The two most feasible ways to limit global warming are planting a trillion more trees and sequestering carbon in the soil. Yet both could do more harm than good. Shall we plant trees in the Arctic and boreal forest? Shall we go vegan or double the livestock herds? Answer: It depends.
Though we should eagerly seize upon most new means of limiting global warming, there are two seemingly brilliant ideas that deserve closer scrutiny: Should we plant a trillion trees? And should we all become vegans? Unless qualified, both of these ideas may bring unanticipated and unwanted consequences. The current state of evidence is too ambiguous to justify any firm conclusions, but we have to make crucial decisions anyway.
Two things are clear: First, we should keep buried carbon buried. Second, we should suck ambient carbon out of the atmosphere and bury it. What remains uncertain is how best to fulfill these goals.Sometimes trees also can do Earth’s temperature more harm than good. That’s why we need to look so carefully at the unsettling evidence, which is the purpose of this paper.
People have little control over the planet’s carbon, for nature is mostly in charge. All living cells contain carbon. It’s everywhere: in rocks, in plants, in the soil, in petroleum, in the air, in crystals at the bottom of the ocean, and in 30,000-year-old muskox carcasses and frozen grass roots in Siberia’s permafrost. Nature moves carbon around continually, smashing ocean waves against rocks to form soil, then blowing it away as dust or feeding it to trees or flooding it into your basement. For eons, nature has balanced the carbon cycle by locking carbon in storage “sinks” that offset other ongoing emissions. But over the most recent dozen decades humans have botched nature’s routine. We’ve pulled petroleum, coal, and methane out of the earth for fuel and cut down forests for farmland. We’ve degraded and desertified areas of land larger than Newfoundland each year, turning fertile earth into barren dust. Land use (including agriculture and forestry) produces about 24 percent of global greenhouse gas emissions, largely through misuse, for if the land were managed well, it would be a sink instead of a source of emissions. Unless we repair the damage quickly, we shall suffer catastrophic consequences.
The repairs must begin by halting our continuing blunders, so the first task is to stop emitting carbon. That’s easier said than done, but by now it’s insufficient anyway. We also have to undo previous mistakes by recapturing some of the carbon that’s already in the air. Global warming will almost inevitably exceed the two-degree target adopted in the Paris Agreement of 2016, but by promptly using effective “negative emissions technologies” (NETs), scientists believe it possible to reduce it afterward to under 1.5 degrees.
Though several NETs are being developed, only two of them are realistic options for the urgent eleven-year target that scientists have set: First, let’s plant a trillion trees and, second, let’s adopt farming methods that recapture more carbon from the atmosphere than we are emitting. These changes will reverse the ongoing deforestation and desertification trends and may enable the expected human population of about 11 billion1 to be fed adequately in 2100. The Intergovernmental Panel on Climate Change (IPCC) has called for an increase of one billion hectares of forest to limit global warming to 1.5 degrees.  At least 20 countries have begun major efforts to reverse farmland and forest losses, and the effort is only getting underway. It can be accomplished for only about $300 billion—equivalent to the world’s military spending every sixty days.3 But we must hurry!
Our tool is photosynthesis: the mysterious biochemical trick every plant uses for capturing carbon dioxide and making it into sugar for its own functions. Even when a plant dies or is harvested, its roots may leave some carbon in the soil, enriching the fertility for future crops. Moreover, wooden houses and furniture can store carbon for centuries, so, as we shall see, both forests and farmland can be vast carbon “sinks”—or not. Today, farming is a major net source of carbon, emitting more to the atmosphere than it sequesters.
A scientific lab in Zurich led by Thomas Crowther has done the most extensive inventory of the world’s forests, estimating that there are now approximately three trillion trees on the planet. Is there room for another one trillion? After examining photos of some 80,000 plots of land around the world, the lab published a report by Jean-François Bastin et al. that gained worldwide attention.4 It noted that, whereas about 8.7 billion hectares (two-thirds of all the soil on the planet) could support forests, only 5.5 billion of that land is actually forested. Of the remaining 3.2 billion hectares, most is either cropland or urban areas. That leaves about 0.9 billion hectares as potentially available for restoration of forests. The researchers conclude that “the global forest restoration target proposed by the IPCC of 1 billion hectares (defined as >10% tree cover) is undoubtedly achievable under the current climate.” Those trees could theoretically store an additional 205 gigatonnes of carbon. Since there is an excess of about 300 gigatons of anthropogenic carbon in the atmosphere now, they infer that such enlarged forests could clean up about two-thirds of the mess we humans have made so far. In theory, then, trees can save us.
But the authors emphasize that we must act quickly, for global warming is reducing the amount of suitable land. At the current rate of warming, about 450 million hectares of tropical rainforests will be lost by 2050. This subtracts 46 gigatonnes from the 205 gigatonnes reductions now possible. Nevertheless, the researchers assure us that there is ample available land for the new forests—especially in six countries. More than 50 percent of the tree restoration potential can be found in diminishing order in Russia, United States, Canada, Australia, Brazil, and China.5
Most readers worldwide rejoiced upon learning of these findings, but not everyone. Adam Rogers, among others, soon published a withering criticism in the same journal.6 He claims that the Zurich research team had greatly over-estimated the total amount of carbon uptake by trees. Correcting such errors would largely negate their upbeat findings.
The report shocked some of us in a different way—by suggesting that many of the anticipated new billion hectares of forest will be in the Arctic. Hadn’t those researchers heard the bad news about forests and permafrost? We wrote to the lead author, Jean-François Bastin, to express our alarm, but he denied that their paper had recommended planting trees anywhere. They had only predicted that trees can, and unless people interfere, probably will proliferate in the tundra of Russia, Canada, and Alaska.
And that is true. Forests can grow in the Arctic and indeed are encroaching into the sparse grasslands of that region.7 However, even if quite large canopies grow there, the forests will sequester far less carbon per hectare than those in the tropics. A tree in a boreal forest (or “taiga,” as it is called in Russia) grows too slowly to sequester much carbon. Worse yet, forests in the Arctic may even be increasing global warming.8 This detrimental effect, which was discovered by climate scientists, initially surprised many foresters, who had assumed that photosynthesis everywhere has the same benign cooling effect on the planet. The trees in the Arctic do sequester some carbon but they also have another, less desirable, effect. Whereas the snow-covered grass reflects sunlight (the “albedo effect”), the trees make the landscape darker and therefore warmer. Second, it seems that some tree roots also stimulate the decomposition of organic material in the soil, so that long-frozen microbes revive and begin producing methane, which is twenty times more powerful as a greenhouse gas than carbon dioxide.9
Iain Hartley has compared carbon stocks of vegetation and soils between tundra and a birch forest. There was far less carbon in the forest than in the tundra nearby.10 Thus, despite sequestering some carbon, trees in a carbon-rich permafrost may have an overall warming effect on the climate. This possibility is so crucial for the climate crisis that much more research is urgently needed to clarify where trees are beneficial and where they are harmful—and more specifically, which trees, in which types of soil. For example, black spruce forests in some regions may actually protect the permafrost and help keep the earth cold, in contrast to birch forests.11
There is a huge amount of carbon involved: the northern hemisphere contains an estimated 1,672 billion tons of organic carbon. If just ten percent of it thaws, one estimate projects that it will release enough carbon to raise global temperature by 0.07 degrees Celsius by 2100.12 Another recent study estimates that already more carbon is lost from the permafrost regions during the winter than is taken up during the average growing season.13
There’s a major policy implication here: Although overall the Arctic is presumably still a carbon sink (sequestering more carbon than it emits), it will become a net source of greenhouse gas if forests continue encroaching there. That means it would be wholly inadvisable to plant billions of trees in carbon-rich permafrost soil—the type that is most widespread in the Arctic, especially Siberia.
An even more impassioned warning against Arctic trees comes from two Siberian ecologists, the father and son Sergey and Nikita Zimov. They have spent most of their lives studying the changing climate in Russia’s eastern Arctic. Contrary to the widespread assumption that the Arctic had always been a desert of ice and thin soils, they say that in the Pleistocene era it was a fertile grassland, rich with huge wild animals, such as bison and woolly mammoths, despite the 5 to 10 degree colder average temperature than today. They find vast numbers of ancient bones in the melting permafrost near the river Kolyma. These animals knocked down any saplings and prevented the warming of soil. By trampling the snow in winter, they also kept the soil cold.
“At the time,” writes Sergey Zimov, “the biomass of big herbivores on the planet reached 1.6 billion tons…. Bison and deer killed trees by eating the bark. Elephants and mammoths simply broke trees. Through fertilizing, harvesting, and trampling, herbivores managed their pastures in any climate.”14 The region still would be entirely grassland, they say, if stone age hunters had not killed off the huge animals —especially woolly mammoths—that had roamed the tundra in herds.
The Zimovs conduct their research in a large reserve called “Pleistocene Park,” which attracts scientist visitors from all over the world. They keep its land colder than the surrounding region by importing large animals and driving a vehicle around, knocking down every tree possible. According to their records, when air temperature sank to –40°C in winter, the temperature of the ground was found to be only –5°C under an intact cover of snow, but –30°C where the animals had trampled down the snow.15 The Zimovs are eagerly awaiting the progress of George Church, a Harvard geneticist who is trying to breed a larger elephant that can thrive in cold, to repopulate the Arctic with a close approximation of the woolly mammoth.
We cannot wait for that strange solution but there is now a sufficient basis for prohibiting the planting of forests in permafrost regions. However, if trees must not be planted in the Arctic, that will reduce the 0.9 billion hectares that Crowther’s team had defined as potentially available. Worse yet, permafrost is not limited to the Arctic, so it may be necessary to avoid reforesting in other places too. Professor Google explains that “Permafrost is widespread in the northern part of the Northern Hemisphere, where it occurs in 85 percent of Alaska, 55 percent of Russia and Canada, and probably all of Antarctica.” But the northern parts of Alaska, Russia, and Canada are the main places where Crowther et al suggest new forests could be established. To limit global warming, must we also reduce the size of our boreal forest and taiga? Surely almost no one would take seriously such a shocking proposal.
But the expansion proposal also looks difficult. A trillion is a lot of trees— a thousand billions. The current human population in 2019 is 7.7 billion. A trillion trees equal 130 trees per person. When prime ministers of countries are in a good mood, they offer to plant two billion trees, as Justin Trudeau has recently done, but even if every country in the United Nations planted two billion, we would reach only about one-third of our goal. And one trillion is not enough. The realism of any particular target number will depend on the effectiveness of the planting program. China is carrying out the most ambitious planting program of all (their target is 100 billion trees by 2050) but some Beijing researchers report that “on-the-ground surveys have shown that, over time, as many as 85 percent of the plantings fail.”16 So shall we aim for two trillion, say, or even three?
And if not in most of Russia, the United States, and Canada, where can even one more trillion trees be planted? The Crowther lab’s paper has explicitly excluded land now being used for crops as well as urban land. Most of the remainder therefore can only be in remote areas, beyond cities and farms, mainly far from roads.
Logically, it seems we must (a) choose very promising species, (b) plant them in the most suitable plots of soil © densely enough to maximize the number of trees per hectare, (d) in places where people can reach them easily and care for them regularly, and (e) protect them from fires and deforestation until they are mature and ready to be replaced. And, even so, we cannot rely entirely on new forests to save us, but must adopt other NETs as well—notably regenerative farming.
Big trees generally sequester more carbon than other plants, but even vegetables, flowers, grass, and grain put a lot of it into the soil. Although human beings are releasing 9.4 billion metric tons of carbon, the actual concentration of CO2 that stays in the atmosphere is only about half that. The rest is already being sequestered by oceans and land. Our challenge is to develop methods that sequester much more—even the 320 billion tons excess that we have put into the air and now must remove. Plants make that possible and there is evidence that increasing soil carbon content also increases the amount and quality of food grown there.
In 2015 France launched an exemplary campaign called “4 per 1000” at the COP 21 meeting. This is a plan to increase global soil organic matter stocks by 4 per 1000 (or 0.4%) per year, which would offset 20–35% of global anthropogenic greenhouse gas emissions. As a strategy for climate change mitigation, soil carbon sequestration would buy time over the next ten to twenty years while other effective technologies become viable.17
These agricultural innovations have come from a variety of different traditions such as organic farming, which are merging now and being called “regenerative agriculture”—farming that goes beyond being “sustainable” by actually reversing carbon loss on degraded land. This regeneration is necessary because poor land management is continuously degrading soil all around the world and, if not reversed, will make it impossible to feed the growing human population.
Techniques that increase carbon storage also tend to increase water retention and support the bacteria, fungi, and other organisms in healthy soil that live on carbohydrates produced by decaying roots and other plant materials.
There are promising genetic discoveries now that may soon improve the quality of several plant foods, such as soybeans. By selective breeding (not modifying genes) it is possible to create “super-plants” with deep roots that greatly increase the amount of carbon they sequester. A biochemical called suberin determines the length of roots, and scientists are developing suberin-rich varieties that may become available to farmers within a decade or so.19
But there are already other practical regenerative methods that about ten percent of North American farmers now are using. And around the world, such innovations are spreading as the extensive use of composts and mulching to avoid chemical fertilizers and pesticides. Leading farmers now keep their land covered year-round with cover crops. They avoid plowing the soil, so as to protect the roots of the plants for transferring carbon downward. And instead of planting crops in furrows, they insert seeds into soil that still is covered with the residue of last season’s crop. They replace annual crops with perennials.
To aerate the surface layer of soil without turning over the earth, some farmers use “key-line” methods, such as slicing narrow grooves into the soil, into which they may pour “compost tea” brewed from special bacteria and fungi, which they serve to the growing plants with minimal damage to the roots.
Such biological additives can multiply the crop yield and the soil sequestration many times over.20 Or they apply biochar— charcoal that is pure carbon, and which can stay in the soil for thousands of years, enriching it and retaining moisture. “Keyline” farming was invented by Australians during droughts; they created ponds and swales to move the water around the contours of hills and allow it to sink in deeper, instead of eroding the topsoil. Indeed, within a few years, these practices together can create 12 inches of new topsoil.21
By now, regenerative practices are well-established and uncontroversial, with one exception: “holistic management,” which involves the use of livestock to regenerate degraded soil. Livestock means meat, and meat is a fighting word nowadays, with almost all environmentalists opposing it.
First let me summarize the overwhelming case against meat. Around the world, lush grasslands and gardens are becoming barren wastelands, and for this, livestock is largely blamed. One-third of the planet’s arable land is used to produce crops for livestock,22 which includes about a billion cows and bulls. Nearly one-fifth of the world’s land is threatened with desertification, which is partly attributed to overgrazing by animals. Farmers are urged to remove their cattle from the land and let it rest until the vegetation recovers. Then the world’s grasslands could sequester carbon equivalent to 0.6 gigatonnes of CO2 per year.23
Moreover, meat production is clearly a source of global warming. Global livestock supply chains are the source of 14.5 percent of all anthropogenic greenhouse gas emissions—5 percent of the carbon dioxide, 44 percent of the methane, and 53 percent of the nitrous oxide emissions. Although less prevalent than carbon dioxide, methane is more potent because it traps 28 times more heat.24 Nitrous oxide is 264 times more powerful than carbon dioxide over 20 years, and its lifetime in the atmosphere exceeds a century, according to the IPCC.
Farmers feed grain to cows, pigs, and other animals before slaughtering or milking them for human consumption. If we ate that grain our selves, we would supposedly be healthier and there would be enough food for the entire human population. Vegetarians say they get along fine without meat and vegans manage without animal protein at all.
Ruminants such as cows are the worst culprits, for they directly add greenhouse gas to the air from both their front and rear ends. In the cow’s extra stomach—the one that enables it to digest the cellulose in grass and leaves —bacteria ferment its lunch and generate the methane. The nitrous oxide is released by decomposing manure.
These arguments for veganism are powerful and valid. The only logical advice seems to be this: Eat plants, not meat! Nevertheless, there are other facts (or at least claims) that may justify this contradictory response: Eat meat if you want to, and raise more livestock!
Let’s run through the health issue first, since in principle that could be settled by empirical research. In reality, though, such studies produce weak evidence. There are two reasons: First, people fib when reporting what they eat and, second, other factors confound the results. For example, vegetarians are so health conscious that they disproportionately exercise, avoid smoking, get plenty of sleep, etc, and these may be the real causes of any health differences.
One major review compared 54 different studies and concluded that, if there is any difference whatever between the mortality rates of vegetarians and omnivores, it amounts to less than one percent over a twenty-year period—too trivial to warrant any dietary changes.25 One study found that vegetarians and vegans suffer slightly fewer heart attacks but slightly more strokes than omnivores.
India is a good place to make these comparisons because most families there are consistently and permanently either vegetarians or not. Dr. Prabhat Jha is studying the health habits of a million households in India where someone had recently died. He finds no differences in mortality between male vegetarians and non-vegetarians, but vegetarian women have slightly shorter lives. He thinks this sex differential will be found only in India, for women there customarily serve the men and children first and eat only the (mainly carbohydrate) leftovers themselves.26 Vegetarian women in India probably consume too little protein.
In any case, health concerns are not a strong reason for choosing whether to raise livestock and eat meat. The consumer’s decision should probably be based mainly on the effects of livestock on global warming and on the importance of livestock for the livelihood on the world’s population.
As for the effect of cattle on sequestration of carbon in the soil, some, but not all, studies have shown that their grazing is beneficial. As one review of the research reports,
“Reeder and Schuman reported higher soil carbon levels in grazed—compared with ungrazed—pastures, and noted that when animals were excluded, carbon tended to be immobilized as above-ground litter and annuals that lacked deep roots. After reviewing 34 studies of grazed and ungrazed sites (livestock exclusion) around the world, Milchunas and Lauenroth reported soil carbon was both increased (60 percent of cases) and decreased (40 percent of cases).”27
The loss of carbon can be attributed to two forms of mismanagement: over-grazing and under-grazing, both of which will degrade the soil, harming not only the world’s climate but also the survival prospects of the world’s poorest people. Over one billion people depend on livestock—including 70 percent of those living on less than US$1 per day.28 It is unreasonable to espouse a doctrine that would deprive these people of the main or only source of their livelihood. Pastoralism is not about to end. The point is to make it more productive.
We have already considered the plight of the Zimovs as they struggle to keep the permafrost from melting around them. One is inclined to smile at their solution: Bring vast herds of giant herbivores—preferably woolly mammoths—back to the Arctic. That does not seem feasible. Cattle would have many of the same effects as super-elephants, but they cannot survive the Arctic winters outdoors. Bison can, and if there were a sufficient demand for their meat, quite large bison herds might be raised there, though not as quickly as they are needed.
Anyway, we should not ignore the ecological basis for the Zimovs’ proposal. During the ice age, the tundra flourished superbly as a grassland, while feeding far more animals than exist on the planet today. Those huge creatures stomped around eating constantly, and the grasses sequestered immense quantities of carbon. Today, buried in the circumpolar region of the Arctic, are 1.4 trillion tons of carbon, two times more than in all the forests on the planet. According to our current assumptions, such “overgrazing” should certainly have desertified the Arctic, but it had precisely the opposite effect! Is there a lesson here for cattle-ranchers elsewhere?
Allan Savory did not learn from the Zimovs but from his own observations of the barren land in Zimbabwe. Nevertheless, his conclusions are completely compatible with theirs. He says that saving the world from desertification will require more cattle, not fewer.
And, like the Zimovs, his evidence comes largely from the past, when vast numbers of huge animals roamed the African savannah.29 There were, as in the Arctic, about as many predators as herbivores, which stayed closely bunched together in herds; those closest to the centre were less likely to be eaten. There was luxuriant grass for these herds, which kept moving around, leaving manure behind. As they moved, their hooves trampled the grass and aerated the top layer of soil. If they stayed too long, their overgrazing would indeed degrade the land, but they would not return to the same spots until their previous deposits of manure and urine had been absorbed. Such herds maintained a thick grassland that retained rainwater that would otherwise have run off in gullies.
Savory learned from ecological history; he teaches regenerative farmers to restore their barren soil by enlarging their herds of livestock. He says the key is not their numbers so much as the way they are maintained. Conventional farmers around the world today let their whole herds stay on the same common paddock indefinitely, loosely spaced and grazing independently rather than in tight herds, for there are no longer predators to encourage crowding. By contrast, Savory’s “holistic management” instead requires the farmer to move his animals around in dense, grazing herds from one paddock to another, on a schedule determined by observing their impact, day by day, on the grass. Such a close herd is often surrounded today by a temporary electric fence that can readily be moved to the next paddock within a day or two, as required.
Another factor that must influence herding practice is the quality of soil being grazed. Savory classifies it as either “brittle” or “non-brittle,” which is a more important distinction than the difference between “arid” or “dry” land. “Brittle” soil receives most of its annual rainfall in a brief period, then remains dry for long intervals. The effect on vegetation is more challenging than that of a “non-brittle” landscape, where the humidity is distributed evenly throughout the year. Brittle land requires the services provided by especially large herds of animals, managed holistically. However, even non-brittle cropland that is producing vegetables, grain, and fruit also benefit from having heavy animal impact on the land, though not necessarily every year.
Livestock perform two other remarkable services: counteracting gravity and maintaining biodiversity. Water runs downhill, taking the nutrients with it. If unchecked, this phenomenon would mean that valleys would be fertile but the soil at the top of hills and mountains would be barren. However, herbivores eat the plants that grow in valleys, then wander uphill and excrete. Their manure contains, not only the nutrients that they have consumed, but a number of seeds from all the plants they have eaten along the way. This re-diversifies plant species and fertilizes the ground where they grow.
Holistic management has its critics—more, it seems, in the popular press than among researchers or ranchers, who are apparently becoming converts. Agronomists cite Savory in their FAO reports, asserting for example that
“Overgrazing is a function of time (grazing and recovery) and not of absolute numbers. It results when livestock have access to plants before they have time to recover. Compromised root systems of overgrazed plants are not able to function effectively.”30
On the Internet one can find hundreds of photos of landscapes split down the center by a fence. The land on one side is degraded but on the other side verdant—allegedly because of the proper grazing methods used there. And on Facebook there are regenerative farming and grazing groups with ten thousand members. They prohibit debates about global warming or vegetarianism but exchange the pragmatic know-how that working farmers need.
Sheldon Frith, a farmer-scholar advocate of holistic management, notes in his book Letter to a Vegetarian Nation that there are about 100 million cattle in Canada and the United States now. He estimates that between 27 million and 135 million are needed to maintain the cropland soil; about 58 million cattle to maintain rangelands; and about 59 million to regenerate and maintain North American tundra. That would mean that the existing livestock should be approximately doubled, and of course maintained holistically.31 And indeed, farmers around the world are increasingly adopting holistic management because it does evidently restore degraded ecosystems.
Unfortunately, Frith’s proposal seems totally incompatible with our earlier acknowledgment that these animals emit huge quantities of methane—a far more powerful agent of global warming than even carbon dioxide. There is obviously a great need for additional research to resolve much contradictory evidence.
It seems to be an established fact that good grazing practices enhance the health of the soil, enabling plants and soil organisms to flourish. However, we must also ask whether good grazing also increases the long-term sequestration of carbon—and that is a controversial question.
The climate crisis requires clear answers, yet the best methods of measuring carbon uptake are unsettled, and there are obviously so many other factors involved that the evidence is questionable. One meta-analysis, for example, reached the upbeat conclusion that “grazing lands generate carbon surpluses that could not only offset rural emissions, but could also partially or totally offset the emissions of non-rural sectors.”32 (In other words, cows can save us.)
Yet another meta-analysis reported flatly that “study after study arrived at similar conclusions. Grazing did not increase carbon sequestration in soils.” (In other words, cows do great things for the environment and can feed us, but they can’t save us from climate change.)
What does ecological history tell us about the equilibrium between methane emissions and uptake? Remember the astounding biomass of herbivores that lived in the Pleistocene period‚ a total far exceeding that of all animals, including humans and livestock, living today. Woolly mammoths and other megafauna also emitted methane. Nevertheless, ice cores from the Pleistocene period show that the atmosphere contained lower levels of methane than today. How so? Probably the answer lies in the balance between methane-excreting animals and methane-eating microbes in the soil.
It is not easy to break methane molecules apart to sequester the carbon in soil, but there is one category of bacteria that do so: methanotrophs, which eat methane and thrive best in areas where it is abundant—ocean floors, swamps, and pastures. During the Pleistocene, methanotrophs must have flourished, fed by the herds of megafauna. Presumably their abundance explains the stupendous quantities of ice age carbon in today’s Arctic soil.
Methanotrophs have a protein called methane monooxygenase, or MMO—an enzyme that contains copper. The metal us stored energy to destroy the super-strong methane bond and make MMO the only known protein that can break apart methane. Scientists are now studying it with the hope that MMO can be cultivated on a large scale for the fight against global warming.33 The methane from ruminant animals would be sequestered by methanotrophs instead of emitted into the atmosphere as greenhouse gas. However, this research is not advanced enough to offer the solution to our current predicament—that, although the health of our soil depends on grazing animals, they are probably also worsening our climate crisis.
In the short term, the most promising way reducing the livestock dilemma may be to find ways of limiting the methane produced in ruminant stomachs. Vaccination may be able to eliminate the causative enteric bacteria. Another solution is to feed cows small amounts of seaweed, which reduces about 80 percent of their methane emissions.34 If successful on a large scale, this would diminish the basis for abolishing livestock and the consumption of meat. Unfortunately, seaweed seems to be more effective with cows kept and fed in pens than with cattle that graze on pastures, restoring the fertility of the land.
So yes, maybe trees and cows can save us—if they don’t kill us first, which is equally likely. Everything depends on how we manage them. A trillion of the right species of trees in the right location might capture and sequester enough carbon to offset our worst past mistakes, giving us a couple of decades to phase in better technologies. But large forests in carbon-rich permafrost might set off a positive feedback loop that becomes irreversible.
Likewise, with proper management, cattle, sheep, bison, and other livestock might restore to fertility a large part of the earth’s degraded land. But poorly managed flocks, especially ones that graze too long or with too little hard impact as a herd, will hasten the desertification of our planet.
Both of these challenges require more scientific information than exists at present. The search for optimum solutions may be the most urgently consequential policy facing humankind, so everyone is obliged to join in the discourse. Every advanced country must immediately speed up the quest for clear answers.
Until more is known, the following policies seem to be the wisest practices:
A. Plant no trees in the Arctic and probably in no other area of permafrost.
B. Do not reduce (and maybe even increase) the number of grazing animals for meat and milk, but use holistic methods of managing them.
Since permafrost areas and savannahs are among the places that Crowther’s lab had counted as potential forest areas, removing them from the plans for afforestation will diminish the prospect of planting a trillion trees—or the several trillion that will be required if they are not cared for properly.
We must recognize the inevitable competition for the use of land, with food crops deserving high priority, and we are ambivalently including meat as one of the foods to be produced. Cities were also excluded from the 0.9 billion hectares that Crowther’s lab initially designated for prospective new forests. Therefore, the remaining available land would mostly be far away from where people live or grow their food. Will governments fly hordes of workers, students, and soldiers out in helicopters with spades and bundles of saplings? And will they fly them back every month to weed and water their trees?
How about less labor-intensive methods? There are stories on the Internet about “seed balls” made of clay and dung containing seeds. They are thrown into vacant lots or even dropped from airplanes with the expectation that they will become new forests. This apparently never happens.
What about drones? We interviewed some people who are using that technique.35 They do know the results of carefully monitored studies but for various reasons would not share that information with us. Probably drone planting succeeds in some environments but we were more pessimistic at the end of our interviews than at the beginning. Tree-planting machines exist too, but no one claims they are quicker than people.
Thus we need a billion hectares of land that will support trees, and we need a lot of human labor to plant them and maintain a good survival rate, so we will have to squeeze many saplings onto land that Crowther’s people declared off-bounds: farms and cities. And perhaps we can plant more trees per hectare than had been planned.
There actually are beneficial ways of maximizing land-use. Silvopasturing, for example, is being praised in FAO publications as a way of raising cattle on pastures where there are also some trees. And some food crops (notably coffee) thrive best in the shade of other trees.
Biodiversity can actually improve the carbon sequestration of trees, though this depends on the combination of trees that are put together, e.g. planting adjacent trees of differing heights, so they do not compete for canopy space.36 Moreover, biodiversity and dense planting can work together to speed up the growth of trees. This is best demonstrated in the forests created by the Japanese botanist Akira Miyawaki, which actually grow ten times faster than the monoculture plantations that are planted by the logging industry.
An Indian engineer named Shubhendu Sharma studied with Miyawaki and has created a company called Afforestt, which is creating mini-forests in cities and degraded plots of land all around the world.
First Sharma’s team collects seeds from a wide variety (say, 60 or 70) of local indigenous trees, rejecting any alien species. They classify them by expected height at maturity, start them growing in pots until they are saplings about two years old. Next they remove the first meter of degraded soil, mix it with an appropriate blend of organic matter from the same locality, and replace it. Then they plant the trees and shrubs very densely—about four per square meter, with all four plants chosen for their differing expected heights. They water and weed them for about two years, after which the trees generate their own water and can continue growing with no maintenance for hundreds of years.
Of course, many or most of these closely-planted trees die, but Afforestt does not thin them out. They see trees as social beings who form their own friendships and alliances. Sharma lets the trees themselves “decide” which of their companions shall survive, for they all benefit from their closeness. It is impossible to walk through a Miyawaki-type forest, for they are all so dense.37
Most of these mini-forests are in cities, and some are only the size of a parking spot or tennis court. Some communities hire Afforestt to plant urban forests so their children can learn the care of trees. Such urban forestry, if done on a mass scale, could locate billions of trees where people live, work, and can conveniently volunteer their spare time. It enhances the community-spirit in a neighborhood. Certainly not all trillion of the new trees can be planted in cities, but possibly enough urban to compensate for preventing Arctic forests.
In North America and much of Europe, huge amounts of urban space can be reclaimed beneficially, not from degraded land but from lawns. In the United States, lawns take up more acreage than the top eight crops combined.38 This was not always the case. Historically, only the wealthy could afford the space and servants to keep lawns. The invention of the lawnmower, the shortening of the work week to forty hours, and the spread of tract suburban housing after World War II enabled the middle class to acquire the habit. Indeed, having a proper lawn became a badge of respectability.
The climate crisis must call this symbol into question. Matt Weber reminds us that,
“We apply more synthetic fertilizers and pesticides to our lawns than an equivalent area of cropland. Not only can this hurt local wildlife, these chemicals can end up in our own drinking water. The manufacture and use of these chemicals require large amounts of fossil fuels and contribute to global warming. Running a single lawn mower for an hour emits just as much pollution as 40 automobiles, according to the EPA. [Each] lawn mower produces more pollution than multiple cars. In a year, a hectare of lawn can contribute as many greenhouse gases as a jet flying halfway around the world… [and] 50–70 percent of all residential water in the United States goes to landscaping. Irrigated lawns take up nearly three times as much space as irrigated corn.”39
Weber did not mention one of the worst offenses of lawn-owners: they are maintaining major sources of nitrous oxide. This greenhouse gas has global warming effects 298 times greater than carbon dioxide on a 100-year timescale. It is increasing in the atmosphere each year because of fertilizer use in landscaping and lawns.40
But perhaps this destructive symbolism is ending. Florida has just passed a law saying that cities cannot prohibit people from growing food on their front yards. Next maybe they will let us plant Miyawaki forests. Those two measures are among the promising changes that can be made on land to save the world. (And we have not even considered here the prospects for increasing carbon sequestration in the oceans. Paul Beckwith helpfully reminds me: “Don’t forget plankton. If you like trees, you’ll love plankton.”)
Current research on forestry and regenerative agriculture is incomplete. The climate emergency requires information that is lacking. Still, we must make fateful decisions in this context of uncertainty. Therefore, the following policies should be considered seriously:
Eat meat if you want to. Raise livestock, using holistic management. Feed them a little seaweed. Replace your lawn with a vegetable garden or a Miyawaki forest. Plant two trillion trees, but none in carbon-rich permafrost areas. Good luck.
Metta Spencer is editor of Peace and Project Save the World.
1 Population Division of the UN Department of Economic and Social Affairs, “The World Population Prospects 2019: Highlights”, 17 June 2019. www.un.org/development/desa/en/news/population/world-population-prospects-2019.html
2 Intergovernmental Panel on Climate Change. “An IPCC Special Report on the Impacts of Global Warming of 1,5 Degrees Centigrade Above Pre-Industrial Levels and Related Global Greenhouse Gas Emission Pathways”. (IPCC, 2018).
3 Adam Majendie and Pratik Parija, “How to Halt Global Warming for $300 Billion,” Bloomberg News, October 24, 2019. business.financialpost.com/commodities/agriculture/how-to-halt-global-warming-for-300-billion.
4 Jean-François Bastin, Yelena Finegold, Claude Garcia, Danilo Mollicone, Marcelo Rezende, Devin Routh, Constantin M. Zohner, and Thomas W. Crowther, “The Global Tree Restoration Potential,” Science, 365, 76-69 (2019) 5 July, 2019.
6 Adam Rogers, “Trying to Plant a Trillion Trees Won’t Solve Anything,” Science, Oct. 26, 2019.
7 Jonathan A, Wang, Damien Sulla-Menashe, Curtis E. Woodcock, Oliver Sonnentag, Ralph F. Keeling, and Mark A. Friedl, “Extensive Land Cover Change Across Arctic-Boreal Northwestern North America from Disturbance and Climate Forcing.” Global Change Biology 2019, 00.1 -1-16.
8 Christa Marshall, “Vegetation May Speed Warming of Arctic,” Scientific American, Sept 1, 2019. www.scientificamerican.com/article/vegetation-may-speed-warming-of-arctic
9 Bartosz Adamdzyk et al, “Plant Roots Increase both Decomposition and Stable Organic Matter Formation in Boreal Forest soil,” Nature Communications, Sept. 04, 2019. www.nature.com/articles/s41467-019-11993-1
10 Bits of Science, “Trees Starting to Grow in the Arctic due to Climate Change Could Cause Carbon Dioxide Release,” June 17, 2012. Hartley’s research was initially published in Nature Climate Change (no date).
11 Argyro Zerva et al, “Soil Carbon Dynamics in a Sitka Spruce (Picea sitchensis (Bong.) Carr.) Chronosequence on a Peaty Gley,” Forest Ecology and Management 205 (2005) 227–240 .Available online at www.sciencedirect.com.
12 Holli Riebeek “The Carbon Cycle”, NASA Earth Observatory, June 15, 2011. earthobservatory.nasa.gov/features/CarbonCycle
13 Susan M Natali, Jennifer D Watts, and Donatella Zona, “Large Loss of CO2 in Winter Observed Across the Northern Permafrost Region,” Nature Climate Change (2019) www.uarctic.org/news/2019/10/large-loss-of-co2-in-winter-observed-across-the-northern-permafrost-region
14 Sergey Zimov, “This Wild Field Manifesto is a Work in Progress,” Revive and Restore. Nov. 25, 2014. reviverestore.org/projects/woolly-mammoth/sergey-zimovs-manifesto
15 S.A. Zimov, N.S. Zimov, A.N. Tikhonov, F.S. Chapin III (2012). “Mammoth steppe: a high-productivity phenomenon” (PDF). In: Quaternary Science Reviews, vol. 57, 4 December 2012, p. 42 fig.17. Archived from the original (PDF) on 4 March 2016.
16 Jon Luoma, China’s Reforestation Programs: Big Success or Just an Illusion?” Yale Environment 360. Jan. 17, 2012. e360.yale.edu/features/chinas_reforestation_programs_big_success_or_just_an_illusion
17 Budiman Minasny et al, “Soil Carbon 4 per Mille,” Geoderma, Vol. 292. Aril l14, 2017, pp 59-86. www.sciencedirect.com/science/article/pii/S0016706117300095
18 David Fogarty, “Crops with deeper roots capture more carbon, fight drought: study” Reuters Aug 5. 2011. www.reuters.com/article/us-crops-carbon/crops-with-deeper-roots-capture-more-carbon-fight-drought-study-idUSTRE77412Q20110805
19 Joanne Chory’s TED talk, “How Supercharged Plants Could Slow Climate Change.” www.ted.com/talks/joanne_chory_how_supercharged_plants_could_slow_climate_change
20 John J. Berger, “Can Soil Microbes Slow Climate Change?” Scientific American Mar 26, 2019.
www.scientificamerican.com/author/john-j-berger. See also videos by David Johnson. www.youtube.com/watch?v=MuW42tFC4Ss and www.youtube.com/watch?v=79qpP0m7SaY
21 Ethan Roland video: “Carbon Farming: Tools for Regenerative Agriculture.” www.youtube.com/watch?v=ljuJhQtLYt8 and see email@example.com.
22 Alastair Bland, “Is the Livestock Industry Destroying the Planet?” Smithsonian.com. Aug. 21, 2012. www.smithsonianmag.com/travel/is-the-livestock-industry-destroying-the-planet-11308007
23 U.N Food and Agriculture Organization: “Key Facts and Findings,” www.fao.org/news/story/en/item/197623/icode
24 FAO, “Key Facts and Findings.”
25 Bradley C. Johnston et al, “Unprocessed Red Meat and Processed Meat Consumption: Dietary Guideline Recommendations From the Nutritional Recommendations (NutriRECS) Consortium Free” Annals of Internal Medicine, 2019. annals.org/aim/fullarticle/2752328/unprocessed-red-meat-processed-meat-consumption-dietary-guideline-recommendations-from
26 Dr. Prabhat Jha reports these results in a lecture to Science for Peace, video www.youtube.com/watch?v=-JcPm_bXISU . See also the defence of meat diets by Chris Kressler, “Do Vegetarians and Vegans Live Longer than Meat-Eaters?” chriskresser.com/do-vegetarians-and-vegans-live-longer-than-meat-eaters. “Eating Meat Reduces Stroke Risk? New Study Says Yes” Topical Thunder, Sept. 5, 2019, reporting on a British study of 48,000 adults. topicalthunder.com/2019/09/05/eating-meat-reduces-stroke-risk-new-study-says-yes/
27 Micharel Abberton, Rochard Conant, and Caterina Batello, “Grassland Carbon Sequestration: Management, Policy, and Economics,” Plant Production and Protection Division, Food and Agriculture Organization of the United Nations (FAO), Rome, April 2009.
28 World Bank, 2009.
29 Allan Savory and Jody Butterfield, Hoiistic Management, Third Edition: A Commonsense Revolution to Restore Our Environment, Kindle Book.
30 Abberton et al. op cit.
31 Sheldon Frith, Letter to a Vegetarian Nation, an e-book available on Kindle, 2016 firstname.lastname@example.org, www.regenerateland.com
32 E.F.Viglizzo et al, “Reassessing the role of grazing lands in carbon-balance estimations: Meta-analysis and review,” Science of The Total Environment Volume 661, 15 April 2019, Pages 531-542. doi.org/10.1016/j.scitotenv.2019.01.130
33 Alex Berr, “The Bacteria that Eat Methane: An Interview with Soo Ro, Molecular Biophysicist.” Helix, Sept. 15, 2017. helix.northwestern.edu/blog/2017/09/bacteria-eat-methane
34 Emma Bryce “Feeding Cows Seaweed Could Reduce Their Methane Emissions,” Anthropocene Magazine, June 21, 2019. www.anthropocenemagazine.org/2019/06/feeding-cows-seaweed-could-reduce-their-methane-emissions
35 “Can drones plant a trillion trees?” Video discussion with Sandy Smith, Eric Davies, Elena Fernadez-Miranda and Eman Hamdan. youtu.be/LU8hCkAaYfs
36 Jean-Baptiste Pichancourt, Jennifer Firn, Iadine Cgades, and Tara G. Martin, “Growing Biodiverse Carbon-Rich Forests,” Global Change Biology (2013) 20, 382-393.
38 Matt J. Weber, “Why Everybody Wants a Lawn, and Why It’s Killing the Planet,” Medium, June 26, 2018 medium.com/s/story/this-is-why-everybody-wants-a-lawn-98066ce7aee3
40 Amy Townsend Small, Diane E. Pataki, Claudia I. Czimczik, and Stanley C. Tyler, “Nitrous Oxide Emissions and Isotopic Composition in Urban and Agricultural Systems in Southern California,” Journal of Geophysical Research, Vol. 116, G01013, 2011.