A bid to clean up shipping industry intensified a coral bleaching event on Great Barrier Reef, study says | Great Barrier Reef

A bid to clean up shipping industry intensified a coral bleaching event on Great Barrier Reef, study says | Great Barrier Reef

January 22, 2026 discoverhiddenusacom Business

Efforts to reduce pollution from the shipping industry have inadvertently contributed to increased heat stress on the Great Barrier Reef, according to new research. A study led by Dr. Robert Ryan at the University of Melbourne found that removing sulphur from ship fuels, while beneficial for air quality, allowed more of the sun’s energy to reach the reef.

The Unintended Consequences of Cleaner Shipping

In 2020, the UN’s International Maritime Organization implemented regulations to significantly reduce the sulphur content of fuels used by ships, lowering the allowable amount from 3.5% to 0.5%. This change was intended to address the negative health and environmental impacts of sulphur pollution, which includes respiratory problems and acid rain. However, sulphur aerosols have a shading effect, reflecting sunlight and providing a degree of cooling.

Did You Know? The Great Barrier Reef has experienced seven mass bleaching events since 1998, with five occurring in the last decade.

Dr. Ryan and his team analyzed ship data from February 18-28, 2022, when heat was building on the reef, focusing on approximately 5,000 vessels in the region. Their modeling indicated that the reduction in sulphur emissions resulted in between 5% and 10% more of the sun’s energy reaching the reef’s waters compared to conditions prior to the regulation change. This increased heat stress contributed to the mass bleaching event observed in early 2022 – the first to occur during a La Niña year, which typically brings cooler temperatures.

Coral Bleaching and its Impacts

Coral bleaching occurs when corals expel the algae living in their tissues, causing them to turn white and become vulnerable. Mass bleaching events, first observed around the Caribbean in the 1980s, are primarily driven by rising ocean temperatures. While corals can sometimes recover from bleaching, prolonged or extreme heat can lead to coral death. The Great Barrier Reef, a vital ecosystem supporting fisheries and tourism, is particularly at risk.

Expert Insight: This research highlights the complex interplay between environmental regulations and unforeseen consequences. While reducing sulphur emissions is a necessary step for public health and environmental protection, it demonstrates that addressing climate change requires a holistic approach considering all potential impacts.

Professor Steven Sherwood, a climate scientist at the University of New South Wales, noted that while the overall global temperature increase from reduced sulphur emissions is small – estimated at a maximum of 0.05C – the localized effect on tropical ocean temperatures, and therefore coral reefs, can be more significant, potentially reaching 0.15C.

Frequently Asked Questions

What caused the 2022 bleaching event on the Great Barrier Reef?

The 2022 mass bleaching event was caused by a combination of factors, including rising ocean temperatures and increased heat stress resulting from the reduction of sulphur emissions from ships.

How does sulphur in ship fuel affect sunlight reaching the reef?

Sulphur pollution creates aerosols that have a shading effect, reflecting sunlight back into space and reducing the amount of solar energy reaching the ocean surface.

How long have mass bleaching events been occurring on the Great Barrier Reef?

Widespread mass bleaching was first observed on the Great Barrier Reef in 1998, and has occurred again in 2002, 2016, 2017, 2020, 2022, and 2024.

Given the complex interactions between air pollution regulations, climate change, and delicate ecosystems, what further research is needed to fully understand the long-term consequences of these changes?