Reduced ozone levels may lead to more carbon being absorbed by Europe's forests

In a new scientific study, researchers have calculated how reduced ozone formation could affect carbon uptake in Europe's forests. The study states that if exposure to ground-level ozone were eliminated, the growth of Europe's forests could increase by an average of nine percent, and carbon uptake into forest biomass could increase by over 30 percent.

The study shows that carbon sequestration in Europe's forests can increase significantly if emissions of ozone-forming substances are reduced. Forests play an important role in limiting climate impacts. Increased forest growth can also enable increased production of forest raw materials, which can replace the use of fossil materials, says article co-author Per Erik Karlsson, researcher at IVL Swedish Environmental Research Institute.

Ozone is formed near the ground through emissions of ozone-forming substances such as nitrogen oxides and volatile organic compounds, e.g. from vehicle exhausts and industry. Ozone is a powerful oxidant that is harmful to humans and plants. In forests, high ozone levels lead to reduced growth.

The article, published in the journal Biogeosciences, is the result of a European collaboration, with Swedish funding from the Swedish Environmental Protection Agency within the ICP Vegetation programme of the Convention on Long-range Transboundary Air Pollution. The article describes how exposure to ground-level ozone affects carbon sequestration in European forests over a five-year period.

The calculations are based on the most current knowledge regarding the impact of ozone on tree growth, combined with statistics on, among other things, forest harvesting in various European countries. The results show that the critical level for negative ozone impact on forests is currently being exceeded in much of Europe.

The researchers' calculations show that reduced ozone exposure, at pre-industrial levels, would increase the average annual growth of European forests by nine percent, and that the annual increase in carbon dioxide uptake by living biomass would increase by as much as 31 percent. Carbon uptake into forest biomass depends on the difference between annual growth and annual harvesting. For many countries this difference is small, which means that a small increase in growth has a large effect.

The study shows that by reducing air pollution problems related to the formation of ground-level ozone, significant climate benefits can also be achieved through increased carbon uptake in forests, both in Europe and globally, says Per Erik Karlsson.

The article is freely available here: Ozone causes substantial reductions in the carbon sequestration of managed European forests External link, opens in new window.

For questions, contact:
Per Erik Karlsson, pererik.karlsson@ivl.se, tel. +46 (0)10-788 67 57