by Three redwoods tower over the Elizabeth Wakehurst Mansion like skyscrapers. But at 40 meters (131 feet) high, these are practically greens – not even 150 years old and already almost twice as tall as Cleopatra’s Needle.
“At the moment they are some of the tallest trees in the UK and are starting to push above the forest canopy. But if they grow to their full potential, they will be three times taller than most trees,” says Dr Phil Wilkes, a member of the research team at Wakehurst, in West Sussex, a center outside Kew Gardens. One or two of these California imports would be curiosities, such as the 100-metre tall redwood that was stripped of its bark in 1854 and exhibited to Victorian crowds at the Crystal Palace in south-east London , until it was destroyed by fire in 1866. .
But there are more than a handful of redwoods in the UK, and Wakehurst has many more than these three. The Victorians were so impressed that they brought seeds and seedlings from the USA in such numbers that there are now about 500,000 in Britain. California has about 80,000 giant sequoias, the official name for giant redwoods, as well as coast redwoods and a few ornamental dawn redwoods imported from China.
When Wilkes and his fellow researchers at Kew and University College London highlighted the numbers last week, they sparked a wave of interest, and visitors to the Wakehurst gardens said little else.
Related: Plantwatch: redwoods make remarkable recovery after California wildfires
“People often worry that they’re an invasive species, but they seem to be quite benign,” says Wilkes. “There is no evidence that they are self-seeding.”
This could be because they are juveniles not yet ready to reproduce – redwoods live up to 3,000 years – or because their cones usually only open in a forest fire. That means every tree is likely to have been planted in the UK. It also explains how half a million giants managed to hide in plain sight.
“They were prized possessions,” says Wilkes. “Often they were built in manors and added driveways with rows of redwoods. And these houses have been burnt or demolished but the redwoods are still there.”
Redwood fans have registered some of the locations, from people’s back gardens to suburban parks and streets where houses are built around the trees. But as the redwoods have grown, so have opportunities for conflict, such as in Canons Drive in Edgware, north London, where some residents are fighting to protect an avenue of giant sequoias threatened by concerned insurance companies. about roots undermining the houses to protect them.
There is no such concern at Wakehurst, where the redwoods are in different parts of the extensive grounds and arranged phytographically, with plants and trees laid out according to their continent of origin, so visitors can walk through gum trees. of Australia down into the North. American valley.
In the redwood grove, sprinkled with sunlight and rain and birdsong, Wilkes’ half-permanent smile turns into a beam. “The feeling of being in a forest, anywhere in the world, is second to none,” he says. His work involves using satellite data and Lidar – a light sensor and radar – to create 3D laser images of trees, a way to measure the size and mass of trees more accurately than the traditional method of measuring tree circumference.
“You go out into these vast forests and they’re just a different world when you get under the canopy, off the beaten track. It really draws you in. It’s really exciting – it’s one of the most complex environments you can work in, and it’s incredibly rewarding.”
Trees have a constant appeal to people. Last year, researchers at the University of Derby found that people value trees more than their neighbors, when they practice forest bathing – a western interpretation of the Japanese relaxation practice known as shinrin-yoku – demand has increased.
Perhaps the unique appeal of the redwoods is their scale; the oldest of which pre-English and the tallest of which, at 115 metres, is higher than St Paul’s Cathedral. And they might have been felled, like most of England’s forests, if they had been discovered by the Elizabethans who built Wakehurst and believed that man’s task was, as the historian Keith Thomas put it, “the woods level to the soil, drive out the predators, kill the vermin, plow up the fern and drain the fens”.
In the more ecologically conscious 21st century, Wilkes recognizes a different risk: that the desire to find solutions to the climate crisis will lead to rash choices.
“In Wales, they are being planted as a way to offset your carbon emissions. Planting redwoods in the Peak Beacons [Bannau Brycheiniog] the right thing to do?”
It is doubtful that native broadleaf woodland has much more benefits than carbon storage.
“Urban trees are undervalued, but they actually have a lot of value,” he says. “Carbon is one way you can value them, but it’s probably one of the least important things they provide – they’re cool cities, there’s flood mitigation, health impacts, biodiversity. They are not a way to offset carbon. Decarbonisation is the only way.”
The great giant of California
For millions of years the world’s tallest trees have graced the peaks and coasts of California, growing through centuries of change. The tall redwoods that first took root in groves through the Sierra Nevada mountain range are as resilient as they are magnificent.
But these landscapes have undergone significant changes in the last century and the forests have suffered. Due to the climate crisis, severe droughts and scorching temperatures have added new stresses to the redwoods, especially the famous giant sequoias, which are now struggling to bounce back after large wildfires.
Part of the problem stems from California’s gold rush era, when settlers came down with an overzealous desire for good timber, cutting down many of the old-growth forests. They also suppressed indigenous land management techniques, including burning “healthy” fires from the forest. A century of fire suppression created too much vegetation which set the stage for larger and more devastating blazes.
Robbing the most resilient ancient trees, forests now face a destructive cycle: the trees that die leave more fuel for dangerous fires. Vulnerable trees are also under increased attack from native bark beetles, insects that eat their red spongy trunks to exhaustion. Scientists estimate that about a fifth of California’s remaining giant sequoias have died in recent years due to this combination of factors, including a very intense 2020 wildfire that destroyed up to 10,000 trees ripe
Efforts are underway in California to protect them as federal, state, and indigenous community agencies work to restore good fire to the land, and seed deprived landscapes with new trees. Threats from global warming are ever increasing and mitigation work is getting better.
Along with their picturesque status, the trees are also critical to maintaining healthy ecosystems in California by sequestering carbon dioxide, providing a cooling effect when temperatures drop, and are vital habitat for other forest creatures. When they are gone, the landscapes will be changed forever, along with the plants, animals, and people who have grown to depend on them.
Gabrielle Canon, San Francisco
