Background: Land

Human wellbeing and ecosystems, both terrestrial and aquatic, are dependent on healthy land. The interactions of soil, air, water, plants, animals and natural processes provide a diverse range of services, including fertile soil for agriculture, clean water production, nutrient recycling, and erosion control. How land is used and managed can significantly affect its capacity to provide these services.

Land use is a key driver of environmental change affecting ecological functions, attributes and the integrity of land health. Many environmental problems in the ACT result from current and historic land use and management. The maintenance of land health requires consideration of the needs of urban and other development in conjunction with environmental protection.

Impacts on land health

The main pressures on land health are from vegetation clearing for urban expansion (particularly greenfield development) and agriculture, and severe fire that can expose and alter the structure of soils increasing the risk of significant erosion. The degradation of land has consequences for both terrestrial and aquatic ecosystems. Poor land health can lead to the loss of vegetation and habitat, and severely impact on water quality and aquatic biodiversity (see Water). Poor land health also impacts on agricultural production through the loss of soil nutrients and organic matter, reductions in crop yields and pasture production, and increased erosion.

The ACT’s land is used for urban areas, conservation, agriculture and plantation forestry. Land use change can be driven by a range of social, economic and environmental pressures such as population growth, land values that support housing development, preference for traditional housing, and agricultural drivers such as climate (for example, water availability) and commodity prices.

Changes in the area of one land use type can have negative consequences for others. For example, urban expansion results in the loss of natural habitat as well as agricultural land. Land use change can also have consequences for a range of other environmental pressures, for example the expansion of urban areas creates increased demand for transport infrastructure such as roads and public transport. This means that urban development can have a greater impact on the environment because of the degree of land change required and the resources consumed.

Climate change will increase pressures on land health with higher temperatures, reduced rainfall, more extreme weather events, and an increase in fire risk and severity. These are likely to affect land use and management through significant changes to landscape functions and vegetation cover.

Background to indicators

Indicator L1: Land use change

Minimising the growth in the ACT’s urban footprint

Much of the growth in the ACT’s urban area has been in the form of single low-density dwellings with fewer and fewer people living in them. To minimise the growth of the ACT’s future urban footprint there needs be an increase in population density, the number of medium and high-density dwellings, and the amount of urban infill compared to greenfield development. The relationship between population density and the growth in urban area is shown in Figure 1. The amount of land required for higher population densities is significantly less than that required for low densities, which reduces the need for new urban areas.

Greenfield versus infill development

Greenfield urban development is that which occurs outside the boundary of the established urban area. This development extends the urban footprint and requires the construction of new utility, transport and social infrastructure. Infill urban development is undertaken within the existing urban area and provides greater intensity and efficiency of existing land and infrastructure. Urban infill can include the redevelopment of commercial and industrial areas, and the development of unimproved land within the urban boundaries.

Greenfield development places greater pressure on the environment through impacts such as:

• vegetation clearance,
• degraded land condition,
• increased waterway pollution,
• increased recreational use and access tracks,
• garden weed invasion, and
• the need for extensive fire management for asset protection.

Greenfield development can also significantly increase demand and consumption of resources as well as greenhouse gas emissions through additional infrastructure and transport needs.

Another consideration for greenfield developments is the potential requirement for the creation of environmental offsets to address potential development pressures. In the ACT, offsets provide for the possibility of environmental compensation for a development that is likely to have adverse environmental impacts on a protected matter (see Biodiversity).

Urban infill generally has a much reduced environmental impact compared to greenfield development because it requires a smaller development footprint and a reduced need for new infrastructure. The benefits can be increased with sensitive design and adoption of low environmental impact types of land use.

Higher rates of urban infill are required for the ACT to meet a range of social, environmental and economic needs, including commitments to a net zero emissions future, improved public transport and demographic trends favouring greater housing choice.

The ACT Planning Strategy 2018 sets a target for up to 70% of new housing to be provided as infill development within the existing urban footprint.

Indicator L2: Land health

Healthy land supports agriculture, native ecosystems and ecosystem services such as clean water. Soil condition is the main driver of land health and a fundamental part of ecosystems and natural processes including biological activity, the cycling and storage of nutrients and carbon, and the decomposition of organic wastes.

Soil health is mostly determined by land use intensity and the degree of modification, or loss of, vegetation cover. The clearing of vegetation can result in accelerated erosion, acidification, salinity, and a reduction in soil nutrients and organic content. Pressures that leave soils bare of vegetation and promote soil degradation include land clearing, fire, high-intensity storms, and agriculture (cropping and grazing). In addition, soil erosion can increase due to the compaction of soil from urban and industrial activities, vehicle use, stock grazing, and invasive species such as horses, deer and feral pigs which can also degrade soil structure.

ACT soils are highly variable, but most are considered to be infertile, fragile, and prone to becoming impermeable and eroded. Consequently, soil management is vital to maintain and improve soil health.

Degraded soil and land health has a range of consequences, including:

• degradation of water quality from increased sediment and other pollutants deposited into rivers and streams (see Water),
• air quality and human health impacts from dust storms (see Air),
• loss of topsoil limiting the establishment of new vegetation, removing native seedbanks, and promoting the spread of weeds,
• reduction in agricultural land productivity through reduced yields and pasture growth,
• increased agricultural costs from greater fertiliser use and land restoration activities, and
• erosion damage to infrastructure such as fencing, roads and buildings.

Land health assessments are most commonly made through soil measures such as salinity, acidity, erosion and carbon. Baseline data and ongoing monitoring are required to determine changes in soil condition.

Climate change impacts, such as more frequent drought, increased storms and fires, will add to current pressures on land health, particularly through the reduction of vegetation cover and erosion of exposed soils.

Land contamination

Contaminated sites include former petrol stations, landfills, and sites with previous chemical uses (such as sheep dips). These sites can impact on human health and the environment through the leaching of chemicals into groundwater and waterways, the release of air toxics, or through direct contact with contaminated soils and other substances.

As the rate of urban infill and greenfield development increases, it is reasonable to expect an increasing number of contaminated sites. The identification of contaminated sites allows their remediation, if required, and allows appropriate land use to be considered for the sites. In this way, development can be a driver for both the increased reporting and remediation of contaminated sites.

The Environment Protection Authority has the regulatory responsibility for the oversight of the remediation of contaminated sites. Contaminated sites such as old petrol stations, or those that were used for fuel storage, often require ongoing monitoring to determine any continuing impacts; other sites may be remediated with no further monitoring required.

Remediated sites are not currently removed from the contaminated sites register to ensure that any future use of these sites is compatible with site remediation. For example, a site may be remediated to a level that can accommodate industrial development, but may not be appropriate for residential development.