What can we say for certain about dredging and the Great Barrier Reef?

Laurence McCook, James Cook University and Britta Schaffelke, Australian Institute of Marine Science

To protect and manage environmental treasures like the Great Barrier Reef requires a strong foundation of science, but what should agencies and political leaders do when the science is as widely debated as it has been for dredging and disposal in the Great Barrier Reef?

Over the past 15 months, we have led a process with a panel of experts to provide an independent overview of the current knowledge of the effects of dredging and sediment disposal in the Great Barrier Reef World Heritage Area. Our panel included a very diverse range of expertise and experience, from years in the dredging industry, to physical oceanographers and coral ecologists.

The report, published yesterday, covers the effects of dredging on the physical and chemical environment, flow-on effects on the habitats and biodiversity, cumulative impacts, effects of land-based disposal, and next steps for management.

The report shows, for example, that although direct effects are localised, dredging and disposal may have been making significant contributions to suspended sediments in inshore waters of the Great Barrier Reef.

Given the complexity of the issue, the report can’t provide conclusive answers to all of the questions reef managers face, but it does provide a comprehensive and balanced interpretation of the available evidence. By clearly distinguishing what is known (and agreed by the experts), what is definitively not known, and what is uncertain (that is, still debated by the experts), the report not only provides a clearer way forward for managers, but clearly identifies the knowledge gaps we still need to address.

So what does the report tell us? It says that dredging and sediment disposal can change the physical and chemical environment, and thus affect the biological values of the Great Barrier Reef World Heritage Area. But these effects will differ between locations, and also be influenced by the different types and extents of dredging and sediment disposal.

Direct removal by excavation, and burial during disposal, only affect relatively small areas, although within those areas the effects are obviously severe. Dredging and disposal don’t occur on coral reefs within the Great Barrier Reef area.

Release of fine sediment is the greatest concern

Both dredging and marine disposal create significant plumes of suspended sediment, causing increased cloudiness in the water and reducing the light available to marine organisms.

Importantly, the report concludes that both disposed sediments and dispersed sediments from dredge plumes have the potential to be re-suspended and transported by waves and ocean currents, and to contribute to the long-term, chronic increase in fine suspended sediment concentrations in the inshore Great Barrier Reef.

The extent to which this occurs and affects marine life was not agreed by the expert panel. In particular, the panellists had differing views on whether sediment from dredging was significant compared with background levels of resuspension and inputs of fine sediments in river run-off from catchments. However, calculations suggest that previous large dredging operations had potentially very significant effects.

Most experts do agree that increased levels of fine sediments, and associated nutrients, are, along with climate change, seriously affecting the long-term health of the Great Barrier Reef. Understanding dredging in the context of inshore sediment dynamics is a serious gap in our knowledge.

In general, dredged material from near the Great Barrier Reef has few chemical contaminants, and there are robust management procedures to avoid disposal of such material at sea.

Different habitats, differing effects

The report breaks down and summarises the risks to coral reefs, seagrass meadows, mangroves and estuaries, pelagic (open water) and seafloor habitats, along with the risks to fish and other wildlife of conservation concern, such as dugongs, marine turtles and seabirds. These effects will vary greatly with the location, timing and extent of dredging and disposal. But if dredging and disposal have been significantly increasing fine sediments supply, it is possible that long-term impacts on inshore ecosystems have been under-estimated. We know that chronic increases in suspended sediments have been affecting inshore coral reefs and seagrass beds.

What is clear is that the extent of future impacts in the marine environment will be very significantly improved with the impending bans on disposal of capital dredging in the marine environment, recently announced by the federal and Queensland governments. The proposed ban on disposal of capital material in the Marine Park is open for public comment until this Friday 27 March.

Future challenges

Following a ban on disposal of capital material within the marine environment, there remains the challenge of managing the remaining impacts of dredging, including disposal of maintenance dredged sediments in marine environments, and disposal of capital dredging material on land.

The Expert Panel identified a number of potentially serious impacts and challenges involved in disposing of dredge material on land or in reclamation, including loss of coastal habitats, runoff of seawater and fine sediments from dredged material, and potential acid sulphate soils.

Our panel prioritised identifying what we do know about dredging, but also found significant areas of insufficient knowledge. Most of the panel also agreed on the need to follow up our report with a similar analysis of the social, economic, cultural and heritage aspects of dredging and sediment disposal, including the impacts on Indigenous culture and heritage.

Given the complexity of the Great Barrier Reef ecosystem, and the range of expert views, the intention of this process was never to provide a single, conclusive answer. Rather, our report provides a strong foundation for progressing both knowledge and management directions, and it appears it is already doing that.

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

Marine science: challenges for a growing 'blue economy'

By John Gunn, Australian Institute of Marine Science

AUSTRALIA 2025: How will science address the challenges of the future? In collaboration with Australia’s chief scientist Ian Chubb, we’re asking how each science discipline will contribute to Australia now and in the future. Written by luminaries and accompanied by two expert commentaries to ensure a broader perspective, these articles run fortnightly and focus on each of the major scientific areas. In this instalment we dive into marine science.

Why are our oceans important to us? How is our health, the health of the environment, the strength of our economy and indeed, our future, dependent on the seas? How can marine science help us, collectively, to sustainably develop our marine-based industries and at the same time protect our unique marine ecosystems so that they can be appreciated and enjoyed by future generations?

In many ways, Australia is defined by the oceans that surround us. We have the third largest ocean territory in the world. The majority of our trade travels by sea, vast offshore oil and gas resources earn vital export income and offer a long term, cleaner energy source than coal and our fisheries and aquaculture industries provide healthy food.

We are custodians of two magnificent marine World Heritage Areas – the Great Barrier Reef and Ningaloo Reef – and we are a nation that loves to sit by, swim, surf, dive, fish and sail in the (mostly) clean waters and healthy marine ecosystems that surround our continent.

Australia’s affinity with our ocean estate is perhaps best exemplified by the fact that 85% of our population lives within 50km of the coast.

Marine industries contributed approximately A$42 billion to our economy in 2010. This is projected to grow to approximately A$100 billion by 2025 with the expansion of current industries and development of new opportunities in areas such as renewable energy. As a nation we will increasingly be dependent on our “blue economy” for our future prosperity.

In addition to their economic and aesthetic value, our oceans also provide a suite of essential “ecosystem services” – most importantly in their role within the global climate system. Since the end of the 18th century, about 30% percent of human-induced carbon dioxide emissions have been taken up by the oceans while over the past 50 years, they have absorbed about 90% of the extra heat generated through the impacts of the greenhouse effect.

The moderating influence of the oceans as our planet warms, and their very strong influences on our island continent’s weather, impact on every Australian, every day.

Six grand challenges facing our marine nation

If Australia, and indeed the world at large, is to continue to enjoy and grow the benefits accrued from our oceans, we need to face up to and meet a number of significant (and in some cases urgent) challenges.

Australia’s marine science community recently collaborated with governments, not-for-profit organisations and the private sector to produce the report Marine Nation 2025: Marine Science to Support Australia’s Blue Economy.

Marine Nation 2025 outlined six, interconnected “grand challenges” facing Australia, each of which has a significant marine dimension with gaps in understanding or requirement for tools that can be addressed by marine science:

1. sovereignty, security, natural hazards: needs improved operational oceanographic forecasting and increased effort on fine-scale hydrographic data and charts
2. energy security: needs support for developing energy resources, particularly liquid natural gas and renewable energy and research to support carbon sequestration
3. food security: needs research to support a booming aquaculture industry, as well as data and tools to improve management of wild-catch fisheries
4. biodiversity conservation and ecosystem health: needs environmental baselines, effective indicators of ecosystem health to guides national marine environmental monitoring, and tools to predict impacts of development on marine biodiversity
5. dealing with changing climate: needs enhanced understanding and skill in prediction of the impacts of sea level rise, increasing sea temperature and ocean acidification and the role of the ocean as a carbon sink
6. optimal resource allocation: needs integrated social, economic and environmental information and tools to assist transparent, robust and accountable decision-making.

The multidisciplinary nature of marine science, the geographic scale and connectedness of marine systems, and the complexity of the challenges above mean that in the majority of cases no one institution (or in the case of industry, one company) can build the evidence base or tools required to adequately address these challenges, even at local scales.

Thus, a dedicated and coordinated effort across our national marine science community, governments and industry is required.

Coordination can (and should) ensure that resources are used efficiently and strategically, and allow the full breadth of the marine science community – from the fundamental work conducted across the university sector, to the translational and applied science conducted by national science agencies such as CSIRO, Geoscience Australia and the Australian Institute of Marine Science (AIMS) – to have the maximum impact.

A couple of recent cases illustrate of how strategic, collaborative efforts across organisations and sustained investment in national-scale infrastructure provide vital support for decision makers across government and private sectors.

CSIRO oceanographer David Griffin has been involved in the search for Malaysian Airlines flight MH370 this year.

He used advanced models of ocean currents around Australia developed through a collaboration between CSIRO, the Bureau of Meteorology and the Australian Navy over the past decade, to determine likely movement of wreckage and allow search and rescue operations to pinpoint their activities.

The same models can also be used to track and predict oil spills, missing boats, valuable fish stocks and guide Navy operations.

The critical data required by the models comes from Australia’s Integrated Marine Observing System (IMOS), a national, collaborative infrastructure facility set up eight years ago. IMOS has become an international leader in ocean observing and is now the critical observational foundation for much of Australia’s marine science.

Two strategic and sustained marine science investments – in ocean observations and modelling – provide the fantastic capability for David’s work, and many other applications to come.

Similarly, following the UNESCO World Heritage Committee’s questions about our management of the Great Barrier Reef World Heritage Area, Australia’s response has relied heavily on the body of evidence provided by strategic investment in marine science conducted over the past 30 years.

Science doesn’t always tell a good news story – the AIMS long term monitoring has shown that half of the Great Barrier Reef’s coral cover has been lost over the past 27 years due to the cumulative impacts of cyclones, Crown of Thorns starfish and bleaching (caused by heat stress).

Importantly though , the research conducted by AIMS, the ARC Centre of Excellence for Coral Reef Studies (lead by James Cook University) and others also provides the evidence base for understanding ecosystem health and development of policy and regulation to stop the decline and rebuild the reef.

The way forward

Australia has world class, and in many areas world leading, marine science capability. Appropriately, over the past few years the marine science community has recognised the need to work together and is increasingly collaborating in providing big-scale science focused on national and global needs.

But if we are to rise to the challenges of our growing “blue economy”, we will need to do much more. We will need to take a long-term outlook and focus effort on both the development of science capability (human and physical) and securing the best possible returns to Australia through its effective coordination and utilisation.

The first steps along this pathway are clear:

1. a stable, sustained and genuinely national approach to maintaining, updating and transforming the infrastructure needed to conduct world-class marine research, along with the human resources to run it
2. targeted training and skills development in marine science (in particular, advanced quantitative skills), along with mechanisms to support and incentives for collaboration
3. direction of greater effort into communicating the relevance and benefits accruing from marine science, to ensure optimal awareness and uptake in policy, legislative and regulatory domains.

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Sabine Dittmann, Associate Professor of Marine Biology at Flinders University

Marine sciences deliver data and modelling on oceanographic patterns benefiting weather forecast and maritime safety, provide information underlying sustainable seafood harvesting and production and knowledge on marine life underpinning biodiscoveries.

Yet it is a challenge to carry out marine research throughout the huge realm of Australia’s maritime jurisdiction. Australia has only a small fleet of research vessels for coastal and offshore waters and needs a better alliance of shore-based marine field stations. Ocean exploration relies on technological innovations.

As much of the oceans are still unexplored, curiosity driven research can provide useful discoveries such as alternative products to benefit human health. The Census of Marine Life illustrated the highly diverse marine life in Australia’s seas, but taxonomy is a threatened skill unless the tide turns for museum research funding.

Rigorous experimental hypothesis testing, using shore- and sea-based facilities equipped with operating funds, technical and research staffing, can support mitigation of cumulative impacts and global warming. Marine research strengthens monitoring into the health of Australia’s seas facing growing economic use, the effectiveness of marine protected areas and biosecurity of marine invasive species.

Understanding marine ecosystems requires multidisciplinary approaches and a well-connected network of scientists. At times of highly competitive research circumstances, appreciation for collaborative skills has to increase.

Higher education in marine sciences, including maritime engineering, provides an informed and versatile work force to address challenging scientific questions and generate knowledge for decision making on the wise use of the seas around us. Continued participation in international programs on ocean exploration will strengthen Australia’s position as a leading nation for marine sciences.

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Mike Coffin, Professor and Executive Director, Institute for Marine and Antarctic Studies at University of Tasmania

How inappropriate to call this planet Earth when it is quite clearly Ocean.
- Arthur C Clarke

The global ocean is humankind’s common heritage and responsibility. Ocean under Australian jurisdiction is significantly larger than the nation’s landmass. Our 0.3% of the world’s population is custodian for 3.8% of the world’s ocean, by far the greatest responsibility per capita among the G20 nations.

Effectively managing our vast public marine domain requires understanding it, yet our ignorance of the dynamic ocean is profound:

• of an estimated 2.2 million species of marine life, 91% await discovery and description
• how changes in factors such as ocean temperature, acidity, light supply, nutrients and trace metals combine to drive marine life to acclimate, adapt or extinction is not understood
• 95% of the world’s seafloor remains to be mapped in detail
• the soundscape of the 98% of the ocean beneath the surface zone, where light doesn’t penetrate and most life uses sound as its primary sense, is virtually unknown.

Australia’s vital and growing blue economy critically depends on understanding and managing the sea, through both national efforts (such as the Integrated Marine Observing System) and international partnerships (such as the International Ocean Discovery Program).

But much of the nation’s capability in the three pillars of marine research — observation, experimentation and modelling — across the major marine scientific disciplines — biology, chemistry, geoscience and physics — is precarious due to short-term and therefore vulnerable support.

In the context of a to-be-developed national strategy for marine science, increased and sustainable investment in exploratory, basic, applied and translational marine research — in both human capability and infrastructure — as well as improved underpinning primary, secondary and tertiary education in science and mathematics are needed to ensure a healthy, productive and resilient ocean for present and future generations.

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This article is part of the Australia 2025: smart science series, co-published with the Office of the Chief Scientist
This article was originally published on The Conversation. Read the original article.

Experts: Great Barrier Reef's biggest threat today is coal

By Iain McCalman, University of Sydney and Stephen Palumbi, Stanford University

Reef historian Iain McCalman, in Sydney, and reef scientist Stephen Palumbi, in California, are monitoring reef degradation from opposite sides of the planet. They compared notes.

Iain McCalman: A recent report found that the Great Barrier Reef had lost 50% of its living coral. This was mainly from cyclones and the damages of Crown of Thorns starfish. Then there are the new threats of coral bleaching and acidification.

Are the problems you are finding in the US old ones that have mounted up and intensified? Or are they new challenges coming from human-stimulated climate change?

Steve Palumbi: All coral reefs in the world suffer from the same problems – they’re smothered by sediment, choked by weedy algae, blasted, dug up and stripped of most of their fish. Then there’s climate change making the oceans hot, sour and stormy.

Worst off are the reefs of the Caribbean, suffering from more than 500 years of incremental impact from western civilization, mostly in the form of poor stewardship. But even the far-flung reefs of the Pacific that the US manages have some combination of local stresses.

It seems to me that what the Great Barrier Reef has – that US reefs do not – is a central place in the hearts and minds of the public. Sure, most people in the US like corals and fish, but our reefs have not reached celebrity status. What kind of extra oomph does celebrity give the Great Barrier Reef? Has it been important in keeping it healthy?

Iain McCalman: The Great Barrier Reef’s popularity has helped control some things such as tourist pollution and the overfishing of parrot fish that graze on algae and keep corals clean.

Yet we haven’t been able to deter our governments from building massive new Reef ports and there are more and bigger coal ports on the way.

What worries me, too, is that waters warmed by greenhouse gases will cause big outbreaks of coral bleaching this coming summer, with stressed corals turning white as they expel the symbiotic algae that normally live within them. Another one degree or so will hurt corals that have been hit before: this time they may not recover.

Steve Palumbi: I’m also worried about coral bleaching. This week along the US Pacific coast we have had record temperatures on land and in Monterey Bay – well, it is still very cold by Great Barrier Reef standards, about 60F (16C), but it is warm for us! And a look at the latest map of ocean temperatures shows a lot of red – these are places where the ocean is 1-2 degrees warmer than the usual annual maximum.

Iain McCalman: We are predicting something similar, especially because we seem to be entering an El Niño weather phase when the Pacific is generally warmer anyway, though Charlie Veron, one of our great coral scientists, says that every year is becoming an El Niño year in Australia as far as corals are concerned.

Steve Palumbi: Every year is a hot one … that seems to be what the world is seeing across the continents and the seas. Way back when people first stumbled on the fact that corals bleached when the temperature rose too much, they found something else: corals in warmer climates near the equator bleached at a higher temperature than corals living in cooler waters.

We have seen this on a small scale in American Samoa where we work, and have shown that individual coral colonies living in warm water acclimate to the heat by changing their physiology. And whole populations of corals adapt to heat by having the right genetic makeup across about 100 genes.

Can we use this discovery? Turns out we can in two ways. We can locate and protect these heat-resistant corals. And we can try transplanting them to see if they in fact retain their heat resistance. We expect them to lose a little ground. How much is the question.

I’d love to think this will give us a leg up in replanting future reefs. I am not sure yet, because reef restoration has been so difficult. Does the Great Barrier Reef have any successful restored, replanted reefs?

Iain McCalman: Not that I know of. Moreover, with a government skeptical about climate change, a good deal of the work of this kind on adaptation is being shelved. Five of the Directors of the Great Barrier Reef Marine Park Authority recently resigned in protest against the cutting of programs concerned with responding to climate change.

Five directors of the Great Barrier Reef Marine Park Authority recently took redundancy packages, among them its former climate change director Paul Marshall, who said budget cuts have left the agency without a dedicated climate program.

But I also wanted to ask you about acidification. As the amount of CO₂ in the atmosphere rises, oceans absorb more and it turns into carbonic acid in seawater. How do you rate the mounting acidification of the oceans from absorption of CO₂ as a threat to corals?

It seems to be the elephant in the room: its consequences go beyond endangering corals to threaten other marine species as well. Some scientists seem to think it will deliver the death blow to coral reefs, if other things don’t get them first. What’s your feeling?

Steve Palumbi: Acidification is not the elephant in the room yet, it’s the elephant on the bus … due to get here any time now. The best data suggest that acidification has huge effects, from slowing down coral growth to changing the behavior of coral reef fish so that they get eaten more easily. Those effects are not strong yet, but they are coming quickly as CO₂ builds up in the atmosphere.

CO₂ and acidification takes 50 years to reverse. Think of stopping distance – a speeding car takes a long time to stop. So too with acidification.

And that is what I worry about. Because by the time the effect of that CO₂ is killing corals, it will be too late to do anything about it. It’s like cancer treatment. If you’re lucky, they find a tumor when it is small and maybe isn’t even bothering you. But that tiny tumor is a huge threat, and we jump on it to fix it.

But I want to circle back to something you brought up at the beginning. Australia is selling coal to China, I hear. What is going on?

Iain McCalman: This issue of coal lies at the heart of current threats to the Great Barrier Reef, and symbolizes an economic mindset that reef lovers everywhere are up against. Our government has decided that Australia’s economic future lies in selling cheap coal to China and India. To do this the Federal and Queensland state governments need to expand existing coal ports on the Reef because these provide the cheapest and quickest shipping routes to Asia.

Quite apart from discouraging investment in renewable energy by backing fossil fuels, this decision has fraught implications for the health of the Reef and its waters.

Because the reef is too shallow for massive container ships, the new coal ports all entail extensive dredging of the seafloor. Thankfully public agitation has temporarily deflected the government’s original plan to dump three million cubic meters of dredged silt from Abbot Point into the reef channel, where it would choke corals and swamp sea grasses. Even so, dredging will stir up immense amounts of sediment as well as coral-threatening bacteria.

The vastly increased tonnage of container ships churning up and down the tricky reef channel represents a further threat from reef accidents and oil spillages, both of which have occurred a number of times in the recent past. There are plans, too, for several new mega-sized coal mines to be opened nearby, requiring similar access to the Great Barrier coastline and lagoon.

To call this policy short-sighted is an understatement. It sacrifices one of the wonders of the world and a substantial economic asset for Australian tourism; and this at a time when even China is trying to wean itself from using polluting coal.

The Great Barrier Reef might be an icon for us in Australia, as you said, Steve, but we seem to have governments that are proud to be icon bashers.

Steve Palumbi: I am thinking about a wonderful passage in your book, about Captain Cook navigating the Great Barrier Reef’s intricate tributaries, straining his considerable navigational skills to delicately thread his small ship up coral-filled canals. Now blast a modern coal ship through there, and what would you expect to happen? Cook’s ship was threatened by the Great Barrier Reef. Now the tables have turned.

I can’t help also to think about one of the last major threats to the whole Great Barrier Reef - the crown of thorns starfish. It wasn’t too long ago that this voracious predator was wasting reefs all along Australia. The way you describe the dangers of mining and ports makes me want to call this new threat the Coal of Thorns.

The Coal of Thorns may prove to be an even bigger threat - because it is something the reef has never seen and it is on an industrial scale that could threaten even this biggest biological structure on Earth. And all to help China pollute their own air! What happens after you build all these ports, you export the coal and China turns to their vast supplies of natural gas? Dead reef and a dead exporting business.

When the coral-eating Crown of Thorns began devastating the Reef in the 1960s, people tried everything to stop it. Folks picked them up by the thousands and burned them. They poisoned them. They fought them up and down the length of Australia. They would have loved to have the problem solved by simply passing a law.

This threat from coal is a problem created specifically by people. And it could be solved by people in a way that was never available for the starfish scourge – a simple sign of a pen could do away with this major threat.

This article was amended on October 28, 2014, to clarify the circumstances of the departure of the five former directors of the Great Barrier Reef Marine Park Authority.

Iain McCalman receives funding from Australian Research Council.

Stephen Palumbi receives funding from the U.S. National Science Foundation, the Gordon and Betty Moore Foundation and the David and Lucile Packard Foundation.

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

Has Queensland really saved lives by killing thousands of sharks?

By Jessica Meeuwig, University of Western Australia

One of the most common justifications for Western Australia’s shark cull is the longstanding use of baited hooks - or drum lines - in regions such as Queensland.

Two key questions need answering. First, is there clear evidence that drum lines reduce the number of human fatalities from sharks? And second, what is their cost in terms of killing marine wildlife?

To that end, I have analysed publicly available figures for human fatalities in Queensland with data on the program’s shark catch, to provide an assessment of its effectiveness.

Over more than half a century, the program has taken a large toll on wildlife, while any increase in human safety has been equivocal at best.

The Queensland cull

As of December 2013, there were 369 drum lines and 30 nets deployed off the Queensland coast, mostly near swimming beaches. The program has grown steadily since it began in April 1962 with the deployment of 24 drum lines on the Gold Coast; it now extends to Cairns across a total of ten regional areas.

Drum lines and shark catches graph Click here to open in new window.

Between 1853 and 2013 there were at least 71 human fatalities due to unprovoked shark attacks in Queensland, with the majority of these attributed to tiger sharks and only a single fatality to white sharks.

Queensland shark fatalities at beaches with drum lines graph Click here to open in new window.

During these 160 years, the average fatality rate varied. From 1850 to 1910 it was 0.32 fatalities per year, but then a spike in fatalities in the 1920s saw the average increase to 1.1 per year. After that, the rate of fatal attacks generally declined, falling to a low of 0.2 per year in the 1990s. Since 1962, when the drum line program began, the fatality rate has averaged 0.37 per year, a number not significantly different than that previous to the 1920s.

The graph shows that there has been a significant decline in Queensland’s rate of shark attack fatalities but that it started 40 years before drum lines were first deployed. There has been no further reduction in fatalities since the program began, despite half a century of increasing drum line deployments.

Note also that these statistics include fatalities in areas with and without drum lines. Of the 71 reported Queensland fatalities, 50 were in areas such as the outer Great Barrier Reef or Moreton Bay, where no drum lines (or nets) are present.

In areas without drum lines, the average fatality rate, calculated on a decadal basis, was 0.34 per year before 1970 (used as a cut off point given the 1960s saw only relatively few drum limes compared to the full program now implemented) and 0.24 afterwards. Even without drum lines, fatalities declined by 28% between these two periods.

In areas with drum lines, fatality rates fell from 0.05 to 0.02 fatalities per year pre- and post installation of the drum lines, a decline of 70%. This suggests that the fatality rate fell more rapidly in areas with drum lines than those without.

However, this result is deceptive. Of the seven locations with drum lines only (no nets), six had recorded only a single fatal attack prior to the installation of drum lines (ranging from 5 to 95 years before the lines were deployed). Only Kissing Point had a history of more than one fatality (in 1916, 1933 and 1955) before drum lines were installed in 1965. So for the most part, this apparently rapid decline represents the difference between one attack that could have occurred up to 95 years ago, and no attacks today at a limited number of sites.

This highlights the problems we face when trying to understand patterns in shark attacks and the effect of mitigation programs – fatalities are such rare events that differentiating between random coincidence and underlying patterns is fraught with difficulty.

What is the cost to marine life?

In contrast to their contribution to human safety, one thing we can be certain of is drum lines' ecological cost. The most recent available data show that Queensland caught some 6250 sharks on drum lines between 2001 and 2013, or an average of 480 animals per year.

This catch included 35 different species, the most common being tiger sharks (41%), bull sharks (17%) and black tip reef whalers (12%). White sharks, although considered a key target species in WA, represent less than 1% of the Queensland catch with about five caught per year.

Only 3% of the sharks killed on Queensland drum lines are considered not to be at conservation risk. According to the International Union for Conservation of Nature, four species, representing 5.2% of the catch, are “endangered”; nine species (9.6% of the catch) are "vulnerable”; and 15 species (80.6%) are classed as “near threatened”. Only six species (1%) are considered to be of “least concern”, while one species (2%) is considered “data deficient”.

Sharks longer than 3 metres have been classified as dangerous to humans, at least in WA. Yet only 11% of the animals culled in Queensland were larger than this – the average size of sharks captured on the drum lines was 1.9 metres.

In terms of reproductive maturity, all of the white sharks and most of the tiger and bull sharks that were caught were juveniles. As a key strategy for shark recovery is the protection of large breeding individuals, this may appear a reasonable outcome. But equally, juvenile deaths will ultimately reduce the future population of breeding adults.

What have we learned?

Based on this analysis, we can conclude that:

• Shark-related fatalities in Queensland have declined in both areas with and without drum lines, with the steepest rates of decline before their installation.

• The effectiveness of drum lines is difficult to evaluate, as the rates of attacks before and after their deployment are both very low. Moreover, 83% of drum lines are deployed at locations where a fatal attack has never occurred.

• The ecological cost of drum lines is high, with 97% of sharks caught since 2001 considered to be at some level of conservation risk, and 89% caught in areas where no fatalities have occurred.

Drum lines: a blunt tool

It could be argued that the drum line program in Queensland is justified simply because it may remove sharks from popular areas. However, it is a very blunt tool and ignores the important ecological roles that sharks play in our oceans.

Moreover, its success in reducing human fatalities is hard to validate. The decreases may simply reflect broader declines in shark populations, driving down encounter rates despite the increased human presence in the ocean. Or they may simply be random.

There are non-lethal techniques that can potentially achieve much better outcomes. Humans and sharks alike could benefit from an approach that embraces new ideas, rather than one that has produced little measurable effect in half a century, other than to kill threatened species.

Correction: data labelling in interactive maps was amended February 23.

Jessica Meeuwig does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

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