The Biggest Estate on Earth

by Bill Gammage

  Salt has spread menacingly since 1788. This is commonly attributed to tree clearing, which erodes soil and lets scalds emerge, water tables rise, and salt surface.40 Yet along southeast inland rivers salt now kills forests denser than in 1788, veterans and flood-borne youngsters alike. Faster water has cut into a salt basin below, or into subsurface salt in nearby land.

  Dryland salinity is extensive, and can occur in quite small seepages. Tree clearing poorly explains its spread: in 1788 the plains may have carried fewer trees, not more, than now (appendix 1). Overgrazing saltbush has been blamed. Saltbush sweats salt to its leaves, whence water or fire recycles it. In the 1830s squatters seeping over the inland stopped at those dry, salty leaves, thinking them useless, but they are palatable and nutritious. John Peter, the squatter who claimed to discover this, made so much from the discovery that even after accumulating over a million acres in Australia, a castle in Scotland and a mansion in London he complained that he could not spend all his money.41 Much of his land had few trees, and he grazed his saltbush so heavily that it is still recovering, yet little of his land is salted now. On Moira on the Murray, Lewes recalled,

  The small strips of plain near the swamp were covered with mesembryanthemum and salt-bush. The higher plains were entirely bare of any vegetation whatever but occasional salt-bushes. The box forests skirting the plains had here and there a few tufts of dry grass . . . the same appearance of intense drought and sterility pervaded the whole.42

  Little saltbush or grass, yet no mention of surface salt. Elsewhere too land almost bare of trees in 1788 was not saline. In short, forests have salted up but open places have not. Why?

  Rain and soil are factors. Over centuries rain on soft red-brown earths filtered finer particles down, leaving loam topsoil over almost solid clay. Fresh water sat on that clay, screened from salt beneath. In the eastern Riverina this precious barrier was only 25–50 centimetres down and farmers tried not to break it when ploughing, although now erosion and compaction have destroyed much of it. At Moira the clay was 4–6 metres down; elsewhere up to 20 metres down. ‘More than 70 per cent of Australia’s landmass’, Peter Andrews says, ‘has a layer of clay beneath it’. This keeps salt down, and is why deepening rivers which cut that clay layer become saline drains.43

  Even so, places above the clay, lightly wooded but not salt in 1788, are saline now. Perhaps those places grew too many trees after 1788, not too few, for trees break the clay barrier where grass does not. As well, fresh water, being lighter, sits above salt water. Trees drink it, letting salt water rise. The more and bigger the trees the more fresh water they drink, and the more readily salt rises to kill them. This argues that tree clearing does not necessarily cause salinity, and that trees do not necessarily prevent it. But perennial grasses mitigate it. In 1788 their dense roots trapped what rain fell, keeping barriers of fresh water and dry earth between the salt below and the plants above. Especially inland where salinity is so far most severe, agronomists now recommend deep-rooted grasses like phalaris and lucerne to avert it, replicating what native perennials did for millennia.44 Burning can increase salinity,45 but in 1788 people could burn perennials without salting the land.

  Change 5. In 1788 people used almost every plant in some way. Losses since 1788 mask how widespread and connected resources were.

  Most plants survived 1788’s calamities, and some thrived, but some valued species became extinct or rare. Local extinctions were continuous—Red Cedar, Cabbage Palm and New Zealand Spinach on the coast, Pituri, Native Truffle and Native Gooseberry inland. Orchids, lilies, herbs and the winter annuals essential for small animals vanished from familiar ground. Any species loss dislocates its ecosystem, no doubt often in unseen ways, but some losses were so extensive that they changed the face and colour of Australia. Daisy Yam’s bright yellow, for example, followed Kangaroo Grass into refuge pockets (ch 10).

  Note 1. Climate, soil and local moderators regulate plant growth and distribution, but almost all Australia supports plants, so people could use it all, including its deserts.

  Australia has 25,000 native plant species, 10 per cent of the world’s total, in myriad associations.46 Some straddle the continent; others defend a few square metres. Few are deciduous: Deciduous Beech and Red Cedar in rainforest, Red Bauhinia, Poplar Gum and bloodwoods in the north. A broad impression is that over millennia drought sensitive species have retreated before drought tolerant neighbours into higher rainfall zones and sheltered pockets.

  Climate, soil type and depth, and local moderators (altitude, aspect, shelter, predators and competition for moisture, light and nutrients) limit where plants grow, and engender both consistency and variety. Mulga grows in dry country but is denser in hollows than on hilltops and shallow soils, and denser on cooler south than north facing slopes. In the Adelaide hills gums prefer deep soils facing north, while Messmate tolerates shallow soils but for moisture likes to face south. Hills east of Hobart carry Risdon Peppermint on north or northwest facing slopes, but Black Peppermint on south facing slopes, with a sharp boundary on crests between.47 In 1788 William Bligh noted that Tasmanian vegetation was more luxuriant on south slopes than on north.48 On Mt Macedon and in Gippsland species vary according to whether a slope faces north or south, and how high or exposed it is.49 On coasts, wind shears scrub height. High country has a line above which trees don’t grow. Shelter lets rainforest species survive in arid gorges, and a few such as Weeping Pittosporum and Ooline have adapted to aridity.50

  Aridity is a significant regulator. Its long dominance is evident in the many plants which reflect heat and conserve water with hard, waxy leaves; in the rapid growth of others if rain falls; and in how well both recover from stress. WH Breton wrote of New South Wales after the 1826–9 drought,

  A circumstance respecting this colony, which must excite astonishment in every one, is the truly wonderful way in which the vegetation will recover itself after a drought. Land so completely burnt up that not a blade of grass is visible, will, within a few days after rain, become covered with a verdure most refreshing to the eye.51

  Floods trigger similar miracles. In 1885 a surveyor described the Cooper as ‘beautifully grassed country, the grass in some instances being as high as the camels’.52 With water the Cooper grows the best feed in Australia. Arid land is not necessarily inhospitable. In 1788 very few places grew no plants, and no climate or region was so harsh people stopped using it.

  Similarly, while soil limits particular species, some plant uses almost every soil, nutrient-poor though 90 per cent are.53 Cracking clay belts from northwest Victoria to Queensland and the Northern Territory supported no trees in 1788 and few now. As the clays wet and dry they swell and shrink, snapping all but the smallest roots.54 Yet they grow good feed, including Mitchell Grass, Bluegrass and sometimes saltbush, and on their creeks and rises scrub like Brigalow can grow densely.55

  Many plants, including such trees as Kurrajong, Bottle Tree, callistemons, many wattles and some eucalypts, use a variety of soils. Mugga Ironbark, tough and beautiful, is native to inland soils from Victoria to Queensland, and to the New South Wales coast. Ghost Gum grows in central Australia and Papua. On Sydney sandstone gummifera is a mallee with lignotubers up to 75 metres square; on better soils it is a bloodwood with no lignotubers.56 Other plants need a specific soil: volcanic or sedimentary, sand or loam or clay, rich or poor in humus or phosphorus or lime.57 Near Barellan (NSW) two eucalypts, Bimble Box on sandy loam and White Mallee on lime, grow within a metre of each other:58 lime can be a nutrient or a poison. On the Cooper, Sturt reported, ‘I stood more than once with one foot on salsolaceous plants growing in pure sand, with the other on luxuriant grass, springing up from rich alluvial soil.’59 Sturt knew how important soil–plant associations were. He cited River Red Gum on flood land beside box off it, ‘though the branches of these trees might be interwoven together, the one never left its wet and reedy bed, the other never descended from its more elevated position’. He pointed to the

>   open grassy and park-like tracts . . . The trees most usual on these tracts, were the box, an unnamed species of eucalyptus, and the grass chiefly of that kind, called the oat or forest grass, which grows in tufts at considerable distances from each other, and which generally affords good pasturage.

  So important did he think such associations that he risked asserting, ‘The light ferruginous dust . . . to the eastward of the Blue Mountains, is as different from the coarse gravelly soil on the secondary ranges to the westward of them, as the barren scrubs and thickly wooded tracts of the former district are to the grassy and open forests of the latter.’60

  Note 2. Plants form communities, so people could group them, predict their whereabouts, and link them to totems in ecologically consistent ways.

  Climate, soil and local conditions shepherd plants into communities—plants sharing common ground under similar conditions. A community might be named for a dominant species (Karri, Brigalow, saltbush, Spinifex), or a climate or terrain (wet or dry rainforest, alpine scrub), or both (pine–box woodland, Mitchell Grass plain, tea-tree swamp). Some species keep to one community, others are comfortable in several. Each community locates animals, which in turn alter communities: birds spread seed, grazers suppress scrub. Jim Noble and his colleagues found that burrowing bettongs, now extinct over most of their 1788 range, were crucial ‘landscape engineers’. Their digging made Mulga soils friable, fertile and absorbent, which with bettong seed storing increased the number and diversity of palatable perennials, attracting kangaroos and other grass eaters onto their warrens.61 Plant–animal communities might blend at boundaries, but locally each was distinct enough for people to see that maintaining the habitat each plant and animal preferred let them predict where each would be.

  Note 3. Two dominant Australians, acacias and eucalypts, illustrate challenges and opportunities people faced in 1788.

  Australians like wattle. They call golden, not merely yellow, its flowers splashing bush and park. Golden Wattle is the national flower, green and gold the national colours. Wattle decorates cards, crests, coats-of-arms. People even admire tough, dusty inland species without bright flowers or perfume, seeing them as battlers, typically Australian, heroic because they survive. Australia has a wattle for every sentiment.

  Acacias may have originated in Australia. Counts vary and species are still being found (ten in the Pilbara alone in the last few years), but Australia has roughly 1000 of the world’s 1300 species, more than any other Australian genus, and they range more widely, almost as widely as all other genera combined. They are sparse in rainforest but nearly reach the continent’s extremes of cold and heat, and they rule the inland. Mulga dominates 20 per cent of Australia; Brigalow, Gidgee and other acacias typify large areas.

  One acacia, Mimosa Bush, arrived before Europeans. Native to south and central America, it was named farnesiana in 1611, from a plant in Italy’s Farnesi Palace gardens. Perhaps the Spanish took it to Europe, and to the Philippines where it is now common, then sailors brought it south. It has thorns and leaves, uncommon in Australian acacias, and has adapted so well that it is now a weed. Other wattles are rare and reclusive: gordonii keeps to Blue Mountains sandstone, quornensis to hills near Quorn (SA), pataczekii to the southeast high country. The tallest wattle, Blackwood, common from north Queensland to Tasmania, prefers wet country; the next tallest, Silver Wattle, cool mountains; the next, Ironwood, desert. Other species are shrubs or ground covers. Variety can occur even within a species. Georgina Gidgee poisons stock in some places and feeds it in others. Mulga has different forms, and its spacing can vary widely.

  Wattles expect drought. They use little nutrient, but in seeking moisture a seedling’s root can be four or five times its height, and it goes straight down: try transplanting one. Most seedlings and some adults have leaves; others mature as phyllodes—sun-dodging, moisture-shielding needles or stem stubs. They point up or down to channel rain down branches and trunk to roots concentrated below. Mulga points up, begging the sky. The drier the season the straighter it points, the harder it begs. When drought kills it, sometimes over hundreds of miles, its seed waits decades, perhaps centuries, for rain. Across Australia acacia seed waits (picture 6).62

  Acacias share Australia with eucalypts. Familiar but distinctive, no other plant so dominates any continent, nor so strongly calls exiled Australians. Sun through canopies, grey-green leaves shining, oil scent on hot days, distant blue ranges—this is the bush, as Australian as gum trees, white Australia’s bush legend: tough, adaptable, battlers in hard times, opportunists in good, conquerors of a continent. Eucalypts could almost teach newcomers how to be Australian.

  Almost. Most newcomers fear drought, suppress fire and dislike poor soils. Most eucalypts tolerate drought, ally with fire and welcome poor soils. They leave to Spinifex and acacias truly dry regions—perhaps half Australia—but for 350,000 years their tuning to Australia’s long drying and swings of cold and heat has entrenched their dominance, and made them so adaptable that they defy rules: one species or another is always an exception. Their responses to drought, light, soil and fire demonstrate their extraordinary flexibility.

  Drought made eucalypts. Even in cool wet habitats their leaves are drought-ready, paper-thin and waxy to reflect heat and hold moisture. As seedlings most have broad horizontal leaves to catch light, but clear of cover the leaves narrow and face down, dodging light and aiming water at their roots. Some have three leaf stages, some one, in the north some are deciduous and put out green or red leaves during the build-up to the Wet. Most prize leaves as drought defences and nutrient stores, and shed them reluctantly.

  Drought, fire or insect predation, except when long sustained, trigger a tree to put on new growth. Mallee trunks stay underground and send only branches above. Three tropical eucalypts sprout from their roots,63 all but Mountain Ash and some northern species sprout beards (ch 1) from trunk and branch, and all but about fifteen species sprout lignotubers—the more marginal the environment the more likely lignotubers are.64 Many a clearing axeman has been broken by a red sea shooting from stumps behind him. If we see that rapid flush as merely a stress response we may not be Australian enough: it reflects opportunity as much as challenge. Other Australian genera deploy beards, but it is rare outside Australia.

  Most eucalypts have another trick. Their bark not only heals wounds, but revives trees seemingly dead. It snakes from the ground up a dead trunk, then sprouts buds. In time branches hold and the dead trunk is covered anew (pictures 7–8). Many eucalypts may be much older than we assume.

  Buds and bark depend on a remarkable capacity. No trees in the world grow so big and so quickly on such poor soils. The size and splendour of eucalypts commonly deceives newcomers about soil quality. Many early settlers attacked the biggest trees, the densest stands, assuming that the best soils lay under them, until years of sweat taught them to link species and soil: don’t clear stringybark, clearing mallee sends topsoil to New Zealand, Yellow Box means good cropland, River Red means heavy ploughing, and so on. On every soil one species or another flourishes.

  Eucalypts grow a lot with little by storing nutrients, some of which they harvest. Roots release chemicals to extract nutrients like phosphorus from iron and aluminium compounds in the soil, and organic acids to generate electric currents which reach beyond the roots to draw in distant nutrients. Leaves drip leaching chemicals, and before dropping a leaf the tree withdraws phosphorus and adds calcium to help cycle polyphenols (chemical compounds) to poison competitors. Bark is similarly treated, and dropped mostly in summer, letting chemicals work by keeping soil moist. If fire or improvident Europeans clear such litter, a tree might reduce its nutrient need by dropping branches, having first re-absorbed their nutrients, or it might burst into flower and seed. It is hard to think of ways to scavenge food and water eucalypts don’t use. That bare patch so common under them signals how well they do it.65

  Most nutrients are ready for instant use, stored in lignotubers or in sapwoo
d cradling epicormic buds. This gives eucalypts an astonishing resilience. In 1990 I planted a Mugga Ironbark on our nature strip. By 1998 it was 4 metres high. One night a neighbour drilled two holes into the trunk and filled them with poison. The tree seemed to die. Three years later it sprouted, and by 2002 was half a metre high. Our boundary was changed and neighbours chopped the tree down, ran a bobcat over the stem, buried it under heavy clay, and dug and filled a 2-metre deep trench beside it. On New Year’s Day 2004 it sprouted again, tiny red leaves breaking through the clay. Within a fortnight it was 10 centimetres high. The neighbour bulldozed it and covered it with bitumen. It hasn’t reappeared, but I’m hopeful.

  As with acacias, Italy named a eucalypt, in 1832—camaldulensis, River Red Gum, from a mature tree in the Count of Camalduli’s Naples garden.66 It is the most widespread eucalypt, flanking water across Australia. About 1928 a log dug from under the Yarra, wood and bark perfectly preserved, was estimated at 250,000 years old.67 Other eucalypts are rare, in tiny enclaves, often on soils poor even by Australian standards. Imlay Mallee was not described until 1980, when about 70 plants were found in a single location on the New South Wales south coast. In the Blue Mountains two copulans were found in 1957 and described in 1991: it may be extinct now. Only two Mongarlowe Mallees are known; Silver-leaved Gum is found in two Blue Mountains locations and two south of Canberra; Risdon Peppermint occupies a few spots in southern Tasmania; Morrisby’s Gum two small areas near Hobart. At Mt Bryan are South Australia’s only known Southern Blue Gums: one might be 2000 years old. Ramel’s Mallee was collected in the Western Australian desert in the 1890s, then not for another 100 years. Thirteen southwest eucalypts are known in only one location. The oldest and rarest eucalypt found, Meelup Mallee, is a single plant probably over 6000 years old, its ligno-tubers covering 40 metres.68