Hidden giants: How Britain’s 500,000 sequoias shade California | Trees and forests

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TThree sequoias tower over Wakehurst’s Elizabethan mansion like skyscrapers. But at 40 meters (131 feet) tall, these are mostly saplings. Although it is less than 150 years old, it is 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 fullest they will be three times as tall as most trees. ”says Dr Phil Wilkes, part of the research team at Kew Gardens’ outpost of Wakehurst, West Sussex. One or two of his Californian imports were stripped of their bark in 1854 and exhibited to Victorian crowds at the Crystal Palace in south-east London until 1866, when they were destroyed by fire. It is a rare item, like a 100-meter-long sequoia. .

But there’s more than just a few sequoia trees in England, and there are many more in Wakehurst than just these three. The Victorians were so impressed that they brought so many seeds and seedlings from America that there are now around 500,000 plants in Britain. In California, there are approximately 80,000 Giant Sequoias, the formal name for Giant Sequoias, as well as coastal sequoias and several ornamental Dawn Sequoias imported from China.

When Mr Wilkes and researchers at Kew and University College London highlighted this figure last week, it generated a lot of interest, but visitors to Wakehurst’s gardens talked about little else.

“People often worry that they’re an invasive species, but they seem to be pretty benign,” Wilkes says. “There’s no evidence that they’re self-seeding.”

This may be because sequoias are juveniles that are not yet ready to reproduce (sequoias can live up to 3,000 years), or because the cones typically open only in the heat of a forest fire. That means each tree in Britain was probably planted. It also explains how half a million giants were able to hide in obscurity.

“They were a valuable asset,” Wilkes added. “Often people would have rows of sequoias planted on mansions or in driveways. And although these homes were burned down or demolished, the redwood forest still exists.”

Sequoia enthusiasts have charted several locations, from people’s backyards to parks to suburban streets where homes are built around sequoias. But as Sequoia grows, so do opportunities for conflict, including in Cannons Drive in Edgware, north London. There, some residents are fighting to protect a row of giant sequoia trees after threats from insurance companies worried that the roots could damage their homes.

At Wakehurst, you don’t have to worry about that. At Wakehurst, sequoias occupy several parts of the extensive grounds and are phytogeographically arranged, with plants and trees arranged according to their continent of origin, allowing visitors to discover Australian rubber trees. You can exit and walk to the north. American Valley.

In a redwood glade bathed in sunlight, rain, and birdsong, Wilkes’ semi-permanent smile turns into a beam of light. “No matter where you are in the world, the feeling of being in the woods is second to none,” he says. His work involves creating his 3D laser images of trees using satellite data and his Lidar (Light Detection and Radar), which is an alternative to traditional methods of measuring the trunk’s circumference. is a more accurate way to measure the size and mass of a tree.

A sequoia tree surrounded by native trees at Kew Botanic Gardens in Wakehurst, Sussex. Photo: Andy Hall/Observer

“When you go out into this vast forest and get under the secluded canopy, it’s just another world.” It’s one of those environments and I’m really happy with it.”

Trees have a charm that attracts people. Last year, researchers at the University of Derby found that while practicing forest bathing (a Western interpretation of the Japanese relaxation practice known as forest bathing), people valued trees more highly than their neighbors. forest bathing – Growing in popularity.

Perhaps Sequoia’s unique appeal is its size. The oldest predate the English language, and the tallest is 115 meters tall, taller than St. Paul’s Cathedral. And perhaps by building Wakehurst, the human mission, as historian Keith Thomas has said, was to “level forests, till the soil, drive away predators, kill pests, plow bracken, clear swamps. Drain the water.”

In the 21st century, where environmental protection is more enlightened, Wilkes points to another risk. That is, the desire to find solutions to the climate crisis leads to hasty choices.

“In Wales we are planting them as a way to offset carbon emissions. Sequoia plantations under construction in the Brecon Beacons [Bannau Brycheiniog] What’s right? ”

He is skeptical, saying that native hardwood forests have many benefits beyond being carbon stores.

“Urban trees are worthless, but they are actually very valuable,” he says. “Carbon is one of the ways we give value to carbon, but it is probably one of the least important things it provides. Carbon cools cities, alleviates flooding, has health impacts and They bring diversity. These are not ways to offset carbon. Decarbonization is the only way.”

California’s teetering giants

For millions of years, the world’s tallest trees have graced California’s mountains and coastlines, growing through centuries of change. The towering sequoia trees that first took root in the groves of the Sierra Nevada mountains are as resilient as they are amazing.

However, these landscapes have undergone significant changes over the past century, and forests have suffered. Spurred by the climate crisis, devastating droughts and scorching temperatures are creating new stressors for sequoias, especially the famous giant sequoias, which are now struggling to recover after massive wildfires. .

Part of the problem stems from California’s gold rush era. At the time, settlers came so eager for quality timber that they cut down much of the old-growth forest. They also suppressed indigenous land management techniques, such as burning “healthy” fires to clear forests. A century of fire suppression has created excess vegetation, setting the stage for larger and more devastating fires.

The most resilient and ancient trees have been taken away, and forests now face a devastating cycle. When trees die, they leave more fuel for dangerous fires. Vulnerable trees are also increasingly under attack from the native bark beetle, an insect that feeds on the spongy red trunks until they fall. Scientists estimate that about one-fifth of California’s remaining giant sequoias have died in recent years due to a combination of factors, including particularly severe wildfires in 2020 that wiped out up to 10,000 mature trees. .

Efforts to protect them are underway in California, as federal agencies, states, and indigenous communities work to restore good fire to the land and plant new trees in destroyed landscapes. The threat from global warming continues to grow, and changes are outpacing mitigation measures.

In addition to their picturesque height, these trees are also important for capturing carbon dioxide, providing a cooling effect when temperatures soar, maintaining California’s healthy ecosystem, and other It is also an important habitat for forest creatures. When they disappear, the landscape changes forever, and so do the plants, animals, and people who have come to depend on it.

Gabriel Cannon, San Francisco

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