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Two studies published today reveal fresh details of how much carbon dioxide is being taken up by the planet's plant life.

According to the first paper, published in Nature1, aerosol pollutants have increased photosynthesis globally in recent decades by diffusing light, which helps plants that can't compete in direct sunshine. In a separate study, also published in Nature2, scientists have issued the first estimate of how much carbon China's vegetation absorbs.

The research on the effects of aerosols is based on the insight that light quality is often more important than quantity when it comes to aggregate plant productivity. When aerosols scatter sunlight, trees in the upper canopy of a forest are not much affected by the loss of direct light, but the diffuse light penetrates lower down and promotes stronger growth in the shade.

Applied globally, this effect helped plants pull nearly 23.7% more carbon dioxide out of the atmosphere between 1960 and 1999 than they otherwise would have, according to a modelling study led by Lina Mercado at the Centre for Ecology and Hydrology in Wallingford, UK. Their work is published in Nature1.

Although the team did not provide a quantitative analysis of how much carbon is at stake, their results suggest the task of stabilizing atmospheric CO2 levels could be even more daunting. As governments phase out emissions of sulphur dioxide, the principal aerosol involved, light diffusion will decrease and so plants will absorb less and less of the CO2 produced by industry.

"The air is going to be cleaner, and this contribution of the diffuse radiation is going to disappear," Mercado says. "We need to take this into account."


De boodschap is dus: 'door schonere lucht te creëren, zullen planten minder C02 opnemen'