Threats to Coral Reefs
Handley et al (2007) Geography Focus Stage Four Pearson: Sydney. p92-3 and p98-9
Human impact on coral reefs, whether deliberate or through accident,
neglect or ignorance, needs to be identified before we can manage or
minimize its effects.
Most threats to Coral Reefs are a direct result of human activities.
Trade in Coral Reef Animals
The collection of both coral and reef fish for sale to aquarium enthusiasts is a serious threat to coral
reefs. The global value of this industry is estimated at $500 million and consists of over 1000 reef
species. Cyanide is used to stun the reef fish in the wild for their capture. The cyanide kills the coral
polyps.
Fishing
Overfishing removes fish stocks and does not leave a large enough population of fish to restock the
area, thus altering the ecosystem. Blasting for fish with dynamite allows for mass collection quickly,
however it significantly effects the coral reef.
Tourism
Tourism is the world’s fastest growing industry. The creation of each resort
affects the reefs by discharging the resort’s waste into the water. The
increased number of visitors to the coral reef environments destroys the coral
through careless tour operators in boats and other activities such as walking on
the reef.
Coastal Development
It is estimated that ½ billion people live within 100kms of a coral reef. The growth of large cities
along the coast places pressure on reefs as pollution from the urban areas enters the water and people
exploit the resources of the reef.
Farming
Farming, logging and land clearing all lead to soil erosion. As it is washed into rivers, soil eventually
ends up in the ocean. When rivers flow across farmland and empty into the sea near coral reefs the
sediment and nutrients encourage algae and limit the sunlight necessary for coral polyps to grow,
killing the reef.
Risk of Destruction
The risks to reefs can be broken down by their causes:36% due to over-exploitation; activities such as fishing and taking coral
30% due to coastal development; building near reefs
22% due to inland pollution; runoff from agriculture and towns
12% due to marine pollution; shipping debris and oil leaks
Your Turn  Convert the above data into a pie graph.
Pest Infestations
Changes in the balance of the reef ecosystem occur when nutrients from urban areas, septic tanks and
agricultural activities enter the water. These nutrients encourage the growth of algae, which is the
favoured diet of the crown of thorns starfish. This increased food supply causes starfish numbers to
increase. When this happens it does not take too long before parts of the reef are destroyed due to the
starfish’s preferred diet of coral polyps.
Tropical Cyclones
Cyclones form over the warm oceans. They are intense tropical storms that create large
waves and big tides that are sometimes large enough to wash completely over coral
cays.
Your Turn  Use the Internet to locate a photograph of a crown-of-thorns starfish.
Study reveals cyclone damage to coral reefs 100 kilometres
from eye of cyclone
When Tropical Cyclone Ingrid crossed the far
northern Great Barrier Reef it left a trail of
destruction to 260 coral reefs across a path
over 200 kilometres wide. Researchers from
the Australian Institute of Marine Science
(AIMS), such as Dr Katharina Fabricius, were
keen to find out about the level of damage.
“We investigated the impact of seven types of
cyclone damage to the reef; coral breakage,
movement of massive corals, stripping of soft
corals, coral sand movement, scarring of coral
by debris, algal blooms, and removal of plants
from the reef.
“These surveys examine how wave damage to
coral communities differs between sheltered
and exposed sites. The corals on outer reefs
appear to be more resistant to breakage
compared with the more fragile inshore reefs.
“The reef provided its own protection from wave
damage, leaving many corals in the protected
areas intact. These surviving corals will help
restore the worse affected areas” Dr Fabricius.
Corals at the outer edge will probably take 2 – 3
years to recover, those at ground zero were
stripped bare and could take up to two decades to
bounce back.
Estimates from the Australian Bureau of
Meteorology suggest that wind speeds reached at
least 250 kilometres per hour and wave heights
as high as 10 metres occurred within the Great
Barrier Reef area.
17 August 2005
Comprehension
Read the above newspaper article and respond to the following question.
a. How many coral reefs were damaged by the cyclone?
b. Name the seven types of cyclone damage to reefs the researchers investigated.
c. What role will the surviving corals play in repairing the damage to the reef caused by the
tropical cyclone?
d. What was the wind speed and wave height caused by the cyclone?
e. Why would these wind speeds and wave heights caused damage to the coral reef?
Research
1. Which is the most likely factors that cause 80% of the coral reefs of South-East Asia to be at
high risk? Provide specific examples for your conclusions.
2. In April 2010 an oil tanker, The Shen Neng 1, crashed on the Great Barrier Reef off Great
Keppel Island off the coast of Queensland.
a) Describe the incident and the threat to the Coral Reef environment.
b) Outline the management strategy of ‘green zones’ in minimizing the threat to the Coral Reef
Environment.
c) Recommend strategies to the Queensland Government to protect the reef against future
accidents.
Begin your research at the website –
http://www.smh.com.au/environment/shipping-crackdown-urged-to-protect-reef-from-disaster20100404-rlry.html