Hello Jim: Although I agree your concerns on the over-claim of many offset methods, the limitations tend to come from practical side (cost, competition for land, etc.), not from some of your basic reasoning. In particular, I think you are "missing the forest for the tree" on this:
jim thomas wrote: > Releasing the carbon from a mature tree takes seconds, refixing it in > another mature tree takes decades - maybe as long as seventy to a hundred > years. All of that time the initial Co2 released is still aloft and still > impacting the climate. That biomass can't even pretend to be carbon neutral > for several decades and as we all know timeframes are critical in addressing > climate change. This 'carbon accounting' is correct only when you look at an individual tree. In a forest, the situation is completely different. A mature forest as a whole has little net carbon uptake because photosynthesis is balanced by decomposition of dead leaves and trees. If you selectively cut a tree, it leaves a gap which enables the smaller trees previously under its shade to grow vigorously. If the tree cut is utilized, either stored for carbon or used for energy, the total carbon benefit would be positive (there will be some overhead from operation for sure). > Environmental journalist david baumann puts it starkly: “it would take over > 100,000 one-year old trees to equal the weight of a 50 year old tree of > similar species. Five year old trees take around 30,000. So you see for every > tree we cut down and burn we’d have to plant 100,000 to resequester that much > carbon in one year, 30,000 in five years. We’d also have to find the space to > plant them.”. > This is really misleading: Each year, a natural forest can regenerate hundreds of thousands of seedlings over just a few square miles. The limitation is space, mostly light, not seeds. Sincerely, -Ning Zeng -- Prof. Ning Zeng Dept. of Atmospheric and Oceanic Science and Earth System Science Interdisciplinary Center Phone: (301) 405-5377 University of Maryland Fax: (301) 314-9482 2417 Computer and Space Sciences Building Email: [email protected] College Park, MD 20742-2425, USA http://www.atmos.umd.edu/~zeng New open-access EGU journal "Earth System Dynamics" http://www.earth-system-dynamics.net -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
