Positive Effects of Pollution

Researchers at the Met Office Hadley Centre at the University of Leeds recently concluded that hazier conditions caused by pollutants in the air have caused plants to absorb 25 per cent more carbon.

The study, which included members from the Centre for Ecology & Hydrology, ETH Zurich - the Swiss Federal Institute of Technology - the Met Office Hadley Centre and the University of Exeter, analyzed the carbon intake of plants from 1960 to 1990.

While aerosols can cause lung problems when people breathe them in, the Met Office Hadley Centre study found that particle pollution in the air makes plants absorb more carbon dioxide from the atmosphere by diffusing sunlight.

"Although people normally believe that well-watered plants grow best on a bright sunny day, the reverse is true," said co-author Dr Stephen Sitch from the Met Office Hadley Centre in a recent interview. "Plants often thrive in hazy conditions such as those that exist during periods of increased atmospheric pollution."

The results of the Met Office Hadley Centre study, published in Nature, notes that the reduction in sunlight reaching the earth over this same period of time has caused photosynthesis in general to decline. However, the 25% increase in carbon absorption more than compensated.

From 1960 to 1990 the Met Office Hadley Centre study noted a 10% increase in the net amount of carbon absorbed and stored by vegetation.

"The overall effect was to enhance the land carbon sink even though the total solar radiation has decreased," said the Met Office Hadley Centre study's lead author Dr Lina Mercado in a recent interview.

However, Mercado noted that the increase in atmospheric particle pollution can only go so far before the benefits of more diffused light no longer compensate for the decease in overall photosynthesis.

Cutting back on atmospheric particle pollution, however, poses its own problems. As we clean "the air of aerosol pollution, plant photosynthesis will fall and part of the carbon sink will no longer be there," said Mercado. "So it will be harder to stop climate change and we will need to make bigger reductions in CO₂ emissions."

The Met Office Hadley Centre study concluded that the challenges of reducing our atmospheric particle pollution may in fact be greater than anyone had previously imagined. In addition to reducing our own output of atmospheric particle pollution we may also have to find a way to compensate for the loss of carbon sink we will experience as the skies clear.

Source:

Lina M. Mercado, 'Impact of Changes in Diffuse Radiation on the Global Land Carbon Sink,' Nature, April 2009

Hazy skies boost plant carbon intake, planetearth.nerc.ac.uk