Even after management actions and resilience are taken into consideration, some pressures can continue to pose a risk to the environment. Identifying and assessing the risk to the environment examines both the likelihood that the impact will take place and the severity of anticipated consequences if it does occur. Risk assessment provides valuable information for determining the need to adjust policies or adapt management approaches to mitigate risks.

The key risks to the Australian environment include the pressures created by climate change, land-use change, habitat fragmentation and invasive species.

As described earlier in this report, strong evidence exists that the climate is changing at a rate unprecedented in the geological record. Climate change poses serious risks to Australia’s population, economy and environment. Without strong action to reduce greenhouse gas emissions, the world is likely to warm by 4 °C by 2100 (Sherwood et al. 2014). For Australia, this would mean temperature rises of 3–5 °C in coastal areas and 4–6 °C inland (CCA 2015).

Average rainfall in southern Australia is projected to decrease, with a likely increase in drought frequency and severity. Extreme daily rainfall events are projected to increase in both frequency and severity.

The sea levels around Australia are projected to rise further, with a subsequent increase in the frequency of extreme sea level events.

The likelihood and impact of risks posed by climate change (discussed in the ‘Pressures’ and ‘State and trends’ sections of this report) depend on the extent to which the implementation of the Paris Agreement is successful in limiting global warming to less than 2 °C. Holding global warming to below 2 °C would require reducing global greenhouse emissions by 40–70 per cent by 2050 compared with 2010 emissions. Effective adaptation policies and actions will also be required to minimise the adverse impact of inevitable climate change, even if global temperature increases are limited to 2 °C.

The cumulative impacts of individual management decisions present a significant risk to the ongoing sustainability of Australia’s land. This is exacerbated by government policies (such as vegetation clearing controls) that support further habitat loss and fragmentation. It is almost certain that the extent and connectivity of native vegetation will continue to decline. In addition, some land management practices, such as inappropriate application of fertilisers and pesticides, and poor irrigation, represent an ongoing risk.

It is clear that invasive species are a major ongoing risk to Australian biodiversity, inland waters and coasts, and this risk is likely to remain in the near future. Climate change may create conditions that exacerbate the range and impacts of invasive species.

Coastal environments are potentially the most at risk of all Australian environments because they simultaneously bear the brunt of population density and urbanisation, habitat loss, invasive species, the downstream impacts of agriculture, and the widespread effects of climate change, including sea level rise, erosion, storms and heat stress.

The risk from these and other pressures can be increased by inertia or lack of timely action before tipping points are reached. For example, lack of timely action can occur when an issue is raised but, because of complex procedures and/or the involvement of multiple jurisdictions and organisations, a decision is not made before an irreversible change occurs (e.g. extinction of a species). This risk can be reduced when there are:

• clearly defined management boundaries for avoiding tipping points
• effective and efficient procedures for responding to issues of concern
• adequate monitoring systems in place that identify when a pressure is approaching, or has reached, a boundary or tipping point.

There is also a risk that efforts to improve policy and management will continue to be hampered by poor understanding of the broader impacts of drivers and pressures on the environment, and the flow-on effects on economic activity and human communities.

SoE 2016 identifies a number of other risks to the Australian environment:

• Built environment
  • increased economic impact and loss of human life as a result of prolonged extreme heat events

• Heritage
  • replacement of heritage-listed buildings with new buildings, including ones perceived as ‘green’ (and therefore more environmentally friendly), rather than retaining and adapting old buildings
  • loss of traditional knowledge that threatens Indigenous cultural heritage
  • incremental destruction caused by the focus of development approvals on site-specific heritage impact, rather than cumulative incremental impact
  • resourcing, including limited funding, lack of incentives, and neglect arising from rural population decline or the loss of specialist heritage trade skills
  • development and resource extraction projects

• Biodiversity
  • inadequate programs and processes for collecting relevant and adequate data to provide early warning of threats and opportunities for biodiversity management
  • inappropriate development in urban and peri-urban areas, and failure to manage human demands on the environment

• Land
  • run-off from managed land that will irreversibly damage parts of aquatic and marine systems, and persistence of this damage even if run-off and nutrient loads are later reduced

• Inland water
  • increased extraction of water from inland water and groundwater systems, which will change water flow regimes and groundwater conditions
  • salinisation of major rivers and aquifers because of historical land clearance
  • extraction and pressure from new sources such as shale gas, coal-seam gas and large coalmining developments, which threaten groundwater quality

• Coasts
  • increasing population density in coastal regions, and the pollution, habitat loss and invasions associated with urbanisation, trade and industrialisation
  • microplastics

• Marine environment
  • marine debris and microplastics.