Frontier-Line Analysis

Maximum carbon storage
The globe is warming, and scientists are now agreed that the cause is the increased concentration of CO2 in the atmosphere in the last 100 years or so. Much of that extra CO2 has come from our burning fossil fuels to heat our buildings and generate electricity. Manufacturing industry and transport have played their parts. So too has agriculture. The clearance of forests, land drainage and cultivation for
arable crops have led to the oxidation of carbon in the soil and the release of huge quantities of carbon as CO2. The International Panel on Climate Change (IPCC) reckons that the globe will soon be 1.5 degrees C warmer than before industrialization. Delegates at the recent meeting COP27 wished to limit that increase by 2050, but they failed to agree on cuts to emissions to achieve it. Worse, if emissions continue at the current rate then an increase to 2 degrees C is likely sometime this century. Such warming is predicted to
have dire consequences: a rise in sea level globally, submergence of island nations and coastal settlements,
increased flooding in some regions and drought in others, more wild fires etc. If we are to avoid such ills and prevent global warming's exceeding L5'c then we need to limit the net increase in CO2 in the atmosphere to zero. Scientists, stake-holders and politicians are therefore turning their attention to the capture and storage of gases and sequestration of carbon; their aim is 'net zero' emissions. The capture and storage of CO2 at source from factories and power stations are matters of technology.
Those from the atmosphere must depend on Nature -by photosynthesis, and on land by storage of carbon in the soil. The soil could store more carbon than it does by more judicious land use and sound management. In that way the soil would provide a more long-lasting store of carbon than that in the vegetation; and it would also improve the soil as a medium for plant growth and ecosystems services such as greater storage of water and reduced run-off, erosion and flooding. The question then is: could the soil store in the long term more c than it does at present while at the same time sustaining its productive use? We know from long-term field experiments that for any given form of land management the amount of carbon in the soil reaches an equilibrium in which gains balance losses, and some experiments seem to show that there is a maximum amount that the soil can store (West & Six, 2007). The soil gains carbon initially as organic residues or manure, largely as only partly decomposed particles. Those are mineralized rapidly by soil organisms, and approximately 90% of the carbon is lost within 30 years (Basile-Doelsch et al 2020). Much of the rest decomposes more slowly into smaller molecules that bind to mineral surfaces where they are protected.