Climate change is considered the biggest threat to our Great Barrier Reef. Mass coral bleaching events due to rising ocean temperatures occurred in the summers of 1998, 2002 and 2006. It’s 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 places to live. This can cause less food for seabird chicks that prey on the fish. Climate change will also affect the population and habitat of marine mammals, including the sea turtles and dugong.
Climate change is also predicted to cause our oceans to become more acidic, having impacts on all marine life, but in particular coral reefs.
In fact, many parts of the Reef are already showing some effects of climate change. More coral bleaching and reduced density of coral structures is happening. Although most of the marine species are currently okay and there have been no records of extinctions, some important species, such as dugongs, marine turtles, seabirds, black teatfish and some sharks have seen significant declines in numbers.
Pest outbreaks of Crown of Thorns starfish seem to be happening more often and with greater impact.
Other Challenges for our Great Barrier Reef
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. More than 90% of this pollution comes from farms. Farm water run-off is polluted because of overgrazing, 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 around to eat the Crown of Thorns starfish due to overfishing. This is a minor cause for starfish outbreaks.
Clearing or modifying wetlands, mangroves and other coastal habitats is a big 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), fishing in unprotected fish spawning areas, and poaching (illegal hunting) of species in protected areas.
What can you do to help our Great Barrier Reef?
Limiting the amount of polluted run-off is the biggest action that needs to be taken. Improvements in farming and extra government programs have reduced the polluted run-off into some coastal river systems. But a long wait 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 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
• If you see rubbish, pick it up and recycle or dispose of it thoughtfully.
• Educate your friends and colleagues
• Support local business and government initiatives to protect the reef
• 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
• Call or Email a Politician to urge them to keep climate change at the top of their list of priorities