Ever since climate change was recognised as the serious challenge it is, attention has been given to ‘carbon sinks’–complexes of natural phenomena that absorb carbon. Forests are the standard carbon sink, leading to strategies of preservation of old growth forests and re-forestation.
Soil too holds significant amounts carbon, through organic matter and root systems, and some chemical complexes. It has therefore been proposed that different methods of farming may increase soil carbon. For example, no till systems may increase soil carbon, as may other tillage systems.
However, a recent study from the University of Melbourne’s Melbourne School of Land and Environment casts doubt on this proposal. A meta-analysis of soil carbon studies concludes that the effect is limited to the top soil layers and is relatively short-lived, (Meta-analysis is a powerful statistical method for combining and evaluating the results of a whole set of studies.) Moreover, under current carbon policy it would not be financially attractive.
Attention therefore needs to revert to preserving and growing forests as the best approach to expanding carbon sinks. Government policy should incentivise farmers in this direction.