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Griffith University
Environmental Pollution 7421ENV
Semester 2 2011 Online
Primary Convenor: Dr Andrew Chan
Essay Assignment
Due date: 14 Oct 2011
Length: 3000 words
Lee Fisher Student No. s2168732 Environmental Pollution Sem 2, 2011
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(W2) Critically evaluate key potential stressors associated with coastal
agriculture and review scientific evidence that evaluate impact of pollutants on
the Great Barrier Reef Marine Park.
The Great Barrier Reef Marine Park (GBRMP) stretches from Bundaberg to Cape
York Peninsula covering 2300 kilometres and an area of 344,400 square kilometers. It
is the worlds largest reef system; one of its great natural wonders and represents 17%
of the worlds coral communities (Department of Employment, Economic
Development and Innovation, 2010, p. 5). Along the Queensland coast there are 38
major catchments that impact the waters of the GBRMP. A critical review of the
current scientific literature will explore the impacts of pollutants from coastal
agriculture on the GBRMP. Whilst an overview of the entire GBRMP is necessary for
an understanding of the impacts of these pollutants, specific examples will be drawn
from the southern section of the marine park, including the Fitzroy River and Keppel
Bay. The future health and survival of the Great Barrier Reef (GBR) ecosystem is
linked to environmental sound management decisions by relevant stakeholders that
consider and mitigate their impacts to ecological appropriate levels.
To achieve this, a holistic approach to understanding the GBR ecosystem is crucial.
Land use and varying climatic zones in the GBR catchments are intrinsically linked to
the marine environment, and catchments are one of the main mechanisms through
which pollutants move into the GBRMP. The catchments that drain into the GBR
cover 424,000 square km (Land Use and the Great Barrier Reef, 2003, p .2).
Figure 1: The diagram below outlines the coastal catchments along the Queensland
coast.
(The Outlook Report, 2009)
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These catchments include a variety of agricultural areas that range over regions
described as dry and wet depending upon the seasonal rainfall. This large bioregion
and the differing climates results in a variety of agricultural based activities and
impacts on the reef due to differing farming practices and land use.
Figure 2: The major agricultural based activities of the GBR catchment.
(The Outlook Report, 2009)
In the southern section of the reef the weather may be considered dry tropics while
further north (above Townsville) it is considered wet tropics with a greater rainfall;
this results in different dynamics to catchment systems and corresponding impacts /
stressors.
The Great Barrier Reef Marine Park Authority (GBRMPA) undertakes an assessment
of the reef every five years. The last assessment in 2009 provides an overview of the
reef’s health and identifies areas of concern. The report holds a high degree of
credibility due to the number of scientists involved in its development, peer review
and input from reference groups. The report identifies climate change, declining water
quality from catchment run off, loss of coastal habitats from coastal development and
remaining impacts from fishing and illegal fishing as priority issues affecting the
resilience of the reef. The report further highlights inshore reefs as declining due to
water quality and climate change (Australian Government, 2009, p. 6). Both of these
impacts are associated with agriculture and its practices / management.
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To evaluate the key potential stressors associated with coastal agriculture the
following framework / overview will be used:
1. Reduced water quality.
Increased sedimentation leading to turbidity (water quality) – major cause is a
change in land practices.
2. Agricultural based fertilizers.
Increased nutrients – nitrogen and potassium associated with fertilizers and
sediments (Australian Government, 2009, p. 62)
3. Pollutants from pesticides and herbicides.
This leads to mangrove dieback and increasing algae on coral reefs (Australian
Government, 2009, p. 7)
4. Increase in greenhouse gases related to agricultural based activities.
Coastal agricultural activities contribute to increased greenhouse gases although at
a minor global level. The changes in land use / land clearing (release of carbon
dioxide), methane from livestock, and use of fossil fuels contributes to increased
stresses related to coral bleaching and ocean acidification due to higher than
historically average temperatures.
Research suggests that agricultural impacts are greater than urban-based impacts
(although there is a growing population within the GBR catchment and these
pressures are likely to increase (Land Use and the Great Barrier Reef, 2003, p. 2).
Therefore, informed decision making, support and appropriate management based
upon scientific understanding / best practice will support the future of the Great
Barrier Reef. The Queensland Governments Reef Water Quality Protection Plan
released in 2009 provides specific goals and targets to non-point of source pollution
(Department of the Premier and Cabinet, 2009). This plan had extensive research and
input from a variety of government and non-government sources and has clear goals
and water quality targets. It provides a plan with specific goals and targets to improve
the GBR water quality in the future.
1. STRESSOR – REDUCED WATER QUALITY FROM SEDIMENTS
Changing land practices related to agriculture in the GBRMP catchments has resulted
in increased sedimentation in the GBR waters. On average, 70 billion cubic metres of
water leaves catchments and enters the reef system. Most of this runoff is during the
summer wet season. The two general climatic zones, “the wet and the dry” function
very differently. In the wet region there are numerous floods each year whereas in the
dry river systems floods occur on average once per decade (Land Use and the Great
Barrier Reef, 2003, p .2). Thus the climate and the resulting agriculture lead to
different impacts. The Great Barrier Reef Outlook Reports states that over the past
150 years sediment inflow on the GBR has increase four to five times and five to ten
for some catchments (Australian Government - Information sheet Outlook Reports,
2009).
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Sediments have increase due to land clearing, approximately half of the GBR
catchments are cleared and most of the clearing is within the Fitzroy and Burdekin
catchments. Droughts and the resulting loss of grass cover and clearing of vegetation
increase erosion. Furthermore, the riparian vegetation acts as a natural filter. Some of
this vegetation has been lost. This is a key issue within these catchment and various
organisations such as the Fitzroy Basin Association and Landcare are working with
landholders to educate and support reforestation of key land areas. The two large dry
river systems, the Fitzroy and the Burdekin account for 64% of the catchment area of
the GBR (Land Use and the Great Barrier Reef, 2003, p. 2). The major land use is
open range cattle grazing on native and cleared pasture (refer to Figure 2). This
represents 75% of the land use of the GBR catchment area. Sugarcane represents
approximately 1% of the GBR catchment, however it is a major source of pollution. It
is interesting to note that CRC research (Land Use and the Great Barrier Reef, 2003)
estimates that 95% of the sediment entering the reef is derived from 13% of the
Burdiken catchment. These identified “hotspots” mean that targeting mitigation work
can occur with environmental benefits being achieved in an effective way.
In terms of freshwater impacts from river systems the general plumes of water moves
north and stays along the coast. Thus the greatest impact from the GBR catchment is
inshore reefs within about 20 kilometers of the coast (Land Use and the Great Barrier
Reef, 2003, p. 4) With the GBR lagoon most of the sediment is deposited close to the
river mouths and carried north and deposited in large bays such as Bowling Green
Bay. The impact of sediments on the GBR includes increased water turbidity,
reducing light for photosynthecitic organisms, covering corals and algae and can
make surfaces less suitable for juvenile organisms to settle. Thus the stress to the
ecology of the reef is widespread and not isolated. Further impacts include fine
sediments that can smother coral and cause them to use additional energy to remove
the sediment. In addition it has been shown that sediments can cause changes to coral
population structure, colony size, growth, recruitment, reproduction and survival
(Water Quality Guidelines for the Great Barrier Reef Marine Park, Revised Edition,
2010, p. 27). This is further demonstrated by Schaffelke, Waterhouse and Christie
(2002) with their review on water quality issues influencing the habitat quality of
dugong protection areas. Their review identifies high risk dugong protection areas and
explores potential impacts of degraded water quality on an endangered marine
mammal.
A recent case study is the Fitzroy River Flood in 2011. Significant time and resources
were contributed to gain a greater understanding of how floods impact the health of
catchments and ecosystems. Proceeding the last major flood in 1991 there was
significant coral mortality in Keppel Bay. The floods events in the dry tropics are
decadal events and during the 2011 flood it was estimated that between 23 November
2010 and 1 February, 2011 the total suspended solids that passed the end of catchment
monitoring system was 6302000 tonnes. This drains into Keppel Bay. This will have a
significant impact upon Keppel Bay and various coral reefs have suffered high
mortality rate to surface corals as a result of this flood event (A focus on the Fitzroy
in Flood, 2011).
An example of positive action is the Department of Environment and Resource
Management and its report on Establishing Environmental Values, Water Quality
Guidelines and Water Quality Objectives for Fitzroy Basin Water (2010). This
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document has extensive consultation to identify high value areas, provide clear
guidelines for water quality objectives. Through the Fitzroy Basin Association it has
an action to reduce sediment (and related nutrients) from agricultural activities by
750,000 tonnes per annum within 10 years and to increase ground cover (Department
of Resource Management, 2010). These appear to be significant actions and worthy
goals that will support the GBRMP.
In order to combat increased sedimentation and declining water quality the Reef
Water Quality Protection Plan has two water quality targets that support improved
water quality relating to sediments. This includes, by 2013, there will be a minimum
of 50% late dry season groundcover on dry tropical grazing land and by 2020, there
will be a minimum 20 % reduction in sediment load at the end of catchments. In
addition the plan has 4 specific targets related to land management. (Reef Water
Quality Protection Plan, 2009). This plan and associated targets and actions represent
a positive step, however it is the accumulative impacts that will continue to impact
upon the reef and addressing water quality is a key action of the GBRMPA and State
and National Government documentation. Addressing water quality is aimed at
supporting the reefs reliance when faced with multiple pressure such as urban
development, climate change and industry stressors.
Given to scale, magnitude and complexity of the issue this plan appears vital and
realistic, however it will need every effort to ensure targets are met as many in the
agricultural industries may see these additional measures as a time and financial cost,
thus education and the cost / benefits to the agricultural industry need to be evident.
2. STESSOR - AGRICULTURAL BASED NUTRIENTS
Historically, nutrients within the GBR have been low. This was due to high vegetation
coverage on the land and vegetation acting as a natural filter using many of the
nutrients in the catchment systems. The increase in sediments entering the GBR is
linked with increased nutrients, namely phosphorous and nitrogen entering river
systems and eventually the GBR. Again the different climatic regions have differing
characteristics. Dry topic river systems are generally more turbid (3000mg per litre)
and much of the nitrogen and phosphorus are carried attached to fine sediment.
Whereas the wet tropic river systems tend to carry less suspended sediment at levels
around 500 mg per litre and thus carry less nutrients. It has been estimated that 40%
of nitrogen and 80% of phosphorus are carried with fine sediments thus the issue of
sediments and nutrients entering the GBR is interrelated (Land Use and the Great
Barrier Reef, 2003, p. 3).
Brodies et al. (2003) estimates that there has been an increase of 4.3 times the natural
export for nitrogen and an increase of 6.1 times for phosphorus. His research aims to
identify sources of pollution and aims to establish effective targeting of management
action to achieve results. Based upon the research there are recommendations of
targeted management actions.
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The increased nutrients provide opportunities for some organisms such as
phytoplankton to bloom. A common measure is chlorophyll a. A link between crown
of thorn starfish outbreaks and extreme rainfall and thus nutrients has also been
suggested. This provides an example of an imbalanced system creating opportunities
for some species (Water Quality Guidelines for the Great Barrier Reef Marine Park,
Revised Ed. 2010). This theory is supported by the work of Brodie et al. (2004) who
examines if increased nutrient inputs are responsible for crown of thorns starfish
(COTS) outbreaks. His research found that larval development, growth and survival
of COTS increase almost 10 fold with doubled concentrations of large phyto-plankton
which are now doubled that of previous times.
In order to understand if management actions are having an impact, monitoring and
collecting data is crucial. However, monitoring the GBR is a challenging task due to it
size and remote locations. Modern technology is providing an excellent opportunity to
establish detailed information and to observe tends to water quality. The Reef Rescue
Monitoring Program: using remote sensing for GBR wide water quality Final Report
2009 / 10 provides a valuable insight into the power of satellite technology to provide
detail information on a broad scale. This report monitors concentrations of
chlorophyll a, total suspended solids, water clarity, and dissolved organic matter. The
report also makes a comparison to the water quality guidelines and any exceedance of
these. There are many benefits to satellite monitoring including whole of marine
system monitoring, cost effectiveness and the ability to monitor individual events to
gain a deeper understanding into the GBR ecology. Whilst this technology is
improving it will aid mangers in monitoring and decision making to support the health
of the reef (Vittorio et al, 2010). This monitoring differs from traditional monitoring
and will support evaluating impacts on the GBR.
In additional to monitoring the GBRMPA has established Water Quality Guidelines
for the Great Barrier Reef Marine Park (revised edition 2010). This provides guidance
for sediment, nutrients and pesticides that aim to support protection and maintenance
of ecosystems. At times these guidelines are exceeded.
3. POLLUTANTS FROM LAND BASED PESTICIDEDS AND HERBICIDES
Pesticide use has increased in areas under crop cultivation within the GBR catchment
and there are now seven main herbicides used. These include diuron, atrazine,
ametryn, simazine, hexazinone, 2,4-D and tebuthiuron with the first three being most
likely to reach marine environments (Water Quality Guidelines for the Great Barrier
Reef Marine Park, Revised Edition, 2010, p. 29). The concentrations found in a body
of water are impacted by numerous factors such as proximity to system, intensity and
methods of application, breakdown rates, temperature, and history of flushing events.
These factors add complexity to there use.
Species within the GBRMP that are sensitive to herbicides include corals, sea grass,
mangroves and algae. Due to significant areas of the GBR catchment being utilized
for agricultural purposes the stressor from pesticides and herbicides are increasing
with increase land being used for agricultural purposes and increase use of
agricultural based chemicals.
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An extensive monitoring program is conducted by the National Research Centre for
Environmental Toxicology and in 2010 a report was release outlining 5 years of
monitoring for pesticides and herbicides in the GBRMP. This type of extensive
monitoring provides important data to determine successes of management action
within the agriculture industry. The report highlighted the significant stressors that
organic chemicals (pesticides / herbicides) are having in the Mackay / Whitsunday
region. Most of this impact comes from the sugar cane industry (Kennedy et al. 2010).
Herbicides, including diuron and atrazine and 2,4-D are used in the sugar industries.
The industry has grown substantially and the use of herbicides has increased in the
magnitude 3 to 7 times in the past 30 to 40 years. Sea grass communities are often
found inshore and the impacts of herbicides could impact sea grass communities close
to river systems. The impact of herbicides may also be considerable upon sea grasses,
which often occur in the inshore zone and are important food sources for dugong and
green turtles. Haynes et al. carried out trails to determine the impact of diuron on sea
grass and reports that at all concentration diuron showed some degree of toxicity
which was demonstrated in a decline in photosynthetic capacity. His studies indicate
that herbicide concentrations present a risk to inshore sea grasses within the GBR.
Haynes also alerts to the combined pressures of other stressors at the same time and
how these combined stressors will impact organisms is unknown (Haynes, 2000).
Lewis et al. (2009) Herbicides: A new threat to the Great Barrier Reef states that little
is known about pesticide residues. Thus further research is required in this field. It is
known that relatively low levels of herbicides residues can decrease marine plant and
coral productivity. The major concern is that this will increase pressures on an
ecosystem, which already has existing pressures. Lewis predicts that the mixture of
herbicides residues in river discharges has the capacity to produce cumulative chronic
effects on sensitive species that may cause a change in community structure of
mangrove, sea grass and coral reef ecosystems. It may also lead to decreased
biodiversity. Lewis acknowledges the work being done by government agencies and
suggests “moderate optimism for the long-term resilience of the GBR (Lewis, 2009).
Further evidence to support the damaging impacts of herbicides includes the work of
Dukes et al. (2004) who correlated severe and widespread dieback of mangroves in
the Mackay region to the use of herbicides, in particular diuron. He further states that
the likely consequences of this dieback include declines in water quality, nutrient and
sediment deposition and further dispersal of toxic chemicals.
To analyse all pesticides and herbicides is beyond the scope, so Diuron will be
discussed as an example of herbicides used. Recently diuron has undergone an
environmental assessment (July 2011) by the Australian Government – Australian
Pesticides and Veterinary Medicines Authority. This report reviewed many
international reviews and the use of diuron appears to be more restricted or being
phased out or phased out in other counties. It suggests that Queensland use of diuron
has increased considerably (Australian Pesticides and Veterinary Medicines
Authority, 2011, p. 7) In addition the Water Quality Guidelines for the Great Barrier
Reef Marine Park, Revised Edition (2010) sets trigger values of 0.9, 1.6 and 2.3 ug/L
for protection of 99, 95 and 90 of species respectively. It has a half life that varies
from 5 to 372 days (Water Quality Guidelines for the Great Barrier Reef Marine Park,
Revised Edition, 2010, p. 71). As greater understanding of the impact of herbicides
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and pesticides grows and best practice models increase, there may be a decrease in
these chemicals entering the GBR. There is much more to be learnt in regards to the
impacts of agricultural chemicals, however clear evidence is available that they are a
stressor to marine ecosystems.
4. AGRICULUTRAL BASED CLIMATE CHANGE IMPACTS
The threat of climate change and warming waters posses a significant threat to the
GBR in terms of coral bleaching and ocean acidification. Whilst the issue is a global
in nature and a solution must involve many other nations, it is the combined impact of
all greenhouse gasses causing impacts. Although the agriculture sector within the
GBR catchment is only a very small percentage of emissions. Agriculture is 20% of
national emissions (Environmental Pollution Course Materials), due to the scale of the
threat, improvements in decreasing emissions (efficiency options) would support the
GBR future. In terms of agricultural impact these include the use of fossil fuels,
methane from livestock and clearing / burning of vegetation. Further actions or
improved management practices could reduce negative impacts from these practices.
Research indicates that the inshore southern section of the GBR is most vulnerable to
the impacts of climate change. With the GBR facing degraded water quality, corals
are less able to recover from bleaching and corals exposed to excess nutrients and
sediments have greater recovery times after mortality events (Johnston, N, et al.
2008). Furthermore, there is evidence to support decreased coral growth in more
acidic waters. In addition climate change related to warmer waters, there may be
increased intensity of rainfall events leading to increased erosion and sediments on
the reef.
The GBRMPA has set a guideline trigger level for sea temperature at an increase of 1
degree above long term average maximum (Water Quality Guidelines for the Great
Barrier Reef Marine Park, Revised Edition 2010, p. 29). If these values are exceeded
the GBR faces significant challenges to its ecology.
Positive actions to address related climate change issues include the Queensland
Government action to reduce land clearing. Queensland had some of the highest rates
of land clearing in the world and this has multiple impacts to the GBR. Furthermore,
The Australian Governments action to introduce a carbon tax is an initiative to reduce
carbon dioxide emission. This measure is critical in reducing emissions to support the
future health of the GBRMP.
CONCLUSION
The Great Barrier Reef faces significant challenges for its long term survival. The
GBRMPA Outlook Report (2009) gives a poor rating to its future health. GBRMPA
acknowledge climate change, as the most significant threat to the GBR and a global
solution and actions must be made to mitigate this threat to the GBR. Australia should
make a reasonable and fair contribution to reduce greenhouse gases or it faces
degraded natural assets including the GBR. In contrast, water quality is within the
scope of our direct management and this provides an opportunity to act with greater
impact. Agriculture is a major contributor to decreased water quality and its key
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related stresses of sedimentation, additional nutrients and increased pesticides and
herbicides. These must be mitigated to ensure the long-term survival of the GBR.
Addressing water quality also gives the reef an improved resilience to combat the
impacts of climate change. Actions taken by GBRMPA reflect sound environmental
management practices including the precautionary and holistic and integrated
principles (Environmental Pollution Study Guide), albeit their effectives to deal with
climate change, water quality and overall outlook is rated poor.
Agriculture, with support needs to change its practices to reduce sedimentation,
reduce nutrients and reduce our reliance upon pesticides and herbicides. This requires
significant changes, education, and willingness for the agricultural industry to strive
for detailed goals and targets. While significant and ongoing progress has been made,
the impacts coastal agriculture is having are significant and require rapid action with a
long-term approach to make improvements. Continued monitoring is also crucial to
determine successes or areas for more drastic actions.
If key Government Agencies and the agricultural industry can foster positive
partnerships and a shared vision that includes continued positive actions, research and
education it will give the GBR its best opportunity for survival as it faces numerous
and significant threats. Landowners and stakeholders must embrace a willingness to
act and change to ensure high water quality water enters to GBR. This will support to
GBR ecosystem and give its best chance of survival for the long term. This will
benefit us ecologically, economically and socially so this great natural resource is
there for future generations.
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