Climate change, whatever the cause, has profoundly affected human societies and the natural environment in the past.
The clearest present-day impacts of climate change in Australia and elsewhere are seen in the natural environment, and are associated with warming temperatures and increases in the number, duration and severity of heatwaves. These impacts include changes in the growth and distribution of plants, animals and insects; poleward shifts in the distribution of marine species; and increases in coral bleaching on the Great Barrier Reef and Western Australian reefs. Some of these changes can directly affect human activities; for example, through the effects of changing distributions of fish and other marine organisms on commercial and recreational fisheries, and the impacts of coral bleaching on tourism.
Ecosystems: Among Australia’s terrestrial ecosystems, some of the most vulnerable to climate change are alpine systems as habitats shift to higher elevations and shrink in area; tropical and subtropical rainforests due to warming temperatures (moderated or intensified by rainfall changes; coastal wetlands affected by sea-level rise and saline intrusion; inland ecosystems dependent on freshwater and groundwater that are affected by changed rainfall patterns; and tropical savannahs affected by changes in the frequency and severity of bushfires.
Climate warming causes land and ocean life to migrate away from areas that have become too warm, and towards areas that previously were too cool. In many places, climate change is likely to lead to invasion by new species and extinctions of some existing species that will have nowhere to migrate.
Bushfires: The number of extreme fire risk days has grown over the past four decades, particularly in southeast Australia and away from the coast. Future hotter and drier conditions, especially in southern Australia, are likely to cause further increases in the number of high fire-risk days and in the length of the fire season. CO2 fertilisation may lead to increased foliage cover and hence increased fuel loads in warm arid environments such as parts of southern Australia.
Food security: In a non-drought year, around three-quarters of Australian crop and livestock production is exported. The range of adaptation strategies for primary producers to meet the challenge of climate change is large, including breed and seed selection, water conservation and changes in the timing of farm operations. Over the next few decades, some Australian agriculture may benefit from warmer conditions and from the fertilisation effect of increased CO2 in the atmosphere.
Looking further into the future, much depends on the effects of climate change on rainfall regimes in Australia’s farming regions. If rainfall increases, climate change may continue to be beneficial for some agriculture. However, for drier, hotter, higher variability climate change scenarios, there are limits to adaptation with anticipated declines in crop yield and livestock production
Health: Heatwaves are among the highest-impact climate events in terms of human health in Australia. In very hot conditions, people can suffer from heat stress, especially vulnerable individuals such as the sick and elderly.
Infrastructure: Climate change can have impacts on infrastructure such as electricity and transport networks. Electricity demand rises sharply during heatwaves because of increased air conditioning. To avoid extensive blackouts there has been investment in generation and network capacity that is only used for a short time.