Science in Action – “Coral Extinctions and Chalky Unknowns”

BBC World Service – October 23, 2025
Host: Ronan Pease

Episode Overview

This episode delves into three major scientific stories:

• The alarming loss and potential “functional extinction” of staghorn and elkhorn corals in Florida, a grim indicator of global reef health as climate change quickens.
• The enormous but uncertain role of microscopic plankton and mollusks in storing carbon—key players in oceanic carbon cycling whose future responses to climate change are unknown.
• An unexpected, encouraging finding: mRNA Covid vaccines seem to boost immunotherapy outcomes in cancer patients.
• A creative, low-tech way to map crops in Africa using GoPro cameras for machine learning and food security.

Ronan Pease guides us through these stories with discussions featuring marine biologist Ross Cumming, biogeochemist Patrizia Zaveri, immunologist Adam Gripen, and remote sensing scientist Catherine Nakalembe.

1. Coral Extinction in Florida: Functional Loss Amid Climate Crisis

The Plight of Florida's Coral Reefs

[01:57–13:07]

• The 2025 Global Tipping Points Report has declared the loss of warm-water coral reefs as imminent, especially if global temperatures surpass 1.5°C above pre-industrial levels.
• A new Science paper documents the “functional extinction” of staghorn and elkhorn corals in 2023 across Florida's 560-kilometer reef tract.
• These branching coral species provide essential three-dimensional habitats for countless marine species.

Key Insights:

• Coral Biology and Importance

  • Staghorn corals: Form long, spiky branches—“large thickets... produce this highly complex three-dimensional structure that provides habitat for many other fishes, invertebrates and animals that live on the reef.” (Ross Cumming, 03:00)
  • Elkhorn corals: Form thick, arm-like branches that build dense canopies.
  • Both suffered catastrophic declines from disease and storms since the 1980s; restoration programs have tried to revive them.

• 2023 Heatwave Catastrophe

  • The 2023 marine heatwave exceeded historical records 2.2–4 times over—“90, 100% mortality throughout most of the Florida Keys and the Dry Tortugas” (Ross Cumming, 05:39).
  • Only a few deeper-water survivors noted; but numbers and reproductive potential are so reduced as to be “functionally extinct.”
  • “If there's not enough of them around, those eggs and sperm won't be able to find each other to fertilize and create new baby corals.” (Ross Cumming, 08:23)

• Regional Implications

  • Similar lethal heat stress recorded across the wider Caribbean region.
  • Scientists are piecing together a regional snapshot, but expect widespread losses.

• Restoration Reconsidered

  • Traditional coral nurseries and planting are overwhelmed by relentless heatwaves.
  • New strategies include:
    • Breeding heat-tolerant corals using cross-regional parent stock, e.g., “the first crossbred corals with one parent from Florida and the other parent from Honduras...” (Ross Cumming, 11:34)
    • Manipulating the algae living inside corals to use more heat-tolerant species.

• Ethical Questions

  • “It’s a bit like farm animals or flowers in the garden, which might be very lovely to look at, but they're not the wild thing.” (Ronan Pease, 12:17)
  • Ross Cumming compares coral breeding for resilience to agricultural selective breeding, noting, “It’s the same type of thing if we were to attempt to breed corals for higher resilience.” (Ross Cumming, 12:41)

Notable Quotes

• “We saw 90, 100% mortality throughout most of the Florida Keys... almost complete loss of staghorn and elkhorn corals.” – Ross Cumming [05:39]
• “If there's not enough of them around, those eggs and sperm won't be able to find each other...” – Ross Cumming [08:23]

2. Chalky Unknowns: The Uncharted Fate of Carbon in the Ocean

[13:07–22:03]

The Unsung Carbon Cyclers

• Ronan Pease turns focus to microscopic ocean creatures—coccolithophores and planktonic mollusks—that help regulate Earth's carbon by locking up CO2 as carbonate in their shells.
• Patrizia Zaveri’s Science review paper highlights critical gaps in our understanding of these organisms’ roles and responses to current climate change.

Key Insights:

• Coccolithophores: Tiny, Mighty Carbon Sinks

  • Unicellular plankton that both calcify and photosynthesize: “Invisible, but very important for us and for the ocean.” (Patrizia Zaveri, 14:16)
  • Leave immense sedimentary records—e.g., the “Cliffs of Dover.”

• Planktonic Foraminifera and Pteropods:

  • Build carbonate skeletons; forams leave a continuous fossil record, pteropods are planktonic mollusks with fragile, “winged” shells.

• Big Questions, Big Uncertainties

  • Ocean absorbs ~30% of human CO2 emissions, but the precise future of this ‘carbonate pump’ is unknown.
  • Rising CO2 changes ocean acidity, which impacts these creatures’ ability to form shells effectively.
  • Increased CO2 may initially boost calcifying plankton, but rising acidity disrupts biomineralization, possibly leading to declines.

• Modeling the Unknown

  • “We need to have the missing information to better understand and reconstruct the future of the carbonate systems... we don’t really understand it fully for sure.” (Patrizia Zaveri, 19:54)
  • No historical analogy exists for the current rate of atmospheric CO2 increase.

Notable Quotes

• “They leave a really incredible sedimentary record since many, many millions of years, so they can be studied also in the Earth history. So it's a very unique group of organisms.” – Patrizia Zaveri [01:19, repeated at 14:16]
• “This is big experiment we are doing at the global scale is quite new... and we don't really understand it fully for sure.” – Patrizia Zaveri [19:54]
• “The carbonic chemistry... is really fundamental, not only for life in the ocean... but also for maintaining the atmospheric CO2 and the carbon cycle... in a balanced way for many, many millions of years.” – Patrizia Zaveri [21:27]

3. An mRNA Vaccine Bonus in Cancer Therapy

[23:16–32:13]

Surprising Medical Synergy

• Adam Gripen reports research showing that patients on immune checkpoint inhibitors for cancer who happened to receive a Covid mRNA vaccine lived nearly twice as long as those who didn’t.

Key Insights:

• Immunotherapies, including “immune checkpoint inhibitors,” only work if the patient has an active immune response against their tumor.
  • “If you don't have any flame, you can fan all day and you will never create a fire.” (Adam Gripen, 24:55)
• mRNA vaccines (including for Covid) act as a potent “siren” to activate the immune system—potentially “resetting” immune cells inside tumors to attack cancer.
• Initially found in “accidental” observations, confirmed in retrospective studies of over 1,000 patients and then in animal models.
• The effect was so robust that median survival for those receiving vaccines doubled.
• Mechanistically, both the mRNA and lipid nanoparticle components appear necessary.
• Clinical trials are planned to validate these results.

Notable Quotes

• “The COVID mRNA vaccine acts like a siren to activate all the components of the immune system throughout the body. And when this happens inside a tumor, those immune cells... start looking around for things to kill...” – Adam Gripen [25:50]
• “Their median overall survival was nearly double what we saw in patients who didn’t receive this vaccine.” – Adam Gripen [27:20]
• “These are very early days in the idea and there have been many false dawns in cancer research. Let’s hope this isn’t one of them.” – Ronan Pease [32:13]

4. Mapping Crops in Africa: High-Tech Meets GoPro Simplicity

[32:13–39:42]

From Satellite Images to Motorbike Surveys

• Catherine Nakalembe uses GoPro cameras mounted on vehicles to collect millions of images of fields in Kenya, building real-world training datasets for machine learning models to better map crops from space.

Key Insights:

• GoPros mounted on car roofs or motorcycle helmets capture 5 million images in Kenya alone, with data processed to identify individual crops (“We were aggressive and we're collecting an image every .05 seconds... we get multiple images per field.” (Catherine Nakalembe, 34:31))
• The images serve as “ground truth”—critical for training AI models to interpret satellite data accurately for crop types and health.
• Crop identification is crucial for food security, yield prediction, and monitoring crops in refugee settlements.
• The method is “low tech and simple”—replicable, cheap, and scalable: “You can just send out an extension agent and they can do it.” (Catherine Nakalembe, 37:42)
• The system has been deployed in Uganda, Tanzania, Zambia, Madagascar, Germany, France, and the US.
• Nakalembe shares the protocol widely: “I call it a kits program. You can fill out a form... and I'll send you a kit.” (38:58)

Notable Quotes

• “Because the ultimate goal is to make a map with satellite data... we need, if we give the model examples, a lot of examples of these different crops in these different contexts, then you can have a voila.” – Catherine Nakalembe [36:26]
• “It does not make sense to do it any other way rather than this way. It’s really fun at the same time.” – Catherine Nakalembe [39:40]

Memorable Moments & Quotes

• On Coral Loss: “If there's not enough of them around, those eggs and sperm won't be able to find each other to fertilize and create new baby corals.” – Ross Cumming [08:23]
• On Ocean Carbonate Cycle: “We need to have the missing information to better understand and reconstruct the future of the carbonate systems.” – Patrizia Zaveri [19:54]
• On Vaccines and Cancer: “When this happens inside a tumor, those immune cells... start looking around for things to kill, and they start programming other immune cells to kill the cancer.” – Adam Gripen [25:50]
• On Mapping Crops: “Low tech and simple... you can just send out an extension agent and they can do it.” – Catherine Nakalembe [37:42]

Timestamps for Key Segments

• [01:57] – Introduction & Florida coral crisis
• [03:00] – Coral morphology and habitat (Ross Cumming)
• [05:39] – 2023 marine heatwave devastation
• [10:35] – Restoration efforts and new approaches
• [13:07] – Ocean carbonate cycle, plankton’s role (Patrizia Zaveri)
• [17:38] – Ocean acidification impacts
• [19:54] – Limits of current knowledge/modeling
• [23:16] – mRNA Covid vaccines and cancer immunotherapy (Adam Gripen)
• [27:20] – Improved survival rates in patients
• [32:56] – GoPro cameras to map African crops (Catherine Nakalembe)
• [34:31] – Mass image collection and data use
• [37:42] – Simplicity and scalability of the method

Tone & Takeaway

The episode’s tone is thoughtful but urgent—often somber in the face of climate-driven losses but buoyed by stories of resilience and innovation, both technological (cancer vaccine synergy, crop AI) and natural (corals’ former glory; planet-wide plankton). The human spirit in science comes through, whether despairing over reefs or joyfully assembling a GoPro field kit. The overarching message: As the world changes rapidly, deep understanding and creativity are both essential tools for the future.