Another obstacle to afforestation as a means of rapidly drawing down CO2 from the climate system:
U.Büntgen, P.J.Krusic, A.Piermattei, D.A.Coomes, J.Esper, V.S.Myglan, A.V.Kirdyanov, J.J.Camarero, A.Crivellaro, C.Körne, “Limited capacity of tree growth to mitigate the global greenhouse effect under predicted warming“, Nature Communications, 2019, 10, Article number: 2171.
This is essentially no analysis, simply an index to recent research on the the matter of the soils reservoir for Carbon, and a little reaction.
To begin, here’s the part of the Carbon Cycle that’s involved:
Should this production increase, particularly if CO2 uptake of terrestrial plants wane, the 45% sink we’ve fortunately lived with could lessen, making our situation worse.
Here are some papers, including reports of large scale experiments. I follow with some thoughts and questions.
- T. W. Crowther, et al, “Quantifying global soil carbon losses in response to warming”, Nature, 540, 1 December 2016, 104-108, with supplementary information.
- N. van Gestel, et al, “Predicting soil carbon loss with warming”, Nature, 554, 22 February 2018, E4-E8, including reply from T. W. Crowther, et al.
- A. F. Talhelm, et al, “Elevated carbon dioxide and ozone alter productivity and ecosystem carbon content in northern temperate forests”, Global Change Biology (2014) 20, 2492-2504.
- A. Baccini, W. Walker, L. Carvalho, M. Farina, D. Sulla-Menashe, R. A. Houghton, “Tropical forests are a net carbon source based on above ground measurements of gain and loss ”, Science, 28 Sep 2017: eaam5962, DOI: 10.1126/science.aam5962.
- J. Smith, “Measuring Earth’s carbon cycle”, introduction to special issue, Science, 13 October 2017: 358(6360), 186-187, DOI: 10.1126/science.358.6360.186
- K. J. van Groenigen, X. Qi, C. W. Osenberg, Y. Luo, B. A. Hungate, “Faster decomposition under increased atmospheric CO2 limits soil Carbon storage”, ScienceExpress, 24 April 2014, Page 1, 10.1126/science.1249534.
- C. E. Hicks Pries, C. Castanha, R. Porras, M. S. Torn, “The whole-soil Carbon flux in response to warming”, Science, 9 March 2017, 10.1126/science.aal1319.
- J. M. Melillo, S.D. Frey, K. M. DeAngelis, W. J. Werner, M. J. Bernard, F. P. Bowles, G. Pold, M. A. Knorr, A. S. Grandy, “Long-term pattern and magnitude of soil Carbon feedback to the climate system in a warming world”, Science, 358, 6 October 2017, 101-105.
- D. B. Metcalfe, “Microbial change in warming soils: Long-term reorganization of microbial communities leads to pulses in Carbon release”, Science, 6 October 2017, 358(6359), 41-42, with supplement.
I am particularly intrigued with Metcalfe, and van Groenigen, Osenberg, Luo, and Hungate. Recent studies examining options to rebalance the Carbon Cycle by means such as enhanced weathering and afforestation by planting large numbers of plants like Jatropha curcas (see more) have revealed the resulting albedo change and moisture capture can change the climate of entire regions. If microbial communities reorganize in a big way, whether in temperate forests, in deserts, or in tundra, could they by themselves achieve change of regional climate? Could they be bioengineered? Do we understand that ecosystem well enough to predict how it would develop? Are there nonlinear surprises lurking there?
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Baccini et al.’s paper has [annoyingly] misleading title despite the “net” qualifier. The ratio of emissions to sequestration of 862/437 is certainly bad news but would be much worse if it was the tropical forest with the net imbalance; the imbalance in forest areas is almost entirely due to land use change ie. deforestation and resulting degradation of soil. I didn’t know nteresting that Jatropha produces 4 times the biomass of soy and grows in temps from 10C-50C and 30cm-1m flooding as well as saline conditions (salinity and drought resistance being 2 of my current lit. review topics). The economics look good at $1 per tree, 2,500 per hectare can sequester nearly 20 tonnes C pa. after 4 years growth. I make that a min. one-off cost for sequestration of $125 per tonne of C on otherwise unusable poor soils if fertilised ie. $42 per tonne CO2 if my arithmetic’s right.
(Slight edit by moderator to fix typo.)