4. Impact of climate change

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The first thought might be that it would be nice to have a warmer and longer summer. But we know that unusual weather events lead to many problems and even disasters.

Questions you may want to consider:

  • What will be the impact of more storms and cyclones?
  • Can ecosystems survive fast changes to the climate?
  • Will our food supply and health be affected?
  • Besides rising seas, can we expect other problems?

Water

The average amount of rain around the world is likely to increase as the climate changes. Many places will have an increase in large storms but may also have longer dry spells. Some areas will receive less rain. As the temperature rises, there will be more evaporation and people will need more water to live.

Scientists who study fossils and geology have found that over the last 20,000 years the climate has changed in Australia. For example, inland Australia had a much wetter climate with large permanent lakes. These lakes supported large communities of Aboriginal peoples. As the climate changed large areas of inland Australia received less rain and became arid.

The prediction for climate change is that, on average, the world will receive more rain. With higher temperatures there will be more evaporation. The tropics are likely to have more storms and the cyclones may be more violent. Most other areas could have longer dry spells but have more storms. It is predicted that southern Australia on average will have less rain and also more storms.

Southern Australia will have significant problems with water. Besides having less rain, there will be more evaporation. The rain may be less evenly spread throughout the year and when it does come down in big storms it has less chance of soaking into the ground. Australia's southwest and southeast including the Murray-Darling Basin already have serious water management issues with continuing drought. These areas seem to be very vulnerable to future climate change.

Tropical northern Australia is likely to receive more violent tropical storms and cyclones. The storm damage and floods will be greater.

Where in the past it took thousands of years for the climate to change, the predicted climate change that will affect our lives might be with us already.

Ecosystems

Major changes in ecosystems are expected to occur across the Earth as temperature and rainfall patterns change:

  • alpine and Arctic ecosystems in particular will shrink or disappear.
  • plants and animals affected by changes in temperature and rainfall will not be able to move to more suitable locations because humans have cleared so much of the land.
  • increased sea temperatures will have a big impact on the distribution of sea life.

Temperature and rainfall patterns are not the only changes that can have a big impact on ecosystems. The additional carbon dioxide in water will make it more acidic and could devastate the world's coral reefs.

Ecosystems evolve to meet a set of climatic challenges. When the climate changes quickly the animals and plants do not have time to evolve to fit in with a changed climate.

The most dramatic impacts of climate change are being seen in ecosystems adapted to cold environments. Polar bears are finding it more difficult to survive, as there is less sea ice in the Arctic. In the Antarctic, species like krill depend on the chilly water. Krill is near the bottom of the food web and all the larger animals directly or indirectly depend on them. Glaciers are shrinking and so are the alpine ecosystems. Even in Australia animals such as the mountain pygmy possum can't survive without their covering of snow.

In southern Australia, less rainfall, combined with greater evaporation from higher temperatures, can threaten ecosystems. There will be more days of extreme fire danger. A larger number of fires can quickly alter the species composition in an ecosystem.

Current climate change is very different to the changes that occurred in the last few million years. During these periods animals had thousands of years to react. Many of the plants and animals that were affected were able to gradually change their distribution. Some were able to adapt to the new conditions. A few became extinct. Animals and plants can't move like they once did. For most, the change is too quick to move or evolve. People have taken up and cleared so much of the world that it is not possible for the animals to move. Our homes, farms, roads, mining and factories are in the way.

Many species of sea animals are very temperature-dependent so many will change their distribution. Some will not be able to change and so will become extinct. Scientists will probably only realise which species are vulnerable once their numbers drop.

Coral reefs are in serious danger of disappearing. A one-degree increase in maximum temperature for a couple of weeks can result in the death of most of a coral reef. As the coral turns white, it is called coral bleaching. Provided there are not other threats to the reef, over many years it can slowly recover. All coral reefs around the world have had some impact from coral bleaching. In the future this will become more frequent. Another problem is that coral can't build its limestone skeleton if the water becomes more acidic. As the sea absorbs more carbon dioxide, the sea's acidity will change enough to destroy the coral reefs. Once the reef is dead all the animals that depend on it will also die.

Climate change will lead to degraded ecosystems, with one outcome being an increased rate of extinction.

It's not all bad news, however. You can help, not only by reducing your greenhouse emissions, but also by getting involved in the monitoring and management of local ecosystems. Join a 'friends of' group, keep records of local wildlife, or go on an expedition to monitor wild ecosystems. Planting indigenous trees and shrubs is always a winner – it increases local habitat, which may become scarce in the future. Just keeping records is very helpful – good observation is always at the foundation of successful programs to save species from extinction.

Coasts

The world's coasts will be very different if sea levels rise. Sea walls won't easily protect the land, and people's homes and farms in low-lying areas may be ruined. Many coastal cities could be flooded, and low-lying islands could become unliveable. The world's largest rivers deposit vast areas of fertile soils before they reach the sea. These are called 'deltas' and are home to hundreds of millions of people. If the sea rises these area will become unliveable. What will happen if millions of people lose their homes and farms?

There are two causes for sea levels rising. As the seawater temperature increases, the seawater expands. This slow process is measured in millimetres over a few years. However there is a great deal of ice locked up on the Antarctic continent and Greenland. Over the past 10,000 years, as ice has melted and icebergs have dropped into the sea from these land masses, the ice has been replaced by new ice and snow. If the melting of land ice increases, the water will add to the sea level. No one can be sure how fast this process would be. Even if Greenland lost half its ice, it would be enough to flood most coastal cities.

Some of the world's largest rivers have created wide fertile deltas that support the homes and farms for millions of people. These people are some of the poorest in the world. In many places these deltas may only be about a metre or so above sea level. As the sea level rises, they will be more vulnerable to cyclones, storms and flooding. This may already be happening. As the sea rises further, the land will become salty and finally covered by sea. A sea wall might protect them from the sea but would cause problems from the flooding river. A rise of only a few metres in sea level will result in millions of these people becoming refugees.

There are many island communities that live on coral islands. Most of these islands are only a few metres above sea level. The lowest of these islands are now having more problems with invading seawater during high tides and storms. This affects their crops and the amount of fresh water available. These people may be some of the first refugees caused by rising sea levels.

Many of the world's cities are on the coast. Most of these cities are vulnerable to rising sea levels. At first they will be flooded when there are storms corresponding with high tides. Governments will want to protect their cities and people's homes. In the future many cities will try and build sea walls. This will devastate the ecosystems along the coasts. Will sea walls be able to protect cities from both rising sea levels and more violent storms? Will the populations of some of the world's largest cities become refugees?

Health

Climate change may have a serious impact on the health of many people. The poor may have less food; people may lose their homes by rising sea levels; severe storms and floods may contaminate water and destroy homes; and tropical diseases might spread.

The health of poor people is at greatest risk from climate change. More violent storms and floods will affect people in deltas and other low-lying areas. When large areas flood, human waste along with dead animals and even dead humans pollute the water. While the area is flooded people will get ill if they drink this water. They will not have firewood to sterilise the water and will depend on relief workers to bring in clean, bottled water. Babies and small children are most at risk.

After a natural disaster, many people lose their homes and may only have a plastic sheet to shelter them from the weather. Under these conditions many types of diseases can quickly spread. Eventually it may not be possible for people to return and restore their homes and farms. The world may have an increasing number of refugees. Such problems raise many questions: Will these people be squeezed into a small area? Will they live in refugee camps? Will they be able to move to other regions in the world?

When weather patterns change in farming regions, the poor can't grow enough food so people will go hungry or even starve. In cities, a lack of food will increase prices and the poor may no longer afford to buy some foods. This may mean they buy less food or food that is of a poorer quality. We may find that the poorer people in more prosperous countries will also have problems buying good-quality food.

Europe has been having more hot days during recent summers. Hot weather particularly affects older people. Hotter weather also worsens summer (photochemical) smog in urban areas, and the combined effect of pollution and heat can be fatal for sensitive people.

As the climate becomes warmer and the tropics wetter many tropical diseases are likely to spread. Malaria, a tropical disease carried by mosquitoes, is likely to spread further as the warmer, wetter climate conditions enable mosquitoes to breed more profusely. Australia is free of malaria, but Australian health authorities are concerned that malaria will take a hold in the tropical north of the country.