The Giant Sequoia
Sequoiadendron Giganteum / Giant Redwood
The Giant Sequoia (aka Giant Redwood) is the world’s largest tree species, as well as the fastest growing conifer. Famous sequoias have grown up to 300 feet tall, 36 feet wide, with volumes over 1400 m3, and are known to be as much as 3500 years old.
Ever seen a Giant Sequoia in the bark? Here is an approximate scale illustration of a mature Oak and Giant Sequoia. A Sequoia Grove can capture as much as 10x more CO2 per acre than a natural UK woodland over the period of 100 years, increasing over time. Each Sequoia is planted on a 100m2 plot. We plant 3 native UK species for each Sequoia to promote biodiversity.
A CONDENSED VERSION OF THE SCIENCE
The world’s largest tree is General Sherman in California, a Giant Sequoia or ‘Redwood’ with a volume of 1486 cubic meters. Giant Sequoia wood density is approximately 480kg/m3, giving a total mass for General Sherman of 714 tonnes. This is however not all carbon, and whereas most trees are about 50% carbon, a Giant Sequoia is closer to 55% carbon. To arrive at the amount of carbon stored in the tree we therefore multiply the total mass of 714 tonnes by a carbon content of 55%, equalling just over 392 metric tonnes.
Carbon dioxide is a three part molecule, with one carbon atom and two oxygen atoms. The carbon accounts for only 27.3% of the molecular weight. When a tree absorbs the carbon it (mostly) releases the oxygen atoms into the atmosphere. Therefore for every 1 tonne of carbon the tree absorbs while growing, it removes 3.66 tonnes of carbon dioxide from the atmosphere.
So General Sherman with a carbon weight of 392 tonnes has in fact removed 1439 tonnes of carbon dioxide from the atmosphere!
A GIANT SEQUOIA GROVE CAN CAPTURE UP TO 10X MORE CO2 PER HECTARE.
The UK Forestry Commission quotes that over 100 years a woodland planted today would sequest 400-600 tonnes of CO2 per hectare. A Sequoia grove where the trees were growing in line with existing UK specimens, where each tree could expect to reach a 100 year volume of 40 tonnes, across 100 trees would sequest over 4000 tonnes of CO2 from the atmosphere.
And Sequoia’s keep on growing. Meaning that they can capture more carbon far beyond our vintage terms.
The world is producing and burning fossil fuels on an industrial and massive scale. We must think about an industrial scale solution to match this problem. The world climate is changing rapidly and we need to act fast and at scale to reduce CO2 in the atmosphere. Giant Sequoias have the scale and land use efficiency to be part of the solution.
OUR TARGET FOR EVERY TREE
Our target is to grow Giant Sequoias that reach a volume of 500 m3, circa 1/3rd of the size of the almighty General Sherman.
The largest Giant Sequoias in the UK today were planted around 170 years ago when the species was first discovered in the USA and seeds were brought back for specimen growth in large estates and gardens. Those trees today have reached diameters over 3m and heights over 50m. Growth rates are between 1 and 1.5ft per annum (we have witnessed 5ft at one of our UK groves!), and growth rings required to get to 3m diameter are just over 2cm in diameter per annum. This gives a fairly accurate trajectory for the trunk volume growth both past and future for UK Sequoias.
A detailed study of the branch volume of The President Giant Sequoia tree by Steve Sillett provided a ratio of branch volume to trunk volume of just under 20%.
For root volume we reference figures provided in Tree Roots: Facts and Fallacies by Thomas O. Perry, where fine or feeder roots are said to represent 5% of a tree’s proportions, and 15% for larger or transport roots.
Therefore a Giant Sequoia’s total volume can be calculated as trunk volume + 20% for branches and 20% for roots. Our target therefore is to grow UK Sequoias to a trunk diameter of 3m (there are already UK Sequoias with trunks larger than this at 3.5m), and to a height of 200ft, not far off UK specimens today that are still growing at 1.5ft per annum (referred to in The Guardian here).