As an avid scuba diver who has explored coral reefs around the world for over 20 years, I have witnessed firsthand the concerning and rapid decline of these incredible ecosystems. Coral reefs are some of the most biodiverse habitats on Earth, yet they are highly vulnerable to the effects of climate change. As global temperatures continue to rise, coral reefs face existential threats on multiple fronts.
Bleaching Events
One of the most visually striking impacts of climate change on coral reefs is the increasing frequency and severity of mass bleaching events. Bleaching occurs when rises in sea temperatures cause corals to expel the symbiotic algae that give them their brilliant colors. This leaves the corals looking stark white and skeletal.
While corals can recover from short bleaching events, prolonged or repeated episodes lead to widespread mortality. According to NOAA, since 2014, there have been five mass bleaching events across the world’s coral reefs—the most widespread and damaging ever recorded. The rate of severe bleaching is predicted to accelerate as the oceans continue to warm. As a diver, it is heartbreaking to see once-vibrant reefs transformed into ghostly white graveyards.
Ocean Acidification
Rising atmospheric CO2 levels not only warm the seas but are also changing ocean chemistry through acidification. Approximately one-third of the CO2 emitted by human activities gets absorbed by the oceans. As seawater becomes more acidic, coral reefs struggle to grow their calcium carbonate skeletons, which form the very foundation of reef structures.
Over multiple dives in locations such as the Florida Keys, I’ve noticed a concerning decline in coral cover and growth rates as acidification takes hold. There are also fewer crustaceans and mollusks due to their inability to form shells in more acidic conditions. Reducing CO2 emissions rapidly is crucial to slowing the acidification process and preventing devastating impacts.
Storm Damage
As climate change influences ocean temperatures and currents, it is also projected to increase tropical storm frequency and intensity. Hurricane damage to coral reefs can be extensive, breaking apart coral skeletons and causing excessive sedimentation, which smothers reefs.
Observing the aftermath of major storms such as Hurricane Maria on Puerto Rico’s reefs illustrates the potency of these disasters. Thriving reefs were reduced to fields of coral rubble. While coral reefs are adapted to some storm damage, the increased frequency of intense storms may hinder recovery.
Marine Heatwaves
Perhaps the most ominous climate change-driven threat comes from marine heatwaves. These periods of extremely high ocean temperatures lasting weeks or months can be catastrophic for coral reefs. The odds of marine heatwaves have doubled since 1982 and are predicted to become 150 times more frequent over the next century.
A record-breaking marine heatwave in 2016 led to the worst bleaching event on the Great Barrier Reef ever documented, with over 90% of the reef affected. The extent of mortality was unimaginable. As marine heatwaves become hotter, longer, and more frequent, corals will be pushed to the brink of their temperature thresholds everywhere.
Hope Remains
While the climate change outlook for coral reefs is concerning, it is not without hope. Some corals have shown the ability to adapt and acquire heat resistance. There is also important work being done to restore and repopulate damaged reefs through methods like coral gardening. And governments worldwide are taking action by expanding marine protected areas.
As a diver who cherishes every moment I spend beneath the waves observing coral magic, I remain optimistic. Seeing reefs face calamity firsthand spurs me to take action above the surface as well. We all have a role to play in using our voices to speak up for change and reducing our personal carbon footprints. Our future and that of wondrous coral reefs are intertwined; together, we can make a difference.
How do coral reefs adapt to climate change?
- Some corals exhibit the ability to adapt by becoming more heat-tolerant through changes in their symbiotic algae.
- Corals may alter their growth forms or depths in response to warming and acidification.
- Evidence suggests corals can pass down “acclimatization” to their offspring through epigenetics.
- Hope remains that rates of adaptation can keep pace with rapid climate change.
Can coral reefs recover from climate change?
- Yes, if given the chance to recover between intensifying disturbances.
- But recovery is hindered by the accelerating frequency of bleaching events, storms, etc.
- Reefs can recover if the global temperature rise is kept below 1.5°C this century.
- Active human restoration efforts like coral gardening can aid recovery.
- Reducing local stressors (overfishing and pollution) also supports resilience.
What is the biggest threat to the coral reef?
- Marine heatwaves that push corals beyond thermal thresholds
- More frequent and severe mass coral bleaching events
- Ocean acidification is impeding coral growth and reef development.
- Destructive tropical storms and cyclones
- Continued global temperature rise if unchecked
In summary, climate change poses an existential threat to the world’s coral reefs through bleaching, acidification, storms, and marine heatwaves. However, there remains hope that, through adaptation and active restoration, coral reefs can recover if decisive climate action is taken immediately. As a scuba diver, I urge us all to value these precious ecosystems and reduce our carbon footprints. The future of reefs depends on it.
