Sea Change
Delay on climate action could doom the world’s coral reefs in our lifetimes
“Ocean acidification already damaging coral reefs” was one of dozens of alarming recent headlines from around the world, reporting on a groundbreaking new study published in Nature few weeks ago. But the problem is even worse than that.
Ocean warming already poses a more imminent, direct, and damaging threat to the world’s coral reefs, one of the most diverse ecosystems in the planet. In fact, ocean warming combined with El Niño is causing today the worse coral bleaching event in the history of the Great Barrier Reef.
Fortunately, the answer to these twin global threats –- ocean warming and acidification — is the same: We must quickly reduce global carbon emissions from burning fossil fuels. Otherwise we could see the downfall of coral reefs in our lifetime, a cascading loss that will ripple through the ecosystem and the local economies that depend on them.
Global warming is a dire threat that we can’t wait a year or five to address. The clock is ticking and we must elect leaders that consider climate change the most important threat facing humanity. If President Obama is really serious about the future of our planet, he should spend his last nine months in office firing executive orders at every possibility of decreasing carbon emissions — and ask other world leaders to follow his example.
Atmospheric concentration of carbon dioxide (CO2), the main greenhouse gas, has already surpassed 401 parts per million, probably higher than at any point in the last 15 million years. The last time there was this much CO2 in our planet’s atmosphere, modern humans did not even exist, the seas were 100 feet higher than today, and coral reefs looked very different.
Since the industrial revolution, the global oceans have absorbed more than a quarter of all the anthropogenic CO2 released to the atmosphere, profoundly changing the seawater chemistry, making it 30 percent more acidic. In these corrosive waters, corals have difficulty producing their calcium carbonate skeletons, so reefs grow significantly slower. A previous study suggested that by the time atmospheric CO2 concentration reaches 560 ppm, which could happen this century, coral reefs may stop growing completely.
The buildup of carbon dioxide in our atmosphere is a double-edged sword that threatens life in our oceans. Besides absorbing CO2, the oceans have retained over 90 percent of all the global warming, and they’re now 1.55 degrees Fahrenheit warmer than in recorded history. That heat has already wiped out extensive areas across the world through coral bleaching and diseases.
A quarter of the world’s coral reefs have already been lost and one-third of all reef-building corals, the foundation species of this ecosystem, face high risk of extinction. While the causes of coral reef degradation are several, global warming is the one that can cause widespread mortality in a matter of weeks. We are seeing this today all around the Great Barrier Reef. By the time coral reefs start dissolving under more acidic waters, large reef-building corals will be likely long gone.
The frequency of heat waves predicted by climate change models will substantially increase in the near future, likely promoting more widespread mortality in corals. We already see these phenomena during strong El Niño years, and last October, the U.S. National Oceanic and Atmospheric Administration declared the third ever global coral bleaching event on record, and that mass coral mortality could continue into 2017. The unfolding mass bleaching event in the Great Barrier Reef that is occurring now was detected only few days after the Marine Park Authority raised the threat level of coral bleaching to the maximum possible alert.
Today’s coral reefs already look very different from those in the near past. Massive reef-building corals are mostly gone and smaller, more resistant coral species are slowly occupying their crumbling space. Future coral reefs will support much less biodiversity with fewer fish and invertebrates species, lower fisheries production, lower local economic revenue, and less likely to provide ecosystem services such as storm protection and coastline stabilization.
Coral reefs are the canary of the coal mine of climate change. Even limiting global warming to 2 degrees Celsius — the goal nations agreed to during the recent Paris Climate Talks — will be unlikely to save more coral reefs.
It took thousands of years for coral reefs to grow and build the tridimensional structure that we can even see from space. Sadly, it has taken only a few decades to rapidly degrade because of our capricious addiction to an outdated energy source.
The common solution for these two major problems, ocean warming and acidification, is the necessary, quick, and drastic reduction of carbon dioxide emissions globally. We need leaders who understand the problem and will act with the urgency it demands. The corals are calling… all we have to do is to listen.
