Threats

Around the world, reefs are under pressure from factors such as pollution, development, climate change and heavy human use of ocean environments. Climate change has been identified as the greatest threat to the future of coral reefs around the world. And Australian reefs are no exception.

The challenge for reefs comes from both the increased pressure and the effects of multiple stressors. Reefs are naturally dynamic systems, but they need time in between disturbance events like cyclones or floods in order to recover. With events happening more regularly and sometime multiple pressures acting at once, then the resilience of the reef is reduced and it can no longer 'bounce back' to its earlier state. This means that reefs run the risk of shifting from complex and incredibly diverse coral habitats, to degraded algae-dominated reefs that cannot support as much life.

But stop and think. As an example, the Great Barrier Reef covers an area the size of Italy. Its composed of complex and diverse habitats, so  pressures and impacts do not affect the reef equally. That is one of the reasons why you might read about divergent commentary on Reef health issues in the media. Some areas are healthy and beautiful, some are showing clear signs of stress with symptoms like coral bleaching and disease; and some areas have been heavily impacted by back to back mass coral bleaching in 2016 and 2017, cyclones or chronic water quality issues. As a system, reefs urgently need our help. We have a window of opportunity to take action together. 

The call to action to look after reefs & oceans is loud and clear. 

Citizen science, community engagement and locally based actions to support reef resilience are all identified as important strategies for managing the Great Barrier Reef and reefs more broadly. We agree! Importantly, these actions close to home must be coupled with quick and notable action on climate change to protect our global icon. We all can, and must, help.

 

 

Climate Change

Climate change is the greatest threat to coral reefs.  Climate change impacts coral reefs through:

  • Increasing coral bleaching episodes and growth of fleshy algae from warmer water temperatures
  • Increasing damage to the reef from more frequent and intense weather events such as cyclones and flooding
  • Reducing the rate of coral skeleton growth and weakening of the limestone reef structures due to ocean acidification

We must rapidly reduce greenhouse gas emissions by reducing fossil fuel use and making the switch to alternative energy sources now to protect our reefs. While we make these transitions, its also important to boost reef resilience by reducing pressures from more local and regional causes (such as poor water quality or overfishing).

Poor Water Quality

Water Quality credit Rory Mulloy

 

Poor water quality is seen as one of most serious threats to reef health. As well as increasing turbidity and restricting access to light, this can make corals more susceptible to bleaching and disease. Water quality is affected by a variety of factors:

  • Land-based industrial processes and dredging which can increase heavy metal, pollutant and sediment levels in the water.
  • Agricultural processes and the use of fertilisers which can increase nutrient levels in the water, especially after a big rain.
  • Removal of coastal habitats and vegetation which can act as a natural filter system for the waterways.
  • Pollution and waste from urban areas.

Understanding how our decisions and actions on land impact the health of reef habitats is crucial to reducing our impact on marine environments, and to good management and conservation of coral reefs. 

 

Coastal Development

Development along Australia's coastline is on the rise. The cumulative impact of these ports is a cause for concern.  Some of the impacts from coastal development (which can include ports, urban areas, mining, agriculture) can include:

  • Reduction in extent and health of coastal and marine habitats
  • Water pollution from sediment, heavy metals, and nutrients from dredging and dredge material 
  • Changes to coastal processes and hydrology
  • Injury or mortality to marine wildlife from shipping/boat traffic
  • Damage to the reef from vessel groundings

Marine Debris

From the smallest bits of plastic, to enormous fishing nets, "the stuff" from our daily lives makes its way to the ocean every day. Over 6 million tonnes of rubbish is dumped into the world's oceans each year. Discarded debris in the ocean is responsible for the death of over a million animals each year, and is found in even the most remote ocean places.

  • Debris harms marine wildlife through entanglement and ingestion
  • Studies indicate that corals exposed to plastic are 20 times more likely to develop coral disease
  • Once underwater, plastic debris can remain there for generations, causing ongoing problems

Everyday we can each choose to limit our use of single use plastic to reduce our impact. 

Unsustainable Fishing

Ocean systems require a delicate balance to maintain the ecosystem. Our activities can shift this balance by taking out more fish than the ocean can sustain (overfishing), or damaging the reef environment (destructive fishing).

Although Australian's waters are managed to maintain healthy fish populations, Unsustainable fishing can impact coral reefs by: 

  • Reducing fish and shellfish populations
  • Disruptions to the reef's ecological balance and food webs
  • Impacts to fish size, abundance, and species composition

Destructive fishing can have a direct physical impact on the reef environment.  Trawling, bycatch, and explosive fishing are some destructive fishing practices that harm marine species and their habitat. 

We can help take action on this by selecting responsible seafood choices.

Poor Recreation Practices

Its so important to visit, enjoy and appreciate reefs, but also to ensure we leave them in the same way we found them (or better!) Boating, swimming, snorkelling, and diving can cause unintended localised impacts if not done carefully. Possible localised impacts to the reef include: 

  • Anchor damage to corals 
  • Littering of rubbish can be consumed and damage marine life
  • Boat strikes on marine mammals and turtles
  • Fin damage to corals when snorkelling and diving

We can each be mindful when choose how to enjoy the reef responsibly by heeding zoning plans, choosing a responsible tourism operator, and off-setting travel (especially flights!)