Coral reef mass bleaching

Great Barrier Reef Emergency

The fifth mass bleaching in the last eight summers is now hitting the Australian Great Barrier Reef: 2016, 2017, 2020, 2022, and 2024. Before 1998 we had not recorded mass bleaching, the bleaching was infrequent and localised. The increased intensity and frequency of mass bleaching are due to human-induced climate change.

The fifth mass bleaching in eight summers: Prof Terry Hughes: The Conversation: 9 Mar 2024.

We risk losing the Great Barrier Reef:

  • The single largest living marine structure on Earth, extending 2,300 km along the Australian coast
  • Extraordinary biodiversity
  • A key part of the regional ecosystem.
  • Protection of the Queensland coast from the full force of the Pacific Ocean.
  • A contribution of about $6.4 billion per year to the Australian economy
  • About 64,000 jobs, many in tourism.

No evident political impact

It seems that this terrible occurrence is making no ripples in our major parties, the ALP and the Coalition, and the expansion of fossil fuel activities is continuing.

Updated March 2024. I wrote the rest of this page in 2021.

(Great Barrier Reef: Most widespread coral bleaching on record: ABC: 7 April 2020)

(We just spent two weeks surveying the Great Barrier Reef. What we saw was an utter tragedy: Australian Geographic: April 2020)

Mass coral reef bleaching is now common around the world.

Bleaching in 2016 and 2017

Here are two maps of the Australian Great Barrier Reef showing the bleached areas in 2016 and 2017.

A map showing where the Great Barrier Reef bleached in 2016 and 2017
  • In 2016, this giant reef experienced its hottest sea surface temperatures for February, March, and April on record from 1900 to 2016.
  • Eight months after this 2016 marine heatwave, nearly one-third of the entire coral reef had bleached and died.
  • The following year, in 2017, there was another mass bleaching. Successive years of mass bleaching have not been recorded before.

Nearly one-third of the reef is dead after 2016, with more mass bleaching in 2017. This reef destruction is alarming evidence of global warming and the need to reduce greenhouse gases in our atmosphere.

(The Great Barrier Reef is vast. It extends for 2,300 km along the Australian coast.)

Other threats to the reef

As well as bleaching, the reef also suffers from:

  • Cyclones: The waves break the corals
  • Ocean acidification: the rates at which some corals are now building their skeletons have declined since 1990.
  • Pollution, and
  • Crown of thorns starfish.

The dangers of inaction

This damage is occurring with the current 1°C rise in average global air temperatures above pre-industrial levels. Governments are reacting very slowly, with some negotiating about a 2°C rise. A 2°C rise would almost certainly mean the collapse of warm water tropical reefs around the world.

The Great Barrier Reef and other reefs worldwide will not survive unless there are rapid, deep cuts in greenhouse gas emissions.


Coral Bleaching Events
Australian Institute of Marine Science

Lethal Consequences: Climate Change Impacts of the Great Barrier
The Climate Council 2018

Reef Health: Summer 2018 – 2019
Australian Government: Great Barrier Reef Marine Park Authority

Updated March 2021, updated March 2024