Transcript details of threats to GBR

Threats to the Great Barrier
Reef
Threats from human activity
• Shipping accidents
• Oil Spills
• Tourist visits
Natural Threats
• Coral bleaching
• Crown of Thorns Starfish
• El Nino/El Nina and Climate Change
Shipping Accidents
• The Great Barrier Reef sees a huge amount of ocean
traffic pass through its waters every day of the year for
tourism and commercial purposes (like coal
transports).
• Debris and other foreign objects from ships enter the
water and remain there for a long period of time.
• Shipwrecks (including ships running aground) can
damage the reef.
• Many 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 where it is released.
Oil Spills
• Oil drilling is banned on the reef but spills caused by passing oil
container ships have still continued to occur,
• The most recent oil spill occurred in 2010 when 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.
• Experts believe the reef may take up to 10 to 20 years to recover
from the incident.
• To date, 283 total oil spills have occurred over the waters of the
Great Barrier Reef since 1987.
Over-fishing
• The fishing industry earns over $1 billion per year to
Australia.
• Fishing on the reef occurs for commercial and
leisure/sport.
• The majority of the reef is off-limits for fishing with an
emphasis on reef sustainability.
• Trawling inevitably leads to other species getting
caught in the nets as a side effect.
• The nets themselves can also damage the ocean floor
and its inhabitants as a result of its “drag effect”.
• Fishing also adds additional pollution from the boats.
Impact of Advances in Fishing
Technology
Tourism
• Millions of tourists visit the Great Barrier Reef
every year.
• Pollution from boats, walking on the reef, runoff
from sunscreens and many other activities all
have a negative impact on the reef.
• This is also not taking into account intentionally
or neglectfully destructive practices such as
littering and various other forms of man-made
pollution.
Coral Bleaching
• Corals are given their vibrant colours as a result of the algae who
inhabit them.
• When the water temperature rises, the warmer waters kill off the
algae which then leads to the coral losing its colouration and results
in the “bleach” effect.
• 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.
• In 2002, 60% of the Great Barrier Reef experienced bleaching.
• The reef can recover from bleaching if the water temperature
returns to normal quickly.
Crown of Thorns Starfish
• The Crown of Thorns starfish feeds 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.
• If there are few predators (such as the Giant Triton)
around, the Crown of Thorns can destroy parts of the
reef.
• 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.
El Nino and Climate Change
• The El Nino effect can cause an increase in water
temperatures.
• This can cause coral bleaching.
• Climate Change is also leading to higher ocean
temperatures.
• Some scientists believe that the reef will become
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.
Now to you…
• In your opinion, what is the greatest threat to
the Great Barrier Reef?