Threats to the Great Barrier Reef

Great Barrier Reef Threats

While the Great Barrier Reef stands as a beautiful testament to the power of natural construction, in recent years there have emerged numerous threats to the existence of the reef that loom and make its future fairly uncertain. The harsh influence of man combined with various cyclical and natural factors have created cause for concern amongst both biologists and conservationist groups who do not want to see this precious natural miracle fall into decline. One of the contributing factors to the reef’s beauty which is simultaneously one of its greatest weaknesses to threats is the level of utter dependence each part of the ecosystem has on one another. That is to say, that if a single organism or species is affected or declines in number, it can have a huge ripple effect both down and up through the Great Barrier Reef’s food chain. Some of the largest factors and threats that have influenced the worrisome current conditions that the reef finds itself in include:

Human Threats

  • Great Barrier Reef Threats 1Shipping accidents: Being such a popular destination for cruises and other sightseeing vessels to pass through – as well as a tourism gateway when heading towards other island destinations such as Fiji – the Great Barrier Reef sees a huge amount of ocean traffic pass through its waters every day of the year. Whilst the number of resulting collisions and groundings has decreased substantially in recent history when compared to the past, their occurrence and the subsequent wreck they leave has an immediate and drastic effect on the surrounding ecosystem as debris and other foreign objects enter the water and remain there for a long period of time. A boat does not have to go to the extreme of becoming wrecked to have an effect on the Great Barrier Reef, however; the mere act of larger vessels passing through the oceans of the reef can release a substance known as Tributyltin (or “TBT”) which is used as to preserve the condition of ship hulls that is toxic to sea water and which can damage marine organisms that it is released on top of.
  • Oil Spills: Despite the best efforts of government agencies to keep the Great Barrier Reef in the best condition possible, there have been a huge number of oil spills over the last few decades that have directly affected the reef and its marine life. While the act of oil drilling is banned on the reef, spills caused by passing oil container ships have still continued to occur, with the most recently recorded happening in 2010 as the Chinese bulk coal carrier Shen Neng 1 – travelling 10 kilometres outside the regulation shipping lane – struck the reef, scraping along its surface for a substantial length and creating a massive grounding scar over 3 kilometres in length (the longest in recorded history). As a result, some of the damaged areas have become uninhabitable for marine life and there are estimates from experts that the reef may take up to 10 to 20 years to recover from the incident. Agencies increased the maximum allowable fine for shipping companies that damage the Great Barrier Reef in response to the incident. To date, 283 total oil spills have occurred over the waters of the Great Barrier Reef since 1987.
  • Great Barrier Reef OverfishingOver-fishing: The fishing industry is second only to tourism in terms of income generation related directly to the Great Barrier Reef, bringing in an annual profit over over $1 billion to Australia. While the Great Barrier Reef Marine Park Authority has made the majority of areas of the reef off-limits for fishing with an emphasis on reef sustainability, it is still a huge drawcard not only for commercial purposes but for leisure/sport fishing as well. While many areas, techniques and species of marine life in the reef are protected by law, trawling for various types of permitted sea life (i.e: prawns, other molluscs) inevitably leads to other species getting caught in the nets as a side effect, while the nets themselves can also damage the ocean floor and its inhabitants as a result of its “drag effect” – not to mention the additional pollution which enters the seas due to the general passage of so many fishing boats.
  • Tourist visits: The millions of visitors that the Great Barrier Reef draws every year are also an unintentional contributor to the general decline of the reef. Not only leisure vessels heading out for tours to the reef but also reef-based activities such as reef-walking, using submersibles and even the runoff from various sunscreens are all thought to be contributing negative factors that – when combined with the sheer volume of tourists who frequent the reef – are much more impactful than they may seem. This is also not taking into account intentionally or neglectfully destructive practices such as littering and various other forms of man-made pollution.

Natural Threats:

  • Coral bleaching: A phenomenon that occurs due to a reaction to increases in water temperature, coral bleaching can be a hugely destructive force on reefs in general and the Great Barrier Reef in particular. Corals are given their vibrant colours as a result of the algae who inhabit them; the warmer waters kill off the algae which then leads to the coral losing its colouration and results in the “bleach” effect from which the condition gets its name. The death of algae in turn results in the death of creatures that use them as their primary source of food, which once again has a ripple effect up the chain and renders the affected section of reef a veritable underwater ghost town. Scientists and researchers largely attribute the relatively sudden changes in water temperature to such natural phenomenon as the El Nino effect.
  • Crown of Thorns StarfishThe Crown of Thorns Starfish: Perhaps highest on the list of dangers to the Great Barrier Reef is an inhabitant of the reef itself. The Crown of Thorns starfish gains its sustenance from feasting on the polyps of coral, releasing neurotoxins to absorb the tissue of the coral and quite literally “sucking the life” out of the reef’s backbone. Once sufficient numbers of Crown of Thorns starfish are grouped together, their impact of the reef can be catastrophic – if the number of over 30 adult starfish reside in a 10 metre squared area, it can be classed as an “outbreak” which is usually a result of a lack of predators (such as the Giant Triton) of the starfish within the area. Many researchers believe that the current abundance of Crown of Thorns starfish could be a result of agricultural runoff which increases the amount of algae which serve as food for the starfish.

Cyclical Threats:

  • Water Temperature and Climate Change: The aforementioned El Nino effect is considered to be the primary culprit in the increase in water temperatures that have begun to strike the Great Barrier Reef with increasing frequency. The impact of coral bleaching is just one of the ways in which higher temperatures effect the reef; climate change in general is believed by many prominent biologists to be a massive threat to the reef’s future, predicting its gradual decline until it becomes practically extinct by the year 2030. A temperature rise of 2-3 degrees C is believed to put 97% of the reef in the danger zone of bleaching every year. The rise in levels of atmospheric greenhouse gases are believed to be another significant factor – particularly carbon dioxide, which if it rises to a level of 450ppm, will put coral and reef habitats in an extremely vulnerable position.