Planting trees will not save the planet: official

Bad news for carbon banking

Bad news for plastic greens: planting trees really isn't going to save us from global warming. Researchers studying pine trees in North Carolina have determined that there is a limit to the amount of extra carbon dioxide a tree can actually turn into more tree.

The decade-long Free Air Carbon Enrichment (FACE) experiment, set up to test the viability of proposals to "bank" humanity's carbon emissions by growing forests, revealed that to make an impact on the amount of CO2 we are pumping out, we'd need to feed the growing trees so much extra water and fertiliser that the societal impact would be unacceptable.

"If water availability decreases to plants at the same time that carbon dioxide increases, then we might not have a net gain in carbon sequestration," said Oren, a professor of ecology at Duke's Nicholas School of the Environment and Earth Sciences. "In order to actually have an effect on the atmospheric concentration of CO2, the results suggest a future need to fertilise vast areas. And the impact on water quality of fertilising large areas will be intolerable to society. Water is already a scarce resource."

Scientists working on FACE bathed four plots of trees in levels of carbon dioxide one and a half times those present in today's atmosphere. Another four plots received no extra CO2. On average, the trees with the extra carbon produced 20 per cent more biomass, but the figures varied substantially, from 5 per cent to 40 per cent, depending on the amount of nutrients and water available.

Carboned-up trees were no more likely than normal trees to "self-thin" (a process by which smaller trees die off as big trees get bigger), and the ratio of carbon stored in long-term wood vs. short-term foliage remained the same. ®

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