Uncharted Territory

March 5, 2009

Greening some Greenwash Debunking

Filed under: Biomass, Forests, Global warming — Tim Joslin @ 10:51 am

Oops, I was going to title this post “Greening some Greenwash”, then I realised that it’s the response to the greenwash that I object to.

I came across an interesting feature in the Indy this morning. It’s presented in a rather annoying fashion as you have to step through each page, rather than scroll down to what you want. A bit like in those PowerPoint presentations with bells, whistles and moving graphics everywhere, the technology has clearly taken over.

The feature became even more interesting when I got to point number 8: Ancient forests must be axed (sic). Red flags to bulls and all that. There’s a picture of some trees and the writer explains:

“It isn’t picturesque but it is practical. It sounds ruthless, but wheezy old trees can’t suck up the carbon like they used to. A tree absorbs roughly 1,500 tonnes of CO2 until it reaches 55 years of age, after which absorption slows. And when that tree decomposes, it belches all the CO2 back out again. So although the results won’t be terribly scenic, if we were utterly rational, our trees should get the axe after reaching their CO2-hoovering peak. The wood can then be used to make furniture, houses and many of the products we currently manufacture from less sustainable materials. We should then plant fresh seedlings to farm.”

No, no, no!

Let’s try and explain this in baby-talk.

1. There’s carbon in the atmosphere, principally in the form of a gas called carbon dioxide (CO2).

2. Trees take up CO2 from the atmosphere and incorporate the carbon in organic matter: leaves, roots, trunk, branches, twigs, bits of these things incorporated into the soil, as well as into the things which eat the above and into the things which eat them. For simplicity, let’s just say they take the carbon from CO2 and turn it into wood.

3. Now, in the case of the existence of a forest compared to its non-existence, the amount of CO2 in the atmosphere is reduced by an amount equivalent to the carbon stored in wood in the forest.

4. The amount of CO2 in the atmosphere does not depend on how quickly the trees are taking up carbon. How quickly trees are taking up carbon affects only the rate of change in the level of CO2 in the atmosphere, not its actual level.

5. Once a forest is fully grown it can hold no more carbon. Strictly, this maximum is reached when the carbon released by decay of old trees is matched by the uptake of carbon by the new trees which naturally spring up to replace them.

6. Chopping down ancient trees in order to plant new trees will not, therefore, lead to more storage of carbon. It will lead to less because the fallen old trees will start rotting and will release carbon faster than the tiny new trees can take it up.

7. The writers suggest that the wood from the ancient trees can be used to make furniture and so on. That’s true. But it will not keep carbon out of the atmosphere if old wooden furniture is thrown out and replaced by the new furniture. The old furniture will start rotting (or be burnt) as soon as it leaves the benign environment of our dining rooms.

8. Sure, we could replace some plastic in our homes with wood, but we have to understand the principle: the minimum amount of carbon in the atmosphere will occur when the maximum amount of carbon is stored in wood. This will be when everyone is using wood as a material where possible, and where all the forests are full grown, not when they’re tiny growing “fresh seedlings”.

9. Forests in general store much more wood than buildings (which may incorporate wood in furniture or otherwise) on the same land. And forests collectively take up more land than buildings. It follows that the main determinants of how much carbon is stored in the forest to wood-product system – and is therefore not in the form of CO2 in the atmosphere – are (a) the amount of carbon stored per unit area of forest and (b) the total area of forest. As I’ve explained, this will be at a maximum in mature forests.

10. So leave those ancient trees alone.

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