According to a study published this week in Science, climate change may lead to a substantial ecosystem shift resulting in the widespread collapse of coral reefs.
The study, led by Richard Aronson and Lauren Toth from the Florida Institute of Technology, inserted 17-foot-long small-bore aluminum pipes through layers of coral and removed cross-sections of the coral reefs. They took these cross-sections from coral reefs along the coast of Panama in the Pacific Ocean. These cross-sections gave the researchers insight into the past 6,000 years of the coral reefs in much the same way that rings from a cross-section of a tree can give insight into the tree’s history.
The results were unsettling. Ms. Toth says: “We were shocked to find that 2,500 years of reef growth were missing from the frameworks. That gap represents the collapse of reef ecosystems for 40 percent of their total history.” The study also examines coral reefs in other locations around the world, some as far away as Japan and Australia. These reefs possessed the same gaps, suggesting a common factor affecting all of the coral reefs.
The common factor, says Ms. Toth, is the El Niño–Southern Oscillation, or ENSO. ENSO is a climate cycle characterized by fluctuation between El Niño and La Niña. El Niño is characterized by warm temperatures and high air pressure in the western Pacific while La Niña is characterized by colder air and low air pressure in the eastern Pacific.
According to the study, the historical reef collapse corresponded to a period of dramatic swings in ENSO. “Coral reefs are resilient ecosystems,” said Ms. Toth. “For Pacific reefs to have collapsed for such a long time and over such a large geographic scale, they must have experienced a major climatic disturbance. That disturbance was an intensified ENSO regime.”
Another period of significant climate change may be approaching, according to the study. Professor Aronson says: “As humans continue to pump greenhouse gases into the atmosphere, the climate is once again on the threshold of a new regime, with dire consequences for reef ecosystems unless we get control of climate change.” The study argues that climate change caused by human action presents a major threat to the coral reefs. Human activities could cause climate change similar to that which collapsed the coral reefs thousands of years ago.
Ms. Toth remains hopeful, however. The coral reefs survived the last period of climate change and she remains confident that, should we be able to reverse or minimize our impact on the climate, the reefs should survive this as well.