Extension 17.7: Planting Trees

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Energy, Ch. 17, extension 7 Planting trees 16 Tundra 0.95 6 121 127 Wetlands 0.35 15 225 240 Croplands 1.60 3 128 131 Total 15.12 466 2011 2477 Source: Reference 73, Table 1 The IPCC has certainly a role to play in this question, and they have. (72) Table E17.7 2 shows in detail the estimated amounts of carbon in the near-surface and above-surface biomass. According to the IPCC, about 270 Gt of carbon has been emitted between 1850 and 2000 due to burning of fossil fuels and 136 Gt from land-use change. (73) After accounting for the amount in the atmosphere, which changed by about 176 Gt in that time, they find that about 230 Gt must have been taken up by the planet by some mechanism (they assume the carbon was divided roughly equally between oceanic and terrestrial uptake). (73) The net planetary uptake was about 0.2 ± 1.0 Gt/yr in the 1980s and 0.7 ± 1.0 Gt/yr in the 1990s. (73,784) As is usual with IPCC, there are several different scenarios used, which give slight differences among the apportionment of carbon storage. An IPCC Definitional Scenario was chosen in order to report everything equally clearly. In this scenario, several estimates of the effects of deforestation and afforestation were given. Between 2008 and 2012, the report expects a carbon sequestration of 197 to 584 Mt/yr of carbon from afforestation and reforestation. The expected deforestation is estimated to be about 1.8 Gt/yr. This means a release of between 1.2 and 1.6 Gt/yr of carbon. The bright side, as the study points out, is that it is feasible to expect a 20% increase in reforestation and afforestation, which would remove a further 11 to 45 Mt/yr of carbon (but unfortunately, this is still small in comparison to the emissions).
Energy, Ch. 17, extension 7 Planting trees 17 Some critics doubt that trees can do the job. The Royal Society says that such measures can take care of just one-quarter of the sequestration needed by 2050. (786) The IPCC report finds that improved forest management, improved cropland management, improved grazing land management, conversion of cropland to grassland, and improved agroforestry could provide about 270 Mt/yr of carbon storage for the Annex I countries (about 260 Mt/yr from better management and 30 Mt/yr from land-use change). (73) This implies that the Annex I countries could virtually wipe out the effects of their carbon emissions by adopting improved management practices and converting some cropland to grass. This, in turn, means that achieving the Kyoto emissions goals will be less costly than had been thought, especially by U.S. politicians who have argued against the adoption of the Kyoto treaty because of its projected huge costs (see the extended discussion of costs and responsibilities of carbon emission in Extension 17.8, Why we should support the Kyoto Protocol). For the world as a whole, the situation looks different, according to the IPCC, as the landuse change contribution totals 335 Mt/yr and better land-use management 570 Mt/yr in carbon storage. (73) This assumes, of course, that land management changes from cropland to grassland or forest will result in greater carbon storage. References in addition to those listed for this chapter are shown in red in the text, and listed below: a. P. Camill, “Permafrost thaw accelerates in boreal peatlands during late-20th century climate warming,” Clim. Change 68, 135 (2005). b. J. N. Klironomos, M. F. Allen, M. C. Rillig, J. Piotrowski, S. Makvandi-Nejad, B. E. Wolfe, and J. R. Powell, “Abrupt rise in atmospheric CO 2 overestimates community response in a model plant–soil system,” Nature 433, 621 (2005).
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Extension 17.7: Planting Trees

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