Ozone pollution is stunting tropical forest growth

It is a well-established fact that the ozone layer shields our planet from harmful ultraviolet radiation, playing a vital role in protecting life on Earth.

Preserving this layer stands as a golden feather in the environmental preservation cap, representing one of humanity’s greatest successes in global environmental cooperation.

However, when ozone managed to take residence at the ground level, it ceased to be a silent guardian; it became a dangerous threat to both the environment and public health.

Impacts of ground-level ozone

Ground-level ozone is a harmful combination of pollutants emitted from human activities such as industrial processes, vehicle emissions, and deforestation.

Under the unforgiving glare of sunlight, ozone pollution is causing considerable disturbance to our ecosystems.

Not only does it pose serious health risks to humans, leading to respiratory and cardiovascular problems, but it also interferes with plants' ability to absorb carbon dioxide, undermining their role in mitigating climate change.

Ozone and stunted forest growth

New research published in the journal Nature Geoscience paints an alarming picture of the growing threat posed by ground-level ozone pollution . It is significantly stunting the annual growth of tropical forests, with an average reduction of 5.1% in new growth.

The situation is even more severe in Asia, where certain regions are experiencing a dramatic 10.9% decline in new forest growth, highlighting the unequal impact of ozone pollution across the globe.

Reduction in forest carbon storage

According to Dr. Alexander Cheesman from James Cook University and the University of Exeter , tropical forests play a crucial role in offsetting carbon dioxide emissions. "Our study shows that air pollution can jeopardize this critical ecosystem service."

The study estimates that ozone pollution has prevented the capture of a staggering 290 million tons of carbon annually since 2000.

This significant loss of carbon sequestration capacity underscores the detrimental effect ozone pollution is having on tropical forests, which are critical for absorbing excess atmospheric carbon and mitigating the impacts of climate change.

"The resulting cumulative loss equates to a 17% reduction in carbon removal by tropical forests so far this century," said Dr. Cheesman.

Ozone pollution and forest restoration efforts

Urbanization, industrialization, and increased burning of fossil fuels have escalated emissions of "precursor" molecules, such as nitrogen oxides, that lead to ozone formation.

"Ozone concentrations across the tropics are projected to rise further due to increased precursor emissions and altered atmospheric chemistry in a warming world," said Dr. Flossie Brown, co-lead author of the study.

These rising ozone levels pose a significant threat to current and future forest restoration efforts, particularly in areas critical to mitigating climate change.

Improving air quality

"We found that areas of current and future forest restoration are disproportionately affected by this elevated ozone. It is clear that air quality will continue to play an important but often overlooked part in the way forests absorb and store carbon," said Dr. Brown.

Improving air quality is vital for enabling forests to effectively absorb and store carbon, noted study co-author Professor Stephen Sitch.

"Embracing a future with greater environmental protection would lead to reduced ground-level ozone, improved air quality, and the additional benefit of enhanced carbon uptake in tropical forests," said Professor Stitch.

The dual nature of ozone

Ozone exists in two forms: one as a protective shield in the stratosphere and the other as a harmful pollutant at ground level.

While stratospheric ozone is essential for blocking harmful ultraviolet radiation, ground-level ozone (also known as tropospheric ozone) forms when pollutants from vehicles, industrial activities, and fires react with sunlight.

This ground-level ozone acts as a greenhouse gas , trapping heat and contributing to climate change.

Ozone pollution is not only a threat to tropical forests but also to a wide range of ecosystems. In addition to stunting forest growth, ozone can damage crops, reduce agricultural productivity, and affect water quality by altering plant and soil interactions.

The broader ecological consequences of ozone pollution are becoming clearer, signaling an urgent need for stricter air quality regulations and the reduction of emissions that lead to its formation.

The study is published in the journal Nature Geoscience .

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