Coral Reefs And Climate Change

by Olivia Draycott

This article was updated by the editing team on 29th May 2025 to reflect new research.

Coral Reefs: Why Are They Crucial For The Climate?

At first glance, coral reefs may appear to be a form of marine vegetation, yet this is not the case. Coral reefs are in fact made up of polyps, animals that take in carbon dioxide (CO₂) and release oxygen (O₂)  during their feeding process [1]. These polyps, despite homing over a quarter of the globe’s marine life, constitute only 0.1% of the ocean floor [1]. Like many other types of fauna and flora, they are facing the brutal threat of climate change given their sensitivity to changing temperatures and rising levels of anthropogenic greenhouse gases including carbon dioxide and methane  [2].

Coral bleaching is the largest threat to polyps, as an increase of 1-2°C in ocean temperatures over a sustained period can result in bleaching. During this process, the coral turns white and, in the most drastic cases, dies [3]. This is an issue as coral reefs are estimated to support over 500 million people worldwide as a form of daily subsistence. The food and livelihoods provided are worth around £300 billion each year, and those who rely on them often come from lower-income countries [1,3]. Additionally, the reefs protect coastlines against extreme weather conditions by reducing the impact of land erosion in coastal areas. The ridged structure of the corals acts as a natural barrier that reduces the energy within waves by up to 97%, thus lowering the impact of tsunamis and hurricanes globally [4]. Consequently, as climate-induced weather events become more extreme, the protective role that reefs play will become ever more important.  

Why Should We Protect Coral Reefs?

As stated, coral reefs house over a quarter of all sea life on earth, provide vital protection for coastal communities, and act as natural carbon sinks. In addition to this multifaceted role, they also contribute significantly to medical advancements, as extracts from reef-dwelling animals and plants have been used to develop treatments for asthma, arthritis, cancer and heart disease [5]. Without true protection and a reduction in global temperatures, this may not be possible in the future.

Coral reefs are also a key indicator of climate change, and are often used to detect threats to more resilient ecosystems, due to their sensitivity to change [2]. If large scale deterioration of coral reefs occurs, the deterioration of other systems may cascade at an unprecedented rate. When global temperatures rose to record levels in 2023, exacerbated  by the El Niño climate pattern, scientists measured a major global coral bleaching event using a satellite monitoring program called NOAA’s Coral Reef Watch [6, 7]. This worrying trend continued in 2024 when global temperatures surpassed 1.5°C above pre-industrial levels for the first time ever, putting coral reefs at further risk of irreversible harm. This harm manifests not just as the destruction of the corals themselves but also includes disruption to fishing communities, alterations in carbon balance and reduced catches for fishing communities of reef fish species [8]. A geo-database of coral reefs at risk of bleaching is available here for further reading and to give a sense of the global scale of the devastation being caused [9].

References:

[1] WWF (2022), Coral reefs and climate change: from cradle to an early grave. Available at: https://www.wwf.org.uk/coral-reefs-and-climate-change (Accessed: 18 February 2022).
[2] SeCore International (2022), How climate change affects corals. Available at: http://www.secore.org/site/our-work/detail/how-climate-change-affects-corals.55.html (Accessed: 18 February 2022).
[3] IUCN (2017), Coral reefs and climate change. Available at:
https://iucn.org/resources/issues-brief/coral-reefs-and-climate-change (Accessed: 18 February 2022).
[4] National Oceanic and Atmospheric Administration (2022), Coral Reef Ecosystems. Available at: https://www.noaa.gov/education/resource-collections/marine-life/coral-reef-ecosystems#:~:text=Coral%20reefs%20protect%20coastlines%20from,food%2C%20income%2C%20and%20protection (Accessed: 18 February 2022).
[5] Natural History Museum (2022), Why are coral reefs important?, Available at: https://www.nhm.ac.uk/discover/quick-questions/why-are-coral-reefs-important.html (Accessed: 18 February 2022).
[6] Great Barrier Reef Corals Hit Hard By Global Warming, Available at: https://eos.org/articles/great-barrier-reef-corals-hit-hard-by-marine-heat-wave (Accessed: 19 March 2025).
[7] NOAA Confirms Fourth Global Coral Bleaching Event, Available at: https://www.noaa.gov/news-release/noaa-confirms-4th-global-coral-bleaching-event (Accessed: 19 March 2025).
[8] Reef Resilience (2022), Bleaching Impacts, Available at: https://reefresilience.org/stressors/bleaching/bleaching-impacts/ (Accessed: 18 February 2022).
[9] Coral Bleaching Locations, Available at: https://www.arcgis.com/apps/dashboards/84ba9c03786e462d960e3172bc1b2204 (Accessed on: 19 March 2025).