A Bloom as Big as Australia
A brilliant paper recently appeared in Nature (Tang et al 2021).
Sometimes, big bushfires distribute nutrients such as iron and nitrates to barren areas of the ocean. This creates blooms of plankton which absorb CO2 from the atmosphere. Admittedly much of this may well be re-emitted to the atmosphere once the bloom is over but a good deal will be removed from the system forever as it sinks to the bottom of the ocean in the form of faecal pellets and the skeletons of the animals which graze the plankton.
The above map shows the plankton bloom due to the 2019/20 Australian bushfires derived from satellite imagery of ocean colour. According the paper:
Satellite-estimated marine net primary production (NPP) and export production (EP) increased substantially during the 2019–2020 Australian wildfire season compared with the monthly climatologies, corresponding to a cumulative net additional uptake of ~186 ± 90 Tg C from October 2019 to April 2020, equivalent to ~95 ± 46% of the CO2 emission (~195 Tg C) from the 2019–2020 Australian wildfires.
Given that we can expect at least a 90% recovery from these fires, we conclude that, in the long run, these bushfires will have caused a net absorption of atmospheric CO2, viz.: 90% recovered on land and 95 ± 46% exported from the atmosphere to the deep ocean by the plankton bloom.
Because of this plankton bloom, the 2019/20 bushfires brought about the removal of nearly twice the amount of CO2 from the atmosphere that they put into it.
Widespread phytoplankton blooms triggered by 2019–2020 Australian wildfires. Weiyi Tang, Joan Llort, Jakob Weis, Morgane M. G. Perron, Sara Basart, Zuchuan Li, Shubha Sathyendranath, Thomas Jackson, Estrella Sanz Rodriguez, Bernadette C. Proemse, Andrew R. Bowie, Christina Schallenberg, Peter G. Strutton, Richard Matear, Nicolas Cassar. Nature 597, 370-389 (2021).
1 Tg = 1012 g = 1 million tonnes.
“Climatologies” means “usual monthly averages”.
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2 Replies to “A Bloom as Big as Australia”
I heard that methane is being stepped up as an issue and probably up for discussion at Glasgow. I suggest that it will be aimed at the farming community especially against livestock. I understand that that in the forest any material that is allowed to rot or to be eaten actually puts the carbon back as methane. Am I mistaken in that? If it is true then surely we have to manage the forests by removing anything that is already dead or dying which not only keeps the forest healthy but eliminates a major global warming gas. It would even be better burning the forest waste – even better if it was burnt to capture the energy – it only puts the carbon back as CO2. Of course larger units can be put to use even storing the carbon but we would need an industry to achieve this. I would even include old growth forest if it has reached a stage where it is rotting faster than it is growing. Is there anything glaring in what I say?
Don, Methane is a more powerful greenhouse gas than CO2 but it only stays in the atmosphere for 4 years because it reacts with Oxygen to form CO2 and H2O. Methane is just the most recent beat up.
Also, remember that more CO2 is removed by plankton than by trees .
The Tang et al paper shows that bushfires can remove CO2 from the atmosphere. This may well be true of all forest fires, This was the first case to be closely investigated. It certainly needs more work but I doubt that the harvesting and burning of timber will be taken into account in Glasgow.
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