A Trillion Trees

Restoring Our Forests by Trusting in Nature

Fred Pearce

• Publisher: Greystone Books
• Year: 2022
• Print ISBN:
  9780807039557
• eBook ISBN:
  9781771649414
• Topic: Biological Sciences
• Subtopic: Ecology
• Index: Biological Sciences

“A vivid, important, and inspiring book.”— Elizabeth Kolbert, Pulitzer Prize winning author of The Sixth Extinction and Under a White Sky

“Eloquently mulls the ecological dynamics of forests as well as the social, economic, cultural, and political forces that determine their fate.”—LA REVIEW OF BOOKS

A powerful book about the decline and recovery of the world’s forests––with a provocative argument for their survival.

In A Trillion Trees, veteran environmental journalist Fred Pearce takes readers on a whirlwind journey through some of the most spectacular forests around the world. Along the way, he charts the extraordinary pace of forest destruction, and explores why some are beginning to recover.

With vivid, observant reporting, Pearce transports readers to the remote cloud forests of Ecuador, the remains of a forest civilization in Nigeria, a mystifying mountain peak in the middle of the Atlantic Ocean, and the boreal forests of western Canada and the United States, where devastating wildfires are linked to suppressing the natural fire cycles of forests and the maintenance practices of Indigenous peoples. 

Throughout the book, Pearce interviews the people who traditionally live in forests. He speaks to Indigenous peoples in western Canada and the United States who are fighting to control their traditional forested lands and manage them according to their traditional practices. He visits and speaks with Nepalese hill dwellers, Kenyan farmers, and West African sawyers who show him that forests are as much human landscapes as they are natural paradises. The lives of humans are now imprinted in forest ecology. 

At the heart of Pearce’s investigationis a provocative argument: planting more trees isn’t the answer to declining forests. If given room and left to their own devices, forests and the people who live in them will fight back to restore their own domain.

Part I Weather Makers

Before the existence of forests, the atmosphere on Earth was baking hot, bone dry, short of oxygen and thick with carbon dioxide. Today, three trillion trees keep us cool and watered, by soaking up the carbon dioxide and by sweating moisture to sustain “flying rivers” that deliver rain across the world. Their breath alters atmospheric chemistry too, making clouds and even generating the winds. Trees, in short, created and sustain the life-supporting climate of our planet. Here is their story.

—1— Trees are Cool

Stomata, Transpiration and a Planet Transformed

TREES ARE THE BIGGEST and longest-living organisms on the planet. They can grow up to three hundred feet tall, weigh more than a thousand tons, and, in the case of North American bristlecone pines, sometimes live for more than four thousand years. In fact, their ability to clone replicas of themselves means they can effectively live forever. One cluster of forty thousand cloned aspens—or should that be aspen—in the Fishlake National Forest in Utah is a single male organism covering around a hundred acres and weighing more than six thousand tons. It is at least eighty thousand years old, making it “probably the oldest mass of connected tree tissue” on the planet, says British naturalist Richard Mabey. It hasn’t grown in a while, so it may be dying.¹ Nobody can be sure of that either.

Still, trees are everywhere, and have been for hundreds of millions o f y ears. C loud forests c ling to mountaintops, m an-groves dangle their roots in tropical coastal waters, steaming jungles straddle the tropics, snow-covered boreal forests gird the Arctic, sporadic woodlands stretch across arid grasslands and half-submerged willows filter swamps in valley bottoms. Nothing is more typical of the land surface of our planet. Most of its biomass is trees. More than half those trees, and two-thirds of their carbon content, are in the tropics. But the largest single forest is stretched across eleven time zones of the Russian far north, which contains a quarter of all the world’s trees.

Trees don’t just dominate our living world; they made it. Before trees, some 300 million years ago, the continents were mostly hot, arid and lifeless. The atmosphere was very different. “Carbon dioxide levels were ten times higher, and temperatures ten degrees warmer,” says Claire Belcher of the University of Exeter. “Oxygen levels were at half today’s level.” There was little soil. Fierce winds whistled across bare rock. But trees created a world in which they, and we, could prosper. “They transformed a barren planet and turned the world green,” says David Beerling of the University of Sheffield.²

In the early days, they began by colonizing the only wet places, on coasts. They transpired moisture into the air, thus recycling rainfall from sea breezes to generate more rain in formerly arid regions inland. That allowed new trees to extend their domain, transforming the atmosphere as they went. As they grew in numbers, they also began to draw down carbon dioxide levels in the atmosphere, cooling the world and often extending still further the places where trees could prosper.

They congregate in vast numbers, remaking their local environments: for instance, by linking their foliage to create closed forest canopies that shade and cocoon the land below. They work together below ground too, being largely responsible for creating the soil in which they grow. Down there in the soil, they connect up once again in a kind of underground canopy. In recent years, it has become clear that the finest threads of tree roots and the fungi that live on them mingle in amazingly sophisticated ways, sharing nutrients, redistributing carbon, and passing chemicals that signal events around them.

Much of this secret subterranean network was uncovered by Canadian ecologist Suzanne Simard of the University of British Columbia, who found fungal links in the soils of local forests of Douglas fir and paper birch. Using radioactive isotopes, she tracked compounds to prove that the trees are using the fungal networks to share resources and information. They look out for each other.

It now seems that most natural forests have such supply systems. Many plants and trees depend on them for essentials, such as nitrogen, water and even carbon created by photosynthesis in other plants. The networks deliver to order, in response to chemical signals from the trees. The fungi will even grab carbon and other resources from a dying tree and redistribute it to those in need. Large older trees that Simard calls “mother trees” are the most connected, but young trees starting out in a forest tap into these fungal networks from an early age, and even trees of species not previously found in the forest get to join in.

Following the word wizardry of an editor writing a cover line for the journal Nature, where the findings were first published, scientists now like to call these subterranean information superhighways the “wood-wide web.” And the rest of us are catching on. In his sci-fi movie Avatar, director James Cameron depicts a distant moon called Pandora, which has a biosphere made up of a glowing underground neural network.

A forest is not just a bunch of trees; it “is a cooperative system,” Simard says. It “behaves as though it’s a single organism,” controlling the forest environment and sharing resources among its inhabitants for what appears to be—and may actually be—a common purpose.³ Some scientists find such language off-putting, unscientific, and decidedly un-Darwinian. How does “survival of the fittest,” the cornerstone of evolution, find a place in this cooperative world? The fungi are not being altruistic, however. They are looking out for themselves, extracting a tithe for their services in the form of sugars made by the trees. And their control over the underground exchanges allows them to favor particular trees that help them most.

THAT’S WHAT WHOLE FORESTS can achieve. Now let’s check what happens under the hood of each tree. Consider not the super-organism, but the tiniest and most vital feature of trees, the one through which they impose most of their power over the planet. These are stomata—the microscopic pores on leaves that take in carbon dioxide from the air and release oxygen and water. “Life on Earth depends in no small part on stomata,” said the late Fred Sack of the University of British Columbia.⁴ The pores take from the air the feedstock necessary for photosynthesis, the most important biological process on the planet, because it makes plants. We, like all other animals, get our food ultimately from plant matter. Plants, on the other hand, make theirs from the air by photosynthesis, a chemical process that uses energy from the sun to combine carbon dioxide from the air with water drawn up from the tree’s roots. This creates glucose from which plant cells form. All this happens in leaves, where the stomata take in the carbon dioxide and then release the main waste products from photosynthesis: oxygen and excess water.

A single leaf can carry more than a million stomata. A single tree may have hundreds of thousands of leaves, so hundreds of billions of stomata. A big rainforest like the Amazon can have hundreds of billions of trees. That makes a lot of stomata. Ten to the power of twenty-one, perhaps. Stomata don’t just open their pores to the air, Sack said. They also act as valves, regulating the inflow of carbon dioxide and outflow of water in ways that allow plants to optimize the use of both. They can shut down during droughts, for instance, while at other times they stimulate the tree to pump more moisture from the soil to boost photosynthesis.

By regulating this flow of oxygen and water for the tree, they also regulate them for the planet. I won’t dwell here on the issue of oxygen. (Trees absorb as well as release oxygen. Things are in balance. It is a bit of a myth that the Amazon produces a fifth of the world’s oxygen. It does, but it also absorbs just as much.) But the process by which trees create water is fascinating. Stomata release water into the air in the form of water vapor. This transpiration is what moistens the atmosphere, recycling the rain to keep the world wet. It happens on a stupendous scale, with stupendous consequences. The planet’s three trillion trees release an estimated 1 4,400 cubic miles of water a year. Forming clouds as it blows downwind, this moisture is responsible for at least half of all the rain and snow that falls on land. In continental interiors that figure rises to more than ninety percent.

On the face of it, this is odd behavior. Pumping up moisture from the soil through the trunk to the leaves takes a lot of energy. It is vital for photosynthesis, but more than ninety percent of the water that reaches the leaves remains unused. It is transpired into the air through the stomata. Why does the tree bother? Certainly, the water cools the tree, but that could be achieved in other ways. There seems, instead, to be a collective purpose. Trees release moisture to make a world fit for more trees.

This role was laid bare a few years ago by Dominick Spracklen of the University of Leeds. He plotted data from thousands of rain gauges across the tropics and then looked at where the winds that brought the rain had come from during the previous ten days. His findings were dramatic.⁵ From the Amazon to the Congo basin and Borneo, the story was the same. Air coming from forested areas delivered more than twice as much rain as air from deforested areas. Forests make rain; taking them away creates if not deserts, then certainly aridity.

The idea that trees increase rainfall is not new, of course. It goes back at least to Pliny the Elder’s Natural History in Roman times. Most forest communities I have visited believe it implicitly. Christopher Columbus noted after crossing the Atlantic how it rained daily on forested Jamaica, yet only rarely on deforested islands he passed along the way, such as the Canaries and Azores.

Much later, British colonialists occasionally planted trees to improve the local climate. My favorite example of this deliberate tweaking of atmospheric conditions was the brainchild of Joseph Hooker, a botanist friend of Charles Darwin and future head of Kew Gardens in London. In 1843, he visited one of Britain’s smallest and most remote outposts, Ascension Island. The arid extinct volcano, stranded in the middle of the South Atlantic more than seven hundred miles from anywhere, was entirely treeless—apart from a few Norfolk pine trees planted by the naval base there, in case they were needed to repair ships’ masts. Water was in short supply. So Hooker came up with the idea of growing a forest on the volcano. “The fall of rain will be directly increased,” he predicted, because foliage would scavenge moisture from passing clouds.⁶

The island was a refueling point for British shipping. So in response to Hooker’s request, the Admiralty, the government department responsible for the navy, instructed sailors coming home from the far-flung colonies to bring trees and plant them on the mountain’s slopes. Which they did. Two decades and some five thousand trees later, the Admiralty reported with satisfaction that the island “now possessed thickets of upwards of forty kinds of trees, besides numerous shrubs.” As a result, it said, rains were improved and “the water supply is now excellent.” The barren volcano was soon renamed Green Mountain, a name it retains to this day.

When I visited the island, the trees were still there too, many naturally reproducing. As I climbed Green Mountain, I walked through South African yews, Bermuda cedars, Persian lilacs, Brazilian guava trees, Chinese ginger, New Zealand flax, taro from Madeira, European blackberries, Japanese cherry trees and screw pines from the Pacific. I also saw monkey puzzle trees, jacarandas, junipers, bananas, vines, palm trees and Madagascan periwinkles. The summit was topped off with several acres of bamboo that rattled in the wind.

The island now has more than three hundred tree species, according to botanist David Wilkinson, currently at the University of Lincoln.⁷ Ecologically, the accidental forest is fascinating. It is made up of trees delivered from all over the world and yet it appears to function as a single ecosystem. Insects that hitched a ride with the trees move indiscriminately from one continent’s vegetation to another. This cacophony of trees had changed the climate and I was curious to find out what this meant for the local environment. Stedson Stroud, the island’s conservation officer and my guide up the mountain, said that while the plains below were drier than before, the mountain was wetter (just as Hooker had predicted).⁸ As we stood on the summit, the cool dampness of the mountain air contrasted with the heat of the plain. When noon approached, a lone cloud formed above us and then descended, shrouding the mountain (and us) in mist. A drizzle of rain followed.

THOUGH ROOTED IN OBSERVATION, the notion that forests generated rain fell out of scientific fashion in the nineteenth century. The new wisdom was that “rain follows the plow.” In other words, that the best way of boosting rains was to get rid of the trees. This catchy phrase was coined by Charles Wilber, an American land speculator and part-time journalist.⁹ It helped make him rich, as he sold off real estate to people seeking their fortune on newly deforested lands. His slogan stuck. It became the received wisdom, repeatedly cited in meteorology textbooks.

Received wisdom is a dangerous thing, however. Wilber’s term had long puzzled Dominick Spracklen. He was troubled by the contradiction between the meteorological convention and what local people told him in the tropics about forests bringing rain. “I thought: let’s see if the local stories are true,” he told me. “And they were.” It was the meteor...

Table of contents

• Cover
• Title Page
• Dedication
• Contents
• Map: A Forest Journey
• Introduction: Myth and Magic
• Part I: Weather Makers
• Part II: From Paradise to Plunder
• Part III: Rewilding
• Part IV: Forest Commons
• Postscript: Back Home
• Acknowledgments
• Notes
• Further Reading
• Index
• Copyright Page