No-till agriculture and climate change mitigation

First, Powlson et al.1 take important information out of context and misinterpret it. In the introduction to the chapter2 we refer to a global mitigation potential of 1.1–4.3 GtCO2e yr1. This does not relate to no-tillage only, as their Perspective suggests, but to the global annual mitigation potential of the entire agriculture sector. The range was taken directly from the 2011 and 2012 UNEP Emissions Gap reports, which derived their estimate from Smith et al.3 and Golub et al.4.Second, Powlson et al.1 would reach similar values when applying the mitigation potentials derived from their review to our activity data. We estimated past mitigation (or rather, avoided emissions) since conversion to no-tillage in a few countries for which the relevant activity data was available, by multiplying climatically disaggregated mitigation potentials with changes in area in a way similar to calculating an inventory. Next to the best estimate of cumulative avoided emissions, we also present here the wide ranges based on the uncertainties reported by Smith et al.3 (Table 1). When applying this approach to the annual mitigation potential of no-till that Powlson et al.1 propose, that is, 0.3 tC ha1 yr1 or 1.1 tCO2 ha1 yr1, the avoided emissions are higher than those presented by us. Even considering a decline in mitigation due to saturation consistent with that proposed in their Perspective would not lead to changes in magnitude. This suggests that all our estimates lie well within the range that can be derived from their study.

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DOI:

https://doi.org/10.1038/nclimate2653

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