Fred Pearce is the author of The New Wild, which challenged the conventional wisdom that native species are inherently superior to non-native species and the closely related assumption that all non-native species are competitors of native species. The New Wild is the most effective of the many critiques of invasion biology, which made his latest book required reading (for me).
A Trillion Trees: Restoring Our Forests by Trusting in Nature (1) examines the popular notion that planting one trillion trees around the world can deliver us from the death grip of climate change. Once again, Fred Pearce challenges the conventional wisdom. The claim that planting a trillion trees can compensate for our continuing burning of fossil fuels is an oversimplification, but with much truth at its core.
Forest Accounting: Debits and Credits
Pearce begins by reminding us of the ecological value of forests and the role they play in reducing greenhouse gas emissions causing climate change. In addition to absorbing carbon dioxide from the atmosphere during photosynthesis, forests also release water into the atmosphere in the form of water vapor. Trees pump moisture from the ground into their leaves where excess moisture is transpired from pores (stomata) in leaves, moistening the atmosphere and returning moisture to the Earth as rain. In a time and place where extreme drought is a major issue, this is a strong argument for retaining our forests.
On a global scale, forests are responsible for carrying moisture from coastal forests irrigated by moist sea breezes into drier regions on streams of moisture transpired by forests, Pearce calls flying rivers. Where coastal forests are destroyed, this moisture delivery system is interrupted, resulting in drought in interior regions. Observational data confirms this cycle: “Air coming from forested areas delivered more than twice as much rain as deforested areas. Forests make rain; taking them away creates if not deserts, then certainly aridity.”
The aerial river of moisture transpired by forests is carried by the wind and forests contribute to the wind. Transpiration emits buoyant water vapor that condenses to water as it rises and cools. Liquid water takes up much less space than water vapor, causing a pressure drop where water vapor becomes liquid water, resulting in wind. Some scientists believe that this “biotic pump” creates stronger wind than the winds that are created by cool ocean breezes meeting hot continental air. These theories are controversial, but Pearce finds them credible.
All trees emit volatile organic compounds, commonly abbreviated VOCs. VOCs neutralize a chemical known to neutralize methane, resulting in increased methane emissions from forests. Methane is the most potent greenhouse gas, although it does not persist in the atmosphere as long as carbon dioxide.
Although forests create their own cooling environment with shade and moisture, they also absorb heat from the sun. Albedo is the technical term used to measure light reflection and absorption. Because dark colors absorb heat and light colors reflect heat, this balance of cooling and heating factors varies. In Northern and Southern latitudes where winter snows reflect sunlight, dark forest canopies absorb more sunlight than treeless snow-covered ground. Likewise, desert sand reflects more light than dark forest canopy. Measuring the net effect of the many intervening factors such as albedo on climate change is controversial, even speculative at this time.
Evaluating Planting Projects
Pearce visited tree planting projects around the world and concluded that many are counterproductive in the short term and others are not sustainable in the long term.
- Some projects are planting plantations of fast growing trees such as eucalyptus and pine with the intention of logging them within about 10 years to produce timber, pulp, or biofuels. The short term objectives of these projects do not address the long term problem of climate change.
- Some projects are planting single tree species that aren’t necessarily well adapted to local conditions. The resulting monoculture is more vulnerable to disease, insects, and changed climate conditions.
- Many huge projects exist only on paper. Elaborate plans don’t necessarily produce new forests.
Israel’s strong commitment to planting trees on its desert land illustrates the pros and cons of tree-planting projects. Trees are important in Jewish culture. Jews around the world celebrate an annual holiday of trees, Tu BiShvat. A national nonprofit group created in 1901 bought land to support the Zionist cause and has planted 250 million trees on a quarter-million acres in the desert in what is now Israel.
One such project has planted 4 million Aleppo pines on the slopes of Mount Hebron near Tel Aviv since 1964. Aleppo pines grow naturally in wetter Mediterranean regions. They cope with drought by growing only briefly during spring rains in Israel and are dormant during most of the dry, hot year. There are limits to this adaptation. A year-long drought in 2010 killed 10% of the forest. Because of the slow growth of the forest, the carbon storing capacity of the forest has yet to match the heat the forest absorbs that would otherwise be reflected by light-yellow desert sands. Scientists who study this forest do not expect the forest to attain net cooling advantage for another 80 years. There is some doubt that the forest will live that long, given rapidly rising temperatures and associated drought.
Deforestation and Rewilding
Pearce also visited places where forests are being destroyed in Indonesia, South America, and Africa. In Indonesia, the economic value of the trees themselves is the primary motivation for destroying forests. In Brazil, the primary goal of deforestation is to convert forests to pastures for livestock and agricultural fields for commodity crops that feed animals.
Developed nations have exported much of their agricultural and animal production to undeveloped nations. As agricultural land in developed nations is abandoned, forests have regenerated. In New England, for example forest cover was only 30% by the mid-19th century after 200 years of timber exploitation and clearance of agricultural land. Industrialization brought farmers into cities and marginal agricultural land was abandoned. Today most of New England is forested again. As that transition from an agricultural to an industrial economy was made in developed nations, forests in undeveloped nations were destroyed to produce agricultural products exported to developed nations.
In Brazil, the rewilding of agricultural land is already occurring. Forests were cleared and seeded with grass for cattle pastures, but the poor soil is quickly exhausted and grass won’t grow after a couple of years. These abandoned pastures recover their forests even on exhausted soil, but they won’t be mature rainforests again for many years. When forests cleared for agricultural crops lose most of their rainfall, agricultural crops fail.
Pearce visited agricultural communities in Africa that have figured out that it isn’t necessary to destroy forests in order to grow crops. Farmers had to ignore the dictates of their government to clear their land before planting crops to learn that planting crops within groves of trees is just as productive. The trees provide shade and moisture that shelter crops as well as create a more comfortable home for the community.
Forests that are embedded in indigenous communities are more safeguarded than forests in so-called protected areas, where indigenous people have been evicted. If forests are sustainably used by the community, the community has a direct economic interest in its preservation. When indigenous people are evicted from forests, a handful of salaried rangers can’t provide the same level of surveillance, making forests more vulnerable to poaching and corrupt encroachment. People have tended their forests for eons and community forestry is an extension of that relationship. They understand the forest as no outsider could.
Pearce believes that protecting the forests we have and allowing forests to regenerate naturally where agricultural land can be abandoned is preferable to planting trees because:
- Planting trees where trees have never grown in the past is not likely to create a sustainable forest. If soil and climate conditions have not supported trees in the past, it is probably an unsuitable location for trees.
- Huge projects that plant millions of trees are often creating monocultures of a single species of fast-growing trees. Such monocultures are vulnerable to pathogens, insect infestations, and changes in climate. Forests that regenerate naturally are more diverse, although they aren’t necessarily the same species as in the past because of epidemics of pests and pathogens. “However clever the foresters were, the planted trees were less well suited to the space they were occupying than those chosen by nature” and “Natural regeneration helps species to shift and adapt to climate change.”
- Newly planted trees require more support than a forest that is regenerating from roots and seedbanks. They must be irrigated while they are establishing the fungal networks that give them access to moisture in the soil. They don’t benefit from moisture and carbon resources shared by their mature neighbors. They aren’t members of an existing, sharing community of trees.
Much of what is done in the name of “conservation” is destructive. Pearce makes a strong case for natural recovery rather than active intervention in natural processes: “Most of the fifteen-percent increase in forest cover across the eastern United States in the past four decades has come from natural regeneration rather than planting.” However, urban areas in America have lost 175,000 acres of trees cover each year for the past decade, according to the US Forest Service. We have experienced such loss of our urban forests here in the San Francisco Bay Area.
Bringing it home
Pearce’s message is consistent with my personal experience based on observations of tree-planting projects in the San Francisco Bay Area. Our urban forests are being destroyed for many reasons: to make way for development, to reduce fire hazards, and to eradicate non-native trees. Little planting is done when trees are destroyed. The tree species that are planted are often not suitable for the location. When new trees aren’t irrigated regularly, they don’t survive.
More effort should be devoted to preserving forests because replacing them is largely a fiction.
- Fred Pearce, A Trillion Trees: Restoring Our Forests by Trusting in Nature, Greystone Books, 2021. All quotes in this article are from this book.
12 thoughts on ““Restoring Our Forests by Trusting in Nature””
Thank you for a wonderful article. If the people doing the forest destruction along Visitation road next to McLaren community garden in San Francisco had seen this article and read the bullet points they would have realized there was no reason to destroy that wood land so they could put in their native Garden. It went from a very lush corner to a scene of destruction with many trees decimated to make way for their seedlings of “native”plants. Some people just don’t get it.
The destruction of large trees and the removal of dead trees standing or fallen in San Francisco it’s totally out of control. They are destroying the air purifying living trees and the food and shelter for the flora and fauna when they remove the dead ones.
“However clever the foresters were, the planted trees were less well suited to the space they were occupying than those chosen by nature” and “Natural regeneration helps species to shift and adapt to climate change.” from the book mentioned above.
I’m sorry that I can’t share your optimism that those who destroyed trees in McLaren with the intention of creating a native garden would have made another choice if they had read Pearce’s book. Like others who make ideological commitments in America, their minds are closed to other viewpoints. They rarely read anything that doesn’t confirm their beliefs. They seem to “see” another reality. While viewing some devastated landscape in San Francisco, nativists have declared it beautiful…or potentially beautiful if they had more money and more help to make it beautiful.
You are welcome to write a guest post about the consequences of destroying trees in McLaren with many before and after pictures. My readers enjoy guest posts. Guest posts provide concrete examples of the consequences of the nativist agenda. Please consider writing a guest post about your experiences with the nativist ideology.
Thank you for your support.
Berkeley Public Library doesn’t currently have A Trillion Trees listed. Even if you prefer to buy your books it is worth your time to go to the website of libraries and recommend worthwhile books for purchase so they will be on the shelves and come up in the data bases for people who have an interest.
I obtained Trillion Trees from the Oakland Public Library. It is available there…or will be soon when I return it if they only have one copy. People who live in Berkeley are eligible to use libraries in Oakland and vice versa. If you prefer to use libraries in Berkeley, I suggest YOU make the suggestion to Berkeley.
Thank you SO much for this important, needed post. I went to Oyster Bay once and found it so depressing. Now I know why. Sharing….
There’s a pleasant grove of mature trees at the southern end of Oyster Bay. It’s an interesting grove because it’s predominantly tree species that are native to California, but not to Northern California. Torrey Pines from San Diego and Catalina Ironwood from the Channel Islands are doing well there. The Ironwood is beautiful in bloom. These species have been newly planted elsewhere in the park and may survive. However, among the new plantings shown in my photo, there were also local native trees, such as coast live oaks that did not survive. I hope that East Bay Regional Parks will eventually learn what tree species will survive. I would prefer that they quit destroying healthy non-native trees and that’s the main point of my article: QUIT destroying healthy trees!!
So important to understand the cycle too. Or be reminded of the need for trees in this process.
If what you’ve posted here is true and if I’m understanding corectly what Pearce wrote in his book, then by removing non-native eucalyptus trees in California, we are proceeding in exactly the wrong direction. If eucs can grow where redwoods cannot, then instead of removing them, we should plant more.
Back east and in parts of upper Midwest, there is a horror brewing among strict nativists because picea abies (Norway spruce) appears to be naturalizing there. HEY! I’m O.K. with this! Norway spruce is a beautiful tree and rather than replacing native trees, it could well augment them and actually improve the forest in some instances.
In any event, I plan to acquire a copy of Pearce’s book.
Fred M. Cain
I just finished reading “The New Wild” by Pearce and am still awaiting the delivery of a “Trillion Trees” from Amazon.
I really enjoyed “The New Wild” but I was just a tad bit disappointed that Pearce didn’t go into any details on the eucalyptus destruction and controversy in California. Also left unmentioned was the naturalization of certain North American pines in South America where they have been declared invasive species. There have been movements to try and have them removed – never mind that they have probably increased diversification rather than reducing it.
In any event, I enjoyed the book and would recommend it. I look forward to reading “A Trillion Trees”.
Fred M. Cain, Topeka, IN
I liked The New Wild too, but like you I wasn’t entirely satisfied with it either. He visited with native plant advocates in the East Bay, where I live and quoted the leader of Friends of Sausal Creek. Then he criticized Professor Art Shapiro for not supporting what he considered the worthy effort of that group. Since destroying eucalyptus is the central element of the agenda of Friends of Sausal Creek, eucalyptus were tangentially covered in The New Wild. Pearce’s criticism of Shapiro was based on Shapiro’s support for preservation of eucalyptus. I wrote to Pearce to defend Shapiro and he sent me a polite, but non-committal reply, as I recall.
I must say that I enjoyed reading Fred Pearce’s book “A Trillion Trees” very much as I also enjoyed “The New Wild”. I believe his point that deforested areas worldwide could regenerate on their own if only they are allowed to, is well taken. Indeed, I think I’m already seeing this happen somewhat in Arizona following huge, high intensity mega fires.
However, Pearce made some points in the book that I have to admit I am just a tad bit skeptical of. For one, he argued that much of the Amazon Basin forest is actually regrowth following human habitation in centuries gone by. How’s that?
I can easily see how there could’ve been some lost civilizations there which were abandoned and the forest later regrew. Therefore, the forest is not a true, “virgin” forest IN THOSE AREAS. However, The Amazon Basin is so huge, so immense, that it’s just a bit of a stretch to believe that the whole forest is secondary growth.
He also suggested that the giant Sequoias in California were actually planted by indigenous people thousands of years ago. Huh? I have had a fascination for redwoods and Sequoias my whole life and have done extensive reading on the subject. I have never come across such a suggestion before. Did Native Americans help manage the Sequoias by conducting controlled burns? Sure, I can see that, but planting them? I dunno about that.
He also tried to make the point that the vast needle leafed conifer forests of the far north are not much help in fighting global warming because of the “albedo” effect. They absorb more heat and heat the air more than snow covered ground because of their darker color. I can see a difference there in albedo effect but left unmentioned is that fact that evergreens can conduct photosynthesis and therefore sequester carbon year-round whereas the summer green, deciduous forests can’t do that. Evergreen conifers can actually carry-on photosynthesis in the winter albeit at a much slower rate so when it comes to fighting climate change, I think that needs to be taken into account.
Another thing that I’m not at all sure I agree with, Pearce made a strong case for letting indigenous peoples and others who actually live in the forests, take care of them; they would be far better at doing that than government agencies.
My fear is that if we were to eliminate the National Park and National Forest services and allow Native Americans and other locals living in the woods to take care of them, our forests could easily fall into the wrong hands at some future point in time. I realize that there are some very serious issues at the U.S. Forest Service but it is my sincere hope that those issues can be addressed.
Perhaps my biggest disappointment was that Pearce made no mention of the ability of eucalyptus trees to cool neighborhoods and capture carbon in California and other parts of the West. He made no mention of this in either book. That’s an unfortunate oversight, really.
An interesting and surprising development, non-native pines have been encroaching on savannah and brush in parts of South America where they are regarded as an “invasive” species. Hard core nativists are upset about this and advocate their removal. It would’ve been swell had Pearce mentioned this in both books.
So, can I recommend A Trillion Trees? Sure, by all means, but having read the book, I would merely like to point out the shortcomings. Shortcomings surely exist in any piece of literature really.
Fred M. Cain,