About 75% of Australia’s land mass is classified as arid, which means the vast majority of the continent cannot support large-scale settlement or agriculture. Most Australians live in a relatively thin coastal ribbon, concentrated along the eastern, southeastern, and southwestern edges of the country. As of 2019, 87% of Australia’s population lived within 50 kilometers of the coast.
The Habitable Coastal Fringe
Australia’s population hugs the coastline for a simple reason: that’s where the rain falls, the soil is fertile, and the temperatures stay manageable. The east coast, from far north Queensland down through New South Wales to Victoria, is the most densely settled corridor. Sydney alone holds 5.48 million people at a density of 407 people per square kilometer. Melbourne, Brisbane, and the smaller cities of the Gold Coast, Newcastle, and Wollongong fill out this strip.
In the southeast, Victoria is the most densely populated state at 27 people per square kilometer. Tasmania, separated by Bass Strait, has cooler temperatures and enough rainfall to support towns across much of the island, though its density sits at just 7.6 people per square kilometer. The southwestern corner of Western Australia, around Perth and down to Albany, forms another pocket of habitable land with a Mediterranean climate and reliable winter rainfall. Between these settled pockets lies a vast interior that most people never live in.
Why the Interior Is Largely Empty
Historical maps of Australia designated roughly a quarter of the continent as “useless” for settlement. That sounds blunt, but it reflects real constraints. The interior receives little rainfall, summer temperatures regularly exceed 40°C, and the ancient soils are nutrient-poor compared to those on younger continents. Without reliable water or productive land, permanent towns simply can’t sustain themselves through farming or local resources alone.
The distribution of Australia’s population has always closely followed the distribution of quality agricultural and pastoral land. Early colonial surveyors recognized this pattern. In South Australia, a boundary called Goyder’s Line, first drawn in 1865 during a severe drought, marks the divide between land where rain-fed cropping is reliable and land suited only to grazing. North of this line, rainfall becomes too scarce and unpredictable. Researchers have since refined the concept, linking it to the ratio between growing-season rainfall and evaporation, but the basic message hasn’t changed: once you move inland past a certain threshold, conventional farming fails.
Where People Live in the Outback
The arid interior isn’t completely uninhabited. Scattered towns, mining communities, and cattle stations exist across the outback, and they owe their survival largely to one resource: the Great Artesian Basin. This massive underground water system stretches beneath roughly 22% of Australia’s land surface, spanning parts of Queensland, New South Wales, South Australia, and the Northern Territory. It supplies water to around 180,000 people, 7,600 businesses, and 120 towns. In many of these locations, it is the only reliable water supply.
The basin works because its main aquifers are pressurized. Water can flow to the surface through bored wells or through natural springs and cracks in the rock, providing a permanent supply even during long dry spells. First Nations peoples relied on these natural springs to live in the dry interior for at least 65,000 years, using them as hunting sites and travel waypoints. Today, the basin also supports the pastoral industry, mining operations, and tourism across regions that would otherwise be uninhabitable.
Even with this water supply, population density in these areas is vanishingly low. The Northern Territory, covering over 1.3 million square kilometers, has a density of just 0.2 people per square kilometer. To put that in perspective, Victoria, one-sixth the size, has a density 135 times greater.
The Tropical North
Northern Australia, including the top of Queensland, the Northern Territory around Darwin, and the Kimberley region of Western Australia, receives heavy seasonal rainfall but presents its own habitability challenges. Extreme heat and humidity for much of the year, combined with cyclone risk, flooding, and limited infrastructure, keep populations small. Darwin is the only city of significant size in the tropical north, and it remains one of Australia’s smallest capital cities.
Early habitability assessments recommended that settlement not spread into tropical regions, partly because of the difficulty of sustaining European-style agriculture in monsoonal climates with poor soils. Indigenous communities have lived sustainably across these landscapes for tens of thousands of years, but large-scale urban development has remained limited.
How Climate Change Is Shifting the Map
The already narrow band of comfortably habitable Australia is projected to face new pressures. CSIRO climate projections indicate that hot days will become more frequent and more intense across the continent. Southern mainland Australia, the region where most people currently live, is expected to see decreasing winter and spring rainfall, longer drought periods, and declining soil moisture from mid-century onward. Southern and eastern Australia also face harsher fire weather conditions.
These changes matter because they threaten the agricultural productivity and water security that made the southeast habitable in the first place. Goyder’s Line, the rainfall boundary in South Australia, has effectively been creeping southward as conditions dry out. Regions that once supported reliable cropping may shift toward grazing-only land, pushing productive agriculture into an even narrower coastal band. For the tropical north, rising temperatures and humidity could make outdoor work and daily life increasingly difficult during summer months, limiting growth potential in places like Darwin and Townsville.
In practical terms, Australia’s habitable zone has always been small relative to the continent’s total size, and the pressures of a warming climate are unlikely to expand it. The southeastern and southwestern corners, the same areas that attracted settlement two centuries ago, remain the most livable parts of the country.