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 in February 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.

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?

Jon Brodie is Senior Principal Research Officer at James Cook University. He receives funding from the Queensland and Australian Governments for his research. He was the lead author in preparing the Reef Plan Scientific Consensus Statement on water quality and the Great Barrier Reef in both 2008 and 2013. He is also being funded to write expert reports for the Shine lawyers fishermen's compensation case in Gladstone.

This article was originally published at The Conversation. Read the original article.