Forest related topics

I've been looking at getting siding put on my house. CertainTeed produces an excellent analysis of the environmental footprint of their siding versus other options. By far, the lowest carbon footprint was old-fashionied wood siding. Presumably that was for the sequestration value of storing the wood, as siding.

But the time perspective for that CertainTeed analysis was only 30 years. In effect, that assumes the building would continue to stand (in perpetuity).

And to me, that's one of two key factors in the analysis of forests and carbon sequestration.
1) How much new forest is needed to make a significant difference.
2) Where is that stored carbon going to be 200 years from now?

1) Current sequestration is already included in current trends. The land requirements for substantial new sequestration are large.

A US southern pine forest absorbs about 1 ton C per year (until it reaches maturity). So we would need about 2.5 giga-acres of new forest to offset annual US (net) C emissions. But the US as a whole is just 2.3 giga-acres. And pretty much anything that can grow something useful is already being used to grow something useful.

So it seems unlikely that we'd be able to find enough currently unused land, suitable for growing trees, that it would make a difference. This isn't a slam on forest sequestration, it's an illustration of how much fossil fuel we burn, relative to fuel that would be available solely via photosynthesis.

2) If we're talking about an additional stream of sequestration (annual carbon uptake) out of a fixed amount of land, in perpetuity, we eventually need a place to store the resulting lumber indefinitely, else you've just kicked the problem down the road a bit. Because the emitted CO2 has a long lifetime.

Based on the best currently available science, if you burn some fossil fuel now, my recollection is that half the resulting CO2 remains in the atmosphere at 50 years, 30% remains at 200 years, and then 20% remains for thousands of years.

(Clearly the long run results are modeled, but are backed by paleo observations. Even the short-run results have observational data suggesting they are roughly right -- Google "bomb carbon" to see the decay rate of the C14 spike induced by the 1962 above-ground nuclear test ban treaty. For a variety of reasons, the decay of the C14 spike is not an accurate proxy for the decay for additional C12 in the atmosphere, but it serves to show an upper bound on effective decay rate of additional C12 in the atmosphere.)

So, my acre of southern pine absorbs its ton per year for (say) 90 years, then the forest is mature. If you can keep that mature forest standing, then you've stored that 90 years of emissions. If you want to keep on emitting, then you have to log the forest, store the wood in perpetuity, and re-grow the forest.

Either way, there's a permanence issue. The seventh-generation question is: Where is that newly-created wood going to be 200 years from now?

So, as with the siding on my house, I question the permanence of the storage. We're just going to use any putative sequestration as an excuse to burn more carbon. And while we might achieve balance between CO2 release and sequestration this year, that will not be true down the road. And with a lot of sequestration plans, in 100 years or 1000 years, both the CO2 from the fossil fuel (or a third of it, anyway) and the CO2 we though we'd sequestered, will be back in the atmosphere.

E.g., in 200 years, it's a fair bet that the wood siding on my house will have reverted to CO2. So the CertainTeed analysis is wrong about the long-run impact. And the net effect is that we'll just use sequestration of this type as a way to kick the problem down the road and let our grandchildren deal with it.

So I feel about forests the way I feel about (e.g. ) white roofs as a solution, or reductions in methane emissions as a solution, or reductions in black carbon emissions. They don't match the permanence of the CO2 emissions.

This is the article that turned my thinking around. I think this guy nailed it:

RealClimate: Losing time, not buying time

Ocean fertilization, where the C will sit on the ocean floor for millenia, OK, that works. Pump it underground with some high likelihood it'll stay there, for millenia, that works. But buying temporary relief from (space-based mirrors, injection of stratospheric sulfates, white roofs, black carbon reductions, methane reductions ...) is a bad bargain for future generations. Because we can't keep the offset going for as long as the CO2 will remain in the atmosphere.

Where forests stand in that continuum, I don't know. But given the projected changes in the climate, I'd argue that they are too fragile to be counted as permanent additional carbon reservoirs. At least, not on the time scale that current CO2 emissions are likely to remain in the air.

 

Something we have in Alabama are wet-lands and swamps where annually a lot of organics collect. Yet I don't think of them 'rising' enough to suggest effective sequestration. Yet I remember photos of German 'brown coal' fueling a power plant. I'm also remembering the Cascade forests with such thick carpets that you can't really see 'dirt.'

I'm wondering, pure speculation, to what extent the non-wood surface of a forest might contributed to more permanent sequestration?

Come the fall, a hundred or so pounds of pine needles will fall on our front yard. If a high wind comes at the right time, the yard is transformed from grass to 'pine needles.' So we dutifully rake them to towards the street and then the 'pine needle fairies' show up with bags and rakes and ask if they can have them. We are always gracious. But I have no doubt they don't go into a fire but add a fractional millimeter to someone's patch.

We tend to see the trees of the forest but the spaces between the trunks look to get a significant load of organics even after maturity. I don't see that material being harvested . . . or did I miss something?

Bob Wilson