April 23, 2009

Plants absorb more carbon under hazy skies

British scientists say they've found plants absorb carbon dioxide more efficiently under Earth's polluted skies than they would in cleaner settings.

Surprisingly, the effects of atmospheric pollution seem to have enhanced global plant productivity by as much as a quarter from 1960 to 1999, said lead author Lina Mercado of the Center for Ecology & Hydrology. This resulted in a net 10 percent increase in the amount of carbon stored by the land once other effects were taken into account.

The scientists said an increase in microscopic particles released by human activities, and subsequent changes in cloud cover, caused a decline in the amount of sunlight reaching Earth's surface from the 1950s up to the 1980s.

Although less sunlight reduces photosynthesis, the atmospheric particles scatter light so a plant's surface receives light from multiple directions rather than straight from the sun. The researchers said plants are then able to convert more available sunlight into growth because fewer leaves are in the shade.

Although many people believe well-watered plants grow best on a bright sunny day, the reverse is true, said study co-author Stephen Sitch of Britain's Meteorological Office Hadley Center. Plants often thrive in hazy conditions such as those that exist during periods of increased atmospheric pollution.

The study, which included University of Exeter Professor Peter Cox, appears in the journal Nature.