Anyone who’s tending a garden right now knows what extreme heat can do to plants. Heat is also a concern for an important form of underwater gardening: growing corals and “outplanting,” or transplanting them to restore damaged reefs.
The goal of outplanting is to aid coral reefs’ natural recovery process by growing new corals and moving them to the damaged areas. It’s the same idea as replanting forests that have been heavily logged, or depleted farm fields that once were prairie grasslands.
I have studied how global stressors such as ocean warming and acidification affect marine invertebrates for more than a decade. In a recently published study, I worked with Gregory Asner to analyze the impacts of temperature on coral reef restoration projects. Our results showed that climate change has raised sea surface temperatures close to a point that will make it very hard for outplanted corals to survive.
Coral Gardening
Coral reefs support over 25% of marine life by providing food, shelter and a place for fish and other organisms to reproduce and raise young. Today, ocean warming driven by climate change is stressing reefs worldwide.
Rising ocean temperatures cause bleaching events – episodes in which corals expel the algae that live inside them and provide the corals with most of their food, as well as their vibrant colors. When corals lose their algae, they become less resistant to stressors such as disease and eventually may die.
Hundreds of organizations worldwide are working to restore damaged coral reefs by growing thousands of small coral fragments in nurseries, which may be onshore in laboratories or in the ocean near degraded reefs. Then scuba divers physically plant them at restoration sites.
Outplanting coral is expensive: According to one recent study, the median cost is about US$160,000 per acre, or $400,000 per hectare. It also is time-consuming, with scuba divers placing each outplanted coral by hand. So it’s important to maximize coral survival by choosing the best locations.
We used data from the National Oceanic and Atmosphere Administration’s Coral Reef Watch program, which collects daily satellite-derived measurements of sea surface temperature. We paired this information with survival rates from hundreds of coral outplanting projects worldwide.
We found that coral survival was likely to drop below 50% if the maximum temperature experienced at the restoration site exceeded 86.9 degrees Fahrenheit (30.5 degrees Celsius). This temperature threshold mirrors the tolerance of natural coral reefs.
Globally, coral reefs experience an annual maximum temperature today of 84.9˚F (29.4˚C). This means they already are living close to their upper thermal limit.
When reefs experience temperatures only a few degrees above long-term averages for a few weeks, the stress can cause coral bleaching and mortality. Increases of just a few degrees above normal caused three mass bleaching events since 2016 that have devastated Australia’s Great Barrier Reef.
Warmer Oceans
Climate scientists project that the oceans will warm up to 3˚C by the year 2100. Scientists are working to create coral outplants that can better survive increases in temperature, which could help to increase restoration success in the future.
When coral restoration experts choose where to outplant, they typically consider what’s on the seafloor, algae that could smother coral, predators that eat coral and the presence of fish. Our study shows that using temperature data and other information collected remotely from airplanes and satellites could help to optimize this process. Remote sensing, which scientists have used to study coral reefs for almost 40 years, can provide information on much larger scales than water surveys.
Coral reefs face an uncertain future and may not recover naturally from human-caused climate change. Conserving them will require reducing greenhouse gas emissions, protecting key habitats and actively restoring reefs. I hope that our research on temperature will help increase coral outplant survival and restoration success.
Truthout Is Preparing to Meet Trump’s Agenda With Resistance at Every Turn
Dear Truthout Community,
If you feel rage, despondency, confusion and deep fear today, you are not alone. We’re feeling it too. We are heartsick. Facing down Trump’s fascist agenda, we are desperately worried about the most vulnerable people among us, including our loved ones and everyone in the Truthout community, and our minds are racing a million miles a minute to try to map out all that needs to be done.
We must give ourselves space to grieve and feel our fear, feel our rage, and keep in the forefront of our mind the stark truth that millions of real human lives are on the line. And simultaneously, we’ve got to get to work, take stock of our resources, and prepare to throw ourselves full force into the movement.
Journalism is a linchpin of that movement. Even as we are reeling, we’re summoning up all the energy we can to face down what’s coming, because we know that one of the sharpest weapons against fascism is publishing the truth.
There are many terrifying planks to the Trump agenda, and we plan to devote ourselves to reporting thoroughly on each one and, crucially, covering the movements resisting them. We also recognize that Trump is a dire threat to journalism itself, and that we must take this seriously from the outset.
After the election, the four of us sat down to have some hard but necessary conversations about Truthout under a Trump presidency. How would we defend our publication from an avalanche of far right lawsuits that seek to bankrupt us? How would we keep our reporters safe if they need to cover outbreaks of political violence, or if they are targeted by authorities? How will we urgently produce the practical analysis, tools and movement coverage that you need right now — breaking through our normal routines to meet a terrifying moment in ways that best serve you?
It will be a tough, scary four years to produce social justice-driven journalism. We need to deliver news, strategy, liberatory ideas, tools and movement-sparking solutions with a force that we never have had to before. And at the same time, we desperately need to protect our ability to do so.
We know this is such a painful moment and donations may understandably be the last thing on your mind. But we must ask for your support, which is needed in a new and urgent way.
We promise we will kick into an even higher gear to give you truthful news that cuts against the disinformation and vitriol and hate and violence. We promise to publish analyses that will serve the needs of the movements we all rely on to survive the next four years, and even build for the future. We promise to be responsive, to recognize you as members of our community with a vital stake and voice in this work.
Please dig deep if you can, but a donation of any amount will be a truly meaningful and tangible action in this cataclysmic historical moment.
We’re with you. Let’s do all we can to move forward together.
With love, rage, and solidarity,
Maya, Negin, Saima, and Ziggy