Coral Bleaching: How To Respond To The Ongoing Emergency?

Coral reefs are facing the worst global bleaching event on record, with over 80% of reef areas affected between 2023 and 2025, threatening biodiversity and the livelihoods of over a billion people. A coordinated global response is essential, involving emissions reduction, local conservation, scientific restoration, effective monitoring, policy reform, and legal action to protect and restore reef ecosystems.

by Dora Scribe

The world is currently experiencing a global coral bleaching event, according to National Oceanic and Atmospheric Administration (NOAA) scientists [1]. This is the fourth global event on record and has become the largest ever recorded [1]. 

Coral reefs are known as the rainforests of the sea thanks to their ability to act as carbon sinks and their high biodiversity, supporting a third of all marine species and a billion people [2]. From January 2023 to April 2025, bleaching-level heat stress has impacted over 80% of the world’s coral reef area, and mass coral bleaching has been documented in at least 83 countries and territories [3]. 

What are the causes and consequences of coral bleaching?

Coral bleaching is caused by rising ocean temperatures, ocean acidification, and local stressors like overfishing [4]. The ocean’s temperature has increased by 1°C since 1900 [8], and ocean acidification has increased by 26% since the beginning of the Industrial Revolution because of the massive absorption of carbon dioxide by the oceans [6].

Corals are sessile animals, meaning they permanently attach themselves to the ocean floor [7]. When corals are stressed by changes in conditions such as temperature, light, or pollution, they react by expelling the symbiotic algae living in their tissues, causing them to turn white [8]. This algae, called zooxanthellae, provides the coral with energy through photosynthesis, allowing them to grow and reproduce [8]. Without it, corals are left without a food source, making them vulnerable to disease and death [4]. 

Global warming causes more frequent and intense marine heatwaves, which can last weeks, months or even years [9]. If ocean temperatures remain high for eight weeks or longer, the coral cannot recover and begin to die [9]. 

The decline of coral reefs has important consequences for marine biodiversity and human communities [4]. Although they cover less than 0.1% of the world’s ocean surface, they provide a home for at least 25% of all marine species [5]. Thousands of marine animals depend on coral reefs for survival, including some species of sea turtles, fish, crabs, shrimp, jellyfish, sea birds, starfish, and many more [10]. 

Coral reefs are also natural barriers that absorb the force of waves and storm surges, helping to keep coastal communities safe [8]. Without them, we must rely on man-made sea walls that are expensive, less effective, and environmentally damaging to construct [10]. Global estimates suggest we have lost half of the world’s corals since 1950 [11]. 

How to respond to the ongoing emergency?

These unprecedented losses underscore the urgent need for decisive and coordinated action. Effectively addressing coral bleaching requires a comprehensive strategy that integrates both climate change mitigation and adaptation, combining global climate initiatives, localized conservation efforts, and scientific innovation [12]. Central to this approach is the reduction of greenhouse gas emissions, as rising ocean temperatures and ocean acidification remain the primary drivers of coral bleaching [4]. At the same time, local actions — such as controlling pollution, promoting sustainable fishing practices, and establishing marine protected areas — are essential to alleviate stress on reef ecosystems [12].

Conservation and restoration efforts also play a vital role. Researchers emphasize the importance of diversifying coral species and genetic varieties in restoration nurseries to enhance reef resilience [12]. In response to increasing bleaching events and disease outbreaks, current strategies focus on cultivating a wide range of coral genotypes and distributing restoration activities across multiple sites. This diversification helps buffer reefs against localized disturbances, including sudden heatwaves and disease flare-ups [12].

Furthermore, mobilizing private sector investment is essential to fund conservation and restoration efforts, but remains a significant challenge due to the hidden nature of coral reefs beneath the ocean surface. Unlike more visible ecosystems such as forests or mangroves, coral reefs often go unnoticed by the public and business leaders, making it difficult to attract financial support [12].

On the policy front, effective global monitoring of coral bleaching is crucial. Monitoring data has already played a pivotal role in shaping international agreements. For example, evidence of the severe impacts of rising sea temperatures on coral reefs influenced the Paris Agreement, which established temperature thresholds to limit global warming to below 2°C — and ideally 1.5°C — above pre-industrial levels [13]. 

Similarly, the Convention on Biological Diversity (CBD) incorporated coral bleaching impacts into its goals, particularly Target 8, which aims to minimize climate change effects on biodiversity and strengthen ecosystem resilience [13]. The Intergovernmental Panel on Climate Change (IPCC) has also integrated detailed heat stress projections into its reports, reinforcing the urgency of both mitigation and adaptation strategies [13]. Building on these insights, the United Nations Environment Programme (UNEP) has issued global guidelines for coral reef management and climate adaptation, embedding reef resilience into marine spatial planning [13]. Additionally, the International Coral Reef Initiative (ICRI) and its operational arm, the Global Coral Reef Monitoring Network (GCRMN), use long-term datasets to produce comprehensive reports that inform global conservation strategies [13].

Finally, integrating climate litigation into marine conservation efforts is emerging as a powerful tool. Legal action — particularly through international courts such as the International Court of Justice — can hold governments accountable and drive policy changes that protect coral reefs and broader marine ecosystems [12].

References:

[1] National Oceanic and Atmosphere Administration, NOAA confirms 4th global coral bleaching event, 15/04/2024, https://www.noaa.gov/news-release/noaa-confirms-4th-global-coral-bleaching-event, accessed on 16/06/2025.
[2] The Guardian, More than 80% of the world’s reefs hit by bleaching after worst global event on record, 23/05/2025, https://www.theguardian.com/environment/2025/apr/23/coral-reef-bleaching-worst-global-event-on-record, accessed on 16/06/2025.
[3] Earth.org, Scientists Confirm Largest Coral Bleaching Event on Record Affecting Nearly 84% of World’s Reefs, 28/05/2025,  https://earth.org/scientists-confirm-largest-coral-bleaching-event-on-record-affecting-nearly-84-of-worlds-reefs/, accessed on 16/05/2025.
[4] Jim Canlon, Why Caribbean Coral Reefs are Dying—And Why It Matters, 28/02/2025, https://www.jointsdgfund.org/article/why-caribbean-coral-reefs-are-dying-and-why-it-matters, accessed on 16/05/2025.
[5] BBC, Coral reefs, https://www.bbc.co.uk/bitesize/guides/z2ntk7h/revision/4, accessed on 20/05/2025. 
[6] Ocean & climate platform, Ocean acidification, https://ocean-climate.org/en/awareness/the-impact-of-climate-change-on-the-ocean/, accessed on 16/05/2025. 
[7] National Oceanic and Atmosphere Administration, Are corals animals or plants?, https://oceanservice.noaa.gov/facts/coral.html#:~:text=Corals%20actually%20comprise%20an%20ancient,own%20food%2C%20as%20plants%20do, accessed on 20/05/2025.
[8] National Oceanic and Atmosphere Administration, What is coral bleaching?, https://oceanservice.noaa.gov/facts/coral_bleach.html, accessed on 16/05/2025. 
[9] Australian Marine Conservation Society, Coral bleaching, https://www.marineconservation.org.au/coral-bleaching/, accessed on 16/05/2025.
[10] WWF, Everything You Need to Know about Coral Bleaching—And How We Can Stop It, https://www.worldwildlife.org/pages/everything-you-need-to-know-about-coral-bleaching-and-how-we-can-stop-it, accessed 16/05/2025. 
[11] The Guardian, Global coral cover has fallen by half since 1950s, analysis finds, 17/09/2021, https://www.theguardian.com/environment/2021/sep/17/global-coral-cover-halves-since-1950s-analysis-finds-aoe, accessed on 20/05/2025.
[12] Perry Institute for Marine science, 7 Key Takeaways from COP16: Confronting Coral Reef Challenges in a Changing Climate, 29/10/2024, https://www.perryinstitute.org/7-essential-insights-from-cop16-tackling-coral-reef-conservation-challenges-amid-climate-change/, accessed on 20/05/2025.
[13] Rivera-Sosa, A., Muñiz-Castillo, A. I., et al., Six decades of global coral bleaching monitoring: a review of methods and call for enhanced standardization and coordination, 26/03/2025, ://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2025.1547870/full, doi: 10.3389/fmars.2025.1547870.