The Increasing Threat of Bleaching Events
By Sandy Smith ‘25
Australia's Great Barrier Reef is currently suffering its sixth "bleaching event," which is also its fourth in the past seven years. These events have been caused almost entirely by climate change "heat stress", which is when corals are impacted by warming weather patterns. The first reported bleaching event was in 1998 and has continued to be observed every few years since then. The 2,300 km reef is in danger, along with those who rely on it. This announcement comes a week "before the start of a 10-day United Nations monitoring mission to the reef ahead of a crucial meeting of the world heritage committee in June" which makes it as important as ever to discuss.
Bleaching events are happening because the "corals are producing these fluorescent pigments in an attempt to protect their tissues from heat and the intense sun during these marine heatwaves," says coral biologist Neal Cantin. The corals are having trouble keeping up with the warmer temperatures and weather changes because those conditions cause the ejection of their symbiotic partner algae, leaving the coral starving. Observations from the Bureau of Meteorology show water temperatures between one and two degrees above average across the broader areas of the reef. Cantin argues that there is an immense need to slow down the warming rate in Australia to combat these events.
The repeated bleaching has made it increasingly more difficult for the corals to recover.
Over sixty percent of the coral has been severely bleached, with the number reaching over four-hundred and fifty of the seven-hundred and fifty reefs. The bleaching has also caused over-drying in the barrier reef, which is highly damaging to the millions of people, and species that "depend on the reefs for food, jobs, and shoreline protection." Back-to-back bleaching events make it impossible for the corals to recover.
This is not the first area to have barrier reef coral bleaching. The United States’ Northern Hawaiian Islands has experienced devastating effects due to bleaching. The bleaching has killed around 50 percent of its corals. Events like this have been reported in other regions of Australia as well, as the weather pattern La Ninas bring cooler temperatures to the water. Cooler temperatures “can have an almost identical outcome to warm water bleaching in coral reefs.” This makes scientists fearful of the damage another La Nina could inflict on the reefs and surrounding areas. Australian corals are also at a higher risk because the reefs are more tropical and therefore more "thermally sensitive."
The good news is that there is still time to fix the problem. "If the water temperature decreases, bleached corals can recover from this stress," said David Wachenfeld, chief scientist of Australia's Great Barrier Reef Marine Park Authority. Immediate action must be taken if it is to be solved. Graham Readfearn with the Guardian says, "Corals can recover from mild bleaching, but if heat stress is too severe, the coral can die."
Some ways that scientists have been working to solve the problem include finding other reefs that can act as refugees because of their naturally colder water and heat-resistant breeding corals. The real problem for the reefs is fossil fuel emissions. If the world warms by one and a half degrees, approximately seventy to ninety percent of coral reefs will die off. It also is essential to learn how to control areas like fishing, coastal development, pollution, and shipping as they will play an essential role in providing defense for the Great Barrier Reef. If you are interested in helping out, the World Wide Fund for Nature website allows you to donate. There are plenty of other places that also take donations to help fight the climate change crisis.
Sources:
https://www.cnn.com/2022/03/25/australia/australia-reef-bleaching-climate-intl-hnk/index.html
https://www.nytimes.com/2022/03/25/world/australia/great-barrier-reef-bleaching.html
https://www.nytimes.com/2022/03/07/health/covid-brain-changes.html
https://www.bbc.com/news/world-australia-60870239
https://www.coralcoe.org.au/for-managers/coral-bleaching-and-the-great-barrier-reef
https://link.springer.com/article/10.1007/s00338-004-0401-2
https://www.worldwildlife.org/initiatives
https://oceanservice.noaa.gov/facts/coral_bleach.html
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