Climate change is already affecting Australia’s heritage (ANU 2009, Australia ICOMOS 2011). Australia’s climate has warmed significantly, rainfall regimes have altered, and extreme fire and weather events are increasing in frequency and intensity (see ‘Climate’ in the Atmosphere report). Cultural heritage places are both directly and indirectly affected. Heritage managers will need to identify and better integrate climate change and extreme weather risk into forward planning and preparation, allocate resources accordingly, and seek out opportunities to respond to the symptoms or pressures that arise from climate change (Australian Government 2015c). In particular, opportunities should be embraced to facilitate appropriate adaptation and increase resilience (Dunlop et al. 2012).
Australia is warming, with temperatures having increased by 1 °C during the past 100 years (BoM & CSIRO 2016; also see the Atmosphere report), and 2013 was Australia’s warmest year on record. Rising temperatures alter ecosystems and may decrease resilience, with potentially devastating effects for niche-adapted rare and endangered species. Other pressures associated with climate change include the arrival or range expansion of other native species or introduced species, and increase in fire frequency and intensity. Climate change is also affecting seasonal patterns, such as plant flowering and pollen distribution. Rising temperatures particularly affect the marine environment, causing adverse impacts such as coral bleaching.
Warmer air temperatures cause deterioration of building fabric, and changes to lifestyles and cultural practices. More frequent extreme temperature events may lead to increased human pressure on heritage places, including the negative effect of abandonment.
Australia’s rainfall patterns have varied greatly during the past century, but there is a long-term trend of declining rainfall in autumn and winter in south-eastern and south-western Australia. Higher rainfall in northern Australia may result in flooding and erosion of heritage places and archaeological sites, and possible destabilisation of historic buildings. Changing rainfall regimes can alter groundwater recharge patterns, and impact on avenues of trees (including memorial avenues of honour) and historic gardens. Lower rainfall in southern Australia is affecting vegetation communities, leading to associated impacts such as habitat loss, increases in invasive species, more frequent and more intense fires, and destabilisation of structures and archaeological sites. Reduced rainfall may also reduce the economic viability of rural communities, or affect Indigenous sites that are water reliant or related to the ability of local communities to live on Country. There is also increasing recognition of the social, cultural and spiritual value of water to many Indigenous Australians, and the importance of recognising the needs of Indigenous communities in relation to water access and management (Australian Government 2015b; see Box HER7).
Rising sea levels
Sea level is rising globally, and the intensity and frequency of extreme sea levels have increased on the east and west coasts of Australia. Australian sea level has risen more rapidly than the global average since 1993, a result of natural climate variability (see the Coasts report for further details). Rising sea levels will place major pressure on Australia’s coastal and island heritage, not only on natural heritage places, but also on cultural sites such as Aboriginal middens, sea cave deposits, archaeological sites and cave art sites. Places such as the Australian Antarctic Territory and the Torres Strait Islands are particularly vulnerable to rising sea levels. Indirect pressures will arise from changes to settlement patterns. Changes to hydrology, soil migration and damage from storm washes may also affect historic sites, such as Port Arthur or the Sydney Opera House.
Altered fire regimes
Fire presents a major threat to reserved lands and their ecosystems, and to Indigenous and historic heritage places (see Box HER8). The pressures and impacts from fire depend on a combination of management regimes and the responses of different plant groups. The nature, intensity, frequency and timing of fires are changing, as are the favourable ‘weather windows’ that allow proactive prevention measures.
Fire management regimes and response procedures have necessarily become more sophisticated and better adapted to the complex issues involved. Although focus understandably remains on protecting people and property, natural and cultural heritage values are increasingly recognised. If well conceived and implemented, wildfire abatement programs may reduce pressure on biodiversity, and Indigenous and historic values. There have also been positive environmental outcomes from active fire management, including emissions reductions (through early dry-season burning), and Indigenous knowledge being cultivated and transferred (through savanna fire management programs). In contrast, inappropriate fire management regimes may pose direct threats or affect cultural values.
More frequent extreme weather events
Climate change is expected to increase the frequency and intensity of climatic events such as extreme rainfall, major sea level changes, severe fire weather, and droughts and floods, causing direct damage to natural and cultural heritage places. For example, respondents to the National Heritage survey (WHAM 2017) reported that more frequent and extreme weather events are the most significant climate change pressure threatening the listed values of National Heritage places (see Box HER9). Damage can also result from rescue and clean-up activities. Some places may suffer further deterioration through loss of economic viability.
Increasing ocean acidification has been formally identified for more than 15 years (Kleypas et al. 1999). Ocean acidification arises from the effect of carbon dioxide on the chemistry of the ocean (see the Marine environment report for further details). Around 30 per cent of the carbon dioxide released to the atmosphere from burning fossil fuels is absorbed by the ocean. Once carbon dioxide has entered the ocean, it reacts with water to create a dilute acid. Since before the Industrial Revolution, the acidity of the ocean has increased by 30 per cent and carbonate ion concentrations have decreased by 30 per cent. Calcium carbonate is the critical mineral that many animals (such as coral) secrete to form their skeletons and shells.
The Intergovernmental Panel on Climate Change has concluded that current rates of ocean acidification are the highest in the past 65 million years (IPCC 2014). Given that it will take more than 10,000 years to restore ocean chemistry (Hoegh-Guldberg et al. 2007), these changes are extremely serious. Ocean acidification is anticipated to lead to changes in ecosystems that will magnify substantially, with major consequences for people and ecosystems in coastal Australia. Ocean acidification presents a substantial risk to marine organisms and ecosystems such as the Great Barrier Reef (see Box HER24). The main impact is to reduce the ability of organisms such as corals to build and maintain structures, leading to wholesale dissolution and break-up, which in turn has serious implications for coastal regions that will be experiencing more intense storms and sea level rise (Professor Ove Hoegh-Guldburg, University of Queensland, pers. comm., March 2016).