Sustainability Corner: Coral reefs and mass bleaching events

How can reefs be preserved as they continue to experience extreme conditions?

Photo courtesy of Danielle.ihde/Wikimedia Commons

The Australian Institute of Marine Science (AIMS) is one of many organizations that have devoted the last several decades to monitoring the Great Barrier Reef and other large reef structures around the world. Over the last two months, via expansive reports and overhead surveys, AIMS has determined that 2025 marks another coral mass bleaching event; this time, possibly more harrowing than before, as reports have stressed that “while less extensive…it is the second time the Reef has experienced consecutive [yearly, mass bleaching] events.” 

Globally, coral reefs are experiencing a phenomenon known as bleaching, which on a mass scale disrupts ecosystems and contributes to the growing issue of fish species dying out. The National Oceanic and Atmospheric Administration (NOAA) describes this phenomenon as such: “When water is too warm [or cold], corals will expel the algae (zooxanthellae) living in their tissues causing the coral to turn completely white…” The Great Barrier Reef Foundation (GBFR) noted that this transformation causes reefs not to immediately die off, but rather become “more at risk of starvation and disease,” and effect of this is the potential to harm and even kill off reef systems. 

As described by WorldWildlife,“once these corals die, reefs rarely come back. With few corals surviving, they struggle to reproduce, and entire reef ecosystems, on which people and wildlife depend, deteriorate.” This notion is further stressed by AIMS, which states that mass bleaching “can result in widespread mortality,” explaining that “the frequency, intensity and area of heat stress causing coral bleaching is increasing over time, as a result of changes to the Earth’s climate.” 

AIMS has spent 40 years monitoring the phenomenon of bleaching in the Great Barrier Reef, noting, “Mass bleaching events on the Great Barrier Reef have been documented with full-scale surveys in 1998, 2002, 2016, 2017, 2020, 2022, 2024 and 2025.” There have been multiple mass bleaching events documented—the fourth, as reported by NOAA, was confirmed to have occurred “From 1 January 2023 to 11 September 2025” in an event where “heat stress has impacted 84.4% of the world’s coral reef area and [caused] bleaching…in at least 83 countries and territories.” 

Furthermore, AIMS Summer of 2024-25 report stated that factors like elevated temperatures, cyclones, rainfall, and the invasive, coral eating, and crown-of-thorns starfish are the current leading causes of degradation during these bleaching events. However, this report stressed that “Climate change remains the greatest threat to the Reef. It influences weather patterns and the ocean’s temperature, pH level and currents, as well as intensifying the effects of other threats.” 

While currently in a period of monitoring—and a reported lull of mass bleaching compared to years prior—reports from the Global Tipping Points Report 2025, which has “A total of 160 authors, from 23 countries and 87 institutions contributed,” stated that these mass bleaching events and other extreme weather-based events will continue to rise as we enter a world where the effects of climate change are not a possibility, but an inevitable reality. The introduction, page 45, of this report states “The world has entered a new climate reality. Global warming will soon overshoot 1.5°C. Already some damaging tipping points are being crossed and others could soon follow – with catastrophic impacts on societies and nature globally.” 

As the world’s climate continues to shift, accelerated by human action, these bleaching events cannot be avoided. However, change can be made to prevent their widespread worsening. This report's introduction continues, urging that “Governance has to change to address this new reality… incremental change will not be enough to avoid the worst impacts. Instead climate action must accelerate radically to eliminate greenhouse gas emissions, to reduce non-climate stressors of ecosystems, and to regenerate nature before it is too late.” 

With the right governmental attention, these events and the damage they cause can be consolidated and relegated to small pockets, rather than widespread blooms. The GBRF notes, “Coral bleaching can’t be stopped entirely, but we can reduce its impact by cutting emissions, limiting local stressors like pollution, and supporting reef restoration efforts. Protecting coral reefs also means reducing coastal runoff, establishing marine protected areas, and investing in research that helps corals adapt to rising temperatures.” 

The way forward is to ensure that we not just petition for, but demand action from our representatives. As the effects of human-caused climate change continue to accelerate , the time to sit idly by has long since passed us; action is necessary to avoid potential mass environmental catastrophes. Please stay informed and up to date on happenings globally, as it could change the course of your tomorrow.