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"Climate change will affect, in profoundly adverse ways, some of the most fundamental pre-requisites for good health: clean air and water, sufficient food, adequate shelter, and freedom from disease" - World Health Organisation 2008 -
Human beings have changed the atmosphere of the earth by the amount of greenhouse gas pollution we have generated. More energy from the sun is now trapped there, rather than being reflected away from the earth. This is altering the balance of nature in ways we can't always predict, and potentially threatening our survival and the survival of our fellow species on this planet.
For a long time it was not common knowledge that the way we use fossil fuels such as petrol and coal was having this effect, but now the scientific evidence is compelling. The end result is that the climate is becoming hotter and more extreme.
When scientists talk about the earth warming by 0.8°C over the last century, it may not sound like such a big a deal. But natural systems operate in a very complex balance, so that even this amount of change has huge consequences. Sea levels are rising, glaciers are melting and rainfall patterns are changing. Extreme weather events are becoming more frequent and intense. We will experience more intense heat in summer, more severe and frequent bushfires, longer and more intense drought. Climate scientists are warning us to act quickly and decisively to avoid even more dramatic changes.
The ecosystems upon which we all depend on for fresh air, clean water, shelter, control of toxins and pathogens, healthy food, relaxation, inspiration, adventure, and the joy of interacting with other species are highly vulnerable to the changes that are occurring. With half of the humans on the planet now living in cities or towns, it is easy to forget how much our health depends on that of the natural world.
Our understanding of how the environment affects humans is still evolving, so we don't have all the answers. However, we know enough already to say that climate change will affect human health in a wide variety of ways, many of these negative.
Impacts may occur directly through the effects of extreme weather (heatwaves, drought, bushfires, floods, storms). Or they may be indirect through changes to ecosystems and biological processes, such as the distribution of disease vectors (e.g. mosquitoes), food and water-borne disease, the quality and availability of food and water, and poor air quality. There are likely to be social and economic effects from these changes, as well as challenges to our physical and mental health and well-being.
Impacts won't be evenly distributed. They will be influenced by local conditions, by how vulnerable people are in a particular place and by how well they are able to adapt. Climate change may act to amplify existing public health problems as well as bringing new ones.
The World Health Organisation says that climate change puts at risk the basic determinants of health, and that it is already causing the loss of thousands of lives. In a strange irony, the poorest populations, who have contributed least to climate change, are the most vulnerable. Children in particular will suffer, as world-wide they already bear most of the brunt of malaria, diarrhoea and poor nutrition. Within countries it is those who are disadvantaged who are most likely to be affected.
If we are fortunate enough to live in an affluent developed country like Australia, does this mean we don't really have to worry? Unfortunately not. We only have to look at the thousands of premature deaths from heatwaves in Europe in 2003, the impact of Hurricane Katrina in the US in 2005, and the 2009 Black Saturday bushfires in Victoria to see that. Let's examine some of the ways changes to the climate may affect our health.
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| This map of Australia shows how the land surface temperature from January 25 to February 1, 2009, compared to the average mid-summer temperatures the continent experienced between 2000-2008 |
CSIRO predicts that Australia will be warmer by about 0.6 -1.5°C by 2030 and about 1-5°C by 2070, with more hot days and fewer cold days. Heatwaves are already becoming more common around the world. Human beings need to keep their body temperature within an optimum range, outside of which they can become ill and may die.
Most of the premature deaths that occur during periods of extreme heat are of the elderly and persons with pre-existing illness, such as heart disease. Being poor or socially isolated and urban living are also risk factors. As the population is aging, we can expect this to become a bigger problem for everyone, but especially for our senior citizens.
The January 2009 heatwave in Victoria had significant impacts on health. Compared to the same period in previous years, there was a 62 per cent increase in deaths and a 12 per cent increase in presentations to hospital emergency departments.
Heat waves often occur together with other potential health threats such air pollution, drought, changes in water quality, fires, and power failures.
Climate modeling forecasts a future of increasing sea levels, increasing frequency of storm surges and heavy downpours when it does rain. In some areas, this may contribute to flooding. For example in 2007, parts of Gippsland experienced severe flooding when several river systems which flowed into the Gippsland Lakes received heavy rain after a period of bushfire, and king tides at the same time made it hard for the water to escape. This affected hundreds of homes and businesses, causing tens of millions of dollars damage.
Flood events can affect health by resulting in death, injury, infectious disease, chemical contamination, and mental health problems. With sudden heavy rainfall, sewerage systems may overflow and contaminate waterways, and septic systems may fail. Microbes and chemicals can contaminate water. Loss of power and damaged infrastructure may cause problems with food and water safety. Mould growth can be a problem in homes and flooding may lead to changes in mosquitoes or rodent populations. Naturally, social dislocation and economic losses can induce stress, anxiety and depressive illness.
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| Tropical Cyclone Larry formed off the northeastern coast of Australia on March 18, 2006. |
There is some evidence that the intensity of tropical cyclones is likely to increase as a result of climate change. We may have to adapt to more severe events such as Tropical Cyclone Larry which hit Queensland in 2006 causing devastation, and the 2007 storm that swept through parts of NSW, resulting in widespread flooding and damage, thousands of homes without power and water, and several people dead.
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| 2009 Black Saturday Bushfires (Victoria, Australia) |
Climate predictions for Australia are that the frequency of very high and extreme fire danger days is likely to rise by up to 25 per cent by 2030. Bushfires can cause death, injury, burns and damage from smoke inhalation, exacerbating asthma and other lung and heart conditions.
This doesn't just affect country people. Toxic gaseous and particulate pollutants are released into the atmosphere and can affect air quality over many kilometres. Recent bushfires have contributed to some severe air pollution in our cities. Fires can stretch the capacity of health care systems and other essential services to cope. Power supplies may be affected, and water quality can be significantly impacted by ash and debris entering rivers and reservoirs. Alternative drinking water supplies may need to be supplied to large numbers of people, and water yield from some catchments may be reduced after fire. Loss, grief and social dislocation can have significant long-term effects on people's mental health and well-being, requiring long-term support.
The Victorian bushfires of February 2009 were the second worst natural disaster in Australian history in terms of deaths caused. Fires starting on the state's hottest day on record, when the temperature soared to 46.4° C, flared across 14 different regions, destroying over 2,000 homes, killing 173 people, with hundreds presenting to hospital for care. Conditions were so severe they were outside of the experience of many frontline personnel.
We need water for drinking, cooking, hygiene and recreation, so reduced water quantity and quality are likely to have significant health effects. Climate predictions are that there will be 20 per cent more months of drought by 2030.
Southern Australia is already experiencing significant water shortages. Over the past 10-15 years the volume of water in Melbourne's water storages has dropped from near capacity in 1996 to less than 40 per cent full. The Murray-Darling Basin provides water for about 70 per cent of irrigated crops and pastures. Annual stream flow there is likely to fall 10-25 per cent by mid-century. Water scarcity affects the price and availability of fresh food, which may make it increasingly more difficult for some people to access a healthy diet.
Dust storms may arise after prolonged drought, travelling thousands of kilometres, creating particulate air pollution, and making it hard for people to breathe, particularly those with asthma or lung conditions. Prolonged water shortage leading to drought causes crop and livestock losses, malnutrition, infection and respiratory disease across the globe, and can act as a trigger for people leaving their homes and becoming migrants, in turn creating other potential health issues. Drought in rural areas in Australia often leads to financial hardship, and reduced liveability, population size and social participation in affected communities, leading to a range of impacts on mental health and well-being.
Although our climate will be drier, when rainfall does occur it is likely to occur in sudden heavy falls. This can wash microbes into waterways, and increased temperatures help them survive and grow. Disease can be spread through inadequately treated water or water used for recreation. Examples of waterborne outbreaks overseas after heavy rainfall include a cryptosporidiosis outbreak in Milwaukee, USA in 1993, and an E.coli outbreak in Walkerton, Canada in 2000, each affecting thousands of people.
Algal blooms can present a major water quality problem in Australia. They are caused by the growth of blue-green algae, also known as cyanobacteria. Conditions where fertilisers and other pollutants are washed into waterways help them develop, and it is likely they may become more frequent and longer-lasting with climate change, as they thrive in conditions of high temperature and low water flows. Harmful algal blooms have the potential to produce powerful biotoxins which can pose a threat to human health through drinking water and recreational water use, and can affect fish and livestock which may be used for food.
Increasing temperatures are predicted to favour transmission of organisms that commonly cause food poisoning. For example, in some studies, increased human infections with Salmonella bacteria have been reported with increasing temperatures.
Some Vibrio bacteria are capable of causing outbreaks of food poisoning if they contaminate shellfish, and their abundance is influenced by the temperature of coastal water. Increasing temperatures may indirectly increase human exposure to some contaminants in food, for example, mercury in fish, and fungal toxins in grain.
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Urban air pollution in Australia comes mainly from vehicle emissions, industrial pollution, wood smoke from home heating, and coal-powered electricity generation. Major components of air pollution include particulate matter, sulphur dioxide, nitrogen oxides, carbon monoxide, ozone and volatile organic compounds.
Concentrations of air pollutants are affected by temperature and humidity. Increasing temperatures tend increase their impact on health. Urban air pollution is associated with increased premature deaths and illness from heart and lung disease. Health effects occur even at levels that meet the current air quality standards.
Concentrations of ozone, a respiratory irritant, are increasing in most urban regions. Exposure to high ozone levels is associated with a range of respiratory diseases, such as asthma, and with premature mortality. It can affect not only those with pre-existing lung conditions, but also healthy people.
Warmer temperatures, and increased levels of carbon dioxide in the atmosphere can promote the growth of some plants and fungi with pollen or spores that can cause allergies. An increase in these "aero-allergens" may contribute to increased rates of asthma and hay fever.
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| Found throughout the world, mosquitoes are known to be vectors for a number of infectious diseases affecting millions of people per year |
There will be increasing challenges to the control of infectious diseases. Many of the diseases that kill most people in the world are transmitted by water, or contaminated food or insect vectors such as mosquitoes. Changing temperatures and patterns of rainfall are expected to alter the distribution of insect vectors that spread diseases such as malaria and dengue fever.
Approximately one third of the world's population currently lives in regions where the climate is suitable for transmission of dengue. Although high rainfall can cause an increase in transmission, so can drought in some circumstances, where household water storages provide favourable breeding sites. With greater water shortages and increasing storage of water in Australia, there is the potential for dengue fever to spread beyond its current range in Queensland, and control measures for the mosquito will remain important.
The most common mosquito-borne disease in Australia is epidemic polyarthritis, caused by Ross River virus or Barmah Forest virus, which has some disabling symptoms including rash, tiredness, joint and muscle pain.
We will have to be on the watch for newly emerging diseases. Animals affected by large environmental changes may help spread disease that eventually threatens humans. A recent example is that of fruit bats driven by loss of habitat due to land clearing, drought and wildfires to seek food in farmed areas. There they came in contact with orchards and pig populations where they triggered an epidemic of Nipah virus in Malaysia and surrounding countries. Australia has experienced outbreaks of Hendra virus in horses, thought to have been spread by bats, and these outbreaks have resulted in human deaths.
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| Adelie penguin on sea ice. Michael Van Woert, NOAA NESDIS, ORA |
Over the last 50 years, an average sea level rise of 20mm per decade has been observed in Australia. Sea levels are predicted to continue to rise, the levels depending on how we control our emissions. In low lying areas, a rise in sea level may cause increased flooding, intrusion of saltwater and erosion. Coastal freshwater aquifers may become saline, and stormwater and sewage disposal may be disrupted. Population growth in the Asia-Pacific region combined with a large rises in sea level is likely to affect millions of people. Large numbers of displaced people becoming environmental refugees may present significant public health problems to countries such as Australia and New Zealand, and may increase the potential for conflict in the region.
Increasingly frequent and severe disasters are likely to carry a significant human cost. Even when people survive and recover physically, these events can have ongoing adverse effects on mental health. Communities such as those affected by Hurricane Katrina suffer post-traumatic stress, anxiety, depression and this can manifest in suicide, domestic violence and substance abuse. Factors such as financial security, employment, access to services and the social fabric of communities may all be affected by climate change and these factors are integral to mental health and well-being. In addition, we have to recognise that acknowledging the substantial threat to the future of our planet that climate change represents can cause us emotional distress.
Yes, there is. We can act now to reduce air pollution, including carbon emissions, and many of these actions have added extra benefits for us as individuals and communities. We also have strong systems in place to deal with some of these challenges, and these can be further improved to help us to adapt to changes that are coming.
By reducing burning of fossil fuels such as coal and petrol, we would be reducing air pollution. This not only helps minimise climate change, but could also reduce the many cases of illness from heart and lung disease and premature deaths related to air pollution. Our petroleum resources are running out anyway, so that is another reason to change our behaviour.
Reducing our energy consumption and switching to clean energy sources reduces the emissions we generate from coal. Making our homes more energy efficient, by for example, good insulation, can save us money and make us more comfortable.
By walking or cycling, rather than driving cars, we not only help reduce carbon emissions, but the more active lifestyle reduces our risk of obesity and other chronic diseases like heart disease and diabetes. Walking to public transport rather than driving to work is a healthier option as well as more environmentally friendly.
By eating less red meat and increasing our vegetable intake, we can reduce our risk of heart disease and cancer, as well as helping to reduce the proportion of greenhouse gas emissions from agricultural sources. Diets high in fruit and vegetables and low in animal products tend to have more fibre and less saturated fat, and generally require less water and energy to produce.
If we plant more trees, we are not only helping to soak up carbon, but we enhance shade, reducing the risks of sun exposure and heat stress, and have a more pleasant environment for daily activity and recreation.
We all make decisions every day that shape our future. We can choose to live sustainably within the limits of the Earth's finite resources. We can choose to consume less, reduce our waste, and recycle. In so doing, we use less resources, burn less fossil fuel, create less pollution, decrease the risk of dangerous climate change. We also can talk to our friends and let our politicians know what is important to us, encouraging them to act for the benefit of the whole community.
The health and well-being of all human populations depends on the health of the natural life support systems of the planet. These are under threat from many environmental problems, the largest of which is climate change. In the words of Margaret Chan, the Director-General of the World Health Organisation, " the real bottom-line of climate change is its risk to human health and quality of life". We can protect our health by protecting the health of the planet.
Contact: Dr Marion Carey
