A new study led by scientists at UCL, in collaboration with experts from the Royal Botanic Gardens, Kew, shows that after giant sequoia trees were introduced to the UK, they grew almost as well as in their original habitat and were able to sequester huge amounts of carbon over their long lives.

A new study led by UCL shows that giant sequoia trees introduced to the UK 160 years ago are highly adaptable and effective at sequestering carbon, capable of absorbing around 85 kilograms of carbon per year. This research, using state-of-the-art technology, provides important insights into the growth patterns of these trees and their potential environmental benefits, and highlights the importance of future research into the adaptation of these trees to the UK's changing climate. Redwood trees in Wakehurst Bridge Forest. Image source: VisualAir ©RBGKew

The new study, published in Royal Society Open Science, found that Sequoia dendronganteum (also known as giant sequoia), the largest of the redwood trees, has the potential to absorb an average of 85 kilograms of carbon from the atmosphere each year. Although redwood was introduced to the UK 160 years ago, this is the first time its growth rate and resilience in the UK have been analyzed.

There are an estimated 500,000 redwoods in the UK and more are being planted, partly due to their appeal to the public. In the wild, redwoods are endangered, with fewer than 80,000 giant redwoods remaining in their native California.

Research methods and results

Lead author Ross Holland, a former master's student in the Department of Geography at University of London, Los Angeles, now works at EastPoint Geo: "Giant sequoias are some of the largest organisms on the planet. In their native range, due to their huge age, they form the world's most carbon-dense forests. We found that British redwoods are well adapted to the British environment and can capture large amounts of carbon dioxide. We hope these findings can help guide future tree planting and management decisions."

A 3D laser scan of a giant sequoia, with green blocks representing human height. Source: Matilda Digby

Researchers stress that the most effective way to slow climate change is to reduce carbon emissions from burning fossil fuels. Trees can help by absorbing carbon emissions, but they also provide other important climate, ecosystem and wellbeing benefits.

Giant sequoias grow rapidly and are among the longest-lived organisms in the world, maintaining rapid growth throughout their more than 3,000-year life. They can grow up to 90 meters tall, and while not the tallest in the world (that title belongs to their close relatives, the coastal redwoods), their wide trunks grow outward, giving them their maximum size. Additionally, they are fire-resistant and can survive fires that would otherwise wipe out forests of other tree species.

Climate change mitigation and future considerations

The trees grow best in their native range in California's Sierra Nevada mountains, so researchers wanted to see how they fare in British climates, which have a milder climate and a wider range of rainfall. They created the first dedicated map of giant sequoias in the UK, charting the distribution of nearly 5,000 known giant sequoias.

The research team looked at three woods at Wakehurst, the Royal Botanic Gardens Wild Botanic Gardens in Sussex, Havering Country Park in Essex and Benmore Botanic Gardens in Scotland. They installed terrestrial laser scanners to perform three-dimensional mapping of the trees, allowing them to measure tree heights and volumes very accurately and create three-dimensional models of 97 representative trees.

Co-author Dr. Phil Wilkes, who worked at UCL and is now at the Royal Botanic Gardens, Kew, said: "Using the latest laser scanning technology, we can accurately 'weigh' these large trees without having to cut them down. This means we can measure more trees and revisit them in the future."

3D laser scan of two giant sequoia trees. Photo credit: Matilda Digby

The tallest tree they found was about 180 feet (54.87 meters) tall, a giant tree compared with most native British trees but dwarfed by its American counterparts. This is partly due to the youth of British redwoods: Britain's oldest giant redwood is Ben Moore's Redwood, with the earliest dating back to 1863.

Knowing when the trees were planted, the team was able to calculate their average growth rate under different climate conditions at three sites in the UK. They found that the trees at Kew and Ben Moor grew at similar rates to their American counterparts, except that the trees at Ben Moor grew slightly taller and slenderer than those at Wakehurst, while the trees at Havering grew more slowly, possibly due to less rainfall in the area and competition from the dense woodland there.

Final words on Britain’s giant sequoias

While giant sequoias are excellent at sequestering carbon, researchers caution that reforestation requires a long-term commitment and requires consideration of how they will thrive in the UK's changing climate over the next 160 years and beyond.

Senior author Professor Mat Disney (Professor of Geography at UCL) said: "These results provide an important baseline for us to estimate how well giant sequoias will fare in UK climate conditions. At the moment, the aesthetic and historical significance of these trees may be more important than solving the climate crisis. But as plantings increase, we need to understand how they fare."

"The history of these trees in the UK is fascinating - from their origins as symbols of wealth and power to now being widely planted in parks and woodlands. They are an iconic British plant, but there has been little research into how quickly they grow and how they perform in the UK's changing climate. It was amazing to see these behemoths spread out everywhere and to see them growing so quickly."

Compiled from:ScitechDaily