Sequoia Tree vs. Human Footprint
How long does it take for a Giant Sequoia, also known as a Giant Redwood, to capture the average UK citizen’s lifetime carbon footprint? This is a question we get asked a lot!
Firstly what is the average UK person’s carbon footprint? The World Bank (2017) puts it at 6.5 tonnes of CO2 per annum. If you take the average life expectancy in the UK of 80 years old, that equates to 520 tonnes of CO2 over a lifetime. Our CO2 output is relatively small in infancy, and diminishes with older age as we become less active, so it is not a flat curve through life.
For the Sequoia, the amount of carbon it captures is an incrementally increasing upward moving curve. The older it gets, the greater the circumference of the tree and height, thus the greater the carbon mass it lays on each year with a fresh growth ring. To give context in year 10 the Sequoia adds 0.02 tonnes (2kgs), in year 50 it adds 0.5 tonnes, in year 100 it adds 1.2 tonnes, in year 250 it adds over 3 tonnes.
To assess the CO2 capture of a UK domiciled Giant Sequoia we had to employ some conservative forecasting, as the oldest of the living UK Sequoias were brought to the UK by the Victorians and planted in the mid 19th century. That means the oldest UK specimens are only 165 years old, barely teenagers in Sequoia terms.
In our interview with David Milarch, Founder of the Archangel Ancient Tree Archive, he is heard to say he has seen Sequoias grow up to 10ft a year! In the UK however, the tallest are only now approaching 200ft in height.
Sequoias, like all tree species, grow best in a friendly microclimate. For a Sequoia that means being surrounded by other trees providing shelter from the elements, in soil alive with forest fungi and uncompacted by human activity, with a space in the canopy from a fallen tree or forest fire. Essentially a natural forest environment with space for them to grow upwards.
Many of the Sequoias brought over and planted here in the UK were given no such opportunity, instead being monument trees in the grounds of family estates, isolated from other trees or forests, planted in compacted lawn soil devoid of life and essential elements. This would not have created optimal growing conditions. Irrespective, and testament to the hardy nature of the species, many have grown and thrived to be magnificent trees.
At our groves we do all we can to optimise growing conditions. We guard the trees to imitate a sheltered microclimate and protect them from browsing deer and rabbits. We give the tree roots a dose of fungal supplement (mycorrhizal) to bring the soil alive. Anyone wanting to understand more about the role of fungi in forests should watch the Netflix documentary ‘Fantastic Fungi’. The most positive element however is that we are planting on land that is previously felled forest, so the soil is already uncompacted and alive with roots and fungi.
We believe in these conditions our Sequoias will grow fast and strong, certainly in comparison to the existing Sequoias which were given less favourable conditions to start with. Our calculations for Sequoia growth rate are based on existing Sequoias in the UK, where growth rings average out at 1.15cm, and a height increase of 1.5ft per annum. From that we can forecast the volume of the tree as it grows year on year, until we reach our target 500 tonnes.
The below graph shows how that looks next to a UK lifetime footprint.
As trees start small and the CO2 uptake is slow to start with, and to promote UK biodiversity and rewilding principles, we plant three native trees for every Sequoia, so in the first 100 years we expect to see a quicker CO2 uptake within our forests.
What does this mean for our Sequoia Patrons? Trees take time to grow, planting a Sequoia does not provide an opportunity to turn a blind eye to climate change. A Sequoia will leave you with a net zero legacy until it falls in a millennia or two, but in the short term we still need to reduce emissions to slow the rate of change now before it is too late.