Emerging threats to Great Barrier Reef posed by pesticides

The world has seen a great deal of natural resources or rather natural
wonders. Of course, these Natural Wonders of the World are scattered in
different parts of the world and come in different sizes and shapes.
Unfortunately, a large number of these natural wonders of the world have
been threatened by global warming or rather the climatic changes that
have been witness in the recent times. Of particular note is the fact
that a large proportion of global warming has been primarily caused by
human activities. While there exists about 8 natural wonders of the
world, none comes with such natural breathtaking beauty than the Great
Barrier Reef in Australia.
Stretching about 2300 kilometers along the Queensland coast, the Great
Barrier Reef is made up of more than 2900 reefs and incorporates
approximately 940 cays and islands. Underlining its importance is the
fact the immense diversity that it represents, as it comes with around
411 types of hard coral, more than 1500 fish species, over 30 species of
marine mammals such as the vulnerable dugong, six of the seven species
of marine turtles that are about to be extinct in the globe, 134 species
of rays and sharks, as well as a third of the total soft corals in the
entire world (Haynes, 2001, pp. 19). Also incorporated in the stunning
marine suite includes thousands of varied sponges, as many as 3000
molluscs, 630 species of echinoderms (that is sea urchins and starfish),
thousands of crustaceans and worms, as well as 215 bird species out of
which 22 come as sea birds (Larcombe & Woolfe, 1995, pp. 17). It is, in
essence, not surprising that the Great Barrier Reef has been listed
under the four criteria of World Heritage thanks to its outstanding or
exemplary universal value (Larcombe & Woolfe, 1995, 17).
The benefits pertaining to the protection of the reef go beyond
conservation as the reef also doubles up as an investment to the
continued security of the coastal communities while offering
considerable benefits to the economy of the country. Indeed, the reef
industries including fishing and tourism, which rake in about $5.4
billion per year to the Australian economy while providing employment
opportunities to approximately 63,000 people are almost entirely
dependent on a healthy environment (Haynes, 2001, pp. 32).
In the past, the Great Barrier Reef was seen as a pristine and well
protected wonderland that provided a safe haven for abundant fish and
delicate corals. Unfortunately, all this has changed with scientists
acknowledging that a completely different picture emerges pertaining to
the reef’s complexities. Varied issues have been identified as posing
serious threats to the reef’s future including pollution, poor
fishing, as well as coral bleaching which has been exacerbated by the
heightened sea temperatures emanating from global warming (McCook et al,
2007, pp. 75). However, immense attention and focus has been placed on
the emerging threats that pollution, especially emanating from increased
use of pesticides, poses to the Great Barrier Reef. Indeed, a report by
the Federal Government has underlined the immense magnitude of damage
that the use of agricultural pesticides has caused to the Great Barrier
Scholars have noted that the Great Barrier Reef receives approximately
28,000 kilograms of pesticides every year through run-off from the 38
key catchments that drain the 424,000km2 of the coastal Queensland.
Indeed, river discharges form the single largest source of nutrients to
the Great Barrier Reef World Heritage Area’s inshore areas (Marshall,
& Schuttenberg, 2006, pp. 37). The data on the amount of pesticides
finding their way into the Great Barrier Reef is based on studies
conducted in 2008 and 2009. This report indicated that about 14 million
tons of sediments emanating from human activities find their way to the
World Heritage natural wonder on annual basis (Turner, 2012 pp. 34). A
large percentage or proportion of runoff emanates from the Whitsunday
and MacKay sugarcane farming region located in North Queensland. In
addition, it was revealed that about 25% of the horticulture producers,
as well as 12% of the pastoral farmers did not observe the industry
standards pertaining to the disposal of pesticides (Turner, 2012 pp.
In December 2011, the Australian government had banned the use of a
pesticide called diuron on tropical crops such as pawpaw, pineapples,
bananas and sugarcane due to the devastating effects that it has on the
coral reefs. The ban was aimed at covering the wet season as this is the
time when the county experiences the largest amount of run-off. However,
this ban was lifted in March 2012 a decision that saw widespread
protests from environmentalists (Turner, 2012 pp. 34). Of course, this
should not have been surprising as diuron is responsible for about 80
percent of the pesticide load that finds its way in the reef, not to
mention the fact that it is toxic and persistent. However, questions
have emerged as to the threats that the use of pesticides poses to the
Great Barrier Reef.
One of the key effects of the is the destruction of the biodiversity in
the Great Barrier Reef especially considering the immense increase in
the population of Crown of Thorns starfish. Scholars have noted that the
introduction of certain pesticides introduces a certain type of
nutrients that are known to be a key trigger of the proliferation of
Crown of Thorn fish that eat corals throughout the Great Barrier Reef.
Indeed, there exists voluminous evident showing that the increase in
this species of fish is primarily caused by water pollution rather than
natural causes or overfishing. Of particular note is that the immense
increase in the population of the starfish dates back to the early
1960s, with every 15 years marking a tremendous increase in this
starfish’s population (Haynes, 2001, pp. 56). Researchers examined the
influence that the levels of chlorophyll from pesticides in reef waters
have on the populations of this starfish and noted that doubling the
level of chlorophyll in water results in a tenfold increase in the
survival rate and populations of the Crown of Thorns starfish larvae
(McCook et al, 2007, pp. 84). On the same note, this research also
showed that the run-off nutrients including phosphorous have been on the
rise in the last five decades, which may have resulted in an increase in
the levels of phytoplankton. They noted that a downward change in the
levels of nutrients found in the water would result in a significant
decrease in the numbers of Crown of Thorns starfish that have caused
immense damage to the Great Barrier Reef.
In addition, pesticides have been identified as decreasing the quality
of water in the Great Barrier Reef. The first identification of the
water quality as a threat to the existence of the Great Barrier Reef was
done in 1989. As noted earlier, the Great Barrier Reef receives its
waters from about 38 key rivers, as well as the hundreds of smaller
streams. With its expansive scale of 423,000 square kilometers of land,
the Great Barrier Reef primarily serves Queensland, which has number of
urban centers such as Rockhampton, Townsville, Cairns and MacKay, as
well as the industrial city named Gladstone. The marine species found in
the Great Barrier Reef area have become adapted to the tolerable
variations pertaining to the quality of water (Marshall, & Schuttenberg,
2006, pp.45). However, in instances where the critical thresholds
pertaining to water quality are surpassed, the marine species are
adversely affected. It is worth noting that river discharges form the
biggest source of nutrients coming with a considerable pollution of the
Reef in the course of tropical flood events. Research shows that more
than 90% of this pollution emanate from the farms (Marshall, &
Schuttenberg, 2006 pp. 46). Scholars have underlined the fact that about
700 out of the 3000 coral reefs are at risk as they stand in the zone
where the quality of water has declined thanks to chemical runoff and
naturally acidic sediment emanating from the farms, as well as the
coastal development coupled with the loss of coastal wetlands that have
been a natural filter. The industries found within the water catchment
area include cotton growing, which comprises of about 262 square
kilometers, horticultural farming including sugarcane and banana
growing, which collectively take up 288 square kilometers, as well as
the growing of maize, sorghum, barley and wheat, which takes up 7000
km², 6000 km², 1200 km² and 8000 km² respectively (McCook et al,
2007, pp. 84). A large number of industrial pesticides used in these
places have been found to contain copper, which is known to interfere
with the development of corral polyps. Phosphorus and nitrogen found in
the pesticides have also been associated with flood plumes, whose runoff
has been found to have reached the outmost regions in the reef.
In addition, the increased use of pesticides in the region has been
associated with the increased global warming. Global warming has been
one of the major concerns in the 20th and 21st century, thanks to the
devastating effects that it has. Indeed, it has been credited with
increased cases of desertification, floods, natural calamities,
increased sea level, melting ice and glaciers among others. Global
warming may be both a cause of and a result of the increased use of
pesticides. Scholars have noted that global warming may have caused
decreased yields in varied parts of the globe, in which case farmers
have increased the use of pesticides in an effort to boost their produce
through the elimination of the pests that damage their crops or animals
(Berkelmans, 2002, pp. 76). However, the prevalence of use of pesticides
may also result in climate change and global warming. Pesticides are
known to attach themselves to dust particles thereby travelling to
far-flung areas away from the destinations where they were intended to
be used. This heightens the likelihood that the chemicals would combine
with other chemicals. In most cases, pesticides generate volatile
organic compounds that are known to pollute the atmosphere upon reacting
with other chemicals or compounds that are in the atmosphere. Scholars
have noted that the reaction generates tropospheric ozone, a type of
ozone that lays closer to the surface of the earth than the natural
ozone (Berkelmans, 2002 pp. 73). This ozone may block ultraviolet light
from the sun, but it traps heat and prevents it from escaping from the
surface of the earth thereby increasing the temperature at the earth’s
surface. On the same note, a large number of base chemicals used in the
creation of a large number of pesticides may be destructive to the
environment even prior to their combination with other chemicals. For
instance, nitrogen-based fertilizes are known to generate unnatural
nitrogen oxide amounts into the atmosphere, thereby resulting in
greenhouse effects that exacerbates global warming. Sulfur dioxide, on
the other hand, blocks out the sun upon accumulation in the atmosphere
thereby contributing to global warming through trapping heat. Global
warming has been credited with the mass coral bleaching, which is a
stress response where the coral animal discards a large part or all of
the endosymbiotic zooxanthellae. Coral bleaching results may, in extreme
cases, result in fatalities of the coral host and even devastate whole
reef-scapes in vast ocean areas (Woolridge, 2009 pp. 745). Warmer
temperatures emanating from climate changes stress the corals, which are
extremely sensitive to modifications in temperature. Indeed, scholars
have underlined the fact that changes of in temperature by as little as
1-2 degrees centigrade would be likely to cause the death of corals
especially when they persist for a number of weeks. Such changes would
cause the departure of zooxanthellae, on which corals depend for their
food, from the corals’ tissue (Woolridge, 2009 pp. 745). This causes
the bleaching of the corals, where they turn white and become
considerably weaker and less capable of combating ailments. This would,
undoubtedly result in the elimination of the coral reefs if something is
not done to limit the use of pesticides in areas close to Queensland. Of
particular note is the fact that the coral reefs are not only affected
by the increased temperatures but also the changing salinity and
concentrations of the sea water (Woolridge, 2009 pp. 746). Indeed,
research has show that the bleaching response in coral reefs may be
initiated by a wide range of stress factors including low temperature,
low salinity, cyanide exposure and high sedimentation, all of which may
occur in cases of increased usage of pesticides in farming. This
underlines the importance of all conservation efforts being channeled
towards controlling the use of pesticides in farming.
Woolridge SA. (2009). Water quality and coral bleaching thresholds:
Formalising the linkage for the inshore reefs of the Great Barrier Reef,
Australia. Marine Pollution Bulletin. 2009, 58, 745-751
BERKELMANS, R., (2002). Time-integrated thermal bleaching thresholds of
reefs and their variation on the Great Barrier Reef. Marine Ecology
Progress Series 229, 73–82.
MARSHALL, P.A.,& SCHUTTENBERG, H.Z., (2006). A reef manager’s guide to
coral bleaching. Great Barrier Reef Marine Park Authority, Townsville,
R., (2007). Ecological resilience, climate change and the Great Barrier
Reef. In: Johnson, J.E., Marshall, P.A. (Eds.), Climate Change and the
Great Barrier Reef: A Vulnerability Assessment. Great Barrier Reef
Marine Park Authority, Townsville, Australia, pp. 75–96.
TURNER, R. (2012). Sediment, nutrient and pesticide loads: Great Barrier
Reef catchment loads monitoring 2009-2010. Brisbane, Qld, Department of
Science, Information Technology, Innovation and the Arts.
HAYNES, D. (2001). Pesticide and heavy metal concentrations in Great
Barrier Reef sediment, seagrass and dugongs (Dugong dugon).
LARCOMBE, P., & WOOLFE, K. (1995). Great Barrier Reef: terrigenous
sediment flux and human impacts. Townsville, Qld, CRC Reef Research

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