โ Scribed by A. Barrie Pittock
No coin nor oath required. For personal study only.
Lashof's comments on the paper by Nix and myself are very interesting and constructive. As Lashof argues, the crucial factor as regards any biospheric feedback on carbon dioxide concentrations in the atmosphere is the net change in biomass or carbon stock not only in the plants but in the soil. He therefore may well be correct in arguing that additional release of CO2 from soils under warmer conditions could outweigh any net increase in above-ground biomass.
The situation is indeed quite complex, with some areas, such as Australia, showing a probable net increase in above-ground biomass due to climatic change alone, but others probably showing the reverse. Moreover, the direct effects of increasing CO2 concentrations on plant growth will in general be to increase above-ground biomass. The extent to which increased plant productivity will also result in increases in litter and soil humus is unclear to us.
The main point we wanted to get across in the final paragraph of our paper was that the potential change in biomass due to climatic change is large in relation to the annual increase in atmospheric CO2. Lashof's comments show that the net global change in biomass, including soil biomass, will not necessarily be positive. This highlights the importance of further study of potential changes, since there is a possibility of a positive, rather than a negative feedback, which would accelerate the greenhouse warming and exacerbate the problem of societal adjustment.
This rather superficial discussion will have served its purpose if it encourages others to make a careful study of the problems raised.
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