Dive in: exploring the Great Barrier Reef ecosystem
Issued: 13 May 2024 15 min read

There’s more to the Reef than meets the eye! Unlock the secret inner workings of this natural marvel and learn what is being done to help protect it.

Australia has no shortage of jaw-dropping natural wonders, but the Great Barrier Reef is up there as one of the true icons of our country – not to mention it’s the biggest living structure on the planet! When someone name-drops the Reef, the first thing that comes to mind is likely the vibrant coral, tropical fish, and adorable turtles that you see splashed all over the promotional material. Spoiler alert: the “famous” parts most folks are familiar with make up just 7% of the Great Barrier Reef. So, what’s the whole story?

The Reef is its own special world that we’re lucky enough to be able to enjoy – but there’s far more to this World Heritage site than you may realise. We’re here to give you the lay of the land (and water) – we’ll explain key aspects of the Great Barrier Reef ecosystem, outline some of its major threats, and keep you in the loop on what’s being done to protect this natural marvel.

    Green turtles are just one of thousands of animals that call the Reef home

    Why is the Great Barrier Reef an ecosystem?

    When we refer to the Great Barrier Reef, it’s natural to imagine it as one giant, monolithic entity. But just like any living thing, the Reef is made up of a bunch of individual components working together to help it thrive. This complex community of living organisms and their environment all interact differently. Let’s break down some of the key elements of the Great Barrier Reef ecosystem and how they play together.

    Biodiversity

    The Reef is home to an incredibly diverse array of marine life, including corals, fish, whales, dugongs, invertebrates, sea turtles, dolphins, sharks, and countless other critters. There are around 9,000 different species all sharing the same space, including 41 species of shorebirds and 20 nesting seabird species. This richness of biodiversity is a huge part of what makes the Reef so special.

    Connections

    The species and habitats within the Reef are interconnected in loads of different ways. For example, coral reefs provide habitat for fish and other organisms, while seagrass beds, mangrove forests, and other wetlands serve as nursery areas for young marine life. These habitats rely on each other to survive, forming a complex web of interactions. For example, fish species like barramundi and mangrove jack move between both freshwater and marine habitats in the Reef as part of their natural life cycle.

    Physical environment

    The Great Barrier Reef ecosystem includes not only the marine life within its waters but also the reef structure itself. Habitats in the Reef include wetlands, reef, seagrass and mangroves, and continental and coral islands. Factors like water temperature, salinity, currents, and sunlight all come into play as well, because they influence the distribution and behaviour of all living things in the Reef.

    Dynamic and adaptive

    Ecosystems are dynamic and constantly changing – environmental factors like climate, weather patterns, and human activities all play a part in how they operate. The Great Barrier Reef ecosystem is no exception – it is impacted by both natural and human-made disturbances like tropical cyclones, coral bleaching events, pollution, and climate change. While the Reef has bounced back before, like any living thing, it becomes harder to recover from frequent damage.

    Great Barrier Reef: Quick Stats

    World Heritage Area: 348,700 square kilometres.

    Width: The Reef ranges between 60 and 250 kilometres in width at different points.

    Length: The Reef stretches over 2,300 kilometres from the northernmost tip of Queensland, all the way down to the Mary River catchment south of Bundaberg.

    Depth: The Reef has an average depth of 35 metres in waters close to shore. On the outer reefs, continental slopes drop to more than 2,000 metres.

    Scale: The Reef is the world’s biggest single structure made by living organisms – so large in fact that it’s visible from space!

    Landscape: The Great Barrier Reef is made up of around 3,000 coral reefs, 600 continental islands, 150 inshore mangrove islands, and 300 coral cays – that’s a lot of real estate to protect!

    Great Barrier Reef map: your visual guide

    Open larger image

    This Scientific Consensus Statement map of the Great Barrier Reef gives a clear, concise overview of all the zones and boundaries.

    As with most large, complex environments, it’s much easier to understand the characteristics of the Great Barrier Reef when you break it down into sections. Below, we talk through the inshore areas, mid-shelf, and outer shelf of the Reef and their defining traits.

    Inshore marine area

    The inshore marine area refers to the nearshore areas closer to the mainland and continental islands. These are the spots with shallow waters, extensive seagrass meadows, coral reefs, and abundant marine life – it's an important area for juvenile fish, turtles, and dugongs. The inshore marine area is a go-to spot for recreational activities like fishing and boating, largely thanks to its accessibility and diverse marine habitats.

    Mid-shelf area

    The mid-shelf area is the filling in the sandwich – it lies between the inner and outer reef zones and encompasses a range of habitats, including patch reefs, “bommies” (isolated coral formations), and seagrass meadows. This zone supports a vast array of marine species and serves as an important habitat for juvenile fish and other marine organisms.

    Outer shelf area

    Farther from the mainland and along the edge of the continental shelf, you’ll find the outer shelf area of the Reef – the offshore areas that attract snorkellers, divers, and those keen to spot some beautiful seascapes. These areas typically have deeper waters and expansive coral reef systems, including large barrier reefs and atolls. The outer reef is known for its pristine coral formations, clear water visibility, and biodiversity.

    North and South

    Due to the sheer length of the Reef, its top and bottom sections have their own distinct features. The northernmost reaches closest to the Torres Strait are characterised by warmer waters and greater coral diversity. The spots down the bottom closer to Bundaberg get cooler temperatures and thus attract more temperate-loving marine life.

    Surrounds

    The Reef’s environment doesn’t stop at the water’s edge – there are coastal areas including wetlands, islands, and mainland regions of Queensland that are all part of its ecosystem. These areas provide safe havens for wildlife, including nesting sites for seabirds and shorebirds, breeding grounds for marine turtles, plus mangrove forests and freshwater wetlands that act as nurseries for fish and other marine species. These connective areas also allow for movement between marine and freshwater habitats, which is vital for fish like barramundi that rely on both.

    Impact beyond the borders

    Don’t get us wrong – zoning is vital to help people identify and understand the most vulnerable parts of the Reef. However, human activity outside of the boundaries of the Reef still has an immense impact on the area’s overall health. You don’t have to be dropping an anchor next to a dugong to be doing damage – land-based things like urban development and agriculture all affect the Reef to different degrees. So, with all that considered, what are the things doing the most damage to the Reef?

    Rising sea temperatures are causing some coral in the Reef to lose its famously brilliant colours.

    Major threats to the Great Barrier Reef ecosystem

    With so many delicate parts at play, it’s understandable that the Great Barrier Reef is vulnerable to threats that throw off its natural balance. There are four main areas that these issues fall under, but this is by no means an exhaustive list.

    Climate change

    It’s no secret that rising temperatures are a big stressor for the environment, but climate change is having a particularly harsh effect on the Reef. A current and immediate threat caused by rising sea temperatures is coral bleaching, where corals expel the algae living within their tissues – this causes them to turn white and become vulnerable to disease and death. Climate change also contributes to ocean acidification, which can weaken coral skeletons and stunt coral growth.

    Land-based runoff

    The main water quality pollutants in land-based run-off that pose a threat to the Reef are primarily from agricultural activities. Excess nutrients from fertilisers and urban sewage that make their way into the water can fuel algal growth. This leads to outbreaks of harmful algae that smother corals and disrupt Reef ecosystems. Sedimentation caused by erosion from grazing lands can also suffocate corals and reduce the lighting levels needed for coral growth. The greatest impacts are on freshwater, estuarine, coastal, and inshore marine ecosystems.

    Coastal development

    Coastal development activities like dredging, land reclamation, and construction can directly damage coral reefs and seagrass beds, as well as mess with critical habitat connectivity and water flow patterns. Increased coastal development also leads to habitat loss and fragmentation, which can make Reef ecosystems more vulnerable to other threats.

    Impacts from fishing

    Overfishing and illegal fishing practices can reduce fish stocks, disrupt food webs, and damage delicate reef habitats. Unsustainable fishing practices and the use of destructive fishing gear like gillnets can directly harm coral reefs and other marine life. Targeted species, like herbivorous fish, play vital roles in maintaining Reef health by grazing on algae and controlling seaweed growth – so when their populations decline, the whole balance of the ecosystem is thrown off.

    Let the barracudas bask! Sustainable fishing practices are a must for protecting the delicate Reef ecosystem.

    What is being done to protect the Great Barrier Reef?

    While there’s no denying that the Great Barrier Reef has a vulnerable status, all hope is not lost. The Traditional Owners of the land and sea, governing bodies, landholders, and independent wildlife foundations are working together to conserve and protect the Reef. Below, we detail some of the most important actions that have come from The Reef 2050 Water Quality Improvement Plan – think of it as a roadmap to Reef health.

    Gillnet bans

    All of the threatened, endangered, and iconic species that call the Reef home need protection. The Australian and Queensland governments are joining forces to phase out harmful gillnets and implement sustainable fishing practices. This will lead to a safer environment for some of the Reef’s most vulnerable species.

    Water quality improvement

    How do we solve the issue of land-based runoff? A big part of this is addressed in the Reef 2050 Water Quality Improvement Plan. This document unifies industry, government, and the community to strive for a common goal – improving the quality of water running into the Reef. The Plan takes a four-pronged approach: to improve land management practices, support innovation, restore catchments, and improve the science and knowledge surrounding solutions.

    What is the Reef 2050 Water Quality Improvement Plan?
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    A short summary of the plan to improve Great Barrier Reef water quality Visit www.reefplan.qld.gov.au for more information.

    Climate change action

    The risks posed by climate change go far beyond the Reef, so it makes sense to invest in limiting its impact as much as possible. The Reef 2050 Long-Term Sustainability Plan brings climate action into the spotlight – there’s a distinct focus on reducing emissions on a global scale, as well as creating pathways for the Reef to adapt. The Queensland Government has also committed to emission reduction targets of 75% by 2035 and net zero by 2050 enshrined in legislation.

    An international approach

    It’s not just up to Australia to keep the Reef safe – the responsibility also falls on the international community. Part of the Reef Plan is to work on international conventions, treaties, and initiatives to decrease plastic litter and pollutants reaching the ocean, which eventually become marine debris in the Reef. Australia is also working on a global scale to protect critical habitat for migratory species like whales, dugongs, marine turtles, sharks, and shorebirds that rely on the Reef during their migrations.

    Laws that protect the Great Barrier Reef

    Want to know what the government is doing to keep the Reef safe? Here’s your cheat sheet for all the legislation that’s currently in place to protect this global icon. We’ve provided brief explainers of the laws, but you can click the links provided for more in-depth info.

    Don’t forget your reusable items! Cutting down on single-use plastics is a quick win for Reef health

    What can you do to help the Great Barrier Reef?

    When it comes to taking action on large-scale environmental issues, it’s natural to feel a bit powerless – can we really affect change on an individual level?

    The answer is YES!

    We’ve rounded up some ideas of small things you can do that have a big impact on not just the Reef’s health, but our natural environment as a whole.

    Tackle your plastic problem: Did you know that around 8 million tonnes of plastics leak into the ocean each year? Cutting down your own plastic use – and encouraging others to do the same – can help make a dent in this intimidating figure. Where possible, ditch single-use plastic and make the swap to reusable items. It’s also worth brushing up on your recycling do’s and don’ts – effective recycling is a crucial step in addressing big-picture issues like climate change and natural resource conservation.

    Buy responsibly sourced seafood: Choose sustainably sourced seafood to reduce pressure on fish stocks and marine ecosystems. Our tip? When shopping, look for the blue Marine Stewardship Council (MSC) or green Aquaculture Stewardship Council (ASC) ticks of approval on any seafood product labels.

    Look for the ASC or MSC ticks of approval to make sure your seafood is sustainable.

    Educate others: Knowledge is power! Educating yourself and spreading awareness about threats to the Reef and getting others on board to take action can help immeasurably – not to mention it feels really good to see people get behind such a great cause.

    Follow reef-friendly travel advice: If you’re keen to see the Reef in person, choose eco-friendly tour operators and activities that prioritise reef conservation and responsible tourism practices. Keep your hands to yourself – avoid activities that harm the Reef, like anchoring on coral or touching marine life.

    Get involved: Getting hands-on is one of the best ways to help save the Reef. Join volunteer programs, citizen science projects, or conservation organisations focused on protecting the Great Barrier Reef. Participate in reef monitoring, restoration efforts, or community events that promote reef conservation and stewardship.

    Take only photographs: When you visit the Reef, be careful not to step directly on soft corals and don’t take coral or shells home as souvenirs - these all play a role in the Reef’s ecosystem and need to stay where you found them!

    A future to strive for

    There’s only one Great Barrier Reef – and it’s everyone’s responsibility to take care of it. By taking the advice of the Traditional Owners of the land and sea, conservation specialists, and the government, we can work together to repair and protect this precious natural wonder.

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