Saran – we’ve been looking at the question of how soils fit into the global carbon cycle, drawing on a paper by Scharlemann et al. (2015) in Carbon Management , and Mishra et al. (2013) in Environmental Research letters.
These more general questions came up from our discussion:
- It is the UN Year of Soils; the UN Food and Agriculture Organisation (FAO) has put out some animations on YouTube. Who are they for, do they engage, are they effective in conveying the most important information? How many people in the world have viewed them?
- Who led and who contributed to the Carbon Management paper and why? How did this group get together – and were they successful in their aims (is their recommendation clear)?
- Is the number on which Fig 1 converges likely to be an accurate number? In general, do we research and refine only numbers that have a large initial estimates (leading to downward revision)? What about issues that are erroneously thought at first to be small or trivial?
- How do we get the right balance between an emphasis on stocks and fluxes of things?
- Extremophiles: microbes that might inhabit Mars, oil wells – or permafrost. Can we really assume that nothing is happening below 4⁰C?
Matthias – https://youtu.be/invUp0SX49g – is animated in a very professional fashion and certainly grabs and doesn’t lose the attention of the viewer. It is informative and summarises the key importance of sols very well I think. The overall tone of the video is rather pessimistic. However, the hope lies in imposing legal protection of soils and this message does get delivered effectively. https://youtu.be/TqGKwWo60yE – uses fast moving headlines to explain the importance of soils (no narration). It does visualise very well I think how fast soil is degraded and lost and how long it takes for only a few centimetres of soil to develop. Though, I think it does not really suggest how the individual could do anything about it.
Hannah – The following figure from Scharlemann et al., (2015) shows the estimates of global soil organic carbon (SOC) since 1950. The variation in these estimates represents the discrepancy in sampling techniques and calculations, which appear to be just as prevalent today as they were previously. This occurs to such an extent that even authors using the same data have arrived at differing total estimates of global SOC stock estimates!
When we take an average of these previous studies, global stocks of SOC are estimated at 1500 billion tonnes. Despite the general arrival on this value by a number of studies, questions regarding the accuracy may still be posed. While there are multiple reasons for doubting the accuracy of this value, the main reason for doing so is the soil depth the studies have used. These studies used existing distributional data that usually only provide data to a depth of 1 m, which means the current estimate is undoubtedly lower than the true global SOC. For example, studies have reported that measuring SOC up to 3 m depth yielded SOC estimates 1.5-times greater than those to only 1 m depth.
Considering that peat soils containing SOC in the tropics are up to 11 m deep, there is an extremely high potential that a global estimate of 1500 billion tonnes of SOC is a gross underestimate. This highlights the need for another look into our global stocks of SOC.
Estimates of global soil organic carbon stocks from the literature through time – Figure 1 in the paper of Scharlemann et al. (2015).
Jakub – Understanding of stocks and fluxes is both equally important in terms of climate change and soil management, because they are intrinsically interconnected. Although stocks are very important, fluxes should be given higher priority because they determine the amount of carbon that is emitted and thus are the main drivers of climate change.
Christie – The bacterium Planococcus halocryophilus is an example of an extremophile, owing to its ability to grow at -15⁰C in soil, and has been found in permafrost in Canada. So we cannot assume there is no decomposition in permafrost. The microbe also has traits which could sustain life on Mars .. on the basis of temperature at least!
Scharlemann JPW, Tanner EVJ, Hiederer R and Kapos V (2014) Global soil carbon: understanding and managing the largest terrestrial carbon pool. Carbon Management 5: 81-91 see: http://www.tandfonline.com/doi/pdf/10.4155/cmt.13.77
Mishra U, Jastrow JD, Matamala R, Hugelius G et al. (2013) Empirical estimates to reduce modelling uncertainties of soil organic carbon in permafrost regions: a review of recent progress and remaining challenges. Environmental Research Letters 8: 035020 see: http://iopscience.iop.org/article/10.1088/1748-9326/8/3/035020
Nadia CS, Mykytczuk RCW and Whyte LG (2012) Planococcus halocryophilus sp. nov., an extreme sub-zero species from high Arctic permafrost. International Journal of Systematic and Evolutionary Microbiology 62: 1937–1944 see: http://ijs.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.035782-0