Australia spans an enormous range of biomes, from the arid deserts that cover roughly a third of the continent to pockets of ancient rainforest along its tropical and temperate coasts. Between those extremes sit tropical savannas, eucalypt-dominated sclerophyll forests, semi-arid mallee scrub, Mediterranean-climate shrublands, alpine grasslands, and a network of inland wetlands that appear and vanish with the country’s irregular rainfall cycles. What makes Australia’s biome map unusual is not just the variety but the degree to which fire, ancient nutrient-poor soils, and tens of thousands of years of Indigenous land management have shaped where one biome ends and another begins.
The Arid Interior
Australia’s deserts are not a single featureless expanse of sand. The arid zone encompasses stony gibber plains, red sand dune fields, salt lakes, and shrublands dominated by species like mulga and spinifex. Mulga (a group of closely related acacias) and spinifex (hummock grasses in the genus Triodia) often form sharply distinct patches right next to each other, with abrupt boundaries that do not always line up with obvious differences in soil type or topography. Research in the Tanami Desert found that spinifex grasslands burned almost three times as often as neighboring mulga shrublands, and that feedback loops between fire, soil crusting, and vegetation appear to maintain those sharp edges.
Fire is the key mechanism. Spinifex builds up flammable biomass that carries fire readily, while mulga stands burn less often and develop biological soil crusts that hold moisture. When fire does sweep through a mulga stand, regeneration depends heavily on seed availability. A study of slender mulga showed that seedbanks pulse dramatically after a masting event, jumping from fewer than four seeds per square meter in a low-production year to over 130 seeds per square meter after a heavy seedfall. Fire after one of those mast years triggered mass recruitment, while unburned areas saw almost no new seedlings regardless of how much seed had fallen.
Tropical Savannas
Stretching across Australia’s northern tier from Queensland through the Northern Territory and into the Kimberley, tropical savannas make up around 1.9 million square kilometers. They are defined by a tree layer, usually eucalypts, over a continuous grass understory, and by a climate split into a distinct wet season and a long dry season. An eddy-covariance study near Darwin measured total gross primary productivity at roughly 2,270 grams of carbon per square meter per year, with the grass understory contributing about a third of that total. That understory contribution shifted dramatically with the seasons: grasses produced around 40 percent of the ecosystem’s carbon uptake during the wet season but only about 18 percent during the dry.
What drives the trees versus the grasses shifts with the calendar. During the wet season, solar radiation is the main limiting factor for productivity in both trees and grasses. In the dry season, soil moisture takes over as the primary control. This seasonal toggle helps explain why savannas look so different from one month to the next, greening explosively when the monsoon arrives and browning off within weeks of the last rains.
Fire is a dominant force here. Averaged over the period 1997 to 2011, about 18 percent of Australia’s tropical savanna area burned each year, with more than two-thirds of those fires occurring in the late dry season months of August through November under severe fire weather. Those late-season fires are hotter and more damaging than early-season burns, a distinction that has become central to land management debates across northern Australia.
Tropical Rainforests
Despite occupying a tiny fraction of the continent’s area, Australia’s tropical rainforests in far north Queensland are among the oldest continuously forested landscapes on Earth. The Wet Tropics, a UNESCO World Heritage Area, contains lineages that trace back to Gondwanan times. Fossil evidence shows that taxa once widespread across the cool, moist forests of the ancient supercontinent survived Australia’s long northward drift and eventual collision with the Sunda region in the late Oligocene. That collision and the uplift of New Guinea opened pathways for some of those ancient rainforest lineages to spread into what is now Indonesia and the broader Malesian region.
These forests are characterized by dense, multilayered canopies, high species diversity, and year-round moisture. They are also extremely vulnerable to drying, which makes them sensitive to changes in rainfall patterns. Unlike the fire-adapted biomes that dominate most of Australia, tropical rainforests have essentially no fire tolerance. A single severe fire can convert rainforest margins to sclerophyll woodland, and recovery takes centuries.
Temperate Rainforests
Further south, fragments of cool temperate rainforest persist in Tasmania, Victoria’s Otway Ranges, and high-rainfall pockets of New South Wales. These forests are dominated by Antarctic beech (Nothofagus moorei in the north, Nothofagus cunninghamii in the south) and coachwood (Ceratopetalum apetalum), both of which are Gondwanan relics. A long-term phenology study in a New South Wales cool temperate rainforest found that leaf fall at the community level was driven primarily by temperature and wind speed for Antarctic beech, and by temperature, rainfall, and solar radiation for coachwood. Antarctic beech flowers in mast events, with a mean interval of three to four years between heavy flowering episodes in about two-thirds of cases.
These forests feel startlingly different from the dry eucalypt country that often surrounds them. Moss-draped trunks, tree ferns, and perpetually damp understories create microclimates that can be 10 degrees cooler than adjacent open woodland on a summer afternoon. Their survival depends on reliable rainfall and protection from fire, and they are among the most climate-sensitive ecosystems on the continent.
Eucalypt Sclerophyll Forests
Eucalypt-dominated forests are probably what most people picture when they think of Australian bush. They range from tall, wet forests in high-rainfall areas to open, dry woodlands on poorer soils. “Sclerophyll” refers to the tough, leathery leaves that characterize eucalypts and many other Australian plants, an adaptation to low-nutrient soils and periodic drought.
Fire is woven deeply into the biology of these forests. Most eucalypts can resprout from buds hidden beneath their bark after a fire sweeps through. Research on six eucalypt species found that the new epicormic foliage produced after fire was higher in total nitrogen than mature leaves from unburned areas, which may sound like a nutritional windfall for herbivores. But those same new leaves also had higher concentrations of certain defensive compounds that deter marsupial folivores like koalas and possums, offsetting the nitrogen boost.
Not every eucalypt plays by these rules. Mountain ash (Eucalyptus regnans), the world’s tallest flowering plant, is a fire-sensitive species. It possesses the epicormic structures found in fire-adapted eucalypts, evidence of its fire-adapted ancestry, but it invests its energy primarily into rapid height growth rather than vegetative survival after fire. A severe blaze can kill an entire stand of mountain ash, and regeneration depends on seeds released from canopy capsules after the fire passes. If a second fire hits before the new generation is old enough to have produced seeds, the population can collapse entirely.
Mediterranean Shrublands and Kwongan
Southwest Western Australia has a Mediterranean climate with hot, dry summers and cool, wet winters. The shrublands there, often called kwongan, are one of the most species-rich plant communities on the planet. What makes this diversity especially puzzling is that it occurs on some of the most nutrient-impoverished soils in the world, ancient weathered sands and laterites that are desperately low in phosphorus.
Plants in this environment have evolved remarkable strategies for scavenging phosphorus. Many species in the Proteaceae family, including banksias and grevilleas, produce cluster roots that release organic acids to dissolve phosphorus locked in soil minerals. A study of Ericaceae in southwest Australia found that heaths in this region also release root carboxylates to mobilize phosphorus, a strategy that works better than relying on mycorrhizal fungi in severely phosphorus-poor soils. The greatest plant species diversity in the region tends to occur on the most phosphorus-impoverished soils, a counterintuitive pattern that suggests the extreme nutrient limitation itself drives diversification by forcing plants into highly specialized ecological niches.
Semi-Arid Mallee
Between the wet forests of the coast and the true deserts of the interior lies a broad belt of semi-arid country dominated by mallee eucalypts. Mallees are multi-stemmed eucalypts that grow from a swollen underground woody organ called a lignotuber. The lignotuber stores starch and buds, allowing the plant to resprout after fire, drought, or damage. Mallee country stretches across vast areas of southern Australia, from western New South Wales through Victoria, South Australia, and into the Western Australian wheatbelt.
The physiology of mallee eucalypts is finely tuned to dry conditions. Research on Eucalyptus behriana found that this species maintained much lower water status than other eucalypts even after extended rain, with leaf water potentials not rising above about −1.2 megapascals compared to values as high as −0.2 in other species. Researchers initially suspected the lignotuber itself was creating hydraulic resistance, but experiments showed the impedance was actually in the soil surrounding the roots. When soil was washed away and the roots placed directly in water, water status quickly rose to levels typical of other eucalypts. The mallee compensated through osmotic adjustment in its leaves, maintaining turgor despite its consistently low water availability.
Below mallee stands, the relationship between roots and soil runs deep in an almost literal sense. Fine lateral roots of mallee eucalypts create structures where fungal filaments, microorganisms, and clay deposits rich in silicon, aluminum, and iron accumulate. These root-zone clay formations represent a slow process of soil building driven by the plants themselves, a reminder that in ancient Australian landscapes, plants do not just respond to soil conditions but actively reshape them.
Alpine and Subalpine Country
Australia’s alpine zone is small compared to other continents, limited mainly to the highest parts of the Snowy Mountains in New South Wales and the Bogong High Plains in Victoria, plus areas of Tasmania’s Central Highlands. Above the treeline, the landscape is dominated by herbfields, sphagnum bogs, and frost-heaved ground. Below the treeline, subalpine woodland is dominated by snow gum (Eucalyptus pauciflora), a tough, often beautifully gnarled tree that survives heavy snow loads and regular freezing.
Snow gum populations carry the scars of Australia’s post-European disturbance history. Sampling in Kosciuszko National Park found that pre-disturbance stem densities ranged from 24 to 240 stems per hectare depending on the site, but current densities following twentieth-century regeneration pulses ranged from 700 to over 5,500 stems per hectare. That dramatic increase reflects heavy regeneration after the cessation of cattle grazing and a series of fires, producing dense thickets of young stems in place of the more open woodland that once existed.
The alpine treeline itself is not marching steadily uphill in response to warming, despite what simple climate models might predict. A study spanning 2002 to 2018 in the Australian Alps found that while some short-distance advance of the treeline did occur, it was largely restricted to areas that had not burned. After two fires, no saplings were found above the treeline despite evidence they had been common before the fires. Below the treeline, snow gums resprouted readily from their lignotubers after a single fire, but stands burned twice within a decade showed reduced numbers of small trees. Fire acts as a strong demographic filter, and the researchers concluded that understanding treeline dynamics requires looking well beyond temperature change alone.
Inland Wetlands
Australia’s interior may be famous for its aridity, but it also contains an extraordinary network of wetlands that pulse with life when water arrives. The Murray-Darling Basin, which drains a seventh of the continent, includes floodplain lakes, riverine wetlands, and ephemeral marshes that fill during wet years and shrink to puddles or vanish entirely during drought. This boom-and-bust hydrology creates a landscape where wetland function shifts dramatically between wet and dry periods.
An analysis of waterbird habitat across the Murray-Darling Basin found that in dry years, riverine and lake systems had the highest priority for waterbirds, acting as refugia where birds could survive until conditions improved. In wet years, the emphasis shifted to lake and marshland systems, which became important breeding grounds. This alternation means that protecting Australia’s inland wetlands requires maintaining connectivity and water flows across the full range of hydrological conditions, not just managing individual sites in isolation.
Fire as a Continent-Wide Force
Fire is not just a feature of individual biomes in Australia but a continental-scale process that shapes where biome boundaries fall. From the tropical savannas where roughly a fifth of the landscape burns annually to the alpine treeline where a single fire can reset decades of upslope recruitment, fire appears in every section of this article for a reason. Recent research identified four alternative biome states across Australia’s terrestrial ecosystems: forest, savanna, grassland, and shrubland, each defined by distinct dominant growth forms. These four states overlap broadly in the climatic conditions where they can exist, suggesting that factors like fire frequency and soil type, not just rainfall and temperature, determine which biome persists in a given location.
Indigenous Australians have managed fire across the continent for tens of thousands of years, shaping the structure and function of ecosystems through cultural burning. These burning practices, which typically involve low-intensity fires applied in a fine-grained mosaic across the landscape, differ fundamentally from the high-intensity wildfires that have become more common since European colonization disrupted traditional management. Research into re-introduced cultural burns in long-unburnt temperate woodlands is now documenting how plant communities respond when traditional fire regimes are restored, adding a contemporary evidence base to knowledge that Indigenous communities have held for millennia.
The Role of Animals in Shaping Biomes
Plants and fire get most of the attention when people think about Australian biomes, but animals play underappreciated engineering roles. Bandicoots, for example, are prolific diggers. Their foraging pits turn over soil, alter moisture levels and water repellency, break up leaf litter, trap organic matter and seeds, and change patterns of seedling recruitment at a local scale. Multiply those small pits across a landscape with healthy bandicoot populations and the cumulative effect on soil processes is substantial.
The catch is that the majority of Australia’s digging mammals are now threatened, with many having suffered severe population and range contractions since European settlement. Their loss is not just a conservation issue in the abstract; it removes a functional process that helps maintain ecosystem health. Where bandicoots and other digging mammals have disappeared, soils may become more compacted and hydrophobic, seed burial rates drop, and nutrient cycling slows. Rewilding efforts and predator control programs that allow digging mammals to recover can restore these functions, but the work is slow and the animals face ongoing threats from foxes and cats.
Subantarctic Outliers
Australia’s territory extends well beyond the mainland and Tasmania. Macquarie Island, a subantarctic speck roughly halfway between Tasmania and Antarctica, hosts a biome found nowhere else in Australian jurisdiction. The island’s plateau features striking vegetation-banked terraces: alternating bands of low cushion plants and bare gravel, shaped by wind, frost action, and slope processes. Previous descriptions treated windward and leeward terrace types as distinct landforms, but more recent fieldwork concluded they are actually two related forms that grade into each other depending on hillside aspect relative to the prevailing westerly winds. Stone-banked terraces, not previously reported from Macquarie, were also documented.
The island’s ecology faces its own pressures. The cushion plant Azorella macquariensis has experienced widespread dieback in recent years, potentially destabilizing the terrace systems that depend on living vegetation to maintain their structure. Macquarie Island is a reminder that Australia’s biome portfolio includes environments far removed from the red deserts and eucalypt forests of the popular imagination, and that even the most remote habitats are not immune to ecological disruption.
Why Biome Boundaries Are Blurrier Than Maps Suggest
Textbook maps of Australia’s biomes draw clean lines: desert here, savanna there, forest along the coast. Reality is messier. The four major biome states identified across Australia, forest, savanna, grassland, and shrubland, overlap heavily in the climate conditions they occupy, meaning that large areas of the continent could plausibly support more than one biome type. What tips the balance in any given spot may be fire history, soil depth, nutrient availability, or the legacy of past vegetation that persists through self-reinforcing feedbacks.
Climate change is adding new pressure to these boundaries. Southern Australia has experienced declining cool-season rainfall linked to the expansion of the Southern Hemisphere Hadley cell, which has pushed storm tracks further south and intensified the subtropical ridge over the continent’s southern fringe. That shift has reduced winter rainfall and runoff across southeastern Australia, with implications for every biome in the region: wetter forests may contract, fire-prone woodlands may expand, and wetlands that depend on winter-spring inflows may dry out more frequently. In the north, changes to monsoon timing and intensity could alter the balance between savanna trees and grasses. In the mountains, fire and warming interact in ways that make simple predictions unreliable, as the treeline research makes clear.
For anyone trying to understand Australia’s landscapes, the key insight is that biomes here are not static backdrops. They are dynamic systems held in place by ongoing interactions among climate, fire, soil, animals, and human management. Remove or alter any one of those factors and the boundaries shift, sometimes gradually, sometimes within a few fire seasons.