The reef runs along the eastern edge of the Australian continental shelf. It is between 30 kilometers (near Cairns) and around 250 kilometers (near Gladstone) from the almost parallel Australian east coast. There are around 1000 islands in the waters of the Great Barrier Reef, such as: B. the Whitsunday Islands or Dunk Island, and numerous sandbanks. The area of ​​the Great Barrier Reef is approximately 347,800 km² and it can be seen with the naked eye from space.

The Great Barrier Reef lost more than half of its corals in 2020 due to high water temperatures caused by global warming, according to several studies published in PNAS.[6][7]

As of March 2024, it was the fifth time since 2016 and the seventh time since 1998 that coral bleaching had occurred on a large scale. The cause of bleaching is increased sea temperatures; They are a consequence of global warming and were partly further intensified by El Ninos.[8] The bleach slows growth and

Warmer sea water temperatures caused by global warming is the leading cause of coral bleaching.[2]

The United Nations Environment Programme says that the longest recorded global bleaching events happened between 2014 and 2016. Coral was killed on an unprecedented scale. In 2016, bleaching of coral on the Great Barrier Reef killed between 29 and 50 percent of the reef's coral.[3][4][5] In 2017, the bleaching got into the central region of the reef.[6][7] The interval between bleaching events has halved between 1980 and 2016.[8]

Recent research showed that the coral-algae relationship is much older than was thought. This suggests it has survived many climate changes.[9]

Some corals change color instead of turning white when they are bleached. The colors can be very bright. In May 2020, scientists from the University of Southampton said that the colors act like sunscreen and protect the coral cells from light. The scientists said this means some corals can lose their algae for a while and might have developed bright colors as a way to make it easier for the algae to come back and to stay alive until then.[10][11]

• disturbance of wildlife

• Social - reduced amenity and perceptions of overcrowding for locals or visitors

• potential loss of core community values;

• loss of cultural values.

• too much waste

• climate change

Scientists have been warning since the 1990s that as global heating took hold, the world’s coral reefs would be among the earliest ecosystems to be affected.

When corals bleach due to higher than average ocean temperatures, they expel the algae that lives inside them and gives them much of their nutrients and colour.

If temperatures fall, corals can survive but scientists say they tend to be more susceptible to disease and struggle to reproduce. In extreme cases of heat stress, corals can die.

Dr Neal Cantin, senior research scientist at Aims, said: “We now need to combine the spatial coverage captured from the air with in-water surveys to assess the severity of coral bleaching

Table of contents

1 Importance of Coral Reefs

2 Bleaching process

3 causes

4 Observed coral bleaching events (selection)

5 Possible recovery

6 countermeasures

6.1 Artificial interventions

6.2 Protection of coral reefs

7 Literature

8 web links

9 individual data sets

Importance of coral reefs

In addition to tropical rainforests, coral reefs are considered to be the most diverse habitats in the world: around 60,000 different species have been discovered here so far. However, it is believed that there are more than 400,000 species in the reefs, e.g. B. more than a quarter of all known marine fish. The size of all reefs is estimated at over 600,000 km². Coral reefs have existed for over 225 million years, making them among the oldest known ecosystems in the world. With their biodiversity, especially fish, and as a tourist diving and snorkeling attraction, they are a source of food and income for large parts of the people living on the respective coasts. Since they can absorb 70 to 90% of the locally occurring wave energy, they protect the respective coasts from mechanical stress and destruction caused by waves.[1] When corals die, biodiversity declines: entire ecosystems or food chains can collapse; Coral species can disappear and with them fish that depend on them as a source of food or as a place to raise their offspring. Fishermen are losing their livelihoods and livelihoods; Diving tourism as a source of income is disappearing (the annual turnover of reef tourism is estimated at 9.6 billion dollars) as is the protection of the respective coast from waves: the financial damage caused by floods and storms in affected coastal regions, e.g. doubles to triples if one meter of reef height is lost.[1]