2018 is the third International Year of the Reef and we should be celebrating the beauty and benefits brought to us by the planet’s healthy coral reefs. Unfortunately, that is not the case, our coral reefs are under serious threat from over-fishing, pollution and coastal development. Most critically, coral reefs feel the impact of climate change and that impact is nowhere more visible than on the world’s largest reef system. The Great Barrier Reef as We Knew it is Gone! is the startling headline in Oceans Deeply following a study on recent mass bleaching events. Over the last two years we have published numerous articles on the Great Barrier Reef, some hopeful, some not, this is one of the most disheartening.
Warmer and More Frequent
Bleaching events triggered by unusually high ocean temperatures have occurred on coral reefs before, but normally these events unfold slowly and then the coral recovers because the ocean warming is brief and infrequent, giving the reef sufficient time to heal. What is different now is that these events occur more frequently, and the temperatures are more extreme. (photo – ARC Center of Excellence for Coral Reef Studies)
In March 2016, Australia’s Great Barrier Reef endured an unprecedented bleaching unlike any experienced in recorded history and the shock killed millions of corals. “The heat exposure was so extreme the coral actually cooked and died very quickly,” said Terry Hughes, lead author of the study and possibly the single most authoritative expert on the reef.
Especially hard hit was the northern, 700 km (435 mile) third of the reef. A second catastrophic bleaching occurred the following year impacting not only the damaged northern portion but also killing 20% of corals further south in the mid-section of the reef. (graph – ARC Center of Excellence for Coral Reef Studies)
The conclusion is stark, the Great Barrier Reef, 25,000 years old and the largest structure of living organisms on the planet; stretching for 2,300km from north to south; composed of 2,900 individual reefs and 900 islands; covering an area of 344,000sq kilometers (133,000 sq mi); a World Heritage Site and one of the seven natural wonders of the world; within the period of one year lost half of all its coral.
“The northern Great Barrier Reef will never look the same again”
“On some of those northern reefs, depending on the heat exposure, we saw 60, 70, 80, even 90 percent mortality,” said Hughes as he explained that the diversity of corals on the mature reef has been lost.
Diversity of Corals is Lost
“The die-off of corals drove a radical shift in the composition and functional traits of coral assemblages on hundreds of individual reefs, transforming large swaths of the Great Barrier Reef from mature and diverse assemblages to a highly altered, degraded system,”
Hughes added, “To lose one in three corals in just nine months is an incredible shock to the system. The Great Barrier Reef is the world’s largest coral reef system and for two-thirds of it to be damaged in two years is heartbreaking.”
“It’s only a matter of time before we get a severe bleaching event in the southern third of the reef,” Hughes added. (photo – ARC)
A Spectrum of Wildlife Effected
The Great Barrier Reef supports a vast diversity of marine life including; thirty species of whales, dugongs, dolphins and porpoises; six species of sea turtles breed there; more than 1500 species of fish and 125 types of sharks, stingrays and skates share its waters; while 215 species of birds visit or roost on the reef’s islands. Without the shelter offered by a healthy, growing coral reef we can only assume that much of this wildlife will have a very bleak future.
“The take-home message is that climate change is not some future threat to coral reefs. It’s here and now. It’s been happening for a few decades and we’re well on the way to a very different-looking set of species on our reefs.”
By Robert Frerck, Blue Ocean Network
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