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Dredging set to swamp decades of Great Barrier Reef protection

After decades of work, A$200 million in taxpayer funding and even more from farmers' pockets, we finally have a rare good news story to tell about the Great Barrier Reef. Thanks to an extraordinary effort…

A scuba diving tourist feeds a giant potato cod in the Great Barrier Reef. Pete Niesen/

After decades of work, A$200 million in taxpayer funding and even more from farmers' pockets, we finally have a rare good news story to tell about the Great Barrier Reef. Thanks to an extraordinary effort, we have stopped at least 360,000 tonnes of sediment and large amounts of other agricultural run-off polluting Australia’s most famous natural wonder.

Yet all that effort to protect the reef looks like it’s about to be swamped.

140 million tonnes of marine sediment are proposed to be dredged during port development in the Great Barrier Reef over the next decade, according to my calculations from port development plans. Most of the dredge spoil will be dumped into the waters of the Great Barrier Reef, with the rest placed in reclamation areas on the coast within the Great Barrier Reef World Heritage Area.

That enormous amount of sediment would have severe effects on inshore coral reefs and seagrass meadows - which provide shelter and food for fish, turtles and dugongs - because the cloudier water reduces the sunlight needed for healthy coral and seagrass growth.

Federal Environment Minister Greg Hunt recently rejected Gladstone Ports' bid to dump 12 million cubic metres of dredge spoils into the Great Barrier Reef World Heritage Area.

But there are other port developments up for approval, including a decision due by 13 December on whether Abbot Point can be expanded to become one of the world’s biggest coal ports, which would involve dumping 3 million cubic metres of dredged spoil into the reef.

United Nations agency UNESCO has raised concerns about proposals to dump dredged soil in the reef’s World Heritage Area, and is due to rule next year on whether to add the Great Barrier Reef to its “World Heritage in Danger” list.

While largely symbolic, that UNESCO listing could hurt Australia economically if it hit reef tourism, which brings in $6.4 billion a year in direct spending and employs more than 64,000 people.

So before any more decisions are made, now is a crucial time to examine how the current port proposals could affect the health of the Great Barrier Reef - and whether there is a better way to develop ports without such a high risk to the reef.

A glimmer of hope

Starting in 2009, the Reef Rescue program has been working to reduce the amount of agricultural sediment being washed from farms into rivers and out into the reef.

On top of the A$200 million in government funding to date, its success has meant that during the election, the federal Coalition pledged to continue spending a further A$200 million over the next five years on the Reef Rescue program, renamed the Reef 2050 Plan.

That A$400 million in government funding comes on top of the money and time farmers have put into the program to introduce better management practices to reduce run-off of sediment, nutrients (nitrogen and phosphorus) and pesticides to the Great Barrier Reef.

Large increases in the amount of sediment discharged from rivers to the Great Barrier Reef have taken place since the beginning of agricultural development of the reef catchments. Current estimates suggest four times as much sediment is now discharged than 200 years ago.

But in the first two years of Reef Rescue, agricultural sediment washing into the reef was reduced by 360,000 tonnes from 2009 to 2011. And there have been signs of further progress between then and this year, although it’s too early to accurately report the latest figures.

The success of this program, part of the broader Reef Plan, is a testament to a 30-year effort to bring together farmers, scientists, natural resource management bodies, state and federal government staff, conservation groups and industry.

A canefarmer tests run-off water for pesticides and nitrogen.

Reef Rescue’s success in reducing pollution of the Great Barrier Reef is a small ray of hope in what is largely a depressing story.

As research published this year has found, there has been a 27-year decline in coral cover in the reef, while we have also seen declining seagrass health and dugong numbers.

I was the lead author on the 2013 Scientific Consensus Statement on the Great Barrier Reef for the Queensland government.

As our report noted, “key Great Barrier Reef ecosystems are showing declining trends in condition due to continuing poor water quality, cumulative impacts of climate change and increasing intensity of extreme events”. But while water quality was still known to be poor, finally some progress was being made to improve it by reducing pollution from agricultural sources.

Yet for all the small gains we’ve made so far, it looks likely that pollution of the Great Barrier Reef is set to soar.

Expanding ports along the reef

As well as agricultural run-off, large amounts of sediment are also generated during dredging for port development along the Great Barrier Reef coast, with suspended sediment being generated both during the dredging itself and then in the spoil dumping process.

Major ports along the Great Barrier Reef (GBR) coast include Cairns, Townsville, Abbot Point (which is between Townsville and Mackay), Hay Point near Mackay and Gladstone’s Port Curtis. However, they all lie outside of the boundary of the GBR Marine Park (GBRMP). All the marine parts of the ports are inside the boundary of the GBR World Heritage Area (GBRWHA). (The difference between the marine park and the World Heritage area is explained here.)

Large exports of coal occur from Gladstone, Hay Point and Abbot Point, while Cairns is mainly a cruise ship and sugar port and Townsville a metal ore and metal product port with sugar and general cargo also important. There are also proposals to develop large ports in Bathurst Bay on Cape York and in the Fitzroy River estuary near Rockhampton.

The ports of Cairns, Townsville, Abbot Point, Hay Point and Gladstone are all planning major developments to improve and expand capacity. In the case of Gladstone, this expansion has been underway for the last two years, particularly associated with the development of currently three, but potentially four or more, large coal seam gas processing and export facilities.

Dredging the coast

The expansion of these ports and the development of new ones involves extensive dredging. In addition to the dredging process the spoil has to be disposed of, usually by dumping at sea or dumping behind bunded areas on the coast.

Both these processes - dredging and spoil dumping - produce suspended sediment plumes. The suspended sediment may then been transported by currents (wind, tidal and ocean current driven) to various distances depending on the strength and direction of the currents.

The dispersal of the dredging and spoil dumping plumes and their suspended sediment content is modelled as part of the environmental impact assessment process by the developer’s consultants. Independent plume modelling has also been done at the same sites by consultants for the Great Barrier Reef Marine Park Authority.

But in all cases, the potential adversely affected areas are much larger in GBRPMA’s modelling than in that done by the developer’s consultants.

Underestimation of the ecological effects of dredging is common in environmental impact assessments when compared with models developed independently of developers. Our recent research - involving experts from James Cook University and the Great Barrier Reef Marine Park Authority - has found that the lack of independence in Australia’s environmental impact assessment process is a large part of why it is so ineffective.

Estimating the impact of dredging

By analysing environmental impact assessments and development applications for current port proposals, it is possible to estimate the likely amount of dredging that will occur if the developments go ahead as planned.

In my estimates, I have included the current dredging program in Gladstone (the Western Basin project).

The table below shows my best estimates of the potential dredging to occur over the next 10 years if all proposals went ahead. I have converted cubic metres (the units used for volume of dredged material) to tonnes by multiplying by 1.8, an estimate of the density of dredged material. This was done so that comparisons could be made with loads of sediment discharged from rivers.

Of course the numbers are uncertain as some projects will not go ahead. For instance, the Xstrata Balaclava Island proposal has recently been withdrawn from the approval process, so it was excluded from my calculations.

In addition, not all dredge spoil may be dumped at sea but some may behind bunds to form reclamation areas for future port activities, as will now be the case in Gladstone.

The probability of any project in the table below proceeding is based on entirely my own opinion.

The amount of dredging associated with current proposals to expand or build ports along the Great Barrier Reef coastline. Drawn by the author from development plans.

From this table it can be estimated that on average 14 million tonnes per year of dredge material could be produced over the next decade, of which a considerable proportion will be dumped within the Great Barrier Reef World Heritage Area, and a large but lesser amount in the Marine Park.

To put that in context, the total human-caused sediment load from agricultural sources, combined with much smaller contributions from urban development and mining, is estimated to average 6 million tonnes a year, out of a total sediment load of 9 million tonnes. (That is, 3 million tonnes is from natural sources.)

So the possible 14 million tonnes a year of sediment pollution from dredging could easily be 2.5 times more than all of the existing agricultural, urban development and mining pollution reaching the reef at present.

And it would dwarf - more than 38 times over, in one year alone - the 360,000 tonnes of pollution avoided by the Reef Plan over 2009 to 2011.

In 2007, CSIRO scientists confirmed that sediment plumes travel to the outer reef and beyond, and that pesticide run-offs may be polluting larger areas of the Great Barrier Reef than originally thought. AAP Image/CSIRO

Coral reefs, dugongs and turtles

The increased turbidity, or cloudiness, of the water would have severe effects on inshore coral reefs and seagrass meadows, by cutting the sunlight reaching the coral or grass and reducing its growth. That would have knock on effects for the local marine life, such as the dugong and turtles feeding on seagrass.

Those reefs and seagrass meadows have already been badly affected by recent large river floods that washed sediment and other pollutants into the coastal Great Barrier Reef and the additional stress of large quantities of additional sediment from dredging is likely to prevent recovery of these valuable assets.

It is sometimes claimed that material in dredge spoil is somehow less harmful to marine ecosystems, such as seagrass, fish and coral reefs, than the sediment from rivers. Yet there is no scientific evidence for this claim.

It is also often claimed that the dredge spoil is dumped into areas that are less sensitive to increased sedimentation and turbidity than the areas where river sediment ends up.

In fact, the reverse is likely to be the case. Sediment discharged out of rivers enters areas where sediment from the rivers has always been present (for the last 10,000 years), only now in greater quantities.

In contrast, dredge spoil is being dumped in areas that are not naturally exposed to large sediment loads.

The management of the dredging process is also defective. As noted earlier, our research found there is no real independence in the environmental impact assessment process, which are used to form the basis of how developments are managed.

Neither is there independence or transparency in the compliance monitoring program, which is also designed by consultants for the developer, and the decisions on the tenderers for the contracts made by the developer.

This has been highlighted by the current fiasco in the Gladstone, where it has just emerged that an outbreak of diseased fish in the Gladstone Harbour two years ago coincided with a toxic algal bloom that may have been fed by a leaking rock wall used to contain dredge spoils.

As The Australian reported this month, Gladstone Ports Corporation had known about the algal bloom and increased sediment from its infrastructure works for more than two years - but only recently made the reports publicly available.

How to develop ports and protect the reef

Yet it is possible to properly manage port developments along the sensitive Great Barrier Reef coast - and to see how, we only need to look at the last capital dredging project in the Port of Townsville in 1993.

In that case, the Great Barrier Reef Marine Park Authority held the funds for the environmental impact assessment and compliance monitoring, let the contracts and directly received the results of the compliance monitoring. No pressure was then placed on the consultants to get “acceptable” results.

A healthy section of the Great Barrier Reef, which stretches for 2000km and is one of the seven natural wonders of the world. AAP Image/James Cook University

Our research recommended that that Townsville process be used as a model for all large development projects. I am hopeful that the current planned expansion of the Port of Townsville will show the way again in how world best management practices can be applied in port developments in the Great Barrier Reef.

If the federal and Queensland governments sign off on the current proposals for port development along the Great Barrier Reef coastline, which are not up to the standard set with Townsville 20 years ago, then we can expect less stringent controls over dredging and spoil dumping processes and more severe effects from sedimentation and light loss on marine communities such as seagrass and corals.

Given that coral and seagrass are already in decline in the Great Barrier Reef, this extra pressure could lead to an increased rate of degradation.

Having spent so much time and money on trying to improve the health of the reef, is it really worth gambling with anything less than world’s best practice dredging and spoil disposal for ports along the Great Barrier Reef?

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56 Comments sorted by

  1. Comment removed by moderator.

    1. In reply to Jim Inglis

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    8. Liz Minchin

      Queensland Editor at The Conversation

      In reply to John Newlands

      For the sake of stopping this comments section degenerating any further into tit-for-tat battles & arguments over topics that weren't even mentioned in the article (like nuclear power, a topic we've published dozens of articles on including here - a good place to debate the merits of nuclear) we've had to remove this thread.

      Please stick to discussing the main issues raised here - such as how do we balance development of the Qld coast against enviro concerns... And please do so courteously.

      Irrelevant or abusive comments & threads will be deleted, otherwise we get complaints from many other readers about comments getting out of hand, and putting them off from participating in a genuine conversation with others.

  2. Paul Prociv

    ex medical academic; botanical engineer at University of Queensland

    Thanks for a very important report. I agree entirely that EIAs tend to be rubber stamp jobs. You commented: "The increased turbidity, or cloudiness, of the water would have severe effects on inshore coral reefs and seagrass meadows, by cutting the sunlight reaching the coral or grass and reducing its growth. That would have knock on effects for the local marine life, such as the dugong and turtles feeding on seagrass."
    I don't think this goes far enough. The suspended mud settles onto everything, corals, sea-grass, sand etc., and sticks almost permanently to it, forming a layer of opaque glue, certainly to the point where it does not wash off, even in fairly strong currents. So, not only is sunlight blocked, inhibiting photosynthesis, but all nutrient and gaseous exchange in sedentary living organisms is effectively smothered - the affected reefs and sea-grass beds are killed, without any prospect of recovery in the short term.

    1. Mustafa Epstein

      Political Scientist

      In reply to Paul Prociv

      Have you noticed that when it rains - any where in Oz, the water goes brown ??? Just a thought. You see, particles of dirt get into the runoff and head to a river and then the sea. It causes turbidity and has been happening since Allah (peace be upon Him) created the Earth.

    2. Paul Prociv

      ex medical academic; botanical engineer at University of Queensland

      In reply to Mustafa Epstein

      Yes, when diving was a big part of my life, I couldn't help but notice the effects of rain, and floods, on oceanic turbidity. But this pales into insignificance compared with the volume of detritus dumped into the sea by dredging, the short time-frame, and the huge variation in suspended particle size, all of which cause blanketing over far greater areas, allowing living organisms almost no opportunities to adapt. I have seen extensive reef systems killed by dredging, but not by flooding.

  3. robert roeder
    robert roeder is a Friend of The Conversation.


    Way back in 1970 these words echoed around the world; They took all the trees and put em in a tree museum, and charged the people a dollar and a half just to see em, don't it always seem to go that you don't know what you've got till it's gone, they paved paradise and put up a parking lot.

  4. Chris Thaler

    Intelligent person

    To a simple layman like myself why not use the empty coal trains returning to the open cut coalfields,which need ongoing rehabilitation. The spoil from the dredging would make a wonderful replacement for the vacant spaces left from coal extraction & could also keep Australia physically intact.
    Are there any valid reasons for not investigating this concept. Would be a double win for our country.

    1. Chris Thaler

      Intelligent person

      In reply to alexander j watt

      Guess we've gotta watch out for all these nasty coral critters !!!
      Not so sure there is much coral in Gladstone harbour or Abbott Point though.

    2. Jon Brodie

      Research scientist

      In reply to Chris Thaler

      On the contrary there's quite a lot of coral in Port Curtis (Facing Island) and a little further offshore in the closer reefs of the Capricorn Bunker group. In addition of course there are seagrass beds, dugongs, turtles, dolphins at risk near both Port Curtis and Abbot Point.

    3. In reply to Jon Brodie

      Comment removed by moderator.

  5. wilma western

    logged in via email

    All power to your arm Jon Brodie. And it's good to see that Greg Hunt disallowed one application - was that the easiest?

    An argument that dredging can happen only if it follows best practice and is planned and supervised by an independent authority surely is the way for the federal Environmental Minister to go. Greg of course might be faced with similar problems with the Vic govt's plans to increase the capacity of the Port of Hastings on Westernport next to Hunt's own electorate.

  6. Colin Creighton

    Chair, Climate adaptation, Marine Biodiversity and Fisheries

    An interesting analysis Jon.
    Some additional $costs and benefits - since 1990 the Banana and Tiger Prawn catch has dropped by about $45M per annum. Yes its an estimate but best we can do given impacts like ponded pastures, further losses of seagrass, changes in effort and controls and so on. We also know both these prawn species life cycles depend on salt marshes and seagrasses.
    I know its not as charismatic as turtles and dugong but it is FOOD and JOBS. Repair the ponded pastures and related…

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    1. Mustafa Epstein

      Political Scientist

      In reply to Colin Creighton

      Strange, Deloittes say the fishing industry, including aquaculture, was only worth $193 million in 2012. You couldn't support your $45 million with facts, could you ??? They did !!!!!

  7. David Arthur

    resistance gnome

    This is an excellent article by Jon Brodie: he describes EXACTLY how appropriate oversight can be put in place to ensure that projects can go ahead without undue environmental damage.

    So what, then, are we to make of EVERY project since 1993 that has not had independent oversight? ... or of Ministerial Statements about all those other projects?

  8. Mustafa Epstein

    Political Scientist

    According to the Deloittes report, researchers account for $98 million worth of expenditure in the GBR area. They employ 881 people.

    Meanwhile, prior the the ALP marine parks which decimated fishing near the GBR, $193 million was generated and there were 533 directly employed.

    Seems we got more value for money from the fishers.

    The report also states that that only 48.7% visit the areas for holiday or leisure. The rest is business, visiting friends, bureaucrats, academics spending grants etc.

    In fact, only $481 million is contributed by the GBR and only 4831 jobs relate directly to the GBR.

    And here we are talking about more government grants of $400 million. Talk about barking up the wrong track.

    1. James Hammond


      In reply to Mustafa Epstein

      Of course this argument only works if we assume that the generation of jobs is the sole value of the GBR. I doubt very much that many would agree with that.

  9. Pat Moore


    Thanks for your effort and dedication on behalf of the reef Jon.

    Yes a complete waste of money and effort over the years to prevent the comparatively miniscule cane farm runoff in the face of the massive destruction to be caused by these mega dinosaur fossil fuel ports. And on ABC radio news today news of another program based in Mackay, controlling runoff and unsurprisingly supported by the government because it is window dressing/ bandaid/ shift the blame approach.

    Until this globalised corporatocracy working through occupied governments (both Queensland and federally now) is stopped, this unregulated environmental vandalism which is also adding masses of carbon to the atmosphere and so acid to the oceans, the despoiling, destructive processes will continue in the service of the mighty dollar.

    1. Pat Moore


      In reply to Pat Moore

      And no wonder the reef scientists are collecting coral spores now to cryofreeze in the hope of a saner future for the Earth.

    2. Mustafa Epstein

      Political Scientist

      In reply to Pat Moore

      Glad you brought that up Pat. It seems the scientists doing the storing haven't heard about global warming and our iminent destruction. These spores are expected to survive when returned to the sea in 100 or 1000 years when the ocean surrounding the GBR is 4-6 degrees higher. They have no chance of survival, so why waste the money in the first place ???

  10. peter mackenzie

    Transport Researcher

    John, has there been any consideration of alternatives such as transporting the coal to Darwin. It could be the catalyst to get the inland rail right through from Gladstone to Darwin.

    There would be the costs of dual-gauging or converting the Qld narrow gauge from the mines to Mt Isa to standard gauge , with a new 400 km connection from there to the Adelaide-Darwin link.

    It would be possible to retain the narrow gauge and tipple into standard gauge waggons atMt Isa.

    Yes, big money, but…

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  11. Liz Minchin

    Queensland Editor at The Conversation

    Just a reminder from

    "Keep it relevant. We know some conversations can be wide-ranging, but if you post something unrelated to the original topic ("off-topic") then it may be removed to keep the thread on track. This also applies to queries or comments about moderation, which should not be posted as comments."

  12. David Kershaw

    logged in via email

    I don't think back of the envelope calculations carry much weight. Calculating that disposal of an estimated dedge spoil at a disposal rate of 14 million tonnes a year for 10 years is 38 times the quantity of sediment "saved" for 2009 to 2011 has no useful purpose unless it is to cause alarm.
    Spoil disposal would not be anything like the essentially fugitive dispersal of sediments and manmade pollutants into gullies, creeks, rivers and estuaries along the entire coast.
    Science should be used to…

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  13. Comment removed by moderator.

  14. Steve Hindle

    logged in via email

    John, your comments on dredging in Gladstone harbour are a bit misleading.
    " I have included the current dredging program in Gladstone (the Western Basin project)." You also describe the dredging as "underway" and "in process"
    In fact there is currently no dredging taking place in Gladstone harbour.
    The current phase of dredging for the Western Basin project finished in September and it is questionable if any further phases will proceed.

  15. Dale Bloom


    As well as stoping dredging for new ports, I really think it necessary to stop cane farming and cattle grazing in sensitive areas adjacent to the reef.

    The reef has been declining for many years, long before dredging for new ports, but I really don’t think soil runoff from cane farms can be stopped entirely.

    Fields of plant cane have no trash blanketing, and there is no barrier to stop soil from washing away.

    If trash blanketing has been carried out on a ratoon crop, the trash blanket only lasts a few weeks before it decomposes away and leaves bare soil.

    Also the entire trash blanket can be washed away if a cane field is flooded, and this frequently happens to cane farming areas during a heavy wet.

    Also clear felling is the norm for cattle grazing, allowing soil to readily wash away during floods.

  16. Brett Kettle

    Marine Scientist at BABEL-sbf

    Interesting you quote 1993 Townsville Capital Dredging as the model for the future. I agree... it worked very well.
    When you read the reference you've cited, you'll see that I managed that monitoring program (start on page 9). So I can say with some authority that you are 100% wrong when you say "the Great Barrier Reef Marine Park Authority held the funds for the environmental impact assessment and compliance monitoring, let the contracts and directly received the results of the compliance…

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    1. Hugh McColl


      In reply to Brett Kettle

      It's great you've turned up Brett. And good that you cleared up some details about the funding (whatever!).
      When readers here see articles about dredging and 'dumping' and 'sea dumps' and coral reefs they often have no conception of the technical details and get misinformed about stuff. Many people have never seen the GBR, never watched a dredge at work, have no idea of the dynamics of a shallow ocean spoil dump and wouldn't know what the truth is or where to find it. I reckon Jon Brodie has…

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    2. Brett Kettle

      Marine Scientist at BABEL-sbf

      In reply to Hugh McColl

      Its been 20 years since I've had much to do with dredging in Cleveland Bay :), and I haven't been following any work thats been done on things like the migration of spoil. But you are right... thats the first place to start.

      I do recall a study that I undertook in about 1991, in the lead-up to the 1993 capital dredging, where we worked out how much had ever been disposed there, and how much remained. It was a little approximate (some of the older dredging records were patchy), but essentially…

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    3. Hugh McColl


      In reply to Brett Kettle

      Thanks Brett. And here's the thing. If you look at some of Jon Brodie's other work on the sediment plumes from the Burdekin River (100 kms south of Cleveland Bay) you notice that those sediments sometimes pass northwards on the coastal currents right through Cleveland Bay and can be found 100 kms further north again, up around Hinchinbrook Island. All that maintenance dredging carried out for access to the port of Townsville continually disturbs and disperses fine sediments which join the plume…

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    4. Brett Kettle

      Marine Scientist at BABEL-sbf

      In reply to Hugh McColl

      I'm not sure that they're all dots which can plausibly be joined, despite what appears to be good logic at first blush... stick with your 'back of the envelope' method for a moment, and check out the Belperio 1978 JCU PhD thesis on a sediment model for the Townsville area (you'll probably need to visit the JCU Library). A few minutes with pen & paper will tell you that even a 30% loss off the disposal area over a 20-30yr period pales into insignificance against the sediments remobilised by…

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  17. Tony Simons

    Director at Bedlam Bay Pty Ltd

    Today I heard Greg Hunt on Background Briefing justifying his decision to hand over environmental monitoring to the Queensland (green tape). Very irresponsible to trust the Newman government with looking after the environment. New mega casino development proposed north of Cairns, Galliliee basin expedited, land clearing.