The Biggest Trends In Great Barrier Reef We'Ve Seen This Year

 

If current trends continue, more than 90% or more of the living corals will disappear from the central and southern parts of the reef in just 10 years. 

Researchers say virtually all coral populations along the Great Barrier Reef have declined due to repeated "bleaching events" over the past 25 years. The resumption of bleaching of the world's largest coral reef confirms that coral reefs around the world are in great trouble, scientists said, many of whom said their anxiety was exacerbated by the government's failure to protect the coral ecosystems they were destroying despite decades of warnings. From the 1,430-mile (2,300 km) Great Barrier Reef in Australia to the Saya de Malla in the Indian Ocean, coral reefs and the diversity of fish species they support are in sharp decline and this trend is expected to continue as how the planet continues to warm up in the 21st century. In the Caribbean, a recent study found that coral reefs were shrinking by about 0.25% per year, and by 2017 only about 10% of the sea floor was covered by living corals. 

At the Great Barrier Reef, sea temperatures have increased by about 0.7 degrees Fahrenheit (0.4 degrees Celsius) over the past century.2,13 Since 1979, there have been eight mass coral bleaching events caused by unusually high water temperatures. Since the first global bleaching event in 1998 shocked coral scientists with its magnitude and intensity, subsequent deaths have affected coral reefs in regions where the bleaching history is unknown, including Hawaii. The last three major bleaching events may have reduced coral reef larvae by 26, 50 and 71 percent chronologically. 

This has made it difficult for the reef to recover, but 13% of the reef has potential coral "sanctuaries" that have managed to avoid temperature spikes. According to the study, these shelters could spread larvae over 58% of the entire reef. 

Although these recent disturbances have affected the health of the reef, long-term changes in coral cover represent a balance of mortality from subsequent disease and recovery in the intervening periods. Although this is the first study to quantify the regional decline in coral recovery rates, deterioration in coral reef recovery was first noted in a study on the effects of COTS on GBR between 1985 and 1996 (7). While it is not possible to attribute this change to tropical sea temperature rise or ocean acidification alone, this study shows that changing conditions in the Coral Sea (which continually increases sea temperature and acidity) are causing some exceptional cases of change in fundamental coral reef processes, such as calcification. 

In a study of 328 long-lived corals across the Great Barrier Reef's range of habitats, calcification rates were found to have decreased by 15% since 1990, an unprecedented rate in 400 years of studied coral core records (Death et al. According to the report, since 2010 there has been a steady decline in stony coral cover, with the strongest impacts occurring in South Asia, Australia, the Pacific Ocean, East Asia, the western Indian Ocean, the Persian Gulf and the Gulf of Oman in recent decades (1 3) These changes have been most pronounced in northern and central parts of the Great Barrier Reef, where the most recent massive coral bleaching has occurred. 

As a result, the loss of older corals can have knock-on effects across the reef system, as larger groups of corals in a population can have a disproportionate impact on the reproduction and genetics of offspring, providing habitat for fish and other reef dwellers and more food. The transition from coral reefs to algae-dominated reefs reduces the architectural complexity and structural integrity of these habitats, making them less biologically diverse and offering fewer goods and services to people. 

The Great Barrier Reef has experienced a five-fold increase in mass bleaching since 1998, as higher-than-average water temperatures cause corals to secrete algae, which provide them with nutrients and color. Research shows that large-scale reef bleaching has become five times more common in the past 40 years. The scientific community has no doubts that high sea temperatures have been responsible for the massive increase in coral bleaching and mortality seen on the Great Barrier Reef over the past 25 years. Warming ocean temperatures caused by climate change have wiped out more than half of the corals on Australia's Great Barrier Reef since 1995, a new study finds. 

NOAA reports that prolonged high temperatures have devastated parts of the reef and bleached corals. With sea surface temperatures above average since early December, the Marine Park has accumulated thermal stress, which increases the risk of coral bleaching. And the southern part of the reef was also hit by record temperatures in early 2020. The southern section of the Great Barrier Reef, which remained virtually untouched during the events of 2016 and 2017, was hit very hard this year. 

And coral reefs are home to the highest biodiversity of any ecosystem in the world, making them some of the most biologically complex and valuable on the planet. Branching and table corals provide important structures for reef dwellers such as fish. 

In addition, ocean acidification has likely reduced reef calcification on southern NSC corals (19). Growth can also be suppressed for several years after bleaching events (20), and some corals change their symbiont populations during times of heat stress, increasing the number of heat-tolerant symbiont types (21). It is known that if bleaching caused by stress is not severe, corals recover. 

One factor to consider is the time it takes the coral to recover from a bleaching episode. The report says that many of the studies used in the projections include an "optimistic" recovery period of about five years. And, even if warming is limited to 1.5°C, about 70-90% of tropical coral reefs could disappear. 

This means that any impact of pollution, overfishing or habitat destruction will be in addition to the expected damage from climate change. Our statistical model showed that coral reefs can quickly recover to 70% coral cover within 7 years if the hereditary effects of acute diseases and the intensity of chronic diseases are reduced (Fig. 

While 40% of the reef remained intact, 25% suffered severe bleaching and 35% moderate bleaching. During that time, the reef experienced several localized cyclones, four mass bleaching events and two major eruptions of crown-of-thorns starfish (not to mention another major bleaching event earlier this year). 

The authors found that coral abundance has drastically decreased in all colony sizes and in all coral taxa. Instead of healthy reef systems, there were miles and miles of bleached white corals. In the 2000s, grim reports of pale and crumbling coral have multiplied from remote atolls in the South Pacific, the Indian Ocean, the Red Sea and, once again this year, from the Great Barrier Reef in Australia, where the overheated Pacific Ocean has scorched corals by an entire eternity. the third time. once every five years. Among the key findings in the IPCC report is that 2°C global warming will result in the loss of 99% of the world's tropical coral reefs.