By Megan Wanner
According to Nancy Knowlton, coral reefs are considered the rainforests of the sea. There are about 1,000 total coral species and about one-third of these reef-building corals face elevated extinction risk from climate change and local impacts. There are about 1 to 9 million reef species in total. This constitutes about a quarter of all marine species, most of them rare.
Knowlton, the Sant Chair for Marine Science at the Smithsonian National Museum of Natural History, spoke Wednesday on the effects of climate change on coral reefs as part of the Voices of Discovery Science Series at Elon University, N.C.
Devastation of Reefs
People are one of the main predators to coral reefs. Humans introduce carbon dioxide, nutrients, toxics, sediments and aliens into the reefs while removing plants that are longer or taller than five centimeters, making it difficult for reefs to regenerate growth or remove the toxins that have been introduced.
Major causes of the decline of coral reefs include disease, sedimentation, invasives, bleaching, storms, seaweeds, osteoporosis and predators. Some of these problems are local, some global, but humans play a role in each of them.
“In the Carribean we’ve lost 80 percent of all the living corals in the last 30 years,” Knowlton said. “That is a huge loss.”
The Effects of Global Warming on Coral
As global warming causes the global temperature to rise, this causes the temperature of the oceans the reefs inhabit to increase. Coral has a narrow thermal tolerance of one degree Celsius above its normal temperature. Due to this narrow tolerance, what coral considers extreme heat or cold is not much and bleaching is easily triggered. Coral bleaching is caused by a breakdown in symbiosis between coral and symbiotic algae. This breakdown is caused by the stress of a change in heat, light, cold and dark.
With global warming comes a greater risk for more severe storms, as well as more storms in general. It is important for people to reduce local impacts so the reefs can protect themselves and recover from natural impacts.
Ocean acidity caused by greenhouse gases makes it harder for coral to lay down skeletons to grow. A study done showed that coral becomes sea anemones in acidified water. Although this proved the coral could survive, sea anemones cannot build reefs.
“Over the course of really just two years we went from reefs that were dominated by corals to reefs that had almost no living coral and were covered in seaweeds,” Knowlton said.
Knowlton highlighted various actions people could take in helping the conservation of the reefs. Among these are conserving energy, consuming responsibly, reducing waste, voting with the environment in mind and talking to people about the risk the reefs are facing.
“I can’t tell you how many taxi drivers I have talked to about coral reefs,” Knowlton said.
On a short term and local scale there are options for helping the reefs become more resilient to destruction. These options include controlling fishing pressure and improving water quality. Taking these measures means buying time for the reefs for more scientific solutions to the problems they are facing. On a longer term and global scale resilience strategies include reducing carbon dioxide emissions as well as capturing and restoring diversity.
In addition to these strategies, Knowlton addressed the idea of a deep freeze of species in order to regenerate the reef at a later time.