With wildfires worsened by climate change, do redwood trees, California’s iconic American treasures, need help reproducing? The debate is preoccupying scientists in the Golden State, at the start of an unprecedented reforestation program.
In 2020 and 2021, gigantic fires ravaged these thousand-year-old giants, potentially forever changing the nature of the state’s forests. Up to 14,000 sequoias are extinct, possibly a fifth of the world’s species.
To repair the damage, the National Park Service (NPS) plans to help the behemoths by replanting young, laboratory-grown sequoias.
“The goal is to restore enough redwoods in the first few years after the fires so that in 60, 100 or 400 years we will have trees,” ecologist Christy Brigham told AFP in the heart of the Redwood Mountain Grove in Kings Canyon National Park.
Nestled in the Sierra Nevada mountains, this forest is home to the world’s largest concentration of these respectable reddish titans.
The largest specimens reach a height of 90 meters and their trunk is sometimes more than 9 meters in diameter. The oldest of them are 3,200 years old.
Once very widespread, they now only occur in a 350 kilometer long strip in California.
These wonders of nature “help us think long-term as we weigh our actions and consider things like climate change and forest management,” Ms. Brigham continues.
– “Never Seen” Desolation –
These two factors are now contributing to the endangerment of sequoias, which many thought were immortal.
Basically, fire is necessary for their regeneration: the flames cleanse and nourish the soil around them, and their cones – plants that resemble a pine cone – require intense heat to sprout the fertile seeds they contain.
But humans have disrupted this natural cycle.
For decades, California has consciously preserved the vegetation of many tall forests to reduce the risk of fire. The sequoias were therefore surrounded by smaller trees or dead wood.
As climate change worsened drought over the last decade, the surrounding greenery turned into a powder keg of fuel.
Under these conditions, the major fires of 2020 and 2021 caused unprecedented devastation. Trees that were thousands of years old were turned into blackened corpses.
The flames reached their peaks and “burned trees to a height of 200 feet (60 meters, editor’s note), something we had never seen before,” recalls Ms. Brigham. According to her passage, “we saw very few cones and virtually no young plants, which has never happened before.”
In some tall forests, the NPS believes there are not enough surviving sequoias or viable young plants to support rebirth. Hence the reforestation program.
Instead of allowing faster-growing trees like pines and oaks to invade tall forests, Ms. Brigham and her colleagues want to plant thousands of mini-sequoia seedlings imported from nurseries.
The project would span several years and is expected to cost $4.4 million if authorities give the green light in October.
– Replanting, a risky step? –
“These high forests will not recover without restoration,” said Andrew Bishop, another park ecologist. Without sequoia trees capable of reproduction, “there is no longer any insurance in the event of future fires (…)” to guarantee the rebirth of the giants.
A diagnosis that is far from consensus. For Chad Hanson, the reforestation program is heresy because nature has already done its work.
In the burned areas, “there are so many young sequoia plants (…) that walking is difficult,” argues the director of the environmental association John Muir Project, also an ecologist.
In his opinion, the NPS simply did its count poorly and the agents and mules responsible for replanting risk crushing the young sequoias, which are so small they are difficult to see.
“They will probably kill a lot more than they want to plant,” he points out.
Introducing young, nursery-grown redwoods also increases the risk of disease transmission to adult trees, he says.
“When people intervene, they are rarely very useful, even when they say so,” summarizes the scientist, who is very reluctant to play with one of the most spared ecosystems in the world.
But for park managers, this idea of untouched nature that can take care of itself is outdated in the age of climate change.
Because of forest management policies and our reliance on fossil fuels, “we have already impacted this wild area,” Ms. Brigham responds. “If we don’t intervene, we will lose parts of this forest.”