There are many environmentalists who believe trees will grow faster with more carbon dioxide (CO2) in the air – but that just ain’t so, according to two professors at the University of Guelph.
Ze’ev Gedalof and Aaron Berg had hoped to have a student complete a study for them to determine if it was true that trees would grow faster with more CO2 – and if trees could help offset carbon footprints in Canada.
A lot of people were fooled into believing that theory, and Gedalof said in an interview last week, “With more carbon dioxide in the air, trees should grow faster. Many scientists have made this argument.”
He said one reason the now discredited theory was so easy for people to believe is because greenhouse operators have actually found CO2 in those buildings does have an effect on the plants grown there.
But, Gedalof said, “We tested trees – and we found it not to be true. They are not growing faster with increased carbon dioxide in the atmosphere.”
Gedalof said he and Berg took over three years working a few hours a week to analyze the data, first making sure that it was correct for “quality assurance.”
Their findings have implications for the Canadian environmental movement and policy.
Gedalof said, “Canada has options under the Kyoto protocol to used forest management to offset carbon dioxide emissions” from such places as oil sands projects. “Our research suggests that … we can’t count on trees to accelerate growth.”
He noted though, Canada has not used that Kyoto option, which he characterized as “quite sensible.”
Gedalof explained forests are more likely to become carbon sinks because forest fires will release far more carbon damage into the atmosphere than they can be expected to take up in carbon dioxide.
“For once, it sounds like all those politicians were listening,” he said with a chuckle about them getting the policy correct, even if it is “for the wrong reasons.”
The duo studied archived tree ring measurements from the National Oceanic and Atmospheric Administration in the United States and found that carbon dioxide increased tree growth at about only 20 per cent of the sites around the world, and 80 per cent of the world’s forests showed no effect at all.
They also determined that faster growth rates would not be attributed to climate change, nitrogen deposits, sensitivity to climate, latitude, or elevation.
They analyzed data from nearly 2,300 forests on six continents and that covered 86 tree species.
Berg said in an interview that since they released their findings, some reports have suggested the two are saying it does no good to plant trees – and he said that is definitely not the case.
“Additional trees have a great impact because you have more stock to pull carbon dioxide,” Berg said.
Gedalof added, “There’s all kind of other evidence why we’d want to produce trees.”
