Why Planting Trees Is Not Enough

How many new trees would be required too offset the emissions from just 581 companies?

We wanted to understand whether planting trees could help solve the climate crisis. So we decided to design a quick and simple thought experiment. Specifically, how many trees would it take to offset the carbon emissions from 581 companies (the number of companies we had 2019 emissions for in early 2021). Please remember these are only approximate figures, and we are not climate scientists.  

Total emissions

The 581 companies emitted the following disclosed emissions in 2019 (see the reference section for definitions):

Scope 1 & 2: 6,976,694,751 MTCO2e

Scope 3: 16,908,314,243 MTCO2e

This makes a total of 23,885,008,994 MTCO2e in 2019. We will presume that these emissions will stay the same for each future year (to keep things simple).

Total trees required to offset these emissions‍

Our calculations:

A typical fully grown tree can absorb around 0.021 MTCO2e a year*. So you would need around 47.6 fully grown trees to absorb 1 MTCO2e each year.

It typically takes several years or decades (depending on the tree species) for a tree to be considered fully grown. Saplings will absorb significantly less carbon than fully grown trees. However, we have discounted this by presuming all trees are fully grown from the beginning to keep things simple again.

23,885,008,994 MTCO2e * 47.6 trees = 1,136,926,428,114.4 trees

Therefore, to offset the annual disclosed emissions (using 2019 emissions as the standard) from 581 companies you would need to plant and keep alive 1.14 trillion new and fully grown trees.

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Important Considerations

Many of these companies do not disclose their full emissions (Scope 1, 2 and 3 emissions). So we are likely missing a significant portion especially for Scope 3. Therefore, it is likely many more trees would be actually be required to offset these companies.

These emissions would only be stored in the tree while it is alive. It is likely that these emissions would eventually be released back into the atmosphere when the tree dies. So it is not a reliable long-term solution.  

More trees in a dense population may lead to a greater likelihood of forest fires, deadly plant diseases, and destruction of local habitats (e.g. loss of ecosystems in meadows).

Trees can't be planted everywhere (e.g. in deserts, or on most farmland etc.). It is also important to note that many trees are cut down every year (more than are planted) to make space for farmland and other activities. These trees need to be replaced for the natural carbon cycle before we plant trees for offsetting purposes.

Current trees can not be counted as they are already absorbing emissions from the natural carbon cycle (e.g. from forest fires, biomass degradation, and volcanic emissions etc.). It is important to note that the natural carbon cycle is much larger than the human carbon cycle.

It is not clear whether trees absorb all seven types of greenhouse gas (GHG) emissions.

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References

MTCO2e = Metric tonne of carbon dioxide equivalent.

Scope 1 = Emissions that are considered direct (from owned or controlled sources).

Scope 2 = Emissions that are considered indirect and are from the generation of purchased energy.

Scope 3 = Emissions that are considered indirect and are from the value chain of the reporting entity (includes both upstream and downstream emissions).

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* Viessmann (2020): How much CO2 does a tree absorb, viewed on 09 September 2021. https://www.viessmann.co.uk/heating-advice/how-much-co2-does-tree-absorb

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