice, Australian fire became more frequent, more intense, more pervasive, more domineering a presence. But there the similarity ends. Ice is profoundly abiotic; fire is inextinguishably tied to life. Where ice reduces, removes, and buries, fire enhances, multiplies, stimulates, recycles, and animates, a plural not a singular process, massaging a varied, subtle biota. It is above all vital—at times awesome but also playful. Always it is associated with life. Life made fire possible—and fire, in return, dramatized Australia’s life. Its history, natural or cultural, could not be understood without it. To invoke the lands that evolved from Old Australia is to conjure up a burning bush.
BOOK I
The Eucalypt
1
The Universal Australian
… round the bases of the barkWere left the tracks of flying forest-fires, As you may see them on the lower boleOf every elder of the native woods.
—HENRY KENDALL, “A Death in the Bush”
The extreme uniformity of the vegetation is the most remarkable feature in the landscape of the greater part of New South Wales … In the whole country I scarcely saw a place without the marks of a fire; whether these had been more or less recent—whether the stumps were more or less black, was the greatest change which varied the uniformity, so wearisome to the traveller’s eye.
—CHARLES DARWIN, The Voyage of the Beagle (1845)
IT IS NOT CLEAR just when the first eucalypt emerged out of the welter of ancient rainforest taxa. The earliest definite pollen appears in the Oligocene, around 34 million years ago, long after Australia had separated from the bulk of Gondwana. Nor is it obvious whether the genus developed from a single protoeucalypt or from several related forms.1
What is incontestable is the degree to which the genus Eucalyptus is endemic to Australia, the extent to which, by Holocene times, it came to dominate the forest and woodland environments of Australia, and the peculiar attributes to which it owes its evolutionary triumph. Its successful coup within the scleroforest, in particular, came from a powerful set of alliances, a triumvirate that Eucalyptus formed with fire and the genus Homo. Found virtually nowhere outside Australia, but within Australia found nearly everywhere, the eucalypt became the Universal Australian.
THE EUCALYPT AS COLONIZER
Amid the Great Upheaval, the family Myrtaceae—flowering trees and shrubs with fleshy or dry fruits—emerged as one of the scleromorphic winners. Although it probably originated in Australasia, Myrtaceae saturated all of Gondwana, a minor element in the ancestral rainforest. When Gondwana divided, so did Myrtaceae. Its fleshy-fruited genera concentrated in South (and Central) America, and its dry-fruited genera in the eastern cratons including Greater Australia. In Australasia the family Myrtaceae featured ninety-five genera, ninety-three of which were endemic. Australia contained sixty-nine genera, of which forty-five were endemic, among them Leptospermum, Melaleuca, Callistemon, Baeckea, Verticordia, and Eucalyptus. By the time Eucalyptus appeared in the fossil record, Myrtaceae had experienced perhaps 30 million years of evolutionary history.2
The Tertiary upheaval completely reformed the status of Eucalyptus. Its genetic inheritance included as a matter of course generalized Myrtaceaen traits and scleromorphic tendencies. Probably it appeared along the margins of rainforest, a weed searching out disturbed sites at least momentarily free of an obscuring canopy. Interbreeding was common; hybridization, frequent. As the Australian ark floated into the Pacific and experienced upheaval, a genus that thrived amid disturbance found itself on an increasingly disturbed