In the midst of a raging heatwave, most people think of the ocean as a nice place to cool down. But heatwaves can strike in the ocean as well as on land. And when they do, marine organisms of all kinds – plankton, seaweed, corals, snails, fish, birds and mammals – also feel the wrath of soaring temperatures.
Our new research, published today in Nature Climate Change, makes abundantly clear the destructive force of marine heatwaves. We compared the effects on ecosystems of eight marine heatwaves from around the world, including four El Niño events (1982-83, 1986-87, 1991-92, 1997-98), three extreme heat events in the Mediterranean Sea (1999, 2003, 2006) and one in Western Australia in 2011. We found that these events can significantly damage the health of corals, kelps and seagrasses.
This is concerning, because these species form the foundation of many ecosystems, from the tropics to polar waters. Thousands of other species – not to mention a wealth of human activities – depend on them.
We identified southeastern Australia, southeast Asia, northwestern Africa, Europe and eastern Canada as the places where marine species are most at risk of extreme heat in the future.
Marine heatwaves are defined as periods of five days or more during which ocean temperatures are unusually high, compared with the long-term average for any given place. Just like their counterparts on land, marine heatwaves have been getting more frequent, hotter and longer in recent decades. Globally, there were 54% more heatwave days per year between 1987 and 2016 than in 1925–54.
Although the heatwaves we studied varied widely in their maximum intensity and duration, we found that all of them had negative impacts on a broad range of different types of marine species.
Humans also depend on these species, either directly or indirectly, because they underpin a wealth of ecological goods and services. For example, many marine ecosystems support commercial and recreational fisheries, contribute to carbon storage and nutrient cycling, offer venues for tourism and recreation, or are culturally or scientifically significant.
Marine heatwaves have had negative impacts on virtually all these “ecosystem services”. For example, seagrass meadows in the Mediterranean Sea, which store significant amounts of carbon, are harmed by extreme temperatures recorded during marine heatwaves. In the summers of both 2003 and 2006, marine heatwaves led to widespread seagrass deaths.
The marine heatwaves off the west coast of Australia in 2011 and northeast America in 2012 led to dramatic changes in the regionally important abalone and lobster fisheries, respectively. Several marine heatwaves associated with El Niño events caused widespread coral bleaching with consequences for biodiversity, fisheries, coastal erosion and tourism.
All evidence suggests that marine heatwaves are linked to human mediated climate change and will continue to intensify with ongoing global warming. The impacts can only be minimised by combining rapid, meaningful reductions in greenhouse emissions with a more adaptable and pragmatic approach to the management of marine ecosystems.
The risk of extreme heat events and the adverse impacts on older people has been extensively discussed in research. Remarkably, very little attention has been paid to the role of urban greenery in reducing heat stress for seniors.
Older people are particularly at risk of heat stress. Pre-existing medical conditions and limited mobility increase their vulnerability. Deaths of older people increase during extreme heat events.
The physical features of urban areas shape the capacity of older adults to engage in many activities when it’s hot. These include vegetation volume and coverage, thermal design, and the extent of shading in public areas and walkways. Increasing urban greenery may offer a way to improve older people’s comfort and social experience.
It is expected 20% of the global population will be older than 60 by 2050. The figure for Australia is even higher, at 23%. This means that by 2050 around one in four Australians will be more vulnerable to extreme heat.
Planning our urban centres to meet the needs of a rapidly ageing population is a matter of urgency. Urban greening to reduce their vulnerability to heat stress should be central to this agenda. It can also improve people’s quality of life, reduce social isolation and loneliness, and ease the burden on health systems.
An important task is matching the design of communities with the needs of an ageing population. Where older adults live and the quality of their local areas strongly influence their lived experiences. Yet recent research found the experiences of seniors were often not accounted for in research on neighbourhood design.
If one in ten Australian seniors live in aged-care facilities, it is clear these should be designed to minimise heat stress. This isn’t just good for residents; it may also benefit operators by lowering health-care and electricity costs.
While these facilities are purpose-built for older people, many in Australia were built well over a decade ago, when heat stress was not such a large concern. Many more facilities are being built now and will be into the future. Yet it is uncertain whether they are being actively designed to reduce the impacts of heat.
We recently conducted a focus group to investigate this issue. Participants were senior managers from four large corporate providers of aged care in Australia. We investigated if and how providers try to minimise heat stress through design. We also sought to understand the rationales used to support these design approaches.
Several participants reported on refurbishments that they expect will have cooling effects. Cited design approaches included green roofs and walls, as well as sensory gardens. Other expected benefits included reducing anxiety and improving the mental health of residents.
The fact that single design interventions could produce multiple benefits improved the potential for corporate buy-in. Participants expected that increasing green space and green cover would give their facilities a competitive advantage by attracting more clients and providing a better working environment for staff.
Participants also reported on challenges of including greening in their projects. For example, the benefits of trees were weighed against concerns about roots disrupting footpaths and becoming trip hazards. Species selection was another concern, with fears that inappropriate plants could die and undermine support for greening programs.
Our research suggests that more can be done to make cities hospitable for older people, especially during extreme heat. Urban greening is a start. Encouraging aged-care providers to adopt green infrastructure will have benefits. But we should also consider reforms to planning systems and urban design to better protect older people who choose to age in place.
Last year was a time of exceptional weather and record-breaking heat according to the Bureau of Meteorology’s annual climate statement, which was released last night.
The Bureau issued four Special Climate Statements relating to “extreme” and “abnormal” heat, and reported a number of broken climate records.
One of the headline stories for the year was drought across eastern Australia — centred on New South Wales, but also affecting Victoria, eastern South Australia and southern Queensland.
With the whole of NSW declared in drought during the latter half of 2018, this drought will be recorded as one of the more significant in Australia’s history, ranking alongside the Millennium, 1960s, World War Two and Federation Droughts. Of those historic droughts, only the Millennium Drought saw similar, accompanying high temperatures.
The below-average rainfall has persisted for around two years across much of NSW and adjacent regions. The drought conditions were particularly severe in the recent spring period, with low rainfall, persistently high temperatures, and record high evaporation.
This exceptionally dry period was influenced by sea surface temperatures to the west of the continent. Perhaps fortuitously, a developing El Niño in the Pacific Ocean failed to mature in the second half of the year. An El Niño would have typically exerted a further drying influence on eastern Australia.
The dry conditions in eastern states were severe enough to see Australia record its lowest September rainfall on record, and the second-lowest on record for any month — behind April 1902, during the prolonged Federation Drought. Over 2018, Australia’s annual rainfall was 11% below average, and the lowest recorded since 2005, during the Millennium Drought.
In contrast, above-average rainfall was recorded across parts of the tropical north, and most significantly in the Kimberley, consistent with recent trends of increasing rainfall in that region.
The drought conditions were exacerbated by record or near-record temperatures across many parts of the country. It was Australia’s third warmest year on record, behind 2013 and 2005. Daytime maximum temperatures were the warmest on record for NSW and Victoria, and second-warmest for South Australia, the Northern Territory and Australia as a whole.
Persistent dry conditions through winter are typically associated with low soil moisture and heatwaves in the following spring and summer, and 2018 followed this pattern — with the added contribution of a warming climate.
The year ended with some record-breaking heat events. Perhaps the most significant of these was the extreme heat along the central and northern Queensland coast in late November and early December, which saw maximum daytime temperatures of 42.6 °C in Cairns and 44.9 °C in Proserpine on the 26th of November.
These temperatures, combined with persistent dry conditions in the preceding months, saw catastrophic fire weather and bushfires along 600km of the Queensland coast, an event that fire agencies have called unprecedented for the state.
The year ended with a burst of heat over the Christmas-New Year period, with temperatures at least 10 degrees warmer than average across southern South Australia, most of Victoria and southern NSW, leading to Australia’s warmest December on record.
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Large parts of Australia are facing a hotter and drier summer than average, according to the Bureau of Meteorology’s summer outlook.
Drier than average conditions are likely for much of northern Australia. Most of the country has at least an 80% chance of experiencing warmer than average day and night-time temperatures.
The threat of bushfire will remain high, with few signs of the sustained rain needed to reduce fire risk or make a significant dent in the ongoing drought.
Expect extreme heat
Large parts of Western Australia, most of Queensland and the Top End of the Northern Territory are expected to be drier than usual. Further south, the rest of the country shows no strong push towards a wetter or drier than average summer, which is a change for parts of the southeast compared to recent months.
Queensland has already seen some extraordinary record-breaking heat in recent days, with summer yet to truly begin. With the summer outlook predicting warmer days and nights, combined with recent dry conditions and our long-term trend of increasing temperatures, some extreme highs are likely this summer.
All of this means above-normal bushfire potential in eastern Australia, across New South Wales, Victoria and Queensland. The bushfire outlook, also released today, notes that rain in areas of eastern Australia during spring, while welcome, was not enough to recover from the long-term dry conditions. The current wet conditions across parts of coastal New South Wales will help, but it will not take long once hot and dry conditions return for vegetation to dry out.
However, not all the ducks are lined up. While ocean temperatures have already warmed to El Niño levels, to declare a proper “event” there must also be a corresponding response in the atmosphere to reinforce the ocean – this hasn’t happened yet.
That said, climate models expect this event to arrive in the coming months. The outlook has factored in that chance, and the conditions predicted are largely consistent with what we would expect during El Niño. In summer, this includes drier weather in parts of northern Australia, and warmer summer days.
Once an El Niño is in place, weather systems across southern Australia tend to be more mobile. This can mean shorter but more intense heatwaves in Victoria and southern South Australia. However, in New South Wales and Queensland, El Niño is associated with both longer and more intense heat waves.
The exact reason why the states are affected differently is complicated, but relates to the fast-moving cold fronts and troughs that sweep through Victoria and South Australia in the summertime, creating cool changes. These weather systems don’t influence areas further north so when hot air arrives, it takes longer to clear.
The heavy rains seen in parts of eastern Australia in October and November have provided some welcome short-term relief to drought-stricken farmers, but longer-term rainfall relief has not arrived yet. If El Niño arrives, this widespread relief may only be on the cards in autumn.
Those most at risk are the elderly, people with chronic illness, those living in socioeconomic disadvantage, outdoor workers, and athletes who play their sport in brutally high temperatures. But extreme heat can affect anyone at any age.
So, what happens in our body during times of extreme heat? And how can it lead to fatal consequences?
Our core body temperature sits at around 37℃. If it rises or falls, a range of very efficient physiological mechanisms come into play. In good health, our body can usually cope well with deviations of about 3.5℃, but beyond that the body begins to show signs of distress.
In hot weather, the body maintains core temperature by losing heat in several ways. One is to transfer it to a cooler environment, such as surrounding air or water, through our skin. But if the surrounding temperature is the same or higher than the skin (greater than 35-37℃) the effectiveness of this mechanism is markedly reduced.
Blood vessels supplying blood to the skin dilate. This allows more warm blood to flow near the surface of the skin, where the heat can be lost to the air. That’s why some people’s skin looks redder in hot environments.
Evaporation (or sweat) is another way to lose heat from the body. If there is enough airflow and humidity is low enough, we can lose large amounts of heat through sweat. But on humid days, the rate of evaporation is reduced, as the air cannot absorb so much if it is already saturated with water vapour.
We can also reduce our heat production by resting. About 80% of the energy produced by working muscles is heat, so any activity will increase the amount of heat the body has to lose. This is why athletes and outdoor manual workers are at particular risk when performing at high levels of physical activity.
Heat stress describes a spectrum of heat-related disorders that occur when the body fails to lose heat to maintain core temperature. Heat stress ranges from heat cramps to heat exhaustion (pale, sweating, dizzy and fainting). If the core temperature rises above 40.5℃, it can lead to heatstroke, which is a medical emergency, can occur suddenly and often kills.
Heatstroke is caused by a failure of the hypothalamus, the region of the brain that works as our thermostat and co-ordinates our physiological response to excessive heat. It’s what leads to mechanisms like sweating and rapid breathing, dilated veins and increased blood flow to the skin. So, when the hypothalamus fails, so does our ability to sweat and lose heat in other ways.
At temperatures higher than 41.5℃, convulsions are common. Irreversible brain damage can occur at temperatures above 42.5℃. Patients with heatstroke can show neurological signs such as lack of co-ordination, confusion, seizures and loss of consciousness.
When sweating stops, the skin may become hot and dry, heart rate and breathing increase and blood pressure is low. Cells and nerves in the body become damaged. Liver damage is also common, but may not manifest for several days. The kidneys stop working, normal blood clotting is impaired, the heart muscle can be damaged and skeletal muscles start breaking down.
Essentially, this is what we describe as multi-organ failure. People with heatstroke can die within a few hours, or several days or even weeks later from organ failure.
Heatstroke could be “exertional”, as with athletes, or “classic”, which occurs in patients with impaired thermostatic responses, as a result of age, illness or medications.
Much of the increase in deaths during hotter temperatures occurs in older patients with a chronic illness. This is because they may have a poorly functioning central nervous system that cannot orchestrate the physiological changes needed to lose heat.
Older hearts may not be able to cope with the changes in circulation needed for more blood flow to go to the skin. Some medications can also interfere with the mechanisms for heat loss.
People experiencing any of the warning signs of heat stress (headache, nausea, light-headedness and fatigue) need to alter their behaviour to reduce it.
The best way to do this is to find a cool spot indoors or in the shade, put on light clothing, avoid physical exertion, put a damp cloth on your skin, immerse yourself in cold water and stay well hydrated.
But for some people, like children who are too young to make changes to their environment (such as those left in cars), this is not possible. Also, for the elderly, perhaps those with chronic mental illness or on certain medications that impair their ability to respond to increasing core temperature, these signs may not be apparent or noticed.
This means we need safeguards to ensure the vulnerable stay cool. This is especially a problem for elderly people who live alone.
So, as our climate warms up, we need to do all we can to minimise the consequences of an increasingly hot environment. That means we must adapt our behaviour, our understanding of the issues, our urban environments, our sporting events and our systems that look out for the vulnerable in our community.
This article was co-authored by Dr Mark Monaghan, an emergency physician, and Dr Liz Bashford, an anaesthetist, who are both members of Doctors for the Environment Australia.
Often when we have warmer winter weather in Australia it is linked to El Niño conditions in the Pacific or a positive Indian Ocean Dipole. Both of these Pacific and Indian Ocean patterns tend to shift atmospheric pressure patterns in a way that brings more stable conditions and warmer, drier weather to Australia.
This year, however, neither El Niño nor the Indian Ocean Dipole is playing a role in the warm weather. The sea surface temperature patterns in the Pacific and Indian Oceans are close to average, so neither of these factors is driving Australia’s record warmth.
A clear human fingerprint
Another factor that might have influenced the July heat is human-caused climate change.
To assess the role of climate change in this event, I used climate model simulations and a standard event-attribution method. I first evaluated the climate models to gauge how well they capture the observed temperatures over Australia during July. I then computed the likelihood of unusually warm July average maximum temperatures across Australia in two groups of climate model simulations: one representing the world of today, and another representing a world without human influences on the climate.
I found a very clear signal that human-induced climate change has increased the likelihood of warm July temperatures such as the ones we’ve just experienced. My results suggest that climate change increased the chances of this record July warmth by at least a factor of 12.
July heat is on the rise
I also wanted to know if this kind of unusual July warmth over Australia will become more common in future.
I looked at climate model projections for the next century, and examined the chances of these warm conditions occurring in periods when global warming is at 1.5℃ and 2℃ above pre-industrial levels (we have had roughly 1℃ of global warming above these levels so far).
The 1.5℃ and 2℃ global warming targets were decided in the Paris Agreement, brokered in December 2015. Given that we are aiming to limit global warming to these levels it is vital that we have a good idea of the climate we’re likely to be living in at these levels of warming.
I found that even if we manage to limit global warming to 1.5℃ we can expect to experience such July heat (which is record-breaking by today’s standards) in about 28% of winters. At 2℃ of global warming, the chances of warm July temperatures like 2017 are 43% for any given year.
Given the benefits of fewer and less intense heat extremes over Australia at lower levels of global warming, there is a clear incentive to try and limit climate change as much as possible. If we can reduce our greenhouse gas emissions and hold global warming to the Paris target levels, we should be able to avoid the kind of unusual warmth we have seen this July becoming the new normal.
Our EcoCheck series takes the pulse of some of Australia’s most important ecosystems to find out if they’re in good health or on the wane.
Think of an Australian landscape and you’re unlikely to picture snow-capped mountains or alpine meadows. But that’s what you’ll find atop the peaks of the country’s southeastern corner.
Although relatively small – covering about 11,000 square kilometres or 0.15% of the continent – these alpine and subalpine ecosystems have outstanding natural value and provide billions of dollars’ worth of benefits to the nation each year.
They are in comparatively good health but are facing numerous threats. However, their health in decades and centuries to come will depend largely on how we deal with these threats now.
Australia’s main alpine and subalpine areas are the Snowy Mountains in New South Wales, the Bogong High Plains in Victoria, and central and southwestern Tasmania. They occur above about 1,400-1,500m on the mainland, and 700-1,000m in Tasmania.
Although Australia’s mountains are relatively low by global standards (Mt Kosciuszko, the continent’s highest peak, rises only 2,228m above sea level), there is true treeless, alpine vegetation above the climatic treeline.
Treeless patches may also occur in the high subalpine zone, just below the treeline, typically on rolling high plains where accumulations of cold air or water prevent trees from establishing and growing.
The alpine climate is cold, wet, snowy and windy, with a short growing season. The soils are highly organic and can hold tremendous amounts of water. Alpine plants are short: mostly tussock-forming snow grasses, rosette-forming herbs such as snow daisies, and ground-hugging shrubs.
The dominant plant communities are grasslands, herbfields, heathlands and wetland complexes rich in peat moss (Sphagnum). The animals are mostly invertebrates such as moths, grasshoppers and ants.
The Australian Alps are hugely important for conservation, water production and recreation. Most alpine areas are within national parks and are home to many unique plants and animals.
Alas, the alps face multiple threats, including global warming, invasive species, disturbances such as fire, increasing pressure from human recreation, and unsound ideas about how to manage the high country.
The climate has already changed. Since 1979, average temperatures during the growing season on the Bogong High Plains have risen by 0.4℃, while precipitation has decreased by 6%. Since 1954, the depth and duration of the snowpack in the Kosciuszko region have declined.
Rising temperatures are a serious problem because the Australian Alps are relatively low mountains and the alpine species, already at their distributional limits, have nowhere else to go. Woody vegetation may increase – the treeline may rise and shrubs are likely to expand into grasslands and herb fields, which may make the landscape more prone to fire.
Mainland alpine ecosystems can regenerate after large fires. But Tasmania’s alpine vegetation is extremely fire-sensitive, and more frequent fire is likely to be detrimental to all alpine ecosystems.
The threat of livestock grazing to alpine ecosystems has all but ceased. However, feral animals and plants are a clear threat and will become more difficult to manage in the future without concerted action now.
Horse and deer numbers are increasing with alarming speed. These animals are occupying habitats well above the treeline. Many alien plant species have invaded the alps over the past half-century, a trend likely to be exacerbated by climate warming.
We also need to be wary of maladaptive ideas and practices, particularly those concerning the putative benefits to the alps of large non-native grazing animals. We have variously been told that “alpine grazing reduces blazing” (it doesn’t); that grazing combined with burning has “actually prevented soil erosion” (it didn’t); and that a “sustainable, viable” feral horse population can “co-exist” with the alpine environment (surely an oxymoron). There may be strong cultural imperatives behind these propositions, but they have no basis in science.
There is cause for hope, however. The Australian Alps are on the National Heritage List, which is protected by federal law.
There is also still time. The world is acting on climate change. Some species may adapt genetically, while some likely changes to vegetation may happen slowly. Scientists and land managers are working together to anticipate and manage change in the alps.
Change is inevitable, but with enough research, imagination and action, our high country will provide Australians with high-value environmental benefits for generations to come.
Are you a researcher who studies an iconic Australian ecosystem and would like to give it an EcoCheck? Get in touch.