This one is really big.
By mid century, if we have not reduced the carbon dioxide in the atmosphere, the pH of almost all the ocean's waters will be too acidic to allow coral reefs to survive.
Their findings, detailed in the Dec. 14 issue of the journal Science, show that if current emission trends continue, 98 percent of present-day reef habitats will be too acidic by mid-century for reef growth.
"Before the industrial revolution, over 98 percent of warm water coral reefs were bathed with open ocean waters 3.5 times supersaturated with aragonite, meaning that corals could easily extract it to build reefs," said study co-author Long Cao, also of the Carnegie Institution. "But if atmospheric CO2 stabilizes at 550 ppm—and even that would take concerted international efforts to achieve—no existing coral reef will remain in such an environment."
So we have just gone from big to potentially catastrophic.
Coral reefs are the most diverse ecosystem on earth. It is estimated that as many as one quarter of all marine species depend on reefs at some point in their life cycle.
They also serve as an important nursery. Fish that stay in a coral reef during their early months and years have a greater chance for survival, since they provide more protection than an open sea floor, increasing the overall number of fish to survive juvenile status. In turn, this means that they will also likely grow larger, and have a greater chance to spawn, further increasing their numbers.
What's more, they exist in mainly nutrient poor regions. Because of the diversity and abundance of marine life present, they manage to recycle nutrients extremely efficiently. Take coral reefs out of the system and marine life will plummet.
And this is something that will not occur due to warming. Even if the earth's temperature were to remain exactly the same, which it likely will not, the CO2 concentration will continue to rise, increasing the acidity of the ocean.
Leaving aside what we are doing to our planet, think what we are doing to ourselves. Billions of people around the world depend on seafood as one of their main staples. Many species of fish were already in danger of collapse due to over fishing. Now one of the main habitats could disappear by mid century.