Mark Sullivan wrote: >Carbon dioxide theory debunked
I read the Science article. Factually, however, increased CO2 does lead to increased plant growth, as evidenced by its commercial use in glasshouses around the world and by forest trials in which local CO2 levels are enriched by gas release in the canopy. This trial, on a single species in a Mo deficient soil, is hardly something to be extrapolated safely. By contrast, the global carbon budget is still short by around 3 gigatonnes of Carbon per annum, implying that there is much more growth going on than there is biomass destruction. Some is due to tree planting, and some to carbon residues in the soil, some to oceanic fixation. This said, European and US forest cover now approach seventeenth century levels although, of course, with completely different distribution. However, this group is all about orchids. Dutch growers use CO2 to accelerate orchid development - as do Phalaenopsis producers in Taiwan, I believe - but I am not aware of systematic studies on its affects on them. Will more CO2 directly harm wild orchids? I would think not, as they have already weathered quite a number of wild changes in CO2 during the family's history. Indirectly, could it cause harm: through rougher weather, denser tree canopies, more forests planted to fix carbon, more wood used in construction to keep it that way? The jury has to be out on that. Human numbers and policy towards the trade in farm products are the two critical variables at the moment, and they dwarf virtually all other factors. Wild collection is also a problem for pretty species, with the central American forests still negatively affected by the British collection mania of the 1890-1914 period, when hundreds of thousands of tonnes of Oncidium and Odontoglossum plants were imported. _____________________________________ Oliver Sparrow Tel: UK (0)20 7736 9716 www.chforum.org www.treknepal.org www.datafreeze.com
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