Approximately half a billion people, as well as 25 percent of all marine life, depend on coral reef ecosystems. Despite being one of the most valuable types of ecosystem on the planet, coral reefs are declining at an alarming rate.
In a new study from Southern Cross University, experts report that if the trend of decline continues at the current rate, coral reefs could stop calcifying by 2054.
Coral growth is called calcification because corals take up calcium carbonate (CaCO3) to produce their skeletons. As the chemistry of seawater changes, calcification rates change as well.
The opposite of calcification is coral dissolution, which is when the skeletons release CaCO3 back into the water. Coral dissolution is typically a result of environmental stressors such as ocean acidification and rising temperatures.
To investigate how coral reefs are responding to environmental stress, the researchers analyzed 116 studies from 53 papers published since the late 1960s.
“It is known that coral reefs have been degrading over time. Our study relies on historical data to quantify the current rate of decline and indicates what could be happening in the future,” said project leader Dr. Kay Davis.
“Our work complements quite a few other studies that indicate net coral reef dissolution by mid-century, between 2030 and 2080.”
The research was focused on coral reefs all over the globe, including those in Australia, Japan, Hawaii, the Red Sea, French Polynesia, and Bermuda.
“Repeat observations at the same sites can provide insight into how coral reefs are responding to changing environmental conditions on a global scale,” said Dr. Davis. “But these repeat surveys of calcification and productivity have only been carried out at seven sites.”
The declining health of the remaining coral may be contributing to reduce global calcification rates, explained the researchers.
“We found that rates of coral ecosystem calcification are significantly declining at an average rate of 4.3% ± 1.9% yr-1 with a concurrent reduction in mean coral cover of 1.8% yr-1. This suggests that loss of coral cover may not be the sole contributor of declining calcification,” said Dr. Davis.
“Stress events, like coral bleaching, can impact calcification, even without coral death. Corals improve their chances of survival during stressful times by temporarily reducing calcification.”
The study is published in the journal Nature Communications.