Coral structures that are a part of the Great Barrier Reef can be seen above the water reef surfaces The largest jewel in this necklace of teeming underwater cities is Australia’s Great Barrier Reef Roughly the size of Germany or half as big as Texas the Great Barrier Reef GBR can be easily seen from space The GBR is the world’s largest barrier reef and the world’s largest living structure It stretches along the northeastern coast of the Australian state of Queensland reaching 1,400 miles 2,300 km from north of Cape York peninsula down south almost to Brisbane The Great Barrier Reef Marine Park which contains and protects the GBR is between 40 and 155 miles 60 and 250 km wide and covers an area of nearly 133,000 square miles 344,000 sq km Its treasures include approximately 3,000 individual reefs and more than 1,000 islands 1 6
The GBR is not only a region of unsurpassed beauty it is also essential to Australia’s life and economy The Australian government protects and manages the GBR through the Great Barrier Reef Marine Park Authority The reef is zoned to allow different sustainable human activities including tourism fishing boating and commercial shipping in different areas of the park Tourism commercial fishing and recreational fishing on and around the reef add 6 9 billion in Australian dollars to the Australian economy every year 2 These industries support approximately 70,000 jobs 3 But this vibrant community is dying Many scientists think it is already doomed The Great Barrier Reef Marine Park which contains and protects the Great Barrier Reef is the size of 70 million football fields 4 BIODIVERSITY OF THE GBR From the air one can see the jagged structures of the GBR curve around the coast of Australia lighter in color than the surrounding water Occasional islands break the surface The structures are masses of hard corals plus sponges and other organisms The corals produce their own hard skeletons of calcium carbonate or limestone The reef has more than 600 species of corals Some are reef-building hard corals Others are soft corals such as sea fans Living coral polyps contain single-celled algae The algae use photosynthesis to provide themselves and the polyps with energy These symbiotic algae plus the reef’s free-living algae support the ecosystem’s food web In deeper waters where the sun can’t reach hard corals cannot build massive reef frameworks but near shore sunlight and therefore reefs extend down to an average depth of 115 feet 35 m The reefs support an ecosystem of amazing complexity 7
Living among the sessile or attached corals are more than 100 species of jellyfish 3,000 species of mollusks 500 species of worms 1,625 species of fish including 133 types of sharks and rays and more than 30 species of dolphins and whales 5 Six of the world’s seven sea turtle species visit the GBR Raine Island in the GBR is the world’s largest breeding site for green turtles At least 242 bird species visit the GBR many of them breeding on the cays and islands 6 The teeming brightly colored life of the coral reef is more diverse than any ecosystem on Earth except the tropical rain forest But the Great Barrier Reef is changing rapidly THE GBR AND CLIMATE CHANGE The major threat to the Great Barrier Reef is climate change a complex process with multiple effects Two effects are especially dangerous to the reef rising temperatures and increasing acidity in the ocean The most visible impact is coral bleaching or whitening caused by high temperatures which puts stress on corals Temperature-stressed corals expel their THE GBR FROM SPACE Reefs along the GBR reach upward from the shallow seafloor The skeletons within the reefs are interconnected by their calcium carbonate structures Corals form most of the reef but trillions of tiny pink coralline algae also secrete calcium carbonate and help cement the reef together This true-color image of the GBR taken by NASA’s Terra satellite on August 26 2000 shows part of the central portion of the reef near the Queensland coast zooxanthellae the tiny algae that live inside their tissues Zooxanthellae keep the corals alive their photosynthesis produces most of the corals food Corals can recover from short periods of increased temperatures but if the heat continues they die An increase of only 8
1 8 to 2 7 degrees Fahrenheit 1 0 to 1 5 C for six weeks results in extensive coral bleaching followed by death unless reef temperatures quickly return to normal 7 Since 1979 the GBR has experienced eight mass bleaching WHAT IS BIODIVERSITY Biodiversity or biological diversity refers to the variety of living organisms in an ecosystem Biodiversity encompasses variety in the species present the genes they contain and the ecosystems they live in The GBR is biodiverse in all of these ways Biodiversity is essential ecologically because it helps stabilize an ecosystem Biodiverse ecosystems are productive healthy self-sufficient and better able to overcome disasters If part of an ecosystem sickens or dies high biodiversity allows the rest to survive and restore the system events as a result of increasing temperatures Two very bad years were 1998 and 2002 During those two years 42 and 54 percent of the reefs respectively were bleached Then during the years 2015 2016 the most extreme bleaching event ever recorded on the GBR occurred Researchers reported that 93 percent of the reefs especially those in the northern region suffered from some level of bleaching 8 All of these bleaching events were associated with an El Niño event a periodic weather pattern that brings warmer-than-average water to the Pacific Ocean When combined with global warming El Niño events result in major bleaching during that year or the next The 1997 1998 El Niño was the strongest in recorded history and the 2015 2016 event was a close second The 2002 weather pattern was moderately strong If the water cools sufficiently reefs may rebound but many corals especially old slow-growing ones take decades to recover In early 2016 divers near Cape York at the reef’s northeastern tip discovered that half of the corals had already died and a full 75 percent in the reef’s northern half were damaged 9 Over the hot still summer the reefs 9
