Having known Dr. Tom Kimmerer for over a year now, I am only slightly embarrassed to tell him I don’t know the first thing about trees. There’s one that stands outside my office, and I certainly appreciate when they line the sidewalks on a hot California day, but the things never seem to do much more than stand there. That’s a misconception Dr. Kimmerer would like to clear up.
“Trees are much more dynamic organisms than we think they are,” he told Planet Experts. “They don’t just change color and the leaves fall off – there’s a much more active process going on.”
Venerable Trees, Dr. Kimmerer’s first book, hit the shelves in September. Its run has already done well, with Amazon selling out its stock on the first day of publication. Filled with gorgeous photographs of Kentucky’s ancient Bluegrass trees (taken by Kimmerer himself), Venerable Trees tells the story of why these dynamic organisms – older even than the United States – are now disappearing.
There’s Something ‘Very Unusual’ About Kentucky’s Trees
Although each of the tree species Kimmerer discusses in the book can be found elsewhere, it is only in the Bluegrass of Kentucky and the Nashville Basin of Tennessee that they form a unique habitat known as a woodland pasture.
“I realized as soon as I arrived in Kentucky 30 years ago that there was something very unusual about the trees of central Kentucky,” said Kimmerer. “When the first settlers arrived here, they found his astonishing landscape that no one had ever seen before, of open-grown trees shading grass and giant cane.”
A woodland pasture is similar to a savanna, which is a rolling grassland populated by shrubs and isolated trees, but there are important differences. A savanna biome falls between that of a tropical rainforest and a desert, where low rainfall and frequent fire ensures that the trees do not grow close enough to form a canopy. “We get too much rainfall for it to be a savanna, and fire is not part of our history,” said Kimmerer of the Bluegrass.
It’s an important distinction, as the delicate balance of temperature and rainfall in the region has yielded some of the most valuable agricultural land in the world. How valuable? Consider this: Of the many cities founded in the eighteenth century, Lexington is the only one west of the Appalachians that is not built on a navigable waterway – unthinkable for a pre-industrial society. “People walked here and they found this open ground,” said Kimmerer. “No big river, but they could farm by simply chasing the bison off and moving the cattle and sheep in. They didn’t have to clear the woodlands.”
The land is ideal for grazing, which is a primary reason why Lexington is the premier horse breeding region in the world. “There’s sort of an emerald ring of horse farms all around us,” said Kimmerer, “and if you go among those farms you’ll find these huge, huge old trees. They’re the exact same trees that were here when the place was settled in 1779.” It is Kimmerer’s belief that many of the bur, chinkapin, Shumard oaks, blue ash and kingnut trees in this region date back to at least 300 years ago. Some may have stood for more than half a millennium.
Trees Have Complex Behavior (and Relationships)
It turns out trees do a lot more than just stand around. They actually sport a complex physiology, exhibit various behaviors, and share relationships that help them protect each other. “When they’re attacked by a harmful insect,” Dr. Kimmerer explained, “they send out a signal to attract predators of the harmful insect.”
If that sounds like a tall order for such immobile organisms, remember that it’s all a matter of perspective. “The more we know about trees, the more we realize how immensely complicated they are,” said Kimmerer. “It’s just that they don’t do things in human time. They do things in tree time. It’s a very different scale.”
That’s in part what drew Kimmerer to write Venerable Trees: Our ever-growing understanding of how trees behave and interact with their environment, and how humans interact with them.
“Effectively, a tree is an immortal organism,” said Kimmerer. “For a long time…we thought that trees slowed down as they got older. It’s only in the last year that we’ve discovered trees keep growing faster and faster their whole life. So a gigantic tree is growing faster than a medium-sized tree of the same species.”
Trees are also exceptionally resilient. They can regrow body parts without difficulty. “Most people now know about stem cells,” Kimmerer explained. “When we’re babies, we have a lot of stem cells. As we age, we only have a few left, like bone marrow. It’s very difficult for us to grow something new – you can’t grow a new colon or a new finger. But trees are made up of repeated modules. They’re all interchangeable and replaceable, and large trees keep a reservoir of billions – literally billions – of stem cells. Trees are almost endlessly capable of growing new parts.”
Human Development and Climate Change Are Killing Our Trees
Central Kentucky boasts one of only two woodland pasture regions in North America, the other being located in the Nashville Basin. Yet despite the Bluegrass State’s admirable land conservation policies, its age-old trees are in decline. They aren’t regenerating.
The problem is people. When the settlers arrived in central Kentucky, they drove out the bison that helped to maintain the ecosystem. Before the Europeans, bison would wander through the woodland pasture in search of water, intermittently grazing and then moving on. The long stretches between bison migrations allowed the vegetation to regrow and thrive. But the Bluegrass hasn’t enjoyed this natural cycle for centuries.
Livestock grazed down the native cane and grasses, necessitating their replacement by non-native species (“Kentucky bluegrass” is actually from Asia). And the damage has been exacerbated in urban areas by modern lawn care techniques. “Over a period of time, a combination of grazing by horses and cattle, mowing, soil damage and compaction…means there’s really no place for these trees to come up,” said Kimmerer.
Lush, green grass is choking the trees in this area, and the tree populations are waning. By repeating research done in 1950 around Lexington, Kimmerer discovered that about 90 percent of the bur oaks in the region have disappeared over the last 60 years. “Even though we have thousands of trees,” he said, “there were probably ten times that many a few years ago.”
There’s also a larger problem at work, one that stretches far beyond Kentucky’s Bluegrass: Human-made climate change as a result of runaway greenhouse gas emissions. “With climate change, we are losing a lot of populations of trees,” said Kimmerer. “Forests in general are growing better than they have in hundreds of years because in the east we have more rain and generally there’s more CO2. But there are a lot of trees that are going to be in trouble.”
The uptick in rainfall and higher amounts of CO2 will benefit trees in the eastern US, but not every region is affected equally. The western US is experiencing longer and more intense droughts, and it’s destroying forests faster than they can regenerate. But that’s a problem that people can solve, said Kimmerer.
“We’re pretty much in charge of where everything goes now, and we need to start planning for a warmer future. Even if we arrest climate change vigorously and soon…we are going to have some substantial climate change: Sea levels are going to rise, droughts are going to become more frequent, fires are going to become more intense. And as a result of that, there are places where trees can grow now that they won’t be able to grow in 50 or 100 years.”
Trees have migrated in the past. It’s a natural part of their reproduction. But they can’t migrate at the rapid rate that climate change is progressing, so some government agencies and conservation organizations are already going for the assist. “The Forest Service and a number of other authorities are beginning to plant trees north of where they grow now in the hopes that they will do well when the south gets too hot,” said Kimmerer.
“We as humans need to be much more conscious of how trees are doing in various parts of their range and what we can do to ensure their futures.”
Making Trees Matter
To the average Joe, considering what a tree is doing, or even what a tree is worth, is not part of his daily ritual. Of course, it’s something Dr. Kimmerer has been doing for the last 40 years.
“I’m trained as a forest scientist but what I actually am is a tree physiologist,” he said. “And when I would say to somebody, you know I’m a tree physiologist, I would get this blank look. And I realized finally that it is because people don’t realize that trees have physiology. It’s like saying you’re a rock physiologist.”
Take any one insight into the life of a tree as told by Dr. Kimmerer and you have a fascinating story. But, busy as he is with his current book tour, it’s unlikely that he’ll abandon his studies to do that, wandering the land and dispensing these tales to each and every American like a modern-day Tommy Appleseed. That’s why he wrote the book with the average Joe in mind.
“All the research that went into this is science – science and history – but the book is written for a lay audience,” he said. “It’s written for interested, non-specialist people, because ultimately what I realized was, even here in the Bluegrass, people who’ve lived here all their life, even people who own farms, are not aware of them. I tell people all the time that we have some of the oldest trees in North America right here and they say, ‘I didn’t know that!’ And I say, ‘Well there’s one right across the street!'”
Trees provide a multitude of invaluable services to the planet: They absorb toxins in the air and make fresh oxygen for us to breathe, they increase atmospheric moisture and conserve water in the soil, cool streets and cities, shelter a diversity of animals, provide food and shade. They are effectively immortal, given the opportunity, but they are not invincible. Humans are the ones who will decide if they’re worth saving, and Venerable Trees is making a case for their survival.
“This book is really an education project,” said Dr. Kimmerer,“so it’s got lots of color photographs, lots of black and white photographs, some diagrams, and very simple writing saying, hey, you have to realize we have this amazing habitat and we’re not taking care of it. We’re going to lose it.”
Dr. Tom Kimmerer is the Chief Scientist at Venerable Trees, Inc., a non-profit corporation dedicated to the conservation of ancient trees in the Bluegrass Region of Kentucky. Earning his PhD in Forestry and Botany from the University of Wisconsin, Dr. Kimmerer has taught forestry, urban forestry, tree physiology and plant physiology in the United States, Indonesia and Malaysia. He is a Fulbright Scholar, Planet Expert and avid conservation photographer.