The climate emergency and what to do about it
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Planting trees is not the answer
There are many good reasons for planting trees. Sadly, tree planting will not make a significant contribution to the climate crisis.
There are two problems.
The amount of CO2 taken up by trees is too smallThe amount of CO2 taken up by forests is 0.5 kg per square metre per year. This is according to a study of north american forests . This is equivalent to 500 tonnes per square kilometre (1 tonne is 1000 kg, and there are 1 million square metres in a square kilometre).
For the UK, to cancel out the 900 million tonnes of CO2 produced per year, we would need 1.8 million square kilometres of forest. This is nine times bigger than the total area of the UK (which is 200,000 square kilometres).
This calculation ignores the energy used in growing the sapplings, and in their distribution and planting. If we were to include these, the area needed would be even greater.
Globally the situation is little better. To absorb the annual 34 Gigatonnes of CO2 would need around 68 million square kilometres of forest. This is about half the planet's land area. Given that almost all of this land is already forested, or is unsuitable for forests, or is in use for growing food, it is not possible for new forest planting to absorb the global CO2 emissions, and suggestions that it is are either wishful thinking or deceitful.
The CO2 taken up by trees is taken up only temporarilyThe CO2 taken up is usually given up again when the trees die and decay. It is only in very exceptional circumstances that fallen trees (or other vegetation) decompose only partially, resulting in peat and coal formation.
ConclusionsTree planting is not an answer to the climate crisis. Instead, we need to move quickly to solutions that will work - including phasing out fossil fuel use by stopping flying, by phasing out cars, by insulating homes, and by local food production and distribution.
Misinformation on tree plantingIt is clear from these simple calculation that planting trees is not an answer to the climate crisis. So it is very disappointing that this method is so often put forward.
As Greta Thunberg keeps saying, we need to follow the science.
Other estimates for CO2 taken up by treesThe source used for the calculations in this article is the paper from the United States Department of Agriculture  giving 0.5 kg CO2 per square metre per year.
A second source gives a roughly similar figure:
According to the Trees in Trust website , an acre of mature trees can capture 2.6 tonnes of CO2 per year (the original source is not given). An acre is 4047 square metres, and so this is equivalent to 0.64 kg CO2 per square metre per year.
Other opinions on tree planting
First published: May 2019
Last updated: 23 May 2019