Climate change

Climate change is an accelerating and cumulative pressure on the land environment. Climate change interacts with other human pressures, leading to greater vulnerability for people and the environment. The past 5 years has seen an increase in observed impacts of climate change on land-based industries and natural ecosystems. Increases in temperature, changes to patterns of rainfall and extreme events (see the Extreme events chapter) are affecting our soils and vegetation. The current changes being experienced in the climate are expected to continue and to intensify in the future (see the Climate chapter).

Climate change is requiring Australia to change practices and technologies to achieve a net zero emissions future, with opportunities for businesses and Indigenous groups to innovate and benefit economically, particularly in concert with recovery following the COVID-19 pandemic (see Management approaches and case study: Arnhem Land Fire Abatement program).

The impact on regions such as the Torres Strait Islands is now becoming about health, culture and human rights. The low-lying islands are particularly susceptible to climate change, which, in turn, will have direct and indirect effects on Island culture, as ‘many Islanders connect the health of their land and sea country to their mental and physical wellbeing and, more broadly, their cultural integrity’ (Green 2006) (see the Coasts and Indigenous chapters).

Greenhouse gas emissions from land use

Soil and vegetation in the land environment can help to mitigate climate change by sequestering carbon (see Carbon), but unsustainable land use can also contribute to greenhouse gas emissions and the level of climate change (see the Climate chapter). Since 2015, Australia’s net contribution to greenhouse gases from land use, land-use change and forestry (LULUCF) reversed, leading to a net sink of ↓26.3 megatonnes of carbon dioxide equivalent (Mt CO₂-e) in 2019 in that sector (see Table ES.01 in DISER (2021d) and Carbon, including above- and below-ground components). The net sink associated with the LULUCF sector (shown for different types of land conversions in Figure 28) provides some balance for net emissions in the agriculture sector (↑69.8 Mt CO2-e in 2019, Table ES.01 in DISER 2021d), but overall Australia’s net emissions in 2019 exceeded 500 Mt CO₂-e, which is 15% less than the levels 30 years ago (in 1990). This trend since 1990 is largely due to reductions in forest land conversions and regrowth on some previously cleared lands (DISER 2021d) (see Land clearing). In the year to March 2021, net emissions from the LULUCF sector declined by 1.1% on the previous 12 months due to an increase in emissions from agriculture (making up 14.9% of that year’s inventory), partially balanced by a continuing decline in land-clearing emissions (DISER 2021e) (Figure 29).

Changing temperatures and hydrology

Climate change increases the frequency and intensity of events such as heatwaves, bushfires, drought and storms, in addition to changing regional rainfall patterns and generally higher temperatures (see the Climate and Inland water chapters). These impacts often combine with other pressures on the land that expose soils and destabilise landforms, contributing to severe erosion events such as rockfalls, landslips, dust storms and overland water flows that move sediments and nutrients into streams and waterways. (See case study: Vegetation cover as a national indicator of soil health and erosion risk.)

Along with their impacts on the environment, changing temperatures and hydrology affect the medium- to long-term viability of agricultural and forestry systems in vulnerable regions of Australia (see Agriculture and Forestry). Adaptation in these production sectors may be at the expense of other natural capital values, if not planned and managed in an integrated way to ensure landscapes continue to function and are resilient to successive environmental shocks. Regions adjacent to the coast and Torres Strait may experience results of climate change more acutely than other parts of Australia.

While fire is an integral part of Australia’s environment to which many (not all) ecosystems have adapted, the increased frequency and intensity of fires under climate change is challenging. Forest fire danger in south-eastern Australia has increased, outside the range of historical experience, consistent with projections made more than a decade ago (Abram et al. 2021). The consequences of fire are substantial: loss of life; economic loss, of built assets and agriculture; and environmental loss (which in turn has short- and long-term economic and quality-of-life implications) (see the Extreme events chapter). The third aspect is the least understood and carries significant threats to our way of life. It is not just fire but the drought–fire–drought cycles that impact ecosystems the most, particularly in fragmented regions dominated by other land uses. The Biodiversity chapter discusses the species affected by increasing numbers of extreme fire events (see the Biodiversity chapter).

Indigenous Australians have traditionally used fire as a tool to manage and sustain healthy Country (see case study: Arnhem Land Fire Abatement program) (see the Extreme events chapter). Traditional ecological knowledge and its application through cultural burning is increasingly being recognised. The Firesticks Alliance, which is a collaborative approach from Traditional Owners on the eastern coast of Australia, has been actively espousing sharing and applying this knowledge as part of fire management and hazard reduction (see the Extreme events chapter). The savanna burning methodology recognised by the Clean Energy Regulator, which is aimed at reducing the risk of bushfires and the level of carbon release, is based on the traditional ecological knowledge system.

However, European-inspired agriculture and land management are more challenged by fire. Climate change is increasing the frequency, severity and unpredictability of bushfires, which in turn can have widespread impacts on the land environment – for example, as occurred in the unprecedented bushfires in the summer of 2019–20 (see the Extreme events chapter). Evidence from past decades of remote sensing of forest burnt area across Australia indicates that fire weather conditions are becoming increasingly more dangerous, and some aspects of this can be associated to varying degrees with anthropogenic (human-caused) climate change (Canadell et al. 2021).

Changing patterns of ecosystems, agriculture and forestry

Climate change is a pressure that applies equally to agricultural systems and natural ecosystems. Natural ecosystems have long been identified as one of the systems most vulnerable to climate change in Australia and elsewhere (IPCC 2020). Climatic conditions strongly influence the distribution, abundance and behaviours of species, and the structure, composition and functions of ecosystems (see the Biodiversity chapter). Of 17 types of pressure implicated in the collapse of 19 Australian terrestrial, marine and Antarctic ecosystems, 10 are related to global climate change (Bergstrom et al. 2021). The other 7 pressures relate to regional human impacts. The impacts of climate change will vary between regions, depending on how the buffering effect of soils and terrain interacts with local climates and land use. Examples of likely climate change–related impacts on flora and fauna, reported by Hoffmann et al. (2019), include tree dieback, changes in vegetation composition, changes in disturbance regimes, local extinctions, and physiological and phenological changes (see case study: Monitoring carbon and ecosystem processes using TERN OzFlux).

Currently, the types of agriculture and the specific animal breeds and seed varieties used in Australia generally match regional conditions, particularly in terms of temperature, available water resources and soil types. However, these regional conditions are changing with climate change, and may require matching changes in agricultural management and choices – for example:

• As regional climates become warmer, more heat- and drought-resistant crop and stock breeds or varieties may need to be cultivated to maintain productivity.
• The growing location of horticulture tree crops may need to change for trees that depend on the timing of particular seasonal conditions to initiate sufficient flower and fruit growth for viable yields and quality.
• Trees grown for timber may slow in growth or senesce due to increasingly unsuitable conditions (Pinkard 2017). Going forward, selecting appropriate species will be critical (Bush et al. 2018, Nolan et al. 2018). To maintain profitability, different farming systems and practices may need to be adopted or intensified, and relatively natural areas committed to agriculture and forestry – with implications for natural capital and ecosystem services. Increasing carbon storage through tree plantings and farm forestry could provide an alternative income stream.

These changes may be already underway, and data and anecdotal observations reveal that patterns of agriculture are shifting. However, the overlap between climate variability and climate change is poorly understood, and there is not enough evidence yet to separate the effects of climate change from market signals. The sector is conducting significant amounts of research into the impact of climate change on patterns of agriculture, which may yield evidence in the next 5 to 10 years.

While warmer conditions and faster plant growth rates caused by the higher levels of CO₂ in the atmosphere may have some benefits to agriculture in some regions (see the Climate chapter), these gains might be balanced by the need to cope with the risks and consequences of extreme events (see the Extreme events chapter).

Indigenous people and other people with close connections to the environment have observed climate change impacts on Australian terrestrial biodiversity and ecosystems. Anecdotes from respondents to a national survey conducted by Prober et al. (2019b) revealed increased mortality in some species, along with changes in recruitment or abundance of others, new arrivals, disappearances, and altered ecological interactions. These changes are consistent with the types of ecological change that have been long forecast and are now actively underway, the rates of which can be fast, slow or abrupt (Williams et al. 2021a).

Fifty of the world’s leading biodiversity and climate experts recently synthesised the most up-to-date scientific knowledge about climate change and biodiversity to inform decision-making and highlight options for action (Pörtner et al. 2021b, Pörtner et al. 2021a). They concluded that limiting global warming to ensure a habitable climate and protecting biodiversity are mutually supporting goals, and achieving those goals is essential for providing sustainable and equitable benefits to people.