The myth of temperate forestation as viable sequestrate of carbon dioxide

This is a guest post by Brychan Davies

 

Global warming is a reality, as is global cooling. Throughout geological time, and throughout the history of mankind there is a natural variance in global temperatures. Geological variance is caused by variations in the tilt of the earth, the polarity switching, and continental drift. The variation on the historical timescale is caused by natural variance in oceanic currents, volcanic activity, and natural oscillations and cyclic proliferation of flora and fauna. Global warning, global cooling is not new. It is part of the natural condition of planet Earth.

Greenhouse Effect

The best example of ‘the greenhouse effect’ is on the planet Venus. A thick soup of acidic water vapour and carbon dioxide ‘traps’ the suns energy and global temperatures are scorching, with an average surface temperature of 300c. The opposite effect can be found on Mars, where the atmosphere which is 95% carbon dioxide but so sparse there is little effect on the atmosphere where global temperatures of –60c. Earth is in the ‘Goldilocks zone’, and naturally oscillates about halfway between these extremes. The mix of naturally fluctuating atmospheric carbon dioxide, and water vapour plays a role in the global temperature.

Fossil Fuels

All coal, oil and fossil fuels on earth was once atmospheric carbon dioxide. In fact the main coal deposits on earth are as a result of carbon dioxide sequestration, 300 million years ago, during the ‘carboniferous’ era. This is the carbon dioxide released back into the atmosphere during the current industrial period, and it is claimed to have a dangerous effect on global warming.

Forestation

It is also claimed that if we now plant trees on land currently used for grazing animals we can mitigate this effect. Is it true?

Well, no. The issue of global warming, and the concentration of atmospheric carbon dioxide was first identified in the early 1990s and proposals to try to manage this on a global scale was in Japan, in 1992, and it became known as the Kyoto Protocol. Coincidentally, Japan is an ideal comparison with the British Islands, both being of a temperate seasonal climate, with a modern industrial heritage, similar moderation of seasons by oceanic currents, and similar natural forests, a mixture of native coniferous forest at elevation and to the north, with a natural forest of deciduous woodland on the main landmass, with natural shrub and grassland at elevation.

Saikai Forest near Nagasaki. Click to enlarge

Japan, both fortunately and unfortunately, has the advantage of having 75 years worth of continuous scientific study of re-forestation. It arose after a nuclear bomb was dropped on Nagasaki towards the end of WWII. It’s a port city very similar in size to Swansea, surrounded by an area of agricultural land on a peninsular, and a backdrop of moderate uplands, and a self-contained river system.

The bomb resulted in all this being taken out of productive use and a programme of forestation initiated, whose purpose at the time was to soak up nuclear contamination. It is the most intensively studied area of temperate reforestation in the world and has been studied for over 75 years. One particular measure being the sequestration of atmospheric carbon to measure ‘dilution’ of nuclear isotopes, but also provides empirical data on the seasonal sequestration of carbon dioxide as well as a net figure by different tree species over the 75 year period.

The key graph is shown below.

Click to enlarge

CO2 sequestration

Tonnes per hectare per year.

Nineteen-sixty-eight was an important year. It was when the forest changed from being a carbon sink to a net carbon emitter. It related to the age of the trees and the natural eco-system. Mature trees decay, this is when the action of fungi, and other parasitic flora and fauna which consumes the wood, leaf litter, and soils, emitting carbon dioxide in quantities greater than that being absorbed by the tree through photosynthesis.

Tadaki, Y.; Hachiya, K. Forest Ecosystems and Their Productivity; Ringyo Kagakugijutsu Shinkosho: Tokyo, Japan, 1968. (In Japanese)

Kyoto Protocol

The Kyoto Protocol committed participants to financing measures to tackle carbon dioxide emissions. The United States blamed the rest of the world, suggesting the issue is in the Amazon, the European Union spent cash on changing agriculture with set-aside schemes, and this has now morphed in the United Kingdom to ‘blame the farmers’. Japan, however, took a more scientific approach and launched satellites to measures their forestation, launched a programme of study to measure carbon sequestration of a forestation programme, and was able to use data previously obtained (1968 tipping point) to give real numbers to the subject.

Estimation of CO2 Sequestration by the Forests in Japan by Discriminating Precise Tree Age Category using Remote Sensing Techniques” – 2015.

The reality is that a newly planted forest does act as an initial carbon sink, but only until the forest reaches maturity. Both show that net gains are negligible after 75 years, although there’s an earlier peak with coniferous forest in comparison to deciduous forest. Gains then become losses. The report is here.

The study concludes with: “The CO2 amount and other important information revealed in this study has provided important data. Do old mature trees sequestrate as much as younger trees? The answer is no when we see the trend of the sequestration as a function of tree age.” Kotaro Iizuka, Ryutaro Tateishi et al.

Wales

So what lessons can we draw on forestation as a method of sequestrating carbon dioxide in Wales? Mass forestation is not the answer. There is flora that does the job – peat bogs. This is where the acidity of the soil does not allow decomposition of vegetation and the result in layer upon layer of peat deposits. To maintain this ground cover, the light grazing of animals is needed, like sheep, to prevent the ingress of trees.

Questions

Why plant forests and remove farmers from the land when doing so has an adverse effect on carbon dioxide sequestration? Why is there an obsession with projects like the ‘Tetrapak Financed Summit to Sea’ project when there is clear scientific evidence that its objective cannot be met by its proposals? If there are short term gains prior to clear felling at sequestration tipping point, why isn’t this a purely commercial proposal? Why use upland grazing land that is already a net carbon sink for projects that scientifically are known to be inferior?

Additional abstract

There is a myth that the large areas of treeless uplands that exist in Wales and the rest of Britain is a ‘man made landscape’ and planting trees in these areas is a form of ‘rewilding’. This is utter nonsense. There is clear scientific evidence that much of upland Britain has been treeless for the last 4000 years, and this is proved by pollen analysis of peat cores. After the last ice age, there were significant natural cyclic oscillations climatic change – dry Boreal, wet Atlantic, dry Sub-boreal, wet Sub-Atlantic. This eradicated almost all upland forestation long before any impact of human activity.

Nant-y-moch from Pumlumon. Click to enlarge

In fact there is ample evidence that forestation in in the 1970s of these areas has caused significant degradation of the diversity of wildlife, the erosion of upland peat deposits, and the net release of sequestrated CO2. There are is currently 589 gigatonnes of carbon in the atmosphere. The current store of carbon in peat deposits is over 600 gigatonnes. Large scale forestation of upland Wales will result in a significant net release of carbon into the atmosphere, and significantly add to global warming.

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