Rapid increase in urban sprawl in Austria

Rapid land consumption is a hotly debated topic in Austria. Heavily urbanized areas have increased fivefold since 1975. A precise analysis, carried out for the first time by BOKU and the IÖR, shows alarming developments in all federal states (except Vienna) from 1975 to 2020.


In this context, the new study provides new insights into the increase in urban sprawl, a problem that has received little attention to date. The area considered to be highly and very highly urbanized increased from around 1,100 km² to around 5,800 km². The biggest changes were recorded in Upper Austria, Carinthia and Styria.


What is the problem with urban sprawl?

Urban sprawl describes the expansion of settlements into the landscape outside of compact settlement structures and at low densities - in particular through detached single-family homes, large-scale commercial areas and shopping centers. This type of development causes particularly high land consumption per person and is extremely resource-intensive.

The degree of urban sprawl is quantified by the proportion of built-up areas, the spatial distribution of these areas and the density of use (number of inhabitants per unit area). In Switzerland, the degree of urban sprawl is part of environmental monitoring. So far, it has not been possible to systematically record and present urban sprawl in Austria over a longer period of time with a high spatial and temporal resolution.

The Institute of Social Ecology at BOKU University, together with the Leibniz Institute of Ecological Urban and Regional Development, Dresden (IÖR), has used the latest data from the Global Human Settlement Layer (Joint Research Centre) to map the degree of urban sprawl in Austria from 1975 to 2020 in five-year increments. With a grid cell resolution of 100 m x 100 m, the maps impressively show the rapid increase in highly urbanized areas and identify the areas with the strongest growth.


What does the study say?

Between 1975 and 2020, the area of built-up grid cells measuring exactly one hectare in Austria grew from around 9,000 to around 12,700 km² - almost the size of Burgenland. The share of built-up grid cells in the permanent settlement area thus rose to 39% by 2020. In 1975, 73% of built-up areas were still low or very low density; by 2020, this figure had fallen to 35%. In the same period, the highly and very highly urbanized area grew fivefold - from around 1,100 km² to around 5,800 km².

"We are on a highway to sprawl in Austria," says study author Anna-Katharina Brenner from the IÖR and the Institute for Social Ecology at BOKU. She concludes that "the rapid increase in urban sprawl in Austria is the result of a policy that has allowed the construction of single-family homes, large-scale commercial areas and shopping centers on greenfield sites for decades."


Degree of urban sprawl and development trends

In Austria, the reduction and prevention of urban sprawl has been the focus of political discussions for years (BMK 2023, ÖROK 2023). "Urban sprawl jeopardizes the achievement of climate and nature conservation goals. They are a particularly ecologically damaging form of development: most land is needed for every new home and every new job," emphasized Helmut Haberl from the Institute of Social Ecology at BOKU. Their construction is particularly resource-intensive, as longer transportation routes have to be built. Their use also leads to higher emissions, for example due to the high mobility requirements and the more difficult supply of climate-friendly energy such as district heating, Haberl continued. "The study shows that almost 40% of the one-hectare grid cells in the permanent settlement area are built on, which was previously unknown. It is particularly worrying that the most land-consuming and resource-intensive form of development, i.e. those with a very high degree of urban sprawl, are growing the fastest."


Importance of urban sprawl for climate protection

Every day, Austria loses around 12 hectares of natural soil. More than half of this is asphalted or concreted over. "This has a significant impact on the climate: soils absorb greenhouse gases from the atmosphere," says Katharina Rogenhofer from the Kontext Institut für Klimafragen. Intact moors are particularly effective at this, but grassland, forests and sustainably managed fields can also store CO2. Well-irrigated soils also cool the environment together with the vegetation. "The importance of functional soils has been particularly evident in recent weeks: they are crucial for water to seep away properly. If they are missing, disasters such as floods and mudslides become more frequent and more serious."


Measures to curb land take and urban sprawl

"Despite some efforts in recent years, there has still been no significant success in solving this problem. We are still building and building," emphasized Gernot Stöglehner from the Institute of Spatial Planning, Environmental Planning and Land Management at BOKU. Effective measures have long been known: "In spatial planning, for example, supra-local building land boundaries could be defined for all localities as part of strengthened regional planning. Living, working, shopping, recreation and education should be located within these building land boundaries according to the principle of short distances and at a moderate density. Priority should be given to the use of gaps between buildings and potential for densification, for example by adding storeys, rather than building on greenfield sites." To make this possible, the availability of building land must be increased. "Leaving gaps between buildings and vacant land should incur costs, particularly through a separate property tax category. A quantitative land protection target is necessary in order to establish effective strategies for reducing land take." In this context, the measurement of the degree of urban sprawl presented here is helpful.