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Future of Great Barrier Reef divides scientists

Marine-park management comes under scrutiny as conservationists descend on Australia.

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Jurgen Freund/naturepl.com

The Great Barrier Reef is struggling to cope with the impacts of climate change and development.

The health of the world’s most famous swathe of ocean real estate — the Great Barrier Reef Marine Park — will take centre stage next week as conservationists from around the world head to Sydney, Australia, for a once-in-a-decade meeting on ecosystem management. The park faces challenges, but scientists disagree over how endangered it is and how well it is being managed. Climate change further complicates the picture.

Every ten years, the International Union for Conservation of Nature hosts the World Parks Congress to decide how to use parks to promote conservation (see page 28). On 12–19 November, a particular focus will be how to enhance and expand marine parks (see ‘Marine parks on trial’).Yet the Great Barrier Reef, which was once held up as a shining example of ecosystem management, has run into trouble.

Lying off the eastern coast of Australia, the park covers an area of ocean approximately the size of Germany, encompasses 3,000 coral-reef systems and is the largest ‘living structure’ on Earth. It is managed by the Great Barrier Reef Marine Park Authority (GBRMPA), which has divided it into zones that impose different restrictions on activities, such as scuba diving or fishing.

This year, protests escalated over a proposed port expansion that would have dumped dredge material within the park boundaries. The plan was abandoned but the United Nations Educational, Scientific & Cultural Organization (UNESCO) will next year be deciding whether damage done to the park through degradation and development means that it should be included on the List of World Heritage in Danger. In August, the GBRMPA itself published a report warning that “the overall outlook for the Great Barrier Reef is poor and getting worse”.

Marine parks on trial

The effect of marine park areas (MPAs) — parts of the ocean that are protected and managed for conservation — is difficult to tease out, not least because ocean ecosystems are affected by so many variables. Now, a study akin to a randomized controlled trial is aiming to do just that in the remote Bird’s Head Seascape in Indonesia.

Sitting in the ‘coral triangle’ north of Australia, the seascape contains more than 2,000 islands, many of which have remained undeveloped. Gabby Ahmadia, a marine scientist at the conservation organization WWF, has been searching for areas that can be used as controls for seven newly created MPAs within the Bird’s Head.

Distance from fishing markets and exposure to waves, for example, must be matched between a park and its control. Ahmadia’s team will then measure factors such as fish biomass to determine whether the park designation is making a difference. “We really need to get to the question of are these MPAs working, and, when they are working, why,” she says.

Among the evidence for problems is a much-cited 2012 study showing that coral cover had halved between 1985 and 2012 (G. De’ath et al. Proc. Natl Acad. Sci. USA 109, 17995–17999; 2012). The report placed much of the blame on cyclones and unusually large swarms of crown-of-thorns starfish (Acanthaster planci), which eat reef-building corals.

Some believe that much of the damage is temporary. Aaron MacNeil, who is studing the Great Barrier Reef at the Australian Institute of Marine Science in Townsville, points out that two huge cyclones — Hamish in 2009 and Yasi in 2011 — hit the reef in a particular way, producing a combined battering expected just once every 600 years. “I think in general the Great Barrier Reef is in pretty good shape but it has had a rough few years of storm activity that have left coral cover unusually low,” he says.

Others, however, say that things are worse than they seem. Marine palaeoecologist John Pandolfi at the University of Queensland in Brisbane has been using sediment cores and other methods to reconstruct the reef’s history over the past 1,200 years. “I am afraid that if you compare the current state of the reef to the kinds of long timescales that my team looks at, then things are even worse than what you might have heard,” he says.

Nature special: Protecting the planet

Pandolfi’s team has documented declines in Acropora corals, which are vital to the reef framework, that date back to the 1920s (G. Roff et al. Proc. R. Soc. B. 280, 20122100; 2013). The losses are probably linked to changes in agriculture that were brought in by European settlers and affected water quality and damaged the reefs. Current reports therefore may underestimate declines in reef quality because they are often based on comparisons to a degraded state of the reef, rather than its truly pristine state, an issue known as shifting baselines. The GBRMPA is using Pandolfi’s work to try and address this problem.

Modern pressures include the effects of nearby land development, such as run-off fertilizer from farming. Russell Reichelt, the GBRMPA’s chairman and chief executive, says that the threat from the proposed dredge dumping was overblown, but that the GBRMPA will encourage government and local businesses to adopt a policy whereby their activities have a positive net impact on the reef, not just a neutral one, as is the case now. It is also introducing targets for maintaining habitats and species as well as systems for assessing cumulative impacts.

Marine scientist Bob Kearney at the University of Canberra says that designating the reef as a marine park has fostered an “inappropriate” focus on fishing, given the bigger threat posed by climate change. The reef is highly sensitive to changing temperatures and ocean acidification, but global action is needed to tackle the carbon emissions that are the root cause of these issues. Similarly, last week, the Australian Academy of Science criticized a multimillion-dollar reef sustainability plan drawn up by the Australian and Queensland governments because it “fails to effectively address” any of the major pressures on the reef.

MacNeil is more optimistic, thanks to the current collaborative approach between the government, universities and the private sector to solving the reef’s problems. “By working together I think we’re in a better position to understand and address threats to the Great Barrier Reef than ever before,” he says.

Journal name:
Nature
Volume:
515,
Pages:
16–17
Date published:
()
DOI:
doi:10.1038/515016a

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