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Without deep cuts in carbon dioxide emissions, the planet’s coral reefs could be in serious trouble. In a world in which humans continue to burn fossil fuels unchecked, ocean conditions will become ultimately inhospitable, according to U.S. scientists.
Katharine Ricke and Ken Caldeira of the Carnegie Institution in Washington and colleagues make their sombre prediction in Environmental Research Letters. Their argument on the face of it seems inconsistent with other recent research on reef response to climate change, which in one case suggests that some corals could vanish, and in another that some corals might adapt, very slowly.
But the debate in all three cases is about the rate of warming, the levels of carbon dioxide in the atmosphere and the ultimate impact of changes in the pH levels of the seas.
Ricke and Caldeira looked not so much at the warming of the seas–tropical corals are very sensitive to temperature–nor at the levels of acidification as such (because rain dissolves carbon dioxide to form a weak carbonic acid and inevitably affects the ocean’s pH levels), but at the chemical circumstances in which crystals of aragonite can form.
All fossil reefs and shell and bone sediments are ultimately calcium carbonate in the form of limestone or chalk. However, calcium carbonate, or CaCO3, exists in two crystal structures, calcite and aragonite, and these fossilized sediments must once have been mostly aragonite.
That is because marine life, in the form of corals, fish and mollusc shells, mainly begins with aragonite. The biochemical availability of aragonite depends on the pH values of the water.
An End to Dumping
Ricke and Caldeira used computer models to calculate ocean chemical conditions under a range of carbon dioxide scenarios, looking for the necessary conditions to support aragonite formation and shell and bone growth, and set a potential aragonite saturation threshold.
In pre-industrial times, 99.9 percent of the oceans that washed over coral reefs were comfortably above this threshold. Under the notorious business-as-usual threshold, in which fossil fuel use continues to grow, ultimately the water surrounding the 6,000 coral reefs they used as a database for their research would be significantly below the threshold.
There would be a point at which the resilience and capacity to adapt that must be inherent in corals would be overwhelmed. The conclusion is a bleak one.
“Our results show that if we continue on our current emissions path, by the end of the century there will be no water left in the ocean with the chemical properties that have supported coral reef growth in the past. We can’t say with 100 percent certainty that all shallow water coral reefs will die, but it is a pretty good bet,” said Ricke.
“To save coral reefs, we need to transform our energy system into one that does not use the atmosphere and ocean as waste dumps for carbon dioxide pollution,” Caldeira added.
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Colorado senator and 2020 hopeful Michael Bennet introduced his plan to combat climate change Monday, in the first major policy rollout of his campaign. Bennet's plan calls for the establishment of a "Climate Bank," using $1 trillion in federal spending to "catalyze" $10 trillion in private spending for the U.S. to transition entirely to net-zero emissions by 2050.
When Trump's Environmental Protection Agency (EPA) announced its replacement for the Obama-era Clean Power Plan in August 2018, its own estimates said the reduced regulations could lead to 1,400 early deaths a year from air pollution by 2030.
Now, the EPA wants to change the way it calculates the risks posed by particulate matter pollution, using a model that would lower the death toll from the new plan, The New York Times reported Monday. Five current or former EPA officials familiar with the plan told The Times that the new method would assume there is no significant health gain by lowering air pollution levels below the legal limit. However, many public health experts say that there is no safe level of particulate matter exposure, which has long been linked to heart and lung disease.
By Andrea Germanos
Animal welfare advocates are praising soon-to-be introduced legislation in the U.S. that would ban the use of wild animals in traveling circuses.
By Tara Lohan
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Mounting bills from natural disasters like these have prompted renewed calls to reform the National Flood Insurance Program, which is managed by Federal Emergency Management Agency and is now $20 billion in debt.