Guest essay by Eric Worrall
Even 1.5C will kill 99% of corals, according to research. But I think there is room for a little doubt.
Corals kill even if global climate goals are achieved: study
by Marlowe Hood
FEBRUARY 6, 2022Coral reefs are home to a quarter of marine wildlife and the livelihoods of more than half a billion people, researchers said Tuesday.
According to the report in the journal, an average increase of 1.5 degrees Celsius above pre-industrial levels would render more than 99% of the world’s coral reefs unable to recover from more frequent heatwaves around the world. sea. PLOS Climate.
According to the study, at two degrees of warming, the mortality rate would be 100%.
Lead author Adele Dixon, a researcher at the University of Leeds’ School of Biology, told AFP: “The reality is that there is no safe limit to global warming for coral reefs.
“1.5C is still too hot for ecosystems on the front lines of climate change.”
…
Read more: https://phys.org/news/2022-02-corals-domed-global-climate-goals.html
Summary of the study;
Future loss of local-scale heat tolerance in coral reef ecosystems
Adele M. Dixon, Piers M. Forster, Scott F. Heron, Anne MK Stoner, Maria Beger
Published: February 1, 2022
Thermal regeneration underpins climate-smart management of coral reefs, but whether current thermal regeneration will continue to do so under future warming is uncertain. . We use statistical scaling to provide the highest resolution (0.01°/1 km, >230,000 reef pixels) thermal stress projections currently available for coral reefs and determine future renewables on locally manageable scales. Here, we show that climate change will overwhelm restraint at the current local scale, with global refugia thermal decline from 84% of global reef pixels in today’s climate to 0.2% at 1.5°C and 0% at 2.0°C of global warming. Local-scale oceanographic features such as countercurrents and strong currents rarely provide future heat reproduction. We confirm that a warming of 1.5°C above pre-industrial levels would be catastrophic for coral reefs. Management efforts focused on heat regeneration may be effective in the short term. Instead, promoting adaptation to higher temperatures and facilitating migration will be necessary to ensure reef survival.
Read more: https://journals.plos.org/climate/article?id=10.1371/journal.pclm.0000004
Given the Great Barrier Reef’s climatic range of at least 6C from the subtropical south to the tropical north pole of the Great Barrier Reef, it is unlikely that 0.5-1C warming could wipe out the entire reef.
So where did the study authors go wrong?
Digging into the research, it looks like they’ve pulled out the marine version of the agricultural research trick.
Agricultural studies that predict climate doom often make completely unrealistic assumptions, such as the assumption that farmers won’t try anything new, that they will continue to grow foolishly. exactly the same crop, year after year, no matter what happens to the yield.
In the same way, the authors of this coral study seem to have assumed that coral mobility is low.
The lack of mobility of corals is not a reasonable representation of nature. Adult corals can be trapped in place, anchored to rocks or other corals, but each year the corals produce countless billions of highly mobile larvae that seek out favorable locations to live.
So any reef that gets too hot will be rapidly colonized by coral larvae by coral larvae whose parents have adapted to warmer water.
The researchers assigned a temperature value to each point on a very fine grid, compared it with modeled pre-industrial temperatures and set a threshold that would soon be violated by climate models. offense. This leads to the unrealistic study conclusion that the stress grid points will rapidly increase from 6.8% of the study area (according to their assumption) to 99-100% of the study area.
There is no serious upper temperature limit for corals’ heat tolerance. Hot water corals are extremely fond of hot water like in the Persian Gulf tolerate much hotter water temperatures than any open ocean, but they are still as mobile as any other coral.
Even if the world experiences unbelievable levels of global warming, extreme coral species will burst out of their limited hot-water ecological niches and invade the rest of the ocean. positive. The mix of species may vary, but the entire reef will remain healthy.
These studies have a place, as a mathematical modeling exercise, or as a foundational exercise. But the suggestion of real-world applicability, the suggestion that corals cannot survive a small temperature change over long periods of time, stands in stark contrast to the wide climatic range of coral reefs in the ocean. real world such as the Great Barrier Reef, which contains more or less continuous stretches of climatic conditions ranging from subtropical to tropical high north.
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