One-third of the Great Barrier Reef has died due to coral bleaching

Graphic by Natalie Kulak '21

Graphic by Natalie Kulak '21


A new study discovered that an underwater heat wave two years ago resulted in the death of one-third of the Great Barrier Reef, according to The New York Times. Though the Reef is a physical and sedentary piece of the Australian underwater landscape, it is a living and vibrant collection of coral and other organisms. 

Jason Andras, a biology professor at Mount Holyoke who has done research on coral reef communities, described the unique construction in greater detail. “Though they’re often mistaken for rocks or plants, tropical reef-building corals are animals that live symbiotically with unicellular algae called zooxanthellae. The zooxanthellae live inside the coral’s tissue, and they share the sugar they make from photosynthesis with the coral,” said Andras.

The damage to the Reef is irreversible and can be attributed to coral bleaching, a phenomenon resulting from the underwater heat wave. “Coral bleaching is essentially the break-down of this partnership. When water temperatures get too hot, the stress prompts the corals to evict their symbionts, leaving them without their main source of nutrition,” said Andras. “Unless they can regrow or reacquire new zooxanthellae quickly, bleached corals will starve and die.” 

Similar large-scale bleachings were noted in 1998, 2002, 2016 and 2017. National Geographic stated that while the last few years caused the most extensive damage to the Great Barrier Reef, the newly reported coral deaths this year are in a different region of the Reef — one that had previously been stable.  

Climate change causes an increase in the temperature of the oceans, which is the prevailing cause of coral deaths. Many organisms, like coral, are unable to adapt to the rapid temperature increase and die. According to NBC, 90 percent of coral species are likely to become extinct by 2050 due to warming waters. Coral reef expert Richard Richmond spoke to National Geographic about the impact of climate change on coral, despite their adaptability.

“Corals are resilient creatures,” said Richmond. “Given a chance they can come back. We’re just not getting any breaks whatsoever, and the severity of the problem is increasing with time.”

In addition to climate change, pollution from fertilizers or from tourism can be harmful to reefs. Tourism to the Great Barrier Reef is a probable contributor to bleaching, but thousands of jobs and large amounts of income for Australia depend on this industry. Experts urge anyone visiting the Great Barrier Reef to minimize their footprint on the Reef and the surrounding waters. In order to do this, scuba divers and snorkelers should be aware of the types of sunscreen that can be harmful to the environment and pick up trash in or near the ocean, according to NBC. 

Corals are essential to the communities that reside within them. Reefs provide a habitat for over a quarter of marine biodiversity so losing corals means losing a variety of other species as well. This loss would impact the seafood industry as well as the environmental richness of these areas. 

Corals also protect the coastline from receiving the brunt of storms by forming a barrier between the ocean and the shore, and inevitably saving human lives. Nicole Palmer ’19, an environmental studies major, believes the loss of coral reefs will be felt widespread. “The advancement of coral bleaching in the Great Barrier Reef is a testament to the lack of human concern for climate change and its unfounded effects on the Earth’s biodiversity,” she said. “Coral reefs are far more connected to us than we believe, and the ecosystem services they provide will be lost as we allow our interests in fossil fuels to dominate. We derive many benefits from systems like the Great Barrier Reef, and they have an inherent value as a part of the natural world that we cannot ignore as we plan for the futures of energy and biodiversity.” 

Andras has witnessed the loss of these vibrant ecosystems firsthand. “I studied coral reefs in the Caribbean throughout my graduate studies, and even over that relatively short period, I saw firsthand the degradation of the reefs I knew well. These are truly tragic losses,” he said. “It’s absolutely clear from the scientific evidence that the primary driver of coral decline is ocean warming caused by anthropogenic climate change. Unless the global community finds a way to dramatically curb its appetite for fossil fuels soon, the loss of corals will accelerate and most of the great reefs of the world, which took millions of years to form, will be gone within our lifetimes.”