What are the impacts of climate change?

The effects climate change could have on oceans, vulnerable animal species, sea level and human lifestyles.

Great Barrier Reef showing coral bleaching

Erik Schlogl © Erik Schlogl

'We're in a giant car heading toward a brick wall and everyone's arguing over where they're going to sit'

David Suzuki, scientist and environmental activist

Rising temperatures - Why do a few degrees matter?

All the fuss appears to be about a tiny change in temperature. In 2020 average temperatures in Australia will be 1.5°C higher than in 1900. In 2070, if we do nothing about climate change, it will be only 3.5°C hotter on average.

However changing the averages also changes the extremes. There will be a lot more days over 35°C. This means more heat waves and fires. There will be more droughts and the droughts will be more severe. Rain is likely to be more intense when it comes, so we'll also have more floods. A small change in average temperature can make a big difference to our lives.


Changing oceans

We take the oceans for granted. They play a vital role in slowing climate change by absorbing heat and greenhouse gases. This is taking its toll and life in the oceans is feeling the impact. Sooner or later, all life on our planet will be affected.


The Great Barrier Reef

A warmer ocean bleaches more coral every year. A more acidic ocean makes coral weaker, so it can't grow properly or survive storms. Some areas are already dead and many more will follow. Animals that rely on the reef for shelter also suffer.

  • Increased greenhouse gases in the air will warm the oceans and make them more acidic.
  • Corals are animals that have tiny plants living in their bodies. These plants help feed the corals, soak up their wastes and give corals their colour.
  • High temperatures cause corals to eject the tiny plants, leaving the corals bleached white. If prolonged, the corals die.
  • Corals make calcium carbonate skeletons. These are harder to make when the ocean is more acidic, so corals will grow more slowly and have weaker skeletons.
  • By 2050, scientists predict we may lose 95 per cent of existing coral reefs as seas become too warm and acidic. Reefs will be dominated by algae.

Acid oceans - an even bigger threat than warming?

As we steadily add greenhouses gases to the air, the oceans absorb them. That sounds like good news but there are side effects. One gas, carbon dioxide, makes the ocean more acidic when it dissolves in water.This has consequences for plankton, krill, crabs, coral and all sea creatures with external shells or skeletons. It's harder to make these structures in acidic water. They can even start to dissolve when acid levels become too high.

Does it matter if shellfish are off the menu? Many of the affected creatures are vital parts of the food chain. Whole ecosystems will suffer if this chain collapses. The impact on all life, in the oceans and on land, will be profound.

What do we mean by 'acidic' seawater?

We measure acidity using a scale called pH: the lower the number, the more acidic the water. Seawater normally has a pH of about 8.2. However, this is decreasing and, if we continue emitting greenhouse gases at the current rate, is expected to reach 7.8 by 2045. This change may sound small but many sea creatures won't survive in these conditions.

Changing life on earth

All life, from the smallest bug to the largest tree, is intricately connected. However, life also depends on the climate and environment. It's a delicate balance as small changes in climate will have consequences for potentially all species, including us.


Why should we care?

The world's habitats and wildlife are important in their own right. They also help maintain the air, water and soil, vital for a healthy planet. And of course they provide us with medicines, food, natural pest controls, raw materials and pleasure. Protecting them is vital.

What are the likely impacts on ecosystems and species?

Global warming has set in motion a chain of effects in ecosystems around the world. Although we do not know exactly what the effects and future trends will be, there is a mounting body of evidence that many species have already responded to changing climatic conditions.

It is expected, and has been documented already in some cases, that

  • species with low adaptability or mobility will face extinction.
  • changes in distribution of species will occur, particularly for more mobile species such as birds and insects, and for those based around coastal areas that may be inundated. Climate change will also aid the spread of some species, native and introduced, that can tolerate the new conditions.
  • movement patterns will change as species that migrate may shorten travel distances or stop migration completely.
  • population numbers will be affected due to increased mortality rates, reduced genetic diversity and reduced reproductive success.
  • changes in phenology (timing of natural events) such as breeding times or mating seasons will occur as many of these events are linked to temperatures or rainfall levels.
  • ecosystems will change as new species of animals and plants appear or disappear.
  • behaviours and physiology of animals will change. This may include body size or metabolic rate due to the need to maintain body temperatures.
  • soil-moisture levels are expected to fall which directly affects frogs, skinks and soil invertebrates, and consequently, the birds that feed on these small animals.

The fastest mass extinction

Scientists have been warning us for decades about the impact of climate change on the world's habitats and wildlife. Profound and complex impacts on most species are now predicted and it is expected to become this century's major cause of species extinction.

An average temperature rise of 2°C may result in the estimated extinction of 20-50 per cent of the world's species by 2030. If this current trend continues, the figure could reach 50-60 per cent by 2100.

Evidence suggests that climate change will occur too quickly for species to adapt and may exacerbate existing threats, such as land clearance, farming and pollution. Those species with biological traits that make them susceptible to change, or with restricted habitats, are particularly vulnerable to extinction.

Quotes:

'Conservationists are entering a new area of conservation, one in which last-ditch stands to save species where they currently exist may not be enough.' Hannah et al, 2005

'Climate change affects ecosystems, habitats and species with increasing velocity and continuity.' Bailein & Huppon, 2004

'Rapid movement of climatic zones is going to be another stress on wildlife...in effect we are pushing them off the planet'. James Hansen, NASA Goddard Inst for Space Studies, 2006

Some Australian species vulnerable to climate change

Changing lifestyles

Climate change at a basic level will affect our food, health and leisure. Many people could also face war, starvation or losing their homes.


Changing sea levels

Slow, but essentially unstoppable, sea level rise is a global threat. Higher temperatures may melt ice and cause oceans to expand. The effects may be irreversible for a thousand years after greenhouse gas levels have stabilised. It would be an unwelcome inheritance for many generations to come.


Do I need to worry about sea level rise?

Hundreds of millions of people around the world live near the coast. This coastal society has developed because sea levels have been very stable for the past few thousand years. Sea level is rising and could rise nearly a metre by 2100.

The impacts of this small rise are huge. Once-in-a-hundred year floods could occur every year. Sandy coastlines could move a hundred metres inland through erosion. Millions of people and a trillion dollars of buildings and roads could be affected.

However, this may not be our biggest problem. If we continue on our current path, by 2100 we could reach the temperature needed to start melting vast ice sheets like Greenland. People today will not see the impact of this, as the melting happens very slowly but we would have caused sea levels to rise dramatically for hundreds of years to come.

See what rising sea levels could do to Australia and the world at Flood Maps.


Catherine Cooper and Fran Dorey
Last Updated: