Deteriorating Reefs

The latest report on the Great Barrier Reef is full of warnings, but if action is taken now damage can be limited

In a massive 374-page report published last August — the third in a series of 5-yearly assessments that began in 2009 — the Great Barrier Reef Marine Park Authority (GBRMPA) assessed our precious marine icon and declared it to be in “very poor” condition, with a grim outlook of further deterioration. The GBRMPA is Australia's lead manager of the reef, responsible for preserving its natural splendour and maintaining the universal values that underpin its World Heritage status. 

SCOPE AND PURPOSE OF THE REPORT

The report is based on evidence from a number of Australian and Queensland government agencies, research institutions, industry stakeholders and Traditional Owners. It examines nine key aspects including biodiversity, ecosystem health, heritage values, resilience and risks, to provide an assessment of the reef’s overall condition and a summary of its long-term outlook.

PREVIOUS REPORTS 

Outlook Reports were released in 2009 and 2014. In 2009, the reef was considered to be “at a crossroads” between a positive, well-managed future and a less certain one. In 2014, it was seen as “an icon under pressure”, with continued efforts needed to address key threats. Since then, the region has further deteriorated. 

BIODIVERSITY

Biodiversity, the variety of all living things in a given area, is measured by the number of species or groups of organisms. This region is one of the most diverse and remarkable ecosystems in the world, not only for containing the largest coral reef system but also for providing habitats for an astonishing number and variety of species — 600 types of soft and hard corals, more than 100 species of jellyfish, 3,000 varieties of molluscs, 500 species of worms, 1,625 types of fish, 133 varieties of sharks and rays, and more than 30 species of whales and dolphins.

In the report, biodiversity was assessed in terms of habitats and populations of species. Due to the vast size of the region and the broad range of habitats within it, not all habitats or species have been affected equally.

Coastal habitats, including mangroves, islands, mainland beaches and coastlines, remain in good condition. Lagoon floors, shoals and the water column are rated good but have deteriorated due to high sea surface temperatures (caused by global warming) and severe cyclones. The water column has deteriorated in some inshore areas due to land-based run-off and is rated good but borderline poor.

Overall, however, habitats are assessed as being in poor condition across the region and two key habitats — seagrass meadows and coral reefs — are rated as poor and very poor, respectively. Seagrass meadows are one of the most important habitats in the region and have not recovered as quickly as expected since disturbances in 2011–12. Record-breaking sea surface temperatures and localised flood plumes in the summers of 2016 and 2017 caused severe coral bleaching in the northern two-thirds of the reef, leading to a downgrading of the condition of that habitat to very poor for the first time in the history of Outlook reporting. 

Habitat loss and degradation have substantially affected many populations of dependent species. The majority of species have declined throughout the region, with over half of those assessed being in poor or very poor condition. There are a few instances where species have improved in condition. Humpback whales and the southern green turtle population continue to recover strongly, and the breeding rate of dugongs has improved since cyclone Yasi and floods in 2011.

ECOSYSTEM HEALTH

An ecosystem is a community of organisms interacting with each other and with the environment in which they live. An ecosystem is considered healthy if it is able to maintain its structure and function in the face of external pressures. The health of the reef ecosystem depends on a range of physical, chemical and ecological processes, the health of connected coastal ecosystems, the impact of disease and pest outbreaks.

Since 2014, acute and chronic disturbances, such as record high sea temperatures and poor water quality, have contributed to an overall decline in ecosystem condition. Of the 31 health indicators assessed, about 40 per cent are in poor to very poor condition.

Above-average annual sea surface temperatures have been observed in the reef every year since 2012, underpinning the deterioration of this factor from poor to very poor. The marine heatwave during the late summer of 2020 produced record sea surface temperatures (SSTs) 2–3 degrees above average across large areas of the reef south of Port Douglas. At the time of writing, heat stress was building across the inshore central and southern reef with reports of coral bleaching occurring in popular tourist locations. Around Magnetic Island, for example, SSTs peaked at 31.7 degrees causing partial bleaching of 65 per cent of coral colonies and giant clams. The pattern matches conditions in 2016 and 2017 that produced back-to-back bleaching events, killing about half the reef’s corals. Water temperatures have since increased so dramatically some analysts were declaring the reef is at the threshold of the most widespread coral bleaching ever seen. 

Ocean salinity within the reef has remained stable and in good condition, largely as a result of low rainfall. However, ocean pH has decreased (become more acidic) making calcifying organisms, such as corals, more brittle and at greater risk of breakage from strong waves. Nutrient cycling continues to be affected by land-based run-off and remains in poor but stable condition. 

Coastal ecosystems that support the reef remain in poor condition overall. The reduction of pollutant loads has been slow, reflecting modest improvements in agricultural land management practices. Deforestation of river catchments, primarily for grazing pastures, continues to increase, contributing to soil erosion and sedimentation of inshore waters through floods and land-based run-off.

The incidence of crown-of-thorns starfish has persisted and gradually spread south for almost a decade, to reefs off Innisfail and Townsville, causing significant coral damage across affected areas.

HERITAGE VALUES

The reef’s heritage values are assessed against natural (world and national), Indigenous, historic and other (social, aesthetic and scientific) criteria. Many of these values are closely tied to the condition of the ecosystem. Overall, many heritage values remain in good condition, with the exception of Indigenous heritage and some aspects of historic heritage, which are assessed as poor.

The reef was inscribed on the World Heritage List in 1981 and included on the National Heritage List in 2007. While the reef remains whole and intact, its condition has deteriorated to varying extents with respect to several criteria for which it was inscribed. One criterion — habitats for the conservation of biodiversity — is assessed as poor, and the overall assessment of the reef’s world and national heritage values is rated good to borderline poor.

RESILIENCE

Ecosystem resilience is the capacity of a system to absorb disturbance and reorganise to retain essentially the same structure and functionality — how well it responds to, withstands, adapts to and recovers from disturbances. The resilience of the reef ecosystem can’t be measured directly but is assessed through a series of case studies, continued from previous reports, focussed on coral reefs, lagoon floor habitats, sea cucumber, coral trout, loggerhead turtles, dugongs and humpback whales.

Some species — sea cucumber, loggerhead turtles and dugongs — show continuing recovery from past impacts, with assistance from significant management intervention. Humpback whales have demonstrated the greatest resilience by continuing to recover strongly since harvesting ended outside the region. Estimates now place populations between 58 and 98 per cent of pre-whaling numbers.

In contrast, the resilience of coral reefs has deteriorated from poor to very poor. Although the reef has bounced back from many disturbances in the past, the overall trend for coral reef habitats within the region is one of long-term, possibly irreversible, decline. Reef resilience is being severely compromised by global warming, which has deprived the reef of sufficient time for coral communities to recover between acute events. The increasing frequency and severity of some threats are also likely to reduce the resilience of dependent species, such as coral trout which are also in decline. As climate change accelerates, recovery windows will shrink, and the effects of other pressures will be amplified.

RISKS TO THE REGION

The report systematically reviews the current and future risks presented by known threats and summarises the residual risk to the region after consideration of existing protection and management measures. 45 threats are considered in the assessment, four of which have been added since 2014. 10 threats identified in 2014 as presenting a very high risk are again rated as very high. The overall risk to both ecosystem and heritage values has increased since 2014 and is now rated as very high.

Many of the threats with the highest risk levels originate outside the region, weakening the effectiveness of management to deal with them. The single most pervasive and persistent threat, continues to be climate change, manifested in increased sea temperatures, altered weather patterns, ocean acidification and rising sea levels. All are expected to become increasingly severe. Other threats posing a high risk are land-based run-off (water quality), coastal development and some aspects of direct use (particularly fishing). 

The risk level has increased for seven other threats: altered ocean currents, artificial light, damage to reef structure, extraction of particle feeders, illegal activities (not including illegal fishing and poaching), grounding of small vessels and wildlife disturbance. Only one risk has decreased since 2014 — the risk posed by disposal of dredge material, which has decreased from high to medium because of new management measures that restrict disposal of material from capital dredging.

While threats are assessed individually, they do not operate in isolation. Not only is the direct influence of each threat significant, they have the potential to exacerbate and amplify the impact of other threats. There is a real and present danger that the combination of threats present will continue to weaken the Reef’s ability to recover from serious and increasingly frequent environmental disturbances.

RESPONSE TO THE REPORT

Since the report was released, environmentalist groups have called for greater global action to tackle the climate crisis, and for the Great Barrier Reef to be given extra protections.

Imogen Zethoven, director of strategy for the Australian Marine Conservation Society, said, “We've had 10 years of warnings, 10 years of rising greenhouse emissions and 10 years watching the Reef heading for a catastrophe. We can turn this around, but only if the prime minister cares enough to lead a government that wants to save it. And saving it means being a leader here and internationally to bring greenhouse gas emissions down.”

Richard Leck, from WWF Australia, said the outlook report was a sombre reminder of challenges facing the reef. He said solutions were available and must be included in a revamped Reef 2050 Plan due from the federal and Queensland Labor state governments next year. “The plan must take climate change seriously and Queensland needs to pass regulations to reduce farm runoff,” he said.

Leeanne Enoch, Queensland Minister for Environment and the Great Barrier Reef, said “A range of actions are underway to improve reef resilience — from ramping up compliance in no-take areas to tackling the outbreak of coral-eating crown-of-thorns starfish at high value sites to improve coral cover. These and other management actions are having a real, measurable and positive impact on the Great Barrier Reef now, and we need to continue to invest in these areas.”

Referring to the Australian Government’s $1.2 billion funding commitment, including the launch of a $6 million “Reef Resilience” vessel, Federal Environment Minister Sussan Ley said steps were already being taken to address the challenges. “This is an outlook we can change and are committed to changing,” she said.

LONG-TERM OUTLOOK

The reef has fundamentally changed since 2009. The overall condition for the region’s ecosystem has become very poor and, without timely and effective action, the current long-term outlook is for continued deterioration.

The threats to a healthy and resilient ecosystem are increasing, compounding and expanding in scale, driven strongly by climate change. Actions to address all threats are imperative. The time to influence the reef’s long-term future is now. Specifically, early and effective global and national action to mitigate climate change, coupled with local actions to maintain condition and facilitate recovery, are needed urgently if the reef is to attain a positive long-term outlook.

Despite the seriousness of the challenges facing the region, there is hope for its recovery. All actions that promote recovery and limit further decline will improve the region’s long-term outlook. It is important not to lose optimism by thinking the job is too big, or to think that a changed reef is far in the future — actions taken now will matter.

A full copy of the report is available online at gbrmpa.gov.au.