Coral reefs, which support a quarter of all marine species, are facing an increasingly dire future as climate change and ocean acidification push these ecosystems toward irreversible collapse—and scientists are now exploring whether emerging technologies to cool the planet could help.
Coral reefs are among the most vital ecosystems on Earth. Beyond supporting marine biodiversity, they supply fisheries that millions of people rely on, protect coastlines from storms, and sustain local tourism economies. Their global economic value is estimated in the tens to hundreds of billions of dollars annually. For United States territories like Guam, American Samoa, the US Virgin Islands, Puerto Rico, and the Northern Mariana Islands, coral reefs are not a distant environmental concern — they are foundational to coastal protection, food security, and economic life.
The threats are mounting. Ocean surface temperatures have risen by 0.5°C since the 1980s, and scientists found that the world’s oceans absorbed a record amount of heat in 2025. When water temperatures rise, corals expel the symbiotic algae living in their tissues in a process known as coral bleaching, leaving them white, vulnerable to disease, and without their primary food source. If hot conditions persist for weeks, bleaching can be fatal. Researchers have warned that most corals could face bleaching events on an annual basis later this century, and that reef systems are crossing tipping points that risk irreversible collapse.
Ocean acidification compounds the crisis. As oceans absorb carbon dioxide emissions, seawater becomes more acidic, weakening coral skeletons and limiting their growth. Even under optimistic climate scenarios, acidification is projected to worsen. Since the 1950s, global coral coverage has already halved.
Cutting carbon dioxide emissions remains essential for addressing the root causes of both ocean warming and acidification. But scientists acknowledge that past emissions have already committed the planet to a hotter, more acidic ocean for centuries to come, and are exploring additional interventions.
One area of growing research is sunlight reflection methods (SRM)—also known as solar geoengineering—a set of approaches designed to reflect a small fraction of incoming sunlight to reduce global temperatures. Two methods have drawn particular attention in the context of coral protection.
Marine cloud brightening would involve ships spraying sea-salt particles into low-lying ocean clouds to make them more reflective, providing temporary regional cooling. Studies suggest this could reduce heat stress on corals and significantly lower bleaching rates, though questions remain about its technical feasibility and whether it could be counterproductive in some cases.
Stratospheric aerosol injection, the most researched SRM approach, would use specially designed high-flying aircraft to release tiny particles into the upper atmosphere, creating a global layer that reflects sunlight. Researchers believe this is technically feasible, and modeling suggests it could significantly reduce coral bleaching. However, it would not address ocean acidification, and scientists caution that it carries side effects, including potential shifts in rainfall patterns and delays in ozone layer recovery.
Governance poses an equally serious challenge. SRM deployment would affect the entire planet, and its benefits and risks would not be distributed evenly—a concern of particular relevance for island territories already on the front lines of climate change. An abrupt halt to large-scale SRM could also trigger what scientists call “termination shock,” a rapid temperature spike with potentially devastating consequences.
A January 2026 primer published by SRM360, a nonprofit focused on solar geoengineering research and governance, concludes that protecting coral reefs will require many measures, and that SRM could play a role in limiting temperature-driven threats, even as it cannot substitute for emissions reductions or address acidification directly.
For the territories, where reefs are inseparable from daily life and economic survival, the stakes of inaction—and the risks of untested interventions—are not abstract. They are existential.
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