Steps to improve the shipping industry by cutting sulphur from fuels have unexpectedly worsened coral bleaching on the Great Barrier Reef, according to a recent study.
Sulphur pollution isn’t just bad for our lungs; it also helps to cool the ocean by shading it from sunlight. When ships emitted less sulphur, more sunlight heated up the waters, leading to increased stress on the corals.
Dr. Robert Ryan, an atmospheric scientist from the University of Melbourne, led the research. He noted that removing sulphur from fuels, while essential for health, has ironically meant more sunlight reaches the reef. His team found that during a recent bleaching event, corals faced 5% to 10% more heat stress because of this change.
In early 2022, the Great Barrier Reef experienced its sixth mass bleaching event, which surprised many as it occurred during a typically cooler La Niña year. The International Maritime Organization had recently tightened regulations on sulphur emissions from 3.5% to 0.5%. The study analyzed data from around 5,000 ships operating in the area during the heat build-up.
Ryan and his colleagues used computer models to predict the impact of the shipping regulations. The prevailing winds would have blown sulphur over the reef, providing natural shade that’s now gone. With fewer sulphur particles in the air, more sunlight reached the coral, leading to devastating heat stress.
Coral bleaching occurs when corals expel the algae that live in their tissues. This process leaves the coral looking white, known as “bleached.” If ocean temperatures stay high for too long, bleached corals can die.
Historically, the Great Barrier Reef has suffered from mass bleaching events since 1998, with a notable increase in frequency in the last decade. Experts warn that shorter recovery times between these events jeopardize coral survival.
While CO2 can linger in the atmosphere for many years, sulphur emissions disappear within days. “This means we need to address both air pollution and greenhouse gases simultaneously,” Ryan said.
Climate scientist Prof. Steven Sherwood pointed out that while the overall global effect of removing sulphur is small, the local impact can be significant. He emphasized that this study highlights a crucial balance we need to achieve in our climate efforts.
For more details on the study, you can read it here. The findings shed light on the complex relationship between air quality regulations and ecological health, underscoring the need for integrated environmental strategies to protect our oceans.
