Burning Bush. Stephen J. Pyne
which it was yet capable of reclaiming under existing conditions of soils and climate—except, that is, for fire. Bushfire surged against rainforest, etching its geographical and historical boundaries. Insinuating itself into a mixed flora, fire selected for and shaped scleroforest and scleroscrub. It crowded rainforest to the margin of the island continent until it resembled a chain of coral reefs, a biotic atoll subsiding in a sea of scleromorphs. Fire seized the Red Centre.
There were many rainforests. Tropical rainforest revolved around the araucarias, supported by a rich understory of vines. Temperate rainforests favored Nothofagus and an understory blanket of ferns and mosses. By stratifying into gallery forests these Gondwanic relicts packed an enormous number of species into small domains. In all their variants, they showed tolerance to degraded soils and often to the peculiarities of eccentric sites. Their tenacity derived from a stability of climate made possible by reliable rainfall, by a precipitation regime that was not simply high but consistent across the seasons; a biotic stability that left true rainforest almost empty of scleromorphs; a stability of nondisturbance, the relative freedom of a site from routine disruptions, or if disturbed, by the capability to repair itself without surrendering to another biota. Together they spared rainforest from fire.16
Australian rainforest shows some tolerance for aridity—it has to—but it does not accommodate prolonged drought or seasonal dryness. Its layered canopies and dense understories work avidly to conserve moisture and preserve a fetid microclimate; dry spells have to work against this powerful moisture gradient. Likewise, few Australian rainforest types exclude completely scleromorphic species. The tropical rainforest is the most successful, being virtually free of scleroforest elements—no pyrophytic grasses; no scleromorphic scrubs; no eucalypts, casuarinas, or melaleucas. The temperate rainforest shows some intermixing, and merges uneasily into wet scleroforest. Thus the border between rainforest and its competitors—savanna or scleroforest—is, in the tropics, sharply etched and, in more temperate climates, blurred. Inevitably, too, there are disturbances. Windstorms, for example, can level tracts of rainforest far in excess of what organic agents can decompose, a shifting cultivation of rainforest by the slashing of cyclones and the burning of lightning fires.
Its fire history sums up the rainforest’s various stabilities. In tropical rainforest leaves make up probably 80 percent of the surface fuels and biological agents quickly decompose them. What persists is sparse, perennially wet, and sheltered from dry winds. When fires reach the rainforest border they flash against a green wall, gasp helplessly for fuel, and expire. If rainforest advances or retreats, it does so as a unit in response to broad shifts in climate. Changes in the dry season—greater moisture, fewer fires—allow the rainforest to advance into scleroforest and savanna. The reverse allows fire to eat a little farther into the frontier. Blowdowns along the border open the canopy, dry out surface fuels, and allow fires that normally flame out along the perimeter to enter into the interior according to a scenario that may become irreversible. The burn alters microclimates; fireweeds and pyrophytes invade the site; the new fuels carry additional fires over the burn and incinerate those slow-growing rainforest flora that demand shade and moisture.
In temperate regions, succession into and out of rainforest is less sharply defined. The borders blur; rainforest intercollates with wet scleroforest. Undisturbed, wet scleroforest will pass, over the course of several centuries, into rainforest. Disturbed—burned—it reverts to scleroforest or scleroscrub. What actually exists on any particular site reflects the unique sequencing of its past fires. Small sites are especially susceptible to irreversible change. Once initiated, a rhythm of frequent fire encourages soil erosion and the loss of nutrient capital. This encourages scleromorphs, which accept more fire. In such a scenario wet scleroforest degenerates into dry scleroforest, scleroscrub, or savanna, and rainforest no longer possesses the means to reclaim the site. Without refugia, rainforest vanishes.17
If its heath miniaturizes Australia’s fire geography, its rainforest miniaturizes its fire history. The uniformity of the Gondwana rainforest fractured under the impress of isolation, aridity, and disturbances. Increasingly, the principal disturbance and the great integrator of new conditions—fire—shaped those new regimes. The fragmentation continued, like rocks spalling off a heated cliff. From it came the unique species and unexampled biotas of Old Australia. With the relict rainforest, the story comes full circle. The flames licking at the wet flanks of tropical vine forest or overturning wet scleroforest on a rhythm of centuries are recapitulating a cycle of fire begun with the Great Upheaval.
4
Land of Contrarities
Drought, dry seasons, and, more than all—that deadliest weapon of the tyrant—the bush-fire, reduces and selects the life of the country.
—W.H.L. RANKEN, The Dominion of Australia (1874)
The aspect of the country was fearful. Brown, burnt-up, and sweltering under a broiling sun! … Imagine all the trees and scrub high above your head blazing—all the ranges, as far as the eye can reach, one mass of smoke and fire.
—MARCUS CLARKE, letters
IN ITS ORIGINS, ancestral Australia was all but indistinguishable from the rest of Gondwana. Its biota was similar, if not identical; its climate was mild and wet; its seasons, invariant. But the breakup of the supercontinent had led, inevitably, to changes that demanded, and forged, new identities. Leaching, drying, and burning, each in turn and with cumulative impact, worked over Australia’s Gondwanic legacy. The tempo of disturbance quickened and beat to irregular rhythms. Isolation ensured that recolonization was negligible, that new biotas would have to evolve from the inherited stocks. The Great Upheaval installed to dominance a dramatically different biota. A second revolution within the emergent scleroforest furthered and confirmed that transformation. After Homo infiltrated the continent, the process was irreversible. Out of Gondwana rainforest emerged, through these trials, Australian bush.
By the time Europeans arrived, the bush presented an inverted world, a parallel universe. It was as if a second ark had escaped the Flood, as though a whole continent had passed through an enchanted looking glass. Compared to northern Europe, Australia exuded the alien, the hostile, the sterile, the bizarre. François Peron alluded to “whimsical freaks of Nature” that defied attempts at scientific understanding. James O’Hara disparaged a Nature that apparently “indulged in whim,” such that nothing—neither animal nor vegetable—resembled anything anywhere else. Charles Darwin mused that here at the antipodes “an unbeliever in everything beyond his own reason might exclaim, ‘surely two distinct Creators must have been at work.’” Marcus Clarke invoked a “Weird Melancholy” to conjure the spirit of the bush, later softening that cry with an appeal to “read the hieroglyphs of haggard gum-trees.” Perhaps the most famous denunciation, already couched in sardonic tones, was the declaration of an anonymous colonial poet of the 1850s:
There is a land in distant seas
Full of all contrarities.1
The nature of Australian exceptionalism was difficult to identify precisely. It was there in the bush, certainly, though the bush echoed bits and pieces of other Gondwanic lands. It meant coming to grips with miserable soils, aridity, desert winds. And, everyone agreed, it involved bushfire. Whatever elements led to the bush, fire integrated and accelerated, like a flask of chemicals held over a Bunsen burner. By geologic standards, the bush was a sudden invention, kindled almost instantaneously from drying Gondwanic tinder and the flint of Homo sharply striking the continent. However the bush defined Australia, so fire defined the bush. In ways both obvious and obscure, the land of contrarities was a land of fire.
AN EVER-LIVING FIRE
The geographical border that so sharply segregates rainforest from scleroforest has a temporal analogue in the veritable explosion of fire that raged across Australia during the Holocene. Fire was abrupt, ubiquitous, grasping. It insinuated itself into malleable biotas. It welded the biotic pieces into a dynamic whole. Not fire alone but its versatility—its ability to