Climate change

In the past the Earth's climate has gone through many cycles that have caused significant changes to the Earth's atmosphere.

More recently it has been acknowledged that human activities over the past 200 years have significantly altered the Earth’s atmosphere (CSIRO 2001) and have lead to a warming of the Earth’s surface.

The cause of the recent change in climate is mainly due to an increase in greenhouse gas emissions. Because greenhouse gas emissions are continuing to increase, this warming will also continue (CSIRO 2001).

Greenhouse effect | What does this mean | Tropical savannas and climate change | References |

Greenhouse Effect

Carbon dioxide (CO₂) and other 'greenhouse gases' including methane and nitrous oxide are released into the atmosphere from the use of fossil fuels. Stored carbon has also been released through the clearing of vegetation. It is thought that increasing the amount of greenhouse gases in the atmosphere increases the atmosphere's ability to absorb heat energy. This is termed the 'greenhouse effect'. Projections indicate that annual average temperatures in Australia could be 0.4–2.0 degrees higher by 2030 and 1.0–6.0 degrees higher by 2070. These estimates are based on world emissions scenarios produced by the Intergovernmental Panel on Climate Change (IPCC).

What does this mean?

Using global climate model simulations, the CSIRO has predicted the following changes in Australia’s climate in the future:

• An increase in average annual temperature of 1–6 °C by 2070 over most of Australia.
• An increase in the average number of extreme hot days and decrease in the average number of extreme cold days.
• A decrease in annual average rainfall in the south-west and in parts of the south-east and in Queensland.
• An overall drying trend for Australia due to increased temperatures and evaporation and changes in rainfall, and
• Rising sea level, stronger tropical cyclones and increasing associated oceanic storm surges.

Climate change will have ecological, social, economic impacts. All of our natural ecosystems are vulnerable to climate change. In the tropical savannas region those ecosystems most at risk include coral reefs, mangroves and wetlands, tropical forests, savannas and remnant native grasslands.

Industries based around agriculture, fisheries, forests and water are likely to be affected as these resources are sensitive to climate change. The speed at which changes in ecosystems will occur in response to climate change will determine in part how successfully ecosystems will adapt to these changes.

However many natural systems will have difficulty adapting to climate change (CSIRO 2001).

Drier conditions could threaten many eucalypt species, often the dominant plants in many native forests and woodlands.

The expansive wetlands of the tropical savannas are certainly vulnerable to climate change and sea level rise. If sea-levels rise significantly, the vast freshwater floodplains of the region will be subject to significant saltwater inundation (CSIRO 2001).

Within the coastal region of the tropical savnnas is also the world’s largest reef system. Rising sea level by itself may not be such a problem to the reef. However the combination of sea level rise with other threats may place much of this ecosystem at risk. These threats include increasing atmospheric carbon dioxide which leads to a decrease in coral growth, increasing sea temperatures which leads to coral bleaching, possible increased river outflow causing low salinity and high pollution and damage from tropical cyclones (ABS 2006).

Feral animals and weeds currently threaten the ecosystems of the tropical savannas region. Climate change is likely to increase the number of severe weather events the region experiences, including fire, floods and cyclones. As the vegetation becomes more stressed from these events, it is also likely to become more vulnerable to weeds and the actions of feral animal.

These severe weather events will also affect people in coastal communities in a number of ways. A study has shown that the number of tropical cyclones around Cairns in northern Queensland could increase by up to 20% by about 2050. Downpours of rain that occur after cyclones, along with the wind generated waves and storm surge will likely increase the occurrence of widespread flooding.

People’s health may be impacted by a change in climate. Parts of the tropical savannas may become more favourable for mosquitoes as temperatures rise. The warm weather will also encourage people to spend more time outdoors, and at the same time expand the mosquitoes range and extend their breeding season. Unfortunately the warmer temperatures will also reduce the incubation period for the viruses that mosquitoes carry.

Tropical savannas and climate change

• Rising sea-level, stronger tropical cyclones and increased intensity of oceanic storm surges are likely with climate change.
• In the tropical savannas the majority of people live in small coastal towns and communities. An increase in severe weather events such as cyclones, storm surges and flooding of rivers will obviously have a large impact on people living in this region.
• If sea-levels rise significantly, the vast freshwater floodplains of northern Australia will be subject to significant change due to saltwater intrusion.
• Various industries are likely to be affected. Agriculture, fisheries, forests and water resources will be sensitive to climate change.
• More extreme events like fires and floods are likely to increase the vulnerability of natural systems to invasion of exotic species.
• With climate change, parts of Australia may become more favourable for mosquitoes, thereby increasing the potential for mosquito-borne disease outbreaks (e.g. Dengue fever and Ross River virus)
• In the tropical savannas there are finely balanced relationships between the flora and fauna that make up communities. Climate change and an increase in carbon dioxide will change this balance, and is likely to change the current distribution of plants and animals.

References 

Australian Bureau of Statistics 2006. 1301.0 Year Book Australia, 2006

Living with climate change: An Overview of Potential Climate Change Impacts on Australia, Australian Greenhouse Office.

Climate Change - An Australian Guide to the Science and Potential Impacts, Australian Greenhouse Office. 

CSIRO 2001. Climate Change: Impacts for Australia.