The Great Barrier Reef (GBR) is the largest coral reef system in the world, extending for about 2000 kilometres along the northeast coast of Australia. The site got inscribed as a World Heritage Site by UNESCO in 1981. It is home to various tropical marine habitats, including coral reefs, seagrass meadows and extensive mangrove forests. It is one of the few living structures visible from space, appearing as a complex string of reefal structures along Australia's northeast coast. The Great Barrier Coral Reef is the richest and most complex natural ecosystem on our planet. It serves as a habitat for species like the dugong (sea cow) and the giant green turtle.
According to the latest IUCN World Heritage Report, the site has been identified as critical, and its condition has been deteriorating since its inscription. Some of the significant threats faced by the GBR are changes in the oceanic waters, shipping, fishing and oil spills. The rising sea surface temperature is responsible for the threat to the survival of many marine species. Coral bleaching, a result of climate change, has occurred in half of the coral population. The Great Barrier Reef Marine Park Act 1975, amended in 2007 and 2008, is aimed at the long-term conservation of the GBR. The Reef 2020 Long-Term Sustainability Plan (2050 LTSP) implemented in 2016 aims to protect the site's Outstanding Universal Value. The management authority (the Great Barrier Reef Marine Park Authority or GBRMPA) has taken extensive measures for the protection and management of the site.
The Great Barrier Reef, located (180 17' 10" S and
1470 41' 60" E) off the east coast of the Queensland
mainland, Australia, is one of the earliest sites to
be inscribed in the world heritage list and is one of
the seven wonders of the natural world. The entire
ecosystem, covering 348,000 square kilometres,
inscribed as the world heritage in the year 1981, is the
most extensive collection of coral reefs globally and is
one of the most complex natural ecosystems on Earth.
The Great Barrier Reef (GBR) has around 2,500 individual reefs of varying sizes and shapes; over 900 islands which can be a small sandy cays or larger vegetated cays to large rugged continental islands, which may rise to 1,100 meters above sea level. The site is home to a unique array of ecological communities, habitats, and species, and the reason for this is the latitudinal and cross-shelf diversity accompanied by the diversity through depths in the water column. The Great Barrier Reef is one of the richest and most complex natural ecosystems on earth. The site consists of various tropical marine habitats, consisting of around 20,000 km2 of coral reefs, -43,000 km2 of seagrass meadows, and extensive mangrove forests (Kroon et al. 2016). The GBR has vibrant biodiversity comprising around 1500 species of fish and more than 400 species of hard corals. More than 4000 species of molluscs and 400 sponges are present in this region (Great Barrier Reef Marine Park Authority 2014). The Great Barrier Reef's inscription on the World Heritage List recognizes the global significance of its species diversity. It is a site of great scientific interest since it serves as a habitat for certain species like Dugong (Sea cow) and the giant green turtle, which are threatened with extinction (Great Barrier Reef Outlook Report 2019). The Northern areas of the park the dugong population is good and stable but in some areas, from 1962 to 1999 there has been severe decline in the dugong population (Marsh et al. 2005).
The GBR is of superlative natural beauty above
and below the water, and provides some of the most
spectacular scenery on earth. It is one of a few living
structures visible from space, appearing as a complex
string of reefal structures along Australia's northeast
coast.
From the air, the vast mosaic patterns of reefs, islands and coral cays produce an unparalleled aerial panorama of seascapes comprising diverse shapes and sizes. The Whitsunday Islands provide a magnificent vista of green vegetated islands and spectacular sandy beaches spread over azure waters. This contrasts with the vast mangrove forests in Hinchinbrook Channel, and the rugged vegetated mountains and lush rainforest gullies that are periodically cloud-covered on Hinchinbrook Island. On many of the cays there are spectacular and globally important breeding colonies of seabirds and marine turtles, and Raine Island is the world's largest green turtle breeding area. On some continental islands, large aggregations of over-wintering butterflies periodically occur.
Beneath the ocean surface, there is an abundance and diversity of shapes, sizes and colours; for example, spectacular coral assemblages of hard and soft corals, and thousands of species of reef fish provide a myriad of brilliant colours, shapes and sizes. The internationally renowned Cod Hole near Lizard Island is one of many significant tourist attractions. Other superlative natural phenomena include the annual coral spawning, migrating whales, nesting turtles, and significant spawning aggregations of many fish species.
The GBR, extending 2,000 kilometres along
Queensland's coast, is a globally outstanding example of
an ecosystem that has evolved over millennia. The area
has been exposed and flooded by at least four glacial
and interglacial cycles, and over the past 15,000 years
reefs have grown on the continental shelf. During glacial
periods, sea levels dropped, exposing the reefs as flattopped hills of eroded limestone. Large rivers meandered
between these hills and the coastline extended further
east. During interglacial periods, rising sea levels caused
the formation of continental islands, coral cays and new
phases of coral growth. This environmental history can be
seen in cores of old massive corals.
Today the GBR forms the world's largest coral reef ecosystem, ranging from inshore fringing reefs to midshelf reefs, and exposed outer reefs, including examples of all stages of reef development. The processes of geological and geomorphological evolution are well represented, linking continental islands, coral cays and reefs. The varied seascapes and landscapes that occur today have been moulded by changing climates and sea levels, and the erosive power of wind and water, over long time periods. One-third of the GBR lies beyond the seaward edge of the shallower reefs; this area comprises continental slope and deep oceanic waters and abyssal plains
The globally significant diversity of reef and island morphologies reflects ongoing geomorphic, oceanographic and environmental processes. The complex cross-shelf, longshore and vertical connectivity is influenced by dynamic oceanic currents and ongoing ecological processes such as upwellings, larval dispersal and migration.
Ongoing erosion and accretion of coral reefs, sand banks and coral cays combine with similar processes along the coast and around continental islands. Extensive beds of Halimeda algae represent active calcification and accretion over thousands of years.
Biologically the unique diversity of the GBR reflects the maturity of an ecosystem that has evolved over millennia; evidence exists for the evolution of hard corals and other fauna. Globally significant marine faunal groups include over 4,000 species of molluscs, over 1,500 species of fish, plus a great diversity of sponges, anemones, marine worms, crustaceans, and many others. The establishment of vegetation on the cays and continental islands exemplifies the important role of birds, such as the Pied Imperial Pigeon, in processes such as seed dispersal and plant colonisation.
Human interaction with the natural environment is illustrated by strong ongoing links between Aboriginal and Torres Strait Islanders and their sea-country, and includes numerous shell deposits (middens) and fish traps, plus the application of story places and marine totems
The enormous size and diversity of the GBR means it is one of the richest and most complex natural ecosystems on earth, and one of the most significant for biodiversity conservation. The amazing diversity supports tens of thousands of marine and terrestrial species, many of which are of global conservation significance.
As the world's most complex expanse of coral reefs, the reefs contain some 400 species of corals in 60 genera. There are also large ecologically important inter-reefal areas. The shallower marine areas support half the world's diversity of mangroves and many seagrass species. The waters also provide major feeding grounds for one of the world's largest populations of the threatened dugong. At least 30 species of whales and dolphins occur here, and it is a significant area for humpback whale calving.
Six of the world's seven species of marine turtle occur in the GBR. As well as the world's largest green turtle breeding site at Raine Island, the GBR also includes many regionally important marine turtle rookeries.
Some 242 species of birds have been recorded in the GBR. Twenty-two seabird species breed on cays and some continental islands, and some of these breeding sites are globally significant; other seabird species also utilize the area. The continental islands support thousands of plant species, while the coral cays also have their own distinct flora and fauna.
The Great Barrier Reef has been identified as
a critical site according to the IUCN World Heritage
Outlook Report, 2020. The values for which the site had
been inscribed have decreased considerably in the past
years. Half of the coral cover has been destroyed in the
past 40 years (Hughes et al. 2015). The GBR has a very
large number of tourists every year, but the tourism is
concentrated to only 7% of the area. Marine tourism in
the area is well established with planning, policy and
permit systems in place (Great Barrier Reef Outlook
Report 2019). The number of tourists visiting the region
has been reduced since Cyclone Debbie hit the site in
2017, and this has led to a massive clean-up in the GBR.
Commercial marine tourism can threaten the ecosystem and heritage values. Defence activity in the region has also caused damage to this critical ecosystem. The ecological damage includes injury or disruption to marine life, discharge of sewage and other wastes in the water body, oil spills and risks due to defence training exercises in this area (Great Barrier Reef Outlook Report 2019). Fishing, both recreational and commercial, is one of the most common activities in this region. It severely impacts the ecosystem in the region. Illegal fishing continues to add burden to the already deteriorating ecosystem. In order to aim for a sustainable fishing in the region, the Australian and Queensland governments are taking a collaborative approach to fisheries management. The fishing practices and management continue to improve in the region (Great Barrier Reef Outlook Report 2019).
Shipping is a major factor causing damage and pollution in the region including physical damage and pollution from toxic anti-fouling paint, oil spills and sediment release from propeller wash, damage to the sea floor due to anchorage, illegal discharge of garbage in the sea, and noise and light pollution. Whales get stuck in the ship, and this is responsible for around 15% of the whale strikes occurring in Australian waters reported to the International Whaling Commission (547 totally reported worldwide up to 2010) (Peel et al. 2018)
The Great Barrier Reef Marine Park Act 1975 was
amended in 2007 and 2008, for the long-term protection
and conservation of the site. The Reef 2020 Long-Term Sustainability Plan (2050 LTSP) was implemented in
2016 on the recommendation of the World Heritage
Committee for sustainable development to protect the
Outstanding Universal Value of the GBR. This has been
a significant step in providing a framework for the site's
management and addressing the multiple threats it is
facing; however, the progress towards achieving the
targets has been slow and is not enough to prevent
the decline of the site (IUCN World Heritage Outlook
2020). A recent amendment to the Federal Environment
Protection and Biodiversity Conservation Act 1999
(EPBC) makes the GBR Marine Park an additional 'trigger'
for a matter of National Environmental Significance
which provides additional protection for the values
within the GBR. Despite the overall good management
practices, there has been a significant decrease in some
of the iconic species and habitats, though there have
been some achievements like the increase in the water
quality and the rise in the population of humpback
whales.
