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Climate change and our Great Barrier Reef

Climate change is considered the most significant threat to our Great Barrier Reef. Mass coral bleaching events due to rising ocean temperatures occurred in the summers of 1998, 2002 and 2006, and it is expected that coral bleaching will become an annual occurrence.

Climate change won’t just affect the coral on our Reef – some fish’s preferred temperature range lead them to seek new areas to live, thus causing chick mortality in seabirds that prey on the fish. Climate change will also affect the population and available habitat of marine mammals including the sea turtles and dugong.

Climate change is also predicted to cause the acidification of our oceans, having vast and dire consequences for all marine life, but in particular coral reefs (click here to read more about Ocean Acidification).

In fact, many parts of the Reef are already showing some effects of climate change, such as the increased frequency and severity of coral bleaching and decreased density of coral structures. Although most of the marine species are currently ok and there have been no records of extinctions, some ecologically important species, such as dugongs, marine turtles, seabirds, black teatfish and some sharks have seen significant declines in numbers.

On top of that diseases in corals and pest outbreaks of crown-of-thorns starfish and cyanobacteria seem to be happening more often and with greater impact.

What’s the impact of increased carbon dioxide in our air and oceans?

The recent Great Barrier Reef Outlook Report for 2009 (by the Australian Government) states that if we want to keep the reef alive we need to halt carbon dioxide (CO2) in the atmosphere at current levels around 400 parts per million (ppm). We are approximately adding a further 2ppm every year. So in 50 years if we keep going with business as usual we will hit 500ppm by 2050.

According to the Reef Outlook Report, “At a concentration of 500ppm, it is predicted that many components of the Great Barrier Reef ecosystem would be highly vulnerable, including seabirds, fish, marine reptiles and plankton. At about this concentration of carbon dioxide, hard corals would likely become functionally extinct and coral reefs would be eroding rapidly.“

Catchment runoff and water pollution

Pollution and declining water quality are also pretty big threats to our Great Barrier Reef. The rivers of north-eastern Australia provide significant pollution of our Reef during tropical flood events with over 90% of this pollution being sourced from farms. Farm run-off is polluted as a result of overgrazing and excessive fertiliser and pesticide use. The increase in coastal development has seen the loss of coastal wetlands that traditionally have acted as natural filters for water running off the land.

Crown of Thorns Starfish

The Crown of Thorns starfish is a coral reef predator that preys on coral polyps. Large outbreaks of these starfish can devastate reefs. They account for most damage to reefs.

Scientists have discovered that outbreaks in Crown of Thorns Starfish numbers on the Great Barrier Reef are closely related to runoff from polluted rivers. This pollution comes from chemicals used to fertilise crops that is washed into rivers after big rains. The pollution helps plankton grow in large numbers and this plankton is the perfect food for young Crown of Thorns Starfish.

There are less large fish due to overfishing. This is a minor cause for starfish outbreaks.

Coastal development

Clearing or modifying wetlands, mangroves and other coastal habitats is a significant conservation concern.

Over-fishing and by-catch

The Great Barrier Reef Outlook Report for 2009 lists a range of actions that are of significant risk to the conservation Reef ecosystems: removing top predators by fishing (e.g. sharks), catch fish of conservation concern while fishing, illegal fishing or collecting, death of discarded species during fishing or collecting, fishing in unprotected fish spawning areas, and poaching (illegal hunting) of species of conservation concern.

What can you do to help our Great Barrier Reef?

Limiting the amount of nutrient run-off is the most significant action that needs to be taken. Recent advances in agricultural practices and additional government programs has seen a reduction in sediment and nutrient inputs into some coastal river systems, but a long lag time is expected before there are positive effects on marine water quality.

OK, these all seem like pretty big challenges that are slipping from our control. Or are they? There are a whole range of things that we can all do in Queensland to help our magnificent Great Barrier Reef, including:

  • Wash your car on the lawn, not on the driveway or road, to minimise detergent runoff into drains
  • Use environmentally-friendly cleaners and fertilisers
  • Keep gutters, sinks and drains free of chemicals and rubbish as what washes down sinks and drains could end up on the Reef
  • Minimise water runoff by planting trees, garden beds and ground cover around your home
  • Use re-useable shopping bags rather than plastic bags
  • Take your rubbish home with you
  • When enjoying any coral reef – don’t touch, don’t take away souvenirs, don’t endanger the marine life
  • Advocate for the protection of our most precious natural wonderland on social networks

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