75% of the world’s coral reefs in the Indian, Pacific and Atlantic oceans in 73 countries and territories have experienced bleaching level heat stress since February 2023, according to a National Oceanic and Atmospheric Administration (NOAA) report. This is the largest mass coral bleaching incidence on record. As water temperatures continue to rise, the likelihood of the coral being able to regrow is becoming increasingly small with experts warning that this may lead to the death of coral reefs and therefore leave half a billion people without one of their main sources of food and income.
What is coral bleaching?
Corals are living marine invertebrates that form a clustered underwater ecosystem called a coral reef. Inside the corals are microscopic brown/green algae called zooxanthellae which generate sugar and energy and are the corals’ food source. Healthy corals are brown/green in colour that matches the algae they consume but when the ocean environment changes, the corals can become stressed. The changes that cause this stress include high or cold temperatures, flooding which exposes the coral to fresh water, low tides or pollution. The stress causes the corals to expel the microscopic plants and they become paler and develop white, pink, yellow, blue or purple colouration. This is coral bleaching.
Prolonged high temperatures are the major reason for mass coral bleaching and also cause ocean acidification that impedes the regrowth and rebuilding of corals’ skeletons thereby increasing the chance of them dying. NASA reports that 90% of global warming has occurred in the oceans where, between 1901 and 2020, temperatures have increased by 2.8 degrees Fahrenheit.
If high ocean water temperatures were to subside, the bleached corals could regain the microscopic algae and recover. However according to David Wachenfeld the Chief Scientist at the Great Barrier Reef Marine Park Authority, the frequency of high temperatures is making the recovery of mass-bleached corals challenging and any recovery could take longer than it would have done twenty to forty years ago because climate change slows reproduction.
See also: Brazil’s economy to incur losses following unprecedented coral reef bleaching
In April 2024, NOAA reported that the current mass coral bleaching is the fourth major global coral bleaching event after those that occurred in 1998, 2010 and from 2014 to 2017. The ongoing coral bleaching event is expected to exceed the 2014 to 2017 incidence which was the most widespread and severe having affected 65.7% of the world’s reef area with bleaching-level heat stress.
Impact of coral bleaching
In 2020, the UN released research that showed that in 10 years from 2009 about 14% of the world’s corals were lost. This research was conducted in 12,000 sites in 73 countries by over 300 scientists. The loss was mostly attributed to rising sea surface temperatures. Although corals can recover from bleaching after high temperatures subside, their reproduction tends to be slower than those that have not been bleached. They are vulnerable to pathogens that cause diseases since their immunity has been compromised. Their energy levels are also low as they have lower densities of their food source, zooxanthellae.
Importance of corals
Corals are vital to ocean ecosystems and to livelihoods. This is why their conservation is important because over half a billion people depend on them for food, income and protection.
The value of goods and services provided by coral reefs annually is estimated to be US$2.7 trillion which includes US$36 billion in coral reef tourism. Collectively, coral reefs are projected to add economic benefits worth US$34.6 billion to US$36.7 from 2017 to 2030 in the Mesoamerica Reef and the Coral Triangle regions respectively.
Coral reefs shield the coastlines from erosion and storms while also providing livelihoods to coastline communities through fishing and recreational activities such as scuba diving. Corals and sponges have also helped in the research and production of medicinal chemicals.
Why coral conservation urgently matters
Reefs host over 4,000 species of fish, corals and other marine life which is why they are dubbed the rainforests of the seas and, although they cover 1% of the world’s oceans or less, they are the habitat of at least 25% of the world’s marine life.
Climate change is the biggest threat to corals according to research undertaken by Intergovernmental Panel on Climate Change scientists. They grimly predict that even if global warming is maintained at 1.5 degrees Celsius, this will still result in the loss of 70 to 90% of the average tropical coral reef cover by 2050 and 99% of the corals will be lost if temperatures rise to 2 degrees Celsius. They further state that climate change induced coral bleaching would increase poverty levels for the global coastline communities that rely on marine ecosystems for their livelihoods. This is why coral restoration needs to be urgently addressed.
Ongoing coral restoration efforts
Different coastline communities and relevant marine stakeholders around the world are involved in coral conservation efforts. In Kenya for instance, it is estimated that only 18% of hard corals remain in the reefs. This decline is attributed to bleaching and marine life overexploitation over the last three decades.
See also: Saving corals can save communities
Organizations like Oceans Alive and Reefolution are involved in reef restoration activities such as coral gardening in nurseries, transplanting, artificial reef placement and protection. In the island of Zanzibar, where 50% percent of Tanzania’s coral reefs are, women are involved in transplanting corals on underwater metal tables that serve as artificial reefs. Other organizations such as the Reef Ball Foundation are building concrete reef balls that are sunk into the Indian Ocean side of Tanzania to act as a coral breeding artificial reef habitat.
Call for funding and collective action in coral conservation
The ongoing threats to corals have led to the need to fund restoration efforts. In July 2024, the Global Fund for Coral Reefs (GFCR) announced a US$25 million grant to scale up resilience efforts among coral nations but, according to research, coral reefs are among the most expensive ecosystems to restore with the costs ranging from US$ 13,000 per hectare to over a hundred million US$ per hectare. This is why Peter Bryant, Builders Initiative’s Program Director for Oceans and GFCR Executive Board Member, is arguing for collective action to ensure 90% of remaining corals are not lost by 2050 as that could have dire consequences for the communities and economies they support.
