08:38, November 15, 2007 Pollution from cars and power stations
which causes an increase in atmospheric carbon dioxide (CO2)
levels is changing the face of autumn, according to a new study
by British scientists. Leaves are turning brown later in the
year than they once did because of rising levels of CO2 in the
atmosphere, researchers at the University of Southampton found.
The Independent newspaper reported Wednesday that the
researchers undertook two large forest ecosystem experiments, in
which poplar trees in separate plots were exposed either to
regular or elevated levels of CO2, from the time of planting to
full maturity. The elevated CO2 concentration was at 550 parts
per million, proposed as representative of concentrations that
may occur in 2050. The current level is just over 380 parts per
million. They found that the trees exposed to elevated CO2
levels retained their leaves for longer, and also experienced a
smaller decline in end-of-season levels of chlorophyll, the
green pigment found in leaves.