Two new studies suggest that trees can do less to mitigate climate change than previously thought.
It would be interesting to hear what people have to say about the implications of this for the growing movement in support of carbon trading as one of the solutions to the climate change problem.
Trees and plants live by consuming the atmospheric carbon dioxide that is exhaled by all animals, including humans, and produced by fossil fuel combustion. They convert the carbon dioxide - along with water, and powered by the sun - into roots, leaves, stems, and wood - a.k.a. biomass.
If this carbon dioxide were not ‘sequestered’, as the process is called, it would long ago have trapped enough solar radiation to cause catastrophic climate change that would have been fatal to life on earth. This much is indisputable, even to the strongest climate change skeptics.
So far, an important strategy for mitigating climate change has been to take advantage of the hypothesized ability of trees to *increase* the amount of carbon they sequester. This presumed increase would be driven by the higher levels of carbon dioxide that humans will be releasing in coming decades - in essence, more ‘fuel’ for tree growth.
The new studies suggest that may have been an overly optimistic belief: they show that the rate at which trees sequester carbon doesn’t go up when more carbon dioxide is available. They show that the amount of carbon each tree sequesters can’t get significantly bigger than it already is.
Why? Because even when more carbon dioxide is available, other limits on tree growth come into effect.
“The discovery implies that future carbon storage by land ecosystems may be smaller than previously thought, and therefore not a very large part of a solution to global warming,” said one of the authors, Bruce Hungate of Northern Arizona University, referring to the wisdom of relying on the previously hypothesized ‘bonus’ sequestration in the presence of elevated atmospheric carbon.
summaries of the articles:
Nature can help reduce greenhouse gas, but only to a point
Hold your breath; Plants may absorb less carbon dioxide than we thought
the original articles (require subscriptions):
van Groeningen et al., Proceedings of the National Academy of Sciences
3 comments
April 20th, 2006 at 12:43 pm
michelle
The research addresses the capacity of plants to store EXTRA carbon in the presence of higher C02 concentrations.
It does NOT imply that current rates of carbon sequestratation are diminished.
Even in light of these estimates of future carbon uptake by plants — retaining land in forest, afforestation, and silvicultural strategies to increase carbon storage in biomass are STILL effective and potentially important short- and long-term strategies as part of the climate change mitigation portfolio.
April 20th, 2006 at 1:33 pm
Richard
Michelle -
Let me know if there’s something in the post that makes it sound like carbon sequestration rates are or will be shrinking. That’s not how I interpreted the findings but if that’s how the posting sounds I will change it.
April 24th, 2006 at 6:17 pm
James Wang
While the future capacity of intact ecosystems to take up additional carbon may be limited, deforestation and other land-use changes result in _large_ emissions of carbon dioxide to the atmosphere. Thus, we should continue to be very concerned about worldwide deforestation and promote preservation of forests.