The Australian Food Web: How It Works and What Affects It

Australia’s food webs are shaped by a set of conditions found almost nowhere else on Earth: ancient, nutrient-starved soils, wildly unpredictable rainfall, a long history of fire, and a cast of species that evolved in relative isolation for tens of millions of years. These factors combine to produce ecosystems where energy moves through unusual pathways and where the loss or arrival of a single species can rewire entire communities. Understanding how these food webs function means looking beneath the surface of familiar categories like “predator” and “prey” and following the flow of energy from soil microbes and algae through termite mounds, eucalypt canopies, coral reefs, and underground aquifers.

Why Australia’s Soils Set the Rules

Most discussions of food webs start with sunlight and plants, but in Australia the real starting point is dirt. Australian soils are among the most phosphorus-poor on the planet, a consequence of geological age and minimal volcanic renewal. Plants that grow in these conditions receive plenty of light and periodic moisture but lack key nutrients like phosphorus and zinc. As a result, they produce carbohydrates faster than they can use them for nutrient-rich foliage and instead channel that surplus energy into heavily defended leaves, woody tissue, and sugary exudates like nectar and sap.¹

This has cascading effects through the food web. Tough, chemically defended leaves are harder for herbivores to eat and digest, which limits the number and body size of leaf-eating animals the landscape can support. At the same time, the abundance of nectar and sap subsidises a large guild of nectar-feeding animals. Honeyeaters, for instance, are commonly the most abundant birds in Australian eucalypt forests and woodlands, where they serve as major pollinators of native plants.² The food web, in other words, is tilted away from the classic grassland model of grasses feeding grazers feeding predators. Instead, a disproportionate share of energy flows through nectar, sap, and detritus rather than through fresh green foliage.

Boom-Bust Cycles in Arid Australia

About 70 percent of Australia is arid or semi-arid, and the food webs in those regions do not tick along at a steady pace. They pulse. Extended dry periods of low productivity are punctuated by sudden floods or heavy rains that trigger enormous bursts of plant growth, insect hatching, and breeding among vertebrates. These boom-bust dynamics drive diverse ecological functions, with populations and communities of animals responding strongly to temporal shifts in productivity.³

During a boom, desert-dwelling raptors shift their diets as different prey species become available. Small mammals and reptiles flourish, and predator populations rise in response. When the bust returns, those predator populations crash or disperse, and the food web contracts back to a narrow base of drought-tolerant species. This means that any snapshot of a desert food web is misleading if taken in only one phase of the cycle. The “normal” state of the web is a state of constant flux, and species that can switch diets or move long distances have an enormous advantage.

The Dingo at the Top

Australia’s best-studied trophic cascade involves the dingo. A large body of research now indicates that dingoes regulate ecological cascades, particularly in arid Australia, and that removing dingoes leads to increases in the abundance of herbivores and invasive mid-sized predators, most notably the red fox.⁴ When dingoes are removed from the landscape, kangaroo and wallaby populations can swell, overgrazing vegetation. Fox populations also rise, increasing predation on small and medium-sized native mammals.

A continent-wide analysis found that dingo abundance was negatively associated with macropod abundance, and macropod abundance was negatively associated with habitat complexity. Likewise, dingo abundance was negatively associated with red fox abundance, and fox abundance was negatively associated with the abundance of ground-dwelling medium-sized mammals.⁵ The dingo’s direct suppressive effects on kangaroos and foxes appear to operate simultaneously, though its indirect effects on species further down the food web are comparatively weak. Still, the pattern holds across large spatial scales and across multiple trophic levels, making the dingo one of the most consequential single species in Australian terrestrial food webs.

Invasive Species and the Unraveling of Food Webs

No account of Australian food webs can avoid the damage done by introduced species. Feral cats, red foxes, cane toads, and European rabbits have each reshaped food webs in distinct ways, and their effects often compound one another.

Feral Cats and Foxes

Feral cats prey most heavily on mammals in an intermediate weight range, peaking at around 400 grams, in drier areas and away from rocky habitat. Previous studies have shown the greatest rates of decline and extinction in Australian mammals to be concentrated among species with exactly those traits, providing a direct continental-scale link between mammal decline and cat predation.⁶ In northern Australia, the cohort of mammals currently declining is smaller-bodied than the species that went extinct earlier in southern Australia, and there is genuine uncertainty about why the steepest declines are happening now despite cats having been present in the region since the late 1800s.⁷

Foxes and cats also interact with rabbits in a way that traps native species in a deadly feedback loop. Abundant rabbits sustain high numbers of foxes and cats, which then prey heavily on native mammals as well. Removing rabbits from arid landscapes can actually benefit native species because the drop in rabbit numbers reduces the predator populations that were feeding on them, weakening the cycle of “hyperpredation” that hits native mammals hardest.⁸

Cane Toads

The cane toad’s advance across northern Australia has removed key predators from the food web. In the tropical north, three species of predatory monitor lizards suffered severe population declines after eating the toxic toads.⁹ With those large monitors gone, smaller lizards that the monitors would normally eat became more abundant in areas of high toad activity, a classic cascade triggered by the removal of a top predator.¹⁰

In temperate southern Australia, the pattern repeats with different players. Populations of land mullets, eastern water dragons, lace monitors, and red-bellied blacksnakes were reduced by 84 to 100 percent in toad-invaded areas. The scarcity of scavenging lace monitors led to a roughly 52 percent decrease in rates of carrion removal and a 61 percent increase in numbers of brush turkeys, a species that benefited from reduced competition at the scavenging table.¹¹ Cane toads also exploit human-built water infrastructure. In arid regions, artificial water points like stock dams provide moisture subsidies that allow toads to survive in habitat that would otherwise be too dry, facilitating their spread into the interior.¹²

Freshwater Food Webs in Dryland Rivers

Australia’s inland rivers behave differently from the permanent, flowing rivers familiar in wetter parts of the world. Many dryland rivers exist as chains of isolated waterholes for much of the year, only connecting during floods. The food webs in these waterholes depend heavily on what floods bring in. After major overland flooding, the high biomass of fish in dryland river waterholes is mostly driven by organic matter produced on the floodplains and carried back into the waterholes as floodwaters recede.¹³ Between floods, benthic algae growing in a narrow band along the waterhole margins takes over as the primary energy source. In some cases, that algal production is remarkably high and supports large populations of crustaceans and fish even under very turbid conditions.¹⁴

These freshwater food webs are therefore at the mercy of flood timing, and water extraction or dam construction upstream can starve them of the floodplain-derived carbon they depend on. Climate change projections for much of inland Australia suggest longer dry spells between rain events, which would extend the periods during which waterhole food webs must survive on local algal production alone.

Marine Food Webs Along the Coast

Australia’s marine ecosystems include both tropical coral reefs and temperate kelp forests, and both face food-web disruptions driven by warming oceans.

Coral Reefs and Herbivory

On coral reefs, herbivorous fish play a critical structural role by grazing algae that would otherwise overgrow and smother corals. A diverse community of herbivorous fish provides more stable levels of grazing than a community dominated by one or two species. This “response diversity,” where different species respond differently to environmental fluctuations, helps maintain herbivory above the threshold levels that could trigger a shift from a coral-dominated reef to an algae-dominated one.¹⁵ Overfishing of herbivores is therefore not just a matter of losing individual fish species. It destabilises the entire food-web dynamic that keeps coral reefs functioning.

Kelp Forest Collapse

Off southeastern Australia, waters are warming at roughly four times the global ocean average, the fastest rate in the Southern Hemisphere.¹⁶ This warming has allowed the long-spined sea urchin to extend its range southward into Tasmanian waters, where it overgrazes kelp beds and converts them to bare rock known as “urchin barrens.” The collapse of kelp beds has been shown to propagate poleward over 15 years, with early-warning signs of overgrazing now widespread along 500 km of coast. Projections indicate that half of all kelp beds within the urchin’s range-extension region could collapse by around 2030.¹⁷ Once kelp is lost, recovery is difficult: when disturbance is severe enough, kelp recruitment stays low and the canopy fails to recover, locking the system into a barren state.¹⁸ The food-web consequences cascade: kelp forests support dense communities of invertebrates and fish that in turn feed seals, seabirds, and larger fish. When the kelp goes, so does the entire community it supported.

Fire as a Food-Web Force

Fire has been part of Australian ecosystems for millions of years, and it plays a distinctive food-web role that goes well beyond simple destruction. Indigenous Australians have managed landscapes with deliberate, low-intensity burning for tens of thousands of years. Research in the Western Desert shows that traditional burning by Martu people increases fine-scale pyrodiversity, meaning a mosaic of vegetation at different stages of regrowth, and ensures the persistence of older successional stages. This mosaic creates preferred habitats for dingoes and sand goannas, both important predators.¹⁹ In general, landscapes managed with Indigenous burning contain a greater diversity of successional stages than those under a lightning-fire-only regime, and the differences are of scale rather than of kind.²⁰

The 2019–20 “Black Summer” bushfires tested the limits of fire resilience. After those megafires, fox activity peaked shortly at highly burned sites while small to medium-sized mammal activity increased more gradually, suggesting that introduced predators exploited the open landscape faster than their native prey could recover.²¹ Yet a broader assessment found that most native species showed resilience to the fires, with few strong relationships between fire severity and population change. Community diversity and predator-prey network structure were largely unaffected, though landscapes with more high-severity fire did have higher abundance and richness of introduced species.²² The picture that emerges is one of evolutionary adaptation: Australian animals have coexisted with fire for a long time, but introduced predators can undermine that resilience by exploiting the window of vulnerability after intense burns.

The Megafaunal Ghost in the System

Australia’s modern food webs still bear the imprint of a much older disruption. During the late Pleistocene, more than 85 percent of the continent’s large-bodied animal species went extinct. Research using sediment cores and fungal spore records suggests that human arrival rather than climate change drove those extinctions, which then triggered a replacement of mixed rainforest by fire-adapted sclerophyll vegetation through relaxed herbivore pressure and increased fire.²³ The magnitude of ecological responses to megafaunal loss varied geographically, depending on regional climate. In wetter regions, the loss of large herbivores led to dramatic vegetation shifts and increased fire. In arid regions that were already sparsely vegetated, the same loss left little visible trace in the pollen and charcoal record.²⁴

This matters for understanding modern food webs because it means the system we see today is already deeply altered. The dominance of fire-adapted eucalypts, the relative scarcity of large browsing herbivores, and the importance of invertebrates and small mammals as the primary consumers of plant material are all, in part, legacies of a missing trophic level that disappeared thousands of years ago.

Underground Engineers and Fungal Networks

Much of the energy in Australian food webs flows not through charismatic vertebrates but through the soil. Termites are among the continent’s most important ecosystem engineers, decomposing wood, grass, litter, and soil organic matter across tropical habitats.²⁵ In savannas especially, termites tend to be abundant and their surveys are important for understanding ecosystem function.²⁶ They process vast quantities of dead plant material and recycle nutrients back into the soil, effectively forming the base of a parallel detrital food web that feeds lizards, echidnas, and numbats.

Digging mammals like bandicoots, bettongs, and potoroos play a complementary role. Their diggings capture seeds and water, promoting seedling germination and plant growth. Many of these mammals eat underground truffle-like fungi, dispersing fungal spores through their droppings. The mutualistic interaction between truffle-like ectomycorrhizal fungi and fungus-eating mammals is fundamental to forest health, supporting fungal dispersal, soil structure, nutrient cycling, and plant community dynamics.²⁷ When digging mammals disappear from an area, the consequences ripple upward. A study comparing soil inside predator-proof sanctuaries where digging mammals had been reintroduced with soil outside found that seedling biomass was significantly greater inside, and the composition of root-zone fungal communities was markedly different. In one sanctuary established 20 years prior, there were more ectomycorrhizal fungi inside and four times as many types of arbuscular mycorrhizal fungi outside, suggesting that the presence of digging mammals reshapes the fungal communities that sustain forest trees.²⁸ The overall effect is increased plant vigour, increased biodiversity, and improved ecosystem functioning.²⁹

Connections Across Ecosystems

Australian food webs are not self-contained boxes. Energy and nutrients move between ecosystems in ways that can be invisible unless you look for them. Flying foxes are one of the most dramatic examples. These large fruit bats travel extreme distances between roost sites, creating ecological linkages across Australia’s fragmented landscape with profound implications for pollination and seed dispersal.³⁰ The spectacled flying fox in north Queensland carries rainforest seeds in its gut over distances of up to about 20 km, linking isolated forest patches.³¹

Seabirds perform a similar trick in the opposite direction, moving marine nutrients onto land. As high-order marine predators, seabirds subsidize island ecosystems with nitrogen-rich guano.³² On subtropical islands, plants and invertebrates sampled near seabird colonies are enriched in nitrogen compared with control sites, meaning seabird guano acts as a natural fertilizer that boosts the terrestrial food web from the bottom up.³³

When a Native Species Becomes the Problem

Not all food-web disruptions in Australia come from introduced species. The noisy miner, a native honeyeater, has become one of the most damaging birds in eastern Australian woodlands. Its aggressive mobbing behaviour drives out smaller insectivorous and nectarivorous birds from woodland patches, a process so severe that it is listed as a Key Threatening Process under national law.³⁴ Habitat fragmentation makes the problem worse: noisy miners preferentially nest near woodland edges, so as patches become smaller and more fragmented, the proportion of habitat they dominate grows.³⁵ The food-web consequence is a loss of the small insectivorous birds that control invertebrate populations, which can cascade into changes in herbivory pressure on woodland trees. The noisy miner story illustrates how land-use change can elevate a native species into a role that reshapes trophic interactions across an entire biome.

Life in Subterranean Aquifers

Some of Australia’s most unusual food webs exist entirely underground. Calcrete aquifers beneath the arid inland host communities of tiny, eyeless invertebrates collectively known as stygofauna. These animals live in groundwater where there are no photosynthetic organisms, so the food web is truncated and depends almost entirely on organic matter filtering down from the surface. Research at the Sturt Meadows aquifer in Western Australia, using isotopic modelling combined with gut-content analysis, found that roots and other plant material constitute a key organic source for subterranean life in an environment characterized by extremely low nutrient levels.³⁶ These underground ecosystems are fragile precisely because they have so few energy inputs and so few species performing each functional role. Groundwater extraction or changes in surface vegetation can sever the link between the surface and the aquifer, collapsing a food web that has no backup energy source.