Humanity - the greatest threat to the Great Barrier Reef

The Great Barrier Reef is expansive and magnificent, yet it faces significant threats from repeated mass coral bleachings. This phenomenon, driven by high ocean temperatures, endangers the coral colonies that form the backbone of the reef. The latest research, published in the journal “Nature,” offers a long-term analysis of ocean surface temperatures. The findings indicate that the recent sea surface warming is unmatched over the past 400 years and confirm that human activities are to blame.

These results starkly confirm that global warming, driven by human actions, will continue to damage the Great Barrier Reef. Preventing this trend is possible, but only if humanity shifts its approach to greenhouse gases; otherwise, our generation is likely to witness the decline of one of Earth’s greatest natural wonders—the coral reefs.

The Great Barrier Reef, located in northeastern Australia, is the world’s largest coral reef system. It stretches about 2300 kilometers along the coast of Queensland, from the Torres Strait in the north to the city of Bundaberg in the south. This immense ecosystem comprises over 2900 individual reefs and 900 islands, forming one of the most diverse and vital ecosystems on the planet. It is home to an incredible variety of biological diversity, including more than 400 types of corals, 1600 species of fish, and 3000 types of mollusks.

The unique beauty of the coral reefs attracts thousands of tourists each year and is a crucial area for scientific research on biodiversity and climate change. The mass bleaching of corals on the Great Barrier Reef, which has occurred over the last three decades, has had serious repercussions for the reef. The Great Barrier Reef has experienced five mass bleachings in the past nine years.

Corals are unique recorders of the past. As they grow, their skeletons chemically reflect the ocean conditions at the time, including water temperature. Especially valuable in this regard are the large, boulder-shaped corals of the Porites species, which can live for centuries and are excellent archivists of marine history.

In the research project, an effort was made to understand the changes in the surface temperature of the Coral Sea and the surrounding reef over the last four centuries, focusing on the warmest months from January to March. Initially, comprehensive, continuous coral records from this region were collected and subsequently analyzed by a group of scientists specializing in marine climatology. This analysis utilized thousands of measurements of Porites corals from across the western Pacific.

Based on these records, average surface temperatures of the Coral Sea from 1618 to 1995 were reconstructed and calibrated to modern temperature records from 1900 to 2024. The results were alarming. From 1960 to 2024, there was an observed annual increase in average summer temperatures of 0.12°C per decade.

Surface temperatures of the sea in the years 2016, 2017, 2020, 2022, and 2024 were analyzed and found to be five of the six highest temperatures recorded in the region over the last four centuries. Human responsibility for the rise in temperatures in the Coral Sea is undeniable. Research using climate simulations, both with and without human influence, showed that without human activity, water temperatures from January to March would have remained stable since 1900. Human impact has caused the region to gradually warm since the early 20th century, with temperature increases intensifying after the 1960s. Climate forecasts indicate further intensification of warming, which threatens nearly annual coral bleaching, reducing their ability to recover. Without decisive action to reduce greenhouse gas emissions, even under the objectives of the Paris Agreement, losses could range from 70% to 90% of the world’s coral population.