This long-read article is part of a series examining in depth the various threats to the Great Barrier Reef.
When the Great Barrier Reef was first placed on the World Heritage List in 1981, it was recognised as being home to a huge diversity of species, many of them threatened. Conserving the reef’s habitats would therefore be a great way to protect many different species all at the same time.
Naturally, some of these thousands of species have attracted more attention than others. Generally these are large animals with high tourism value – often called the “charismatic megafauna” – such as marine mammals, turtles, sea snakes, sharks, rays and seabirds. Many of these species are listed as either threatened or migratory under Australia’s environmental legislation.
Yet this hardly scratches the surface. Even counting only vertebrates, the Great Barrier Reef (GBR) boasts a diversity of species (see page 23 onwards here) that can be found in few other places on the planet. It features 1,625 species of bony fish, six of the seven marine turtle species, 30 whale and dolphin species, dugong, 20 breeding seabird species, and some 136 species of sharks and rays.
There are also hugely valuable places such as Raine Island, the world’s largest breeding location for green turtles, which also hosts breeding colonies of 14 seabird species and provides habitat for up to 20 shark and ray species.
Yet of these thousands of species, we only have data on population trends for a small few, and most species have never been assessed. There are nine species or species groups of marine vertebrates in the GBR – six are rated as being in poor condition and four have deteriorated since 2009.
The lack of specific data makes it hard to work out which species will be vulnerable to human-generated risks, and to decide on policies to safeguard them. And of the ones that have been assessed, the news is a mixed bag of good and not-so-good.
Good news stories
Humpback whales were hunted to near extinction in eastern Australia during the 1950s and early 1960s. Since whaling was banned in the early 1960s the population has recovered by an estimated 11% per year, and humpback and dwarf minke whales now support a multimillion-dollar whale-watching industry (see page 32 of the GBR Outlook Report).
Loggerhead turtles breeding in Queensland declined between the 1980s and 2000s as they were hit hard by egg predation and fishing bycatch. Combinations of land based-management, protected area designations and fisheries regulations (such as the 2001 requirement for turtle excluder devices) led to population recovery, although it has still not regained its original level.
Reef shark populations have declined in some areas, probably as a result of previous fishing pressures. However, there are early indications of recovery for some species since the rezoning of the GBR and fisheries management changes introduced in 2004. The public has also shown increasing awareness of the need for and value in sustaining healthy shark populations.
Sad news stories
Hawksbill turtles on the northern GBR are declining by around 3% per year. The key threats are international turtle hunting, and predation of eggs on Australian islands by native and introduced fauna. Without action, the population is forecast to decline by more than 90% by 2020.
Most sawfishes and the speartooth shark have seriously declined in abundance and distribution along the Queensland coast, with some species such as the green sawfish facing potential localised extinctions. Although these species are listed as protected species, they continue to be threatened by fishing and habitat loss and degradation.
Inshore dolphins such as the Australian snubfin and Indo-pacific humpback live in small, often isolated, local populations around the coastal areas of the GBR. Although there are no population size estimates for either species they are believed to be in decline and under considerable risk from human activities.
Dugong, despite being more abundant in the Torres Strait than anywhere else on Earth, are thought to be in decline in the southern GBR, according to aerial surveys, and there are concerns that declining sea grass abundance coupled with fisheries and boating related mortality are affecting the population.
Conserving homes and habitats
Rather than focus on individual species, it is perhaps easier to look at the broad habitat types where they live. The different habitats that cover the GBR World Heritage Area include islands, beaches and coastline, seagrass meadows, coral reefs, mangroves, the lagoon floor, shoals, halimeda banks, continental slope and open waters.
The GBR Marine Park Authority’s Outlook Report states that the condition of five of the ten habitat groups have deteriorated between 2009 and 2014, and for three habitats rated as “good”, their condition was inferred on the basis of limited evidence. Each of these habitats is important for many of the GBR’s most recognised species.
In particular, there have been well-documented declines in seagrass and hard coral cover across the World Heritage Area, particularly in the southern inshore region of the GBR. Additionally, coastal, estuarine and lagoon floor habitats are also affected by impacts from land-use changes such as coastal modification. Restoring the condition to these habitats is complicated and will take a long time. What’s more, when habitats change we have little idea of the longer-term flow-on consequences for many species.
There are still crucial unanswered questions: how do seagrass seeds disperse along the coast and between coastal bays? What is the abundance, distribution and status of key species (and new ones yet to be discovered)? How and why do coastal species move within and between coastal habitats and coral reefs?
How does bottom-trawling affect seafloor invertebrate species and the flow on impacts to turtles? What is the impact of high seas and International fisheries on the GBR’s marine turtles? How will marine mammals and other vertebrates react to underwater noise from human activities?
What can be done?
The Commonwealth and Queensland governments' Reef 2050 Long-Term Sustainability Plan, released earlier this year, is big on ambition but low on detail. Targets are well defined for water quality, having been the subject of much discussion. But for marine vertebrates and their habitats the targets are often generic, and there is no guarantee that there will be enough resources to do the necessary monitoring to make them any better.
Yet we believe there are several things that can be done. Several of the threatened and declining species are migratory, so one thing we can do is strengthen international cooperation through jointly funded conservation projects. We should also strengthen Indigenous partnerships for research and management, not just in the World Heritage Area but in the neighbouring Torres Strait and southeast Queensland.
We need to strengthen the transfer of knowledge between groups doing work on the ground and people in Government who make decisions. There also needs to be concerted effort and political will focused on reviving the integrated planning and management schemes designed to manage and protect the coastal ecosystems that drive and support coastal and reef dwelling species.
From the sheer volume of media discussion about issues such as the Abbot Point port redevelopment, it could be inferred that the people are uncertain about the government’s ability to safeguard the reef’s outstanding value. Community attitudes and support are vital for a healthy reef, and we believe that a concerted effort is needed to restore community confidence and engage the community in conservation efforts.
Meanwhile, we need to identify the species of highest priority. For each species or group of species we then need to understand the threats, work out how to manage them, and properly evaluate the effectiveness of management actions put in place to protect them.
It is unlikely that sufficient resources will be available to address each individual threat for each species or multi-species group, so we need to develop tools which allow decision makers to determine priority actions which when complete provide best conservation bang for buck.
Marine parks work, but are they generally too small to protect mobile or migratory species, so we will need to work out how to conserve species on larger scales.
Monitoring marine populations and habitats is always challenging, especially in near-shore regions with cloudy water, but if we are to save the valued animals of the Great Barrier Reef, we will need research, results, and a solid plan with realistic priorities on which we can rely on to obtain the best conservation outcomes.
Mark Hamann receives funding from the Australian Government's Marine and Tropical Sciences Research Facility and the National Environmental Research Program. He is affiliated with James Cook University.
Andrew Chin receives funding from the Australian Government Fisheries Research and Development Corporation, and is affiliated with the Center for Sustainable Tropical Fisheries and Aquaculture at James Cook University. He is an executive officer of the Oceania Chondrichthyan Society, a scientific organisation promoting the research and sustainable use of sharks and rays.
Authors: The Conversation