In 2005, in the forest I owned about 15 acres (0.06 square kilometers) in the northern Rocky Mountains of Montana, several centuries-old pines died suddenly. I soon discovered that they had been killed by mountain pine beetles, deadly killers as big as the eraser at the end of a pencil and would dig holes in trees.
The following year, the number of dead trees increased exponentially. I felt powerless and sad as I saw these huge, towering trees fade away around me, and I couldn't stop them from dying.
While native insects are the direct cause, the indirect cause of tree death in my hometown and throughout the Rocky Mountains is that winters no longer get cold. When I first moved to Montana in the late 1970s, the temperature in the winter was usually minus 34 degrees Celsius, and sometimes it was below minus 40 degrees Celsius for weeks. Montana's lowest temperature ever recorded was minus 57 degrees Celsius. Today, winter minimum temperatures rarely fall below -18 degrees Celsius. If there were, it would only be a day or two. This low temperature is not enough to kill pine beetles that are naturally resistant to frost.
Within three years, more than 90 percent of the trees in my forest were dead. We hired lumberjacks to cut down the trees and truck them to the factory, where they were pulped and made into fiberboard.
It's not just happening in Montana. Trees are dying throughout western North America. In 2006 and 2007, British Columbia lost 80 percent of its mature pine trees, going from carbon sinks to carbon sources. Throughout the West, trees continue to die; A few years ago, 129 million trees died in California.
Watching my forest die, it piqued my interest in figuring out what was wrong with these trees. In Montana and around the world, I began a 20-year survey of the lives and deaths of trees and forests.
Trees make our water sources clean, make the climate pleasant, provide wood for buildings, and provide a food source for humans and the animals they eat. They are even related to stars in some way. Surprisingly, however, we know very little about what they do.
We also lack knowledge about tree genes: especially the impact of the largest and strongest trees that have been cut down over centuries on the gene pool. Nor do we know how the trees that survive will survive in a hotter, drier world.
Over the past few years, however, scientists have begun to study the importance of ancient tree genes, and there is growing evidence that ancient tree genes will play a key role in forests. The study, which was carried out on the basis of a group of tree enthusiasts trying to plant these giant tree species to protect the ancient DNA they call the "library of life," seems prescient.
Craig D Allen spends most of his time observing forest deaths. Eager to understand how trees are dying from climate change, he was called a "tree coroner." Despite his recent retirement from the US Geological Survey, he is now busier than ever studying the world's forest crisis and has also served as an adjunct professor of ecology at the University of New Mexico.
Many years ago today, I walked with him through the nearby Santa Fe in the form of small, dying pine forests that had been killed by prolonged drought and heat. When I saw him again recently, he told me that global deforestation was accelerating.
Allen's team has meticulously uncovered the impact of climate change on the world's ancient forests — forests that live for at least a few hundred years — that we all love. It's a complex subject, but Allen notes that research papers published over the past decade have summarized the adverse effects of global warming on these ecosystems.
One of them, a 2012 paper that Allen co-authored, combines tree ring data, climate records, and future climate projections for the Southwestern United States. The study found that future mega-droughts triggered by climate change could have devastating effects on the region's forests. The crux of the matter is that the temperature of the air rises linearly, while the ability of the atmosphere to conserve moisture grows exponentially. This means that the atmosphere is getting drier and drier at an alarming rate, and drought is rapidly reducing moisture in soil, trees and other plants.
In 2012, an Australian research team published a second study that collected data on hundreds of tree species — about the path of water within the tree from its roots to its canopy. The study found that exacerbated droughts are pumping water away from forests at a faster rate, and in many places, trees can no longer keep up with increasing water stress, which leads to symptoms similar to embolism.
The third study, published in 2015, looked at the adaptation of trees around the world to drought. Allen told me, "The report says that every major forest tree, from Arizona and Algeria to Alberta and Argentina, whether wet or dry, is dying in ways rarely seen in history because of heat and drought." ”
On top of that, the increasingly frequent and hotter droughts of high temperatures and droughts have pushed the trees to their limits.
William Hammond, a plant ecologist and global change ecologist at the University of Florida, says that because a warming atmosphere can hold more precipitation, in some places that are both warm and humid, some forests grow very well and better than ever. But in hot, arid regions, the number of dead trees is also increasing. "Extreme weather kills trees," Allen said. "It's getting worse." Unprecedented extreme events are taking place, such as the 49 degrees Celsius temperature in British Columbia this summer.
In this ever-changing world, the brunt is ancient trees, many of which are over 200 feet (61 meters) tall or even 300 feet (91 meters).
Hammond said: "One of the risks faced by giant ancient trees is that the cost of their survival becomes very high. "They need more water, they need more energy to pump water into the canopy." They can be destroyed by drought, or severely weakened, falling victim to insects, disease, or fires.
More frequent high-temperature droughts also mean less time for trees to recover. Anna Trugman, an assistant professor at the University of California in Santa Barbara who studies the impacts of climate change on forests, said: "After the drought is over, the trees are fully irrigated again and they have the opportunity to regrow and restore some of their damaged organs. But if droughts become more frequent and continuous, they can lead to a longer-term decline in growth quality because they cannot recover. “
Those tall old trees have little resistance.
This is a problem because these ancient trees are not only huge, ancient, and awe-inspiring, but also vital to storing carbon to prevent an accelerated warming of the world. The largest 1% of trees store 50% of the forest's carbon.
Even as we strive to understand the knowledge of trees, the terrible future of trees will come. Suzanne Simard, an ecologist at the University of British Columbia, has found that there is an association between trees, and through roots and fungi, they communicate with each other and transfer resources. Researcher Diana Beresford Kroeger believes that trees release large amounts of aerosols, such as terpenes and limonene, which are natural antibiotics, antivirals and chemopreventors that help maintain the health of nature, including humans.
Hammond and Allen predicted that the world's largest trees and forests would go extinct. Studies have shown that forests today are very different from those of history, in part because of hotter and drier environments. Hammond said: "Forest lifespans are getting shorter and younger, and dominant species are shifting. The trees will continue to grow and will stay with us for a long time. But they will change. “
So what can we do? Reducing carbon dioxide emissions to slow climate warming is a top priority, but it may not get better for decades. In some places, artificial deforestation or regular arson can help. Some forests have 800-1000 trees per acre, which means that trees compete fiercely for water; The tree density of a healthy forest should be one-tenth of it. In addition, some sequoia forests are being considered for irrigation.
In addition, attempts have been made to replicate the largest surviving tree species.
Back in the 1990s, a father and son in rural northern Michigan planned to breed one of the largest tree species in the United States using asexual propagation cuttings.
It's a program called the Champion Tree Project. David Milarch is a fourth-generation farmer who planted shade trees. He consulted the largest tree species in the National Register of Big Trees maintained by American Forests, a Washington, D.C.-based nonprofit. He and his son Jared drove to the champion tree and asked its owner if they could take some cuttings.
They unloaded the ladder from the back of the pickup truck, and Jared climbed into the tree to pick a few small branches. The cuttings are sent to the nursery for cultivation replicas. Milachi and his son will then plant cutting saplings in different environments, such as cemeteries or parks, which Milachi calls a "living herbarium." The idea is to preserve the genes of trees that are 800, 2,000 or 5,000 years old around the world in case the original tree dies.
"The genes of the big tree are disappearing," he told me when I reported on the plan in 2001. "Someone has to cut them and keep them down. No one knew what it meant at the time. ”
Milachi's project focuses on the oldest and most iconic tree species in the United States: the sequoia. More than 20 years ago, I saw his team climb several of the world's largest trees so they could cut down conifers from a height, which is the best material for cuttings. Among them is the spectacular Waterfall Tree, a giant redwood in a private forest farm in central California, a species of whale with orange-red bark that dwarfs humans. The cover of my book uses a photograph of this tree, which tells the story of a tree planter who desperately cut cuttings to cultivate the world's largest tree species and reproduce it around the world.
I continued to do other things, but in the summer of 2021, my 20 years of experience with Mirage became critical again. Wildfires swept through California's famous sequoia forests, killing one-fifth of all trees. The waterfall tree is one of them – burned into coke.
These trees have long been thought to be indestructible, but in recent years, the number of deaths has increased. Christy Brigham, director of resource management and science at Sequoia and Kings Canyon National Parks, said, "What we're seeing now is that wildfires can burn large numbers of giant redwoods. We have 100 years of experience fighting wildfires, but climate change is making the environment hotter and drier, which makes it worse. ”
The disappearance of giant sequoia populations is also a concern. Brigham said, "We don't know what we might lose. But we're talking about a species that is already at risk of extinction, and only 78 trees have this tree. Now the mountain fire destroys 19% of the adult trees. In a small forest, 80% of the saplings were destroyed. ”
Milachi's agency, the Archangel Ancient Tree Archive, is still propagating trees by cuttings, and they are traveling to California in search of tree species in hopes of cultivating a "lost" redwood forest that Milachi thinks could be a record size.
They are also planting groves. "We planted 75 redwoods from cuttings in Presdio, San Francisco," he told me recently, referring to a former military base, the San Francisco Fortress, which has now been turned into a park. "As part of the transplant, we have planted sequoia in 41 cities in the Puget Sound area."
The idea of the Archangel Tree Archive is that while these 2,000-year-old trees can't move, their genes can. While cuttings are planted to create a new forest won't save the species, they do preserve their original genes. In the fall of 2021, the group planted cuttings in its own greenhouses, planted waterfall trees and other tree species in places where forests were destroyed by fire this summer, and further north, where future warming could be more conducive to sequoia growth. "A 2,000-year-old tree needs to be preserved," Milachi said. ”
The importance of the ancient tree gene inspired composer and music producer Timothy Smit, who bred 49 cloned redwoods from the archangel Ancient Tree Archive's collection of the Eden Project in Cornwall, England, which included thousands of plant species from around the world. He recently told me, "These saplings were only 3 feet (0.9 m) tall when they came, and now they are 15 feet (4.6 m) tall." All survived. ”
After two decades of cuttings, a study published this year confirmed Milachi's approach to preserving the genes of ancient trees. The study concludes that ancient trees fundamentally contribute to genetic diversity, thereby contributing to the long-term resilience and adaptability of surrounding forests.
"These ancient trees represent individuals who have survived a long history," said Chuck Cannon, co-author of the study and director of the Morton Arboretum's Center for Tree Science at morton Arboretum's Center for Tree Science in Illinois. "The special combinations of genes they contain can span centuries and provide beneficial genes in extreme environments that occur once in centuries." They are critical to the long-term resilience of forests. ”
Still, Cannon said, there have been few studies of ancient tree genes because they are both rare and difficult to identify. That's why he thinks it's so important for the Archangel Ancient Tree Archive to clone ancient trees.
"Learning to reproduce these living materials can be priceless so that we don't lose the unique combination of genes that these trees represent," he said. "Essentially, creating these ancient tree gene forests could help other forests increase genetic diversity and adapt to a rapidly changing world."
These days, as I walk through my woodlands, I feel heartened to see the offspring of dead pine trees return. Although the ancient trees that once stood are gone, the mountains and forests have not disappeared, at least not yet.
However, I no longer take forests and trees for granted. They are becoming increasingly vulnerable, and the loss of their loss will be immeasurable.