Issue 91: Tipping Points: Coral Reefs
September 7, 2023
In this week’s issue:
- The coral reef tipping point
- Less burn, more mud
- Greek island shipwreck
This is an archived issue. Sign up here to receive the Planet Snapshots newsletter every Thursday morning.
Welcome to the second issue of Tipping Points, a series on the most urgent and concerning climate thresholds. Check out our first issue on Greenland’s ice sheet in case you missed it.
Feature Story: Tipping Points: Coral Reefs
There’s only one thing more frightening than an ocean filled with large predators, and it’s an ocean filled with nothing living at all. Just because we may not like everything that swims in the deep (we’re looking at you, blobfish) doesn’t mean we don’t support every being that calls the ocean their home. But unfortunately, warmer temperatures are bleaching Earth’s corals into white tombstones and turning reefs into biological graveyards at an alarming rate.
About 90% of all that infamous atmospheric warming has been absorbed by Earth’s oceans, creating a multitude of problems including the destruction of its beloved biodiversity hotspots: coral reefs. A warmer ocean significantly disrupts coral balance that 25% of the planet’s marine species and about 1 billion humans rely on. Scientists further fear that its collapse won’t be slow and gradual but rather sudden and catastrophic. Dead men may tell no tales, but dead corals speak plenty.
Corals are living colonies of invertebrate animals that can group together to create giant calcium carbonate reefs. The reason why they’re depicted as aquatic cities in movies like Finding Nemo is because they pretty much are. A large number of marine organisms call these living structures their home, and together they provide countless ecosystem services for ocean and terrestrial species alike. Some began forming over millions of years ago and others like the Great Barrier Reef cover such a huge area that if it were a country it’d be the 64th largest, just after Germany.
Yet despite their age and size, the coral reef tipping point is both unnervingly close and frustratingly uncertain. The reefs that color Earth’s oceans and support tremendous biodiversity are rapidly dying. But the dieoff is also uneven. Some corals are more resilient to changes in marine chemistry than others. So while the prevailing science places a likely major collapse of low-latitude coral reefs between 1.5 to 2°C of additional warming, we’re still unsure where the tip into the deep end is exactly.
Reports from the IPCC indicate that a global warming of 1.5°C above pre-industrial levels would likely result in a decline of 70 to 90% of coral reefs. At 2°C that percentage reaches 99%. And recent studies point to crossing that warming threshold by mid-century. Which means that for this tipping point, our metaphorical toes are gripping the edge.
The science goes something like this: when ocean temperatures rise between 1 to 2°C above average, corals expel the symbiotic algae that live within them. The process is called coral bleaching and the result is the once colorful, vibrant reefs turn bone-white. This process doesn’t immediately kill the coral, but it makes it far more vulnerable to further stressors. And if the waters stay warm, the coral can’t bounce back.
There’s not a metaphorical boiling point for this tipping point. It’s literal. Florida’s surface ocean temperature clocked in at 101.19°F (38°C) this summer, an ideal figure for hot tubs and an exceptionally bad one for corals. Heat waves exacerbated by climate change are instigating these mass coral bleaching events with alarming frequency and ferocity. The Great Barrier Reef has had four since 2016, with the 2021–2022 summer one affecting 91% of all reefs surveyed.
To say a mass dieoff of coral reefs would be catastrophic for biodiversity and food webs would be an understatement. And it’s going to take more than curbing emissions to prevent the worst of its effects. With mass bleaching events already common and further warming expected, scientists are taking more drastic measures. Some use satellites to monitor sea surface temperature to anticipate vulnerable areas or to assess the extent of a bleaching event once it’s happened. Others are taking more drastic measures, such as cross-breeding corals to create a climate-resilient super species.
Corals in the oceans are a sort of canary in the coal mine, an indicator that something is going horribly wrong. The white graveyards just below the waves are alarming, but perhaps also a touch hopeful. For if corals can bounce back after major stress, maybe we can too.
In the News: Mud Man
The Burning Man festival has ended, but tales from the event continue. The usually hot and dry event took a wet and cold turn after torrential rain transformed the desert lakebed into a muddy mess. Gates opened after a brief lockdown, with a large queue seen forming Monday. The spectacle drew some criticism across the Internet, with many questioning the principles (like leave no trace) that the event upholds. But if burners can’t handle a light roast, then who can?
While event organizers pledge not to leave any trace on Black Rock Desert, storm clouds make no such promises. On Friday, September 1st, the first rains fell on the ancient lakebed. Additional showers throughout the weekend brought a total of 2 to 3 months worth of rain to the desert in the country’s driest state. Soil water content data from August 29 to September 5th shows a steady increase in moisture across the region.
Remote Sensations: Shipwreck Cove
If we had to choose a location to be shipwrecked, we’d likely pick the Greek island Zakynthos too. And while the sailors of the MV Panagiotis didn’t intentionally wreck their ship, they sure did crash a fine cove. The diesel coaster was originally built in Scotland (then named MV Saint Bedan) and was reportedly used to evacuate soldiers from Dunkirk during World War II. There are a few theories as to how the ship ended up on Navagio Beach. But the prevailing story appears that it crashed in 1980 after Greek authorities chased the ship as it transported contraband cigarettes to Turkey. As further evidence, supposedly no official cigarettes were sold on the island for years following the wreck. We can only confirm that the ship is indeed on the beach and not any of its background, but we’re fond of good stories here at Snapshots so we’ll choose to believe.
All imagery Ⓒ 2023 Planet Labs PBC
Editor: Ryder Kimball | Images: Ryder Kimball, Max Borrmann, Julian Peschel, and Maarten Lambrechts
