Though we knew that trees alone wouldn't provide the silver bullet needed to single-handedly fix global warming, a new study from scientists at Duke University in North Carolina seems to have cast doubts on the notion of using trees at all as a strategy to reduce carbon emissions. It's not that trees in themselves can't store carbon dioxide well: it's just that, to do so, the trees need to receive substantial amounts of water and nutrients — a requirement not always easy to meet (especially in the case of adverse weather events).
Ram Oren and his colleagues spent a period of 10 years bathing plots of pine trees in extra carbon dioxide every day (1.5 times the current levels of GHG in the planet's atmosphere). This project — dubbed the Free Air Carbon Enrichment (FACE) experiment — compared 4 different plots exposed to higher levels to 4 matched plots lacking the extra carbon dioxide. They found that while the trees typically grew more — producing approximately 20% more biomass on average — only those trees supplied with the most nutrients and water could store enough carbon dioxide to effectively offset the effects of global warming.
"In some areas, the growth is maybe five to 10 percent more, and in other areas it's 40 percent more," said Oren. "So in sites that are poor in nutrients and water we see very little response. In sites that are rich in both, we see a large response."
Furthermore, Oren and his team noted that only a few parts of the trees stored carbon for long periods of time. And, as Oren added, the problem is that fertilizing large areas of trees is impractical — largely because of the consequences for the local environment and the water supply.
So, the next time you consider purchasing carbon offsets, keep this study in mind as you peruse the range of projects offered.
Via ::LiveScience: Trees Won't Fix Global Warming (news website), ::Climate Progress: Trees Won’t Fix Global Warming (blog)
See also: ::U.S. Forest Service Takes Aim at Global Warming, ::Planting Trees Helps Fight Global Warming, but Only in the Tropics
Image courtesy of pfly via flickr