Ozone Pollution Threatens Tropical Forests’ Role in Climate Mitigation

By Vivek Saini

A recent study has revealed that ground-level ozone pollution is significantly stunting the growth of tropical forests. These crucial ecosystems absorb vast amounts of carbon dioxide from the atmosphere. Tropical forests mitigate climate change by sequestering roughly 25% of human-generated carbon dioxide emissions. However, the study finds that ground-level ozone, formed from the interaction of human-made pollutants and sunlight, impairs plants’ ability to capture carbon, substantially reducing carbon absorption.

The Role of Tropical Forests in Carbon Capture

Tropical forests have long been recognised as essential “carbon sinks,” helping to mitigate global warming by absorbing large amounts of carbon dioxide from the atmosphere. In addition to their climate-regulating role, they provide habitat for biodiversity and support ecosystem services that benefit humanity. Yet, the new research indicates that this critical function is under threat from increasing levels of ozone pollution. The damage caused by ozone is not limited to forest growth but also impacts broader ecological stability​.

The study published in Nature Geoscience found that tropical forests, particularly in Asia, are experiencing growth reductions as high as 10.9%, well above the global average of 5.1%​. These forests are already vulnerable to deforestation and other environmental pressures, and the added stress from ozone pollution may accelerate their decline. The implications extend beyond the tropics, as diminished forest growth undermines global carbon sequestration efforts, potentially accelerating climate change​.

Dr. Alexander Cheesman, co-lead author of the study from James Cook University and the University of Exeter, says Tropical forests play a crucial role in mopping up our carbon dioxide emissions. Our analysis shows that air pollution can jeopardise this critical ecosystem service. “We estimate that ozone has prevented the capture of 290 million tonnes of carbon annually since 2000. The resulting cumulative loss equates to a 17% reduction in carbon removal by tropical forests so far this century.” he added.

Impact on Forest Growth

Ozone pollution is not uniformly distributed, and its impact on tropical forests varies by region. The research highlighted that Asian tropical forests face the most significant challenges, with some areas losing more than 10% of their new annual growth​. This growth loss is particularly concerning because tropical forests are critical to absorbing excess carbon dioxide, helping slow the effects of global warming. These ecosystems capture more carbon than any other land-based biome, making their protection an international priority.

Ground-level ozone is formed when pollutants from industrial activities, fossil fuel combustion, and fires combine with sunlight. As human activities continue to generate these pollutants, ozone levels in tropical regions are expected to rise further, exacerbating the already concerning impact on forest productivity. The study emphasises the urgent need for action to reduce these emissions, as ongoing damage to tropical forests could severely undermine international climate targets​.

Ozone’s Rise and Future Projections

Ground-level ozone is formed when pollutants, such as nitrogen oxides from industrial activities, fossil fuel combustion, and forest fires, react with sunlight. This issue is expected to worsen as global emissions increase and atmospheric chemistry shifts in a warming climate​. Ozone concentrations across the tropics are projected to rise, exacerbating the substantial losses in forest productivity​.

The study called for enhanced environmental protection measures to address the threat posed by ground-level ozone. By improving air quality standards and reducing emissions of ozone-forming pollutants, policymakers can help tropical forests restore their vital role as carbon sinks​. Strengthening these protective measures will support climate mitigation efforts and benefit biodiversity and human health.

References:

https://www.nature.com/articles/s41561-024-01530-1

https://www.indiatoday.in/environment/story/ozone-pollution-hitting-growth-of-tropical-forest-affecting-carbon-capture-2599041-2024-09-13

https://www.downtoearth.org.in/pollution/ozone-pollution-slows-tropical-forest-growth-by-halting-carbon-absorption

Ozone pollution reduces tropical forest growth

Photo by Vishal Yadav on Unsplash

Banner Image:
Photo by Eelco Böhtlingk on Unsplash