Thinking about knocking down a few trees in the backyard? Think again. Felling even a handful of trees can change the local climate, according to a new study.
Think twice before cutting…
It’s been known for some time that clearing forests can have regional-scale impacts on climate by reducing evapotranspiration (the emission of water vapor by plants, which cools the land) and changing albedo (how much solar radiation gets reflected away from the ground surface).
But now it appears these effects happen at surprisingly small scales. Especially in warmer parts of the world, clearing even a football field-sized area is enough to provoke significant heating of the immediate area.
So, spread the word: Cutting down trees doesn’t just have a global impact, by increasing carbon emissions; or a regional impact, by changing evapotranspiration and albedo.
Killing trees also has a sizable local impact, meaning it directly affects the quality of life of those living nearby.
The impacts of climate change are likely to be “severe, pervasive, and irreversible,” the chair of the Intergovernmental Panel on Climate Change said Sunday night in Yokohama, Japan, as the world’s leading climate experts released a new survey of how our planet is likely to change in the near future, and what we can do about it.
Here’s what you need to know:
We’re already feeling the impacts of climate change. Glaciers are already shrinking, changing the courses of rivers and altering water supplies downstream. Species from grizzly bears to flowers have shifted their ranges and behavior. Wheat and maize yields may have dropped. But as climate impacts become more common and tangible, they’re being matched by an increasing global effort to learn how to live with them: The number of scientific studies on climate change impacts, vulnerability, and adaptation more than doubled between 2005, before the previous IPCC report, and 2010. Scientists and policymakers are “learning through doing, and evaluating what you’ve done,” said report contributor Kirstin Dow, a climate policy researcher at the University of South Carolina. “That’s one of the most important lessons to come out of here.”
Heat waves and wildfires are major threats in North America. Europe faces freshwater shortages, and Asia can expect more severe flooding from extreme storms. In North America, major threats include heat waves and wildfires, which can cause death and damage to ecosystems and property. The report names athletes and outdoor workers as particularly at risk from heat-related illnesses. As the graphic below shows, coastal flooding is also a key concern.
Globally, food sources will become unpredictable, even as population booms.Especially in poor countries, diminished crop production will likely lead to increased malnutrition, which already affects nearly 900 million people worldwide. Some of the world’s most important staples—maize, wheat, and rice—are at risk. The ocean will also be a less reliable source of food, with important fish resources in the tropics either moving north or going extinct, while ocean acidification eats away at shelled critters (like oysters) and coral. Shrinking supplies and rising prices will cause food insecurity, which can exacerbate preexisting social tensions and lead to conflict.
Coastal communities will increasingly get hammered by flooding and erosion. Tides are already rising in the US and around the world. As polar ice continues to melt and warm water expands, sea level rise will expose major metropolitan areas, military installations, farming regions, small island nations, and other ocean-side places to increased damage from hurricanes and other extreme storms. Sea level rise brings with it risks of “death, injury, ill-health, or disrupted livelihoods,” the report says.
We’ll see an increase in climate refugees and, possibly, climate-related violence.The report warns that both extreme weather events and longer-term changes in climate can lead to the displacement of vulnerable populations, especially in developing parts of the world. Climate change might also “indirectly increase” the risks of civil wars and international conflicts by exacerbating poverty and competition for resources.
Climate change is expected to make people less healthy. According to the report, we can expect climate change to have a negative impact on health in many parts of the world, especially poorer countries. Why? Heat waves and fires will cause injury, disease and death. Decreased food production will mean more malnutrition. And food- and water-borne diseases will make more people sick.
We don’t know how much adaptation is going to cost. The damage we’re doing to the planet means that human beings are going to have to adapt to the changing climate. But that costs money. Unfortunately, studies that estimate the global cost of climate adaptation “are characterized by shortcomings in data, methods, and coverage,” according to the IPCC. But from the “limited evidence” available, the report warns that there’s a “gap” between “global adaptation needs and the funds available.”
There’s still time to reduce the impacts of global warming…if we cut our emissions.Here’s the good news: The IPCC says that the impacts of climate change—and the costs of adaptation—will be “reduced substantially” if we cut our emissions of greenhouse gases.
Old-growth Amazon tree canopy in Tapajós National Forest, Brazil. A new NASA study shows that the living trees in the undisturbed Amazon forest draw more carbon dioxide from the air than the forest’s dead trees emit. Image credit: NASA/JPL-Caltech
A new NASA-led study seven years in the making has confirmed that natural forests in the Amazon remove more carbon dioxide from the atmosphere than they emit, therefore reducing global warming. This finding resolves a long-standing debate about a key component of the overall carbon balance of the Amazon basin.
The Amazon’s carbon balance is a matter of life and death: living trees take carbon dioxide out of the air as they grow, and dead trees put the greenhouse gas back into the air as they decompose. The new study, published in Nature Communications on March 18, is the first to measure tree deaths caused by natural processes throughout the Amazon forest, even in remote areas where no data have been collected at ground level.
Fernando Espírito-Santo of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., lead author of the study, created new techniques to analyze satellite and other data. He found that each year, dead Amazonian trees emit an estimated 1.9 billion tons (1.7 billion metric tons) of carbon to the atmosphere. To compare this with Amazon carbon absorption, the researchers used censuses of forest growth and different modeling scenarios that accounted for uncertainties. In every scenario, carbon absorption by living trees outweighed emissions from the dead ones, indicating that the prevailing effect in natural forests of the Amazon is absorption.
Until now, scientists had only been able to estimate the Amazon’s carbon balance from limited observations in small forest areas called plots. On these plots, the forest removes more carbon than it emits, but the scientific community has been vigorously debating how well the plots represent all the natural processes in the huge Amazon region. That debate began with the discovery in the 1990s that large areas of the forest can be killed off by intense storms in events called blowdowns.
Espírito-Santo said that the idea for the study arose from a 2006 workshop where scientists from several nations came together to identify NASA satellite instruments that might help them better understand the carbon cycle of the Amazon. In the years since then, he worked with 21 coauthors in five nations to measure the carbon impacts of tree deaths in the Amazon from all natural causes — from large-area blowdowns to single trees that died of old age. He used airborne lidar data, satellite images, and a 10-year set of plot measurements collected by the University of Leeds, England, under the leadership of Emanuel Gloor and Oliver Phillips. He estimates that he himself spent a year-and-a-half doing fieldwork in the Amazon.
“It was a difficult and audacious study, and only Espírito-Santo’s dedication made it possible,” said Michael Keller, a research scientist at the U.S. Forest Service and co-author of the study.
Correlating satellite and airborne-instrument data with ground observations, Espírito-Santo and his colleagues devised methods to identify dead trees in different types of remotely sensed images. For example, fallen trees create a gap in the forest canopy that can be measured by lidar on research aircraft, and dead wood changes the colors in a satellite optical image. The researchers then scaled up their techniques so they could be applied to satellite and airborne data for parts of the Amazon with no corresponding ground data.
“We found that large natural disturbances — the sort not captured by plots — have only a tiny effect on carbon cycling throughout the Amazon,” said Sassan Saatchi of JPL, also a co-author. Each year, about two percent of the entire Amazon forest dies of natural causes. The researchers found that only about 0.1 percent of those deaths are caused by blowdowns.
This study looked only at natural processes in Amazonia, not at the results of human activities such as logging and deforestation, which vary widely and rapidly with changing political and social conditions.
The other institutions participating in the study are the University of New Hampshire, Durham; the Universities of Leeds and Nottingham, U.K.; Oxford University, U.K.; James Cook University, Cairns, Australia; U.S. Forest Service International Institute of Tropical Forestry, Puerto Rico; EMBRAPA Satellite Monitoring Center, Campinas, Brazil; National Institute for Research in Amazonia, Manaus, Brazil; EMBRAPA Eastern Amazonia, Santarém, Brazil; National Institute for Space Research (INPE), São José dos Campos, Brazil; the Missouri Botanical Garden, Oxapampa, Peru; and the Carnegie Institute for Science, Stanford, Calif.
NASA monitors Earth’s vital signs from land, air and space with a fleet of satellites and ambitious airborne and ground-based observation campaigns. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records and computer analysis tools to better see how our planet is changing. The agency shares this unique knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.
Idea debunked that young trees have the edge on their older siblings in carbon accumulation. by Jeff Tollefson
Native forest in Ancares Mountains, NW of Iberian Peninsula. Rubén Portas Copyright.
Many foresters have long assumed that trees gradually lose their vigour as they mature, but a new analysis suggests that the larger a tree gets, the more kilos of carbon it puts on each year.
“The trees that are adding the most mass are the biggest ones, and that holds pretty much everywhere on Earth that we looked,” says Nathan Stephenson, an ecologist at the US Geological Survey in Three Rivers, California, and the first author of the study, which appears today inNature1. “Trees have the equivalent of an adolescent growth spurt, but it just keeps going.”
The scientific literature is chock-full of studies that focus on forests’ initial growth and their gradual move towards a plateau in the amount of carbon they store as they reach maturity2. Researchers have also documented a reduction in growth at the level of individual leaves in older trees3.
In their study, Stephenson and his colleagues analysed reams of data on 673,046 trees from 403 species in monitored forest plots, in both tropical and temperate areas around the world. They found that the largest trees gained the most mass each year in 97% of the species, capitalizing on their additional leaves and adding ever more girth high in the sky.
Although they relied mostly on existing data, the team calculated growth rates at the level of the individual trees, whereas earlier studies had typically looked at the overall carbon stored in a plot.
Estimating absolute growth for any tree remains problematic, in part because researchers typically take measurements at a person’s height and have to extrapolate the growth rate higher up. But the researchers’ calculations consistently showed that larger trees added the most mass. In one old-growth forest plot in the western United States, for instance, trees larger than 100 centimetres in diameter comprised just 6% of trees, but accounted for 33% of the growth.
The findings build on a detailed case study published in 2010, which showed similar growth trends for two of the world’s tallest trees — the coast redwood (Sequoia sempervirens) and the eucalyptus (Eucalyptus regnans)4, both of which can grow well past 100 metres in height. In that study, researchers climbed, and took detailed measurements of, branches and limbs throughout the canopy to calculate overall tree growth. Stephen Sillett, a botanist at Humboldt State University in Arcata, California, who led the 2010 study, says that the latest analysis confirms that his group’s basic findings apply to almost all trees.
The results are consistent with the known reduction in growth at the leaf level as trees age. Although individual leaves may be less efficient, older trees have more of them. And in older forests, fewer large trees dominate growth trends until they are eventually brought down by a combination of fungi, fires, wind and gravity; the rate of carbon accumulation depends on how fast old forests turn over.
“It’s the geometric reality of tree growth: bigger trees have more leaves, and they have more surface across which wood is deposited,” Sillett says. “The idea that older forests are decadent — it’s really just a myth.”
The findings help to resolve some of these contradictions, says Maurizio Mencuccini, a forest ecologist at the University of Edinburgh, UK. The younger trees may grow faster on a relative scale, he says, meaning that they take less time to, say, double in size. ”But on an absolute scale, the old trees keep growing far more.”
The study has broad implications for forest management, whether in maximizing the yield of timber harvests or providing old-growth habitat and increasing carbon stocks. More broadly, the research could help scientists to develop better models of how forests function and their role in regulating the climate.
Allan Savory’s livestock hypothesis hinges on what he calls “holistic management and planned grazing.”Photo by Vyacheslav Oseledko/AFP/Getty Images
When Allan Savory finished his TED talk early last month, foodies worldwide collectively salivated. In roughly 22 minutes, Savory, a biologist and former member of the Rhodesian Parliament, challenged the conventional wisdom blaming livestock for the degradation of global grasslands into hardpan deserts. It has long been a basic tenet of environmentalism that 10,000 years of overgrazing has caused this desertification. Environmentalists insist that to restore degraded landscapes, we must reduce the presence of cattle, eat less meat, and allow ecosystems to repair themselves. Savory, who admits that he’s suggesting “the unthinkable,” wants humans to do the exact opposite: Add cattle to the deserts, manage them with obsessive precision, and eat more meat. Most of the world’s land, he says (at about 18:40), “can only feed people with animals.”
Savory’s hypothesis hinges on what he calls “holistic management and planned grazing.” These methods are designed to re-enact the movements of the prehistoric herds that once nurtured global grasslands with their manure deposits and “hoof action” (gentle trampling that increases the soil’s ability to hold water). By mimicking the natural symbiosis between plants and animals, holistic grazing would, Savory argues, encourage the regrowth of carbon-sequestering grasslands. These grasses would absorb enough carbon to counteract the methane production that’s associated with cattle husbandry (thanks to cow burps and farts) and halt global warming. (To put that claim in perspective, note that the Earth’s oceans and plants currently absorb only half of the 7 billion metric tons of carbon that human activities release into the atmosphere each year.) In order for Savory’s plan to work, the stocking density of livestock—the number of animals grazing a given area of land—would need to increase, in some cases, by as much as 400 percent. And for ranchers to make a living, they would sell their beef.
Savory’s speech quickly attracted praise. Chris Anderson, the TED host, said to Savory after his show, “I’m sure everyone here … wants to hug you.” Michael Pollan, apassionate advocate of pastured beef, called Savory’s talk the “highlight of TED” in a tweet that provocatively asked, “Eat MORE meat?” The Organic Consumers Association published an article that used Savory’s presentation to assert that “what we need is MORE moving, grazing animals, not less,” and to argue that holistic grazing “would be beneficial for the environment, the health of the animals, and subsequently the health of humans consuming those animals.” The takeaway was clear: If you’re interested in saving the planet, sharpen your steak knives.
Well, not so fast. For all the intuitive appeal of “holistic management,” Savory’s hypothesis is beset with caveats. The most systematic research trial supporting Savory’s claims, the Charter Grazing Trials, was undertaken in Rhodesia (Zimbabwe today) between 1969 and 1975. Given the ecological vagaries of deserts worldwide, one could certainly question whether Savory’s research on a 6,200-acre spot of semiarid African land holds any relevance for the rest of the world’s 12 billion acres of desert. Extrapolation seems even more dubious when you consider that a comprehensive review of Savory’s trial and other similar trials, published in 2002, found that Savory’s signature high-stocking density and rapid-fire rotation plan did not lead to a perfectly choreographed symbiosis between grass and beast.
Instead, there were problems during the Charter Grazing Trials, ones not mentioned in Savory’s dramatic talk. Cattle that grazed according to Savory’s method needed expensive supplemental feed, became stressed and fatigued, and lost enough weight to compromise the profitability of their meat. And even though Savory’s Grazing Trials took place during a period of freakishly high rainfall, with rates exceeding the average by 24 percent overall, the authors contend that Savory’s method “failed to produce the marked improvement in grass cover claimed from its application.” The authors of the overview concluded exactly what mainstream ecologists have been concluding for 40 years: “No grazing system has yet shown the capacity to overcome the long-term effects of overstocking and/or drought on vegetation productivity.”
The extension of Savory’s grazing techniques to other regions of Africa and North America has produced even less encouraging results. Summarizing other African research on holistically managed grazing, the same report that evaluated the Charter Grazing Trials found “no clear cut advantage for any particular form of management,” holistic or otherwise. It noted that “more often than not” intensive systems marked by the constant rotation of densely packed herds of cattle led to a decline in animal productivity while doing nothing to notably improve botanical growth.
A 2000 evaluation of Savory’s methods in North America (mostly on prairie rangelands in Wyoming, Oklahoma, Texas, and New Mexico) contradicted Savory’s conclusions as well. Whereas Savory asserts that the concentrated pounding of cow hooves will increase the soil’s ability to absorb water, North American studies, according to the authors, “have been quite consistent in showing that hoof action from having a large number of animals on a small area for short time periods reduced rather than increased filtration.” Likewise, whereas Savory insists that his methods will revive grasses, “the most complete study in North America” on the impact of holistic management on prairie grass found “a definite decline” of plant growth on mixed prairie and rough fescue areas. It’s no wonder that one ecologist—who was otherwise sympathetic toward Savory—flatly stated after the TED talk, “Savory’s method won’t scale.”
Even if Savory’s plan could scale, foodies would still have to curb their carnivorous cravings. The entire premise of any scheme of rotational grazing, as Savory repeatedly notes, is the careful integration of plants and animals to achieve a “natural” balance. As Dr. Sylvia Fallon of the Natural Resources Defense Council has shown, symbiosis between grazing herds and grasses has historically worked best to sequester carbon when the animals lived the entirety of their lives within the ecosystem, their carcasses rotted and returned their accumulated nutrients into the soil, and human intervention was minimal to none. It is unclear, given that Savory has identified this type of arrangement as his ecological model, how marketing cattle for food would be consistent with these requirements. Cows live up to 20 years of age, but in most grass-fed systems, they are removed when they reach slaughter weight at 15 months. Cheating the nutrient cycle at the heart of land regeneration by removing the manure-makers and grass hedgers when only 10 percent of their ecological “value” has been exploited undermines the entire idea of efficiency that Savory spent his TED talk promoting.
Further weakening Savory’s argument for the wholesale application of holistic management to the world’s deserts is his distorted view of desert ecology. There are two basic kinds of deserts: genuinely degraded landscapes in need of revival and ecologically thriving ones best left alone. Proof that Savory fails to grasp this basic distinction comes when, during his talk, he calls desert algae crust (aka “cryptobiotic crust”) a “cancer of desertification” that represses grasses and precipitate runoff. The thing is desert algae crust, as desert ecologists will attest, is no cancer. Instead, it’s the lush hallmark of what Ralph Maughan, director of the Western Watersheds Project, calls “a complete and ancient ecosystem.” According to the U.S. Geological Survey, “Crusts generally cover all soil spaces not occupied by green plants. In many areas, they comprise over 70 percent of the living ground cover and are key in reducing erosion, increasing water retention, and increasing soil fertility.” Savory, whose idea of a healthy ecosystem is one with plenty of grass to feed cattle, neglects the less obvious flora—such as, in addition to algae crust, blackbrush, agaves, and creosote—that cattle tend to trample, thereby reducing the desert’s natural ability to sequester carbon on its own terms. “It is very important,” Maughan writes, “that this carbon storage not be squandered trying to produce livestock.”
Savory’s most compelling and controversial assumption—one that’s absolutely central to his method—is that humans can viably “mimic” (a word he uses about a dozen times in the TED talk) “all of nature’s complexity.” This is a stunning claim. The conceit of mimicry as a virtue of Savory’s technique is challenged in part by the fact that not all deserts rely on the presence of herd animals for their ecological health. In many desert ecosystems, desert grasses evolved not alongside large animals but in concert with desert tortoises, mice, rats, rabbits, and reptiles. It’s difficult to imagine how a human-managed ecosystem such as Savory’s—dependent on manipulating the genetics of livestock, building sturdy fences, manufacturing supplemental feed, and exterminating predators—is more representative of “nature’s complexity” than a healthy desert full of organisms that have co-evolved over millennia.
In 1990, Savory admitted that attempts to reproduce his methods had led to “15 years of frustrating and eratic [sic] results.” But he refused to accept the possibility that his hypothesis was flawed. Instead, Savory said those erratic results “were not attributable to the basic concept being wrong but were always due to management.” In a favorable interview with Range magazine in 2000, Savory seemed unconcerned with the failure of his method in scientific trials: “You’ll find the scientific method never discovers anything. Observant, creative people make discoveries.”
Understandably, given his adherence to scientifically questionable conclusions in the face of evidence to the contrary, scientific institutions have not gone out of their way to work with Allan Savory. As a result, Savory has built his own institutions. From theCenter for Holistic Management (later the Allan Savory Center for Holistic Management) to the Savory Center to Holistic Management Internationalto theAfrica Centre of Holistic Management, Savory has kept his ideas in motion. Today, Savory, nearing the end of his career, heads the for-profitSavory Institute. Whether desert landscapes or the foundation’s coffers become any greener remains to be seen. In the meantime, the evidence continues to suggest what we have long known: There’s no such thing as a beef-eating environmentalist.
“We were once just as certain that the world was flat. We were wrong then, and we are wrong again.” That’s what Allan Savory had to say at TED about science’s view of desertification, a form of land degredation in which land loses its vegetation and bodies of water1. For years, scientists have believed that overgrazing by livestock is a major cause of desertification, and Allan Savory shared this opinion as a young biologist. Now Savory argues that we can prevent desertification by grazing more animals, with their movement carefully planned to mimic nature.
TED curator Chris Anderson dubbed Savory’s talk the highlight of the year’s conference and the official TED Twitter feeds described the talk as “profound and important.” Predictably, the talk was cheered by pastured meat enthusiasts, with Michael Pollan appearing ready to recant his advice to eat “mostly plants”:
Savory’s talk was also well-received in typically level-headed corners of the Twittersphere, with Discover Magazine calling it “one of the most thought-provoking” talks of the year, and Michael Shermer declaring it “moral progress in climate change.”
As C.J. Hadley’s profile in the February 2000 issue of the journal Rangelands makes clear, Savory has led an interesting life. He was born and raised in Zimbabwe (then Rhodesia), and worked in biology, military, politics, and other fields. Once a staunch opponent of grazing, he came to believe that we need more cows rather than fewer. As he told Hadley, “Severe grazing is absolutely essential to maintain biodiversity.” Overgrazing, he argues, is not the cause of desertification, arguing that grasslands have historically evolved with grazing animals. He now believes that the problem is poorly-planned grazing, and he now advocates for “holistic management and planned grazing” in order to address “all of nature’s complexity and our social, environmental, economic complexity.” According to Savory, well-planned grazing promotes plant growth, and the action of animal hooves on the soil improves the soil’s absorption of water. These ideas support the view that well-planned animal grazing can prevent and reverse desertification, thereby helping to combat climate change.
Savory’s methods have found little support from mainstream science. The same issue of Rangelands that featured Hadley’s profile of Savory also included an article by Jerry L. Holechek and others, which attempted to review the evidence for a number of Savory’s claims. Their review of studies from 13 North American sites and additional data from Africa found little evidence for any of the environmental benefits which Savory claimed for his methods. Moreover, the research consistently indicated that “hoof action from having a large number of animals on a small area for short time periods reduced rather than increased infiltration,” seemingly contradicting a key assumption of Savory’s methods.
In a letter to the editor of Rangelands that June, Savory dismissed Holechek’s findings, pointing out that the cited studies considered “short duration grazing” schemes rather than the Holistic Management methods for which Savory advocated. He explained, “The work Holechek et al. describe is unlike any range management practice I have ever advocated…In fact I have consistently stated that all grazing systems and rotations, including short duration grazing, will fail.” 3 As Savory explained in 1983, a key difference between short duration grazing and Savory’s Holistic Resource Management is that the latter method is “time-controlled,” adjusting grazing periods in accordance with the rate of plant growth.
Savory went on to describe what he identified as the only research trial ever conducted on his methods, which took place in Zimbabwe in the 1960s. The experiment, known as the Charter Grazing Trials and undertaken with Savory’s involvement, tested the claim that “we could double the stocking rate on any land under conventional management, improve the land and make more profit” with Savory’s methods. Savory reports, “The only trial ever conducted proved what I have always advocated and continue to advocate when livestock are run on any land.”
In general, it is unlikely that a single study on a few plots of land will definitively prove a statement about “any land.” Moreover, while I haven’t seen the original papers (which were published in the Zimbabwe Agricultural Journal), Holechek summarized the published work in a later issue of Rangelands, finding relatively weak support for Savory’s methods.
A further complication with the Charter Grazing Trials is that, as Savory’s letter notes, it tested “the planned grazing process then called short duration grazing, but today called Holistic Planned Grazing.” Indeed, Savory wrote in his 1983 Rangelandspiece, “For those without a deep knowledge of Short Duration Grazing, I am extremely familiar with this grazing system as I developed it.”
The best I can do to make sense of all this is to put everything in the context of Savory’s explanation of his method. In his 1983 article in Rangelands, Savory explained that the best analogy for what was then called the “Savory Grazing Method” was a computer:
If you know what you want to do with the computer and you feed in the right information it will aid you in achieving the result rapidly and surely. If some factors change and you observe the changes and feed in the new information the computer will again aid you efficiently in getting to your goal.
Thus, it is not necessarily contradictory for Savory to claim to have developed short duration grazing, that short duration grazing doesn’t work, and that the methods for which he has always advocated have been proven to work. The key is that the method that would become short duration grazing was the output of Savory’s “computer” when he fed in the information that was relevant to that situation. 4
That said, this ought to serve as a warning against the folly of claiming a single study as proof of anything. If the Charter Grazing Trials are proof of something, why is it not short duration grazing which was validated by its results? It is, after all, the method that was employed in the study. For Savory to now say that short duration grazing is a failure, he has to concede that a single study doesn’t prove the effectiveness of a method on “any land.”
Holechek’s 2000 article also claims that Savory had “expressed doubt that holistic resource management could be validated experimentally.” While I was not able to find a precise reference for this claim, Savory did not deny it in his response, and elsewhere he has expressed some reservations about scientific testing. For instance, in Hadley’s (mostly favorable) profile, he made it clear that he saw little use for the scientific method:
You’ll find the scientific method never discovers anything. Observant, creative people make discoveries. But the scientific method protects us from cranks like me.
While the intended irony of this statement has not escaped me, it’s hard to read it without concluding that he sees the scientific method as an obstacle to progress, rather than a tool for achieving it.
That is problematic because the scientific method is what will tell us whether Holistic Management works. Savory would like us to graze more cattle to fight desertification and climate change, even as scientific evidence indicates that his “solution” will actually exacerbate these problems. If we were to employ Savory’s methods on a large scale and they were to succeed in stopping desertification, that would constitute excellent experimental validation of those methods. 5 If we can’t experimentally validate his methods, then we cannot know them to work in real life, either. It is thus perfectly reasonable to ask for evidence on a smaller scale before we try such a thing, particularly as existing evidence indicates that this would make the problems worse. As Chad Kruger writes, “Being ‘unconventional’ is not, in itself, a problem, but when what you are arguing for is unconventional, you’d better ‘bring data.’”
It is also important to note that for all Savory’s insistence that his methods work, it has been associated with a number of failures. For instance, Hadley mentions a test farm in Zimbabwe, which collapsed as soon as Savory fled that country. Whereas those on the farm blamed the collapse on drought, Savory blamed on their lack of proper planning in his absence.
This is typical of Savory’s response to failure. The fault never lies in his methods but in people’s implementations of them. For instance, in a 1990 paper in the journal Ecological Economics6, Savory explains away “15 years of frustrating and eratic [sic] results” with the admission that “we had confused the integrated approach with the holistic approach, thinking that the terms were synonymous,” emphasizing that “the breakdowns we were experiencing were not attributable to the basic concept being wrong but were always due to management–of the people and the finances.” 7 Even after Savory realized that “the integrated approach and the holistic approach were opposites,”8 he had to struggle with “understanding not only what ‘holistic’ meant, but even more difficult, how to apply such an approach in day-to-day management.” Even when his own implementation of his own ideas leads to failure, he believes that the problem isn’t that the methods were flawed but that he didn’t fully understand them.9 It is this kind of convoluted reasoning that allows him to claim that his methods work.
In a review of Savory’s 1988 book Holistic Resource Management, M.T. Hoffman wrote “The apparent inconsistencies and lack of definitions (eg. for concepts such as complexity, stability, resilience, diversity and production which have a number of different meanings in the ecological literature), render it frustratingly difficult to compare his [Holistic Resource Management] approach with the broader literature.” Imprecise language doesn’t just make it hard to compare Savory’s methods with the existing literature. It also makes it nearly impossible to evaluate his approach scientifically because it allows Savory to blame any failures on a misunderstanding of the method. So long as nobody can understand Savory’s ideas, those ideas can’t be tested or disproven. In this framework, problems are solved not by trying different methods but by developing a “better” understanding of the existing one. It is therefore little wonder that after members of the Department of Range and Forage Resources at the University of Natal – Pietermaritzburg–Savory’s alma mater–met with Savory, they reported that it would be “extremely difficult” to test Savory’s ideas because “it would be difficult to evaluate even a short-term research endeavour (of 5 to 10 years), as the approach taken by Holistic Management proponents would surely have changed by then, as it has in the past.”
Changing one’s mind in response to new evidence isn’t bad at all. Indeed, it’s the scientific thing to do. However, that is not the kind of change that one finds in Savory’s writings. Savory insists that he’s been correct all along and that his evolution flows naturally from an improved understanding of his own bulletproof ideas. Whereas the scientific method lends itself well to self-correction, Savory’s vague language and inconsistency will lead to trying many different things without reason to expect improvement.
Savory argued at TED that Holistic Management “offers more hope for our planet, for your children, and their children, and all of humanity.” What Savory does not tell us is that there is the distinct possibility that if we try to implement those ideas, we will fail. In this case, he will tell us that we misunderstood his ideas. How comforting it will be to know that his ideas were correct, as they always have been!
In December, TED responded to concerns that independent TEDx authorized events were “dragging the TED name through the mud” by sending a letter to “the TEDx community” warning that bad science could lead to revocation of the TEDx license. The letter also included some advice for identifying bad science. I can’t help but think that Savory’s work should have raised concerns for anybody familiar with that list. At the least, Savory’s work “has failed to convince many mainstream scientists of its truth,” much of it “is not based on experiments that can be reproduced by others,” it comes from an “overconfident fringe expert,” and it uses imprecise vocabulary to form untested theories.
Of course, TED has no contractual incentive to apply the standards it sets for TEDx organizers to its own talks. However, the letter emphasizes that “your audience’s trust is your top priority,” and I think it’s fair to ask what TED did to respect that trust in this case. Did they research the science behind Allan Savory’s ideas? Are they satisfied that his talk amounts to “good science”? If Savory’s talk had run at a TEDx event, would that event’s license have been revoked? Now that TED has reined in TEDx, perhaps its next move should be to look in the mirror.
Although the reason for Allan Savory’s departure from Holistic Management International is not clear to me, Butterfield has editedSavory’s Wikipedia page to remove references to Holistic Management International, which seems to hint at less friendly relations between the organizations.↩
Curiously, Savory’s 1978 article “A Holistic Approach to Ranch Management Using Short Duration Grazing,” published in the Proceedings of the First International Rangeland Congress devoted several paragraphs to explaining short duration grazing, not once mentioning that it would fail. Instead, the article stated, “An immediate doubling of production is not uncommon on ranches which were considered fully stocked before changing to short duration grazing.”↩
Savory has used a number of terms for his methods over the years, including short duration grazing, Savory grazing method, holistic resource management, holistic management and holistic planned grazing.↩
This would not necessarily confirm that Savory had identified the correct mechanisms by which Holistic Management worked. It would merely show that they worked.↩
An earlier version of this post included a link to the wrong article here. I corrected the link at 7:30PM on April 4, 2013.↩
I added the end of this sentence post-publication (March 12, 2013 around 2:00AM PDT), starting from “emphasizing” because I thought it improved clarity. ↩
Savory goes on to write, “Since then an Englishman (Goldsmith, 1988) came to the conclusion not that [holistic and integrated] are opposites but that the integrated approach is still disciplinary while the holistic approach is non-disciplinary. I prefer his description which I think is more accurate than my own.”↩
In the language of his analogy, Savory points out that early computers were capable of performing computations correctly, but it was hard to achieve accurate results because the machines were not user-friendly.↩
Allan Savory delivered a highly publicized talk at a “Technology, Entertainment, Design (TED)” conference in February of this year (2013) entitled “How to fight desertification and reverse climate change.” Here we address one of the most dramatic claims made – that a specialized grazing method alone can reverse the current trajectory of increasing atmospheric CO2 and climate change.
The talk was attended by many conferees and has since been viewed on the TED website over 1.6 million times. It has received substantial acclaim in social media, some of which is available at the Savory Institute website, but it has also received considerable criticism (of particular note is ablog post from Adam Merberg and an article in Slate magazine. Although these criticism quickly followed Mr. Savory’s presentation and are broadly supported by the available science, his sweeping claims have continued to resonate with lay audiences. An apparent example is his invitation to deliver a speech to Swiss Re during their 150 year anniversary celebration in London in September, in which he is quoted as saying “…only now due largely to my TED talk on the desertification aspect of the global problem, was the public becoming aware of such hope in a world so short on solutions…”.
As a result of the continuing discussion regarding this presentation, we felt compelled to interpret these claims within the context of Earth System science to facilitate broader discussions and evaluation. It is important to recognize that Mr. Savory’s grazing method, broadly known as holistic management, has been controversial for decades. A portion of this controversy and the lack of scientific support for the claims made for his method on livestock productivity and grassland ecosystem function may be found in peer-reviewed papers (e.g. Briske et al. 2008). This presentation, however, argued for an additional application to climate change.
We focus here on the most dramatic claim that Mr. Savory made regarding the reversal of climate change through holistic management of grasslands. The relevant quote (transcript by author from video provided on TED website) is as follows:
“…people who understand far more about carbon than I do calculate that for illustrative purposes, if we do what I’m showing you here, we can take enough carbon out of the atmosphere and safely store it in the grassland soils for thousands of years, and if we just do that on about half the world’s grasslands that I’ve shown you, we can take us back to pre-industrial levels while feeding people. I can think of almost nothing that offers more hope for our planet, for your children, for their children and all of humanity…”
While it is understandable to want to believe that such a dramatic outcome is possible, science tells us that this claim is simply not reasonable. The massive, ongoing additions of carbon to the atmosphere from human activity far exceed the carbon storage capacity of global grasslands.
Approximately 8 Petagrams (Pg; trillion kilograms) of carbon are added to the atmosphere every year from fossil fuel burning and cement production alone. This will increase in the future at a rate that depends largely on global use of fossil fuels. To put these emissions in perspective, the amount of carbon taken up by vegetation is about 2.6 Pg per year. To a very rough approximation then, the net carbon uptake by all of the planet’s vegetation would need to triple (assuming similar transfers to stable C pools like soil organic matter) just to offset current carbon emissions every year. However, the claim was not that holistic management would maintain current atmospheric CO2 levels, but that it would return the atmosphere to pre-industrial levels. Based on IPCC estimates, there are now approximately 240 more Petagrams (Pg) of carbon in the atmosphere than in pre-industrial times. To put this value in perspective, the amount of carbon in vegetation is currently estimated at around 450 Pg, most of that in the wood of trees. The amount of carbon that would need to be removed from the atmosphere and stabilized in soils, in addition to the amount required to compensate for ongoing emissions, to attain pre-industrial levels is equivalent to approximately one-half of the total carbon in all of Earth’s vegetation. Recall that annual uptake of carbon is about two orders of magnitude smaller than the total carbon amount stored in vegetation.
At a global scale, grasslands are generally distributed in regions of low precipitation across a wide range of temperatures, with precipitation particularly limiting grassland productivity. Within a zone, grassland carbon cycles respond significantly and sometimes dramatically to fluctuations in inter-annual precipitation. This is because soil water is essential for vegetation to remove carbon from the atmosphere in the process of photosynthesis and it also drives variation in microbial processes that affect the loss of carbon from soils. Consequently, soil water availability represents a much greater limitation to maximum carbon storage in global grasslands than does grazing management. Grasslands represent approximately 30-40% of the planet’s land surface and only a fraction of annual global productivity and carbon sequestration (~20% of global carbon stocks). It is simply unreasonable to expect that any management strategy, even if implemented on all of the planet’s grasslands, would yield such a tremendous increase in carbon sequestration.
Humanity faces many challenging problems in this period of human domination of planet known at the Anthropocene. These problems, including that of climate change, require efforts to find solutions in all sectors of society and that we engage in diverse and dynamic dialogue about potential solutions, including those that may lie far outside the current mainstream. However, potential solutions must be assessed with a dispassionate and rigorous treatment of risks, benefits, and costs. We should pursue solutions that are most likely to succeed on the basis of scientific validity and societal acceptance . Extravagant claims like those in Mr. Savory’s TED video must be weighed against known physical realities to credibly serve society.
Rangeland management strategies appropriately emphasize conservation of previously stored soil carbon, rather than sequestration of additional carbon, based in part on the limitations previously described. Emphasis should be placed on climate change adaptation, rather than mitigation as advocated by Mr. Savory, to support the well-being of millions of human inhabitants. Mr. Savory argues that we adopt his grazing method as a simple solution to resolve a key Anthropocene contributor – the ongoing perturbation of Earth’s carbon cycle. The appeal of this claim to casual observers is enhanced in that it does not require humans to face any tradeoffs. The implication is that we can continue to use fossil fuels and emit carbon into the atmosphere because application of holisitic management on the Earth’s grasslands provides a ‘silver bullet’ that will sustainably solve the climate change problem and provide abundant livestock products as well. We would be thrilled if a simple solution such as this existed. However, it clearly does not, and it is counter-productive to believe that it does. Humanity must look beyond hope and simple solutions if it is to successfully navigate its way through the Anthropocene.
A new study shows that the predator-prey relationship can affect the flow of carbon through an ecosystem. This previously unmeasured influence on the environment may offer a new way of looking at biodiversity management and carbon storage for climate change mitigation.
The study, conducted by researchers at the Yale School of Forestry & Environmental Studies, comes out the week of June 17 in the Proceedings of the National Academy of Sciences. It looks at how the relationship between grasshoppers and spiders — herbivores and predators in the study’s food chain — affects the movement of carbon through a wild grassland. The study shows that predators can cause increased carbon retention in plants in the ecosystem.
“We’re discovering that predators are having important effects on shaping the make-up of ecosystems,” says Oswald Schmitz, professor of ecology and one of the co-authors of the study. “But we’ve not really spent a lot of time measuring how that translates into other functions like nutrient cycling and recycling.”
Carbon, the basic building block of all organic tissue, moves through the food chain at varying speeds depending on whether it’s being consumed or being stored in the bodies of plants. However, this pathway is seldom looked at in terms of specific animal responses like fear from predation.
The researchers manipulated the food chains of grassland ecosystem to see how the levels of carbon would change over time. Schmitz and his team created several controlled ecosystems: Some that contained only native grasses and herbs, others that had plants and an herbivore grasshopper, and some others that had plants and herbivores along with a carnivore spider species — all three tiers of the food chain. In addition, a form of traceable carbon dioxide was injected into sample cages covered with Plexiglas, which allowed the team to track the carbon levels by periodically taking leaf, root, and dead animal samples.
The study found that the presence of spiders drove up the rate of carbon uptake by the plants by about 1.4 times more than when just grasshoppers were present and by 1.2 more times than when no animals were present. It also found that the pattern of carbon storage in the plants changed when both herbivores and carnivores were present. When predators were around, the grasshoppers damaged grasses less because they were afraid of being eaten by the spiders, which caused them to be alert and eat less frequently and eat more herbs instead of grass as a preference. Herbivore consumption can cause plants to reduce their photosynthesis and increase respiration, which lets out carbon in the form of carbon dioxide. The predators reverse this physiological process by reducing herbivore damage to plants, leading to greater carbon uptake and storage.
Moreover, the grasses stored more carbon in their roots after the predators alleviated herbivore impacts on plants. These stress responses, then, caused both the plants and the herbivores to change their behaviors and change the composition of their local environment.
The findings have significance for biodiversity conservation and ecosystem management, according to Schmitz. Although the study was carried out on a small scale, the principles that were learned could inform practices done in much larger areas. Places such as the Alaskan wilderness, for example, are home to animals that have the same predator-and-prey dynamics that drive the carbon cycle, and so protecting lands and storing carbon could be linked at the same time. Appreciating the role of predators is also important now because top predators are declining at rates faster than that of many other species in global trends of biodiversity loss, as the study points out.
“It’s going to force some thinking about the vital roles of animals in regulating carbon,” said Schmitz, noting that the UN’s body of scientific experts who study climate change don’t consider these multiplier effects in their models. “People are arguing for a paradigm change.”
CONTACT: Oswald Schmitz 203-432-5110 or oswald.schmitz@yale.edu
CITATION: Michael S. Strickland, Dror Hawlena, Aspen Reese, Mark A. Bradford, and Oswald. J. Schmitz. Trophic cascade alters ecosystem carbon exchange. PNAS (2013)
The total forest area of the world is about 4 billion hectares, which represents nearly 30 percent of the Earth’s landmass. Approximately 56 percent of these forests are located in tropical and subtropical areas.
Forest cover is unevenly distributed. Only seven countries possess about 60 percent of it, 25 countries around 82 percent and 170 countries share the remaining 18 percent.
Planted forests account for approximately 3.8 percent of total forest area, or 140 million hectares.
Forest loss2
Net global forest loss is estimated to be about 7.3 million hectares per year for the period 2000-2005.
This represents a decrease from the period 1990–2000, for which the average deforestation rate was 8.9 million hectares per year.
The highest amounts of deforestation occurred in South America, with 4.3 million hectares per year, followed by Africa with 4 million hectares per year.
Forests and livelihoods
More than 1 billion people rely heavily on forests for their livelihoods.3
More than 2 billion people, a third of the world’s population, use biomass fuels, mainly firewood, to cook and to heat their homes.
Hundreds of millions of people rely on traditional medicines harvested from forests.4
In some 60 developing countries, hunting and fishing on forested land supplies more than a fifth of protein requirements.5
Forests and the economy6
In 2003, the international trade in sawn wood, pulp, paper and boards amounted to almost US $150 billion, or just over 2 percent of world trade.
The developed world accounted for two-thirds of this production and consumption.
In many developing countries, forest-based enterprises provide at least one-third of all rural non-farm employment and generate income through the sale of wood products.
The value of the trade in non-timber forest products has been estimated at US $11 billion. These products include pharmaceutical plants, mushrooms, nuts, syrups and cork.
Forests and climate change7
It is estimated that 1.7 billion tonnes of carbon are released annually due to land use change. The major portion is from tropical deforestation.
This represents about 20 percent of current global carbon emissions, which is greater than the percentage emitted by the global transport sector with its intensive use of fossil fuels.
Sources:
[1] Food and Agriculture Organisation of the UN (FAO) 2007. State of the World’s Forests 2007, FAO, Rome. [2] FAO 2009. State of the World’s Forests 2009, FAO, Rome. [3] World Bank 2004. Sustaining Forests: A Development Strategy, Washington. [4] UN Department of Economic and Social Affairs 2009. Indicators of Sustainable Development (1 June 2009). [5] Mery, G., Alfaro, R., Kanninen, M. and Lobovikov, M. (eds.) 2005. Forests in the Global Balance: Changing Paradigms, IUFRO World Series 17. International Union of Forest Research Organisations (IUFRO), Helsinki. [6] World Bank 2004. Sustaining Forests: A Development Strategy, Washington D.C. [7] IPCC 2007. Summary for Policymakers In: Climate Change 2007: The Physical Sciences Basis (1 June 2009).
He’s been called the Jedi master of data visualisation, dubbed a statistics guru and introduced as the man in whose hands data sings. When it comes to celebrity statisticians, Hans Rosling is firmly on the A-list.
In the years since his first TED talk (Stats that reshape your worldview), which thrust him into the spotlight in 2006 with millions of online views, Rosling’s now signature combination of animated data graphics and theatrical presentations has featured in dozens of video clips, a BBC4 documentary on The Joy of Stats, and numerous international conferences and UN meetings.
Instead of static bar charts and histograms, Rosling, professor of global health at Sweden‘s Karolinska Institute, has used a combination of toy bricks, cardboard boxes, teacups and vibrant, animated data visualisations to breathe life into statistics on health, wealth and population. With comic timing and a flair for the unusual, Rosling’s style has undoubtedly helped make data cool.
When Time magazine included him in its 2012 list of the world’s 100 most influential people, it said his “stunning renderings of the numbers … have moved millions of people worldwide to see themselves and our planet in new ways”. However, Rosling, 64, is less convinced about his impact on how people view the world.
“It’s that I became so famous with so little impact on knowledge,” he says, when asked what’s surprised him most about the reaction he’s received. “Fame is easy to acquire, impact is much more difficult. When we asked the Swedish population how many children are born per woman in Bangladesh, they still think it’s 4-5. I have no impact on knowledge. I have only had impact on fame, and doing funny things, and so on.”
He’s similarly nonplussed about being a data guru. “I don’t like it. My interest is not data, it’s the world. And part of world development you can see in numbers. Others, like human rights, empowerment of women, it’s very difficult to measure in numbers.”
Rosling is strikingly upfront about the limitations of data. Sometimes, the problem is that different countries measure things – like unemployment – in different ways, he says. In other cases, there are real uncertainties in the data that must be assessed: child mortality statistics are quite precise, whereas maternal mortality figures are not; global poverty measurements are infrequent and uncertain.
“That unit [at the World Bank] which assists countries, trains the staff, and helps them to compile [poverty] data, how many persons are working there? Four half-time. For the world. It’s a joke. They’re very competent, they’re very good. But it’s not serious … The uncertainty of 1.3 billion [people living in poverty] is plus or minus half a billion. And we will not know whether the MDGs [millennium development goals] have been achieved until 2019, the later part. We only get poverty measurements every fifth year.”
These issues are well known, he says, but still underappreciated and infrequently discussed. “It’s like the emperor’s new clothes, and I’m the little child saying ‘He’s nude! He’s nude!'”
Still – when handled with care – global statistics can help challenge common myths and misconceptions about the world, Rosling hopes. Chief among the myths still to be debunked, he says, is the idea that the world is split in two – with a developed world on one side and a developing world on the other. “We don’t have two types of countries any longer, we have four or five types … [and] the idea that the western world will be ahead of the rest for ever is wrong.”
Anxiety about population growth is another of Rosling’s targets. “If you save the lives of poor children you destroy the planet. There are so many who think that death keeps control of population growth. That’s just wrong!” Child mortality has plummeted over the past half-century, so it’s no longer death that determines population growth, he insists, but fertility rate – and this too has decreased in so many countries. “The average number of children in the world is 2.4. The number of children below eight years of age in India has stopped growing. The number of children in the total world has stopped growing. Most of the fertility transition is done.”
“I can show you! Let me show you the world,” he enthuses, interrupting our interview only briefly to pull from his pockets a series of props. Laying out toy bricks and a handful of counters on the table, he shows in 3-D how the dynamics of global population, child mortality and carbon emissions have changed over the past 50 years – and how the world might look by the end of the century.
“[We now have] 7 billion people, [with] 7 million children dying. Six [million] of these die in the poorest 2 billion, 1 die here in the middle and here almost no one. Can you see?” he asks, waving his hands over his display. “There is no developing world with high child mortality! It is 2 billion people that still have three or more children per woman, where still girls cannot go to school, or very few, and where you have almost all the child mortality and almost all the maternal mortality.”
If Rosling comes across as advocating for a shift in focus towards the poorest countries, he’s adamant he’s not. “I don’t debate. There are too many debates. Too much Word, not enough Excel.
“If people want to help with something, it’s good to know where the problem is … [for example] the problem of lack of schooling for girls is not a global problem. It is not a developing world problem, it’s a problem in the poorest 2 billion. But there it’s an extremely severe problem … Men in Afghanistan have half the schooling of women in the world. But young women in Afghanistan have one-seventh of the men in Afghanistan. This is the world I would like to explain.
Disappointed with his perceived lack of impact on public understanding of global progress, the self-styled “edutainer” is now turning his attention towards teachers. Over the next few years, his Gapminder foundation will push through a school project to provide materials on the basic macro-trends on population, economy, living conditions and energy, to help teachers in high school and college to better communicate the realities of the world.
“Fame is a dangerous thing. It’s what the post-industrial society wants. They want fame and many followers on Twitter. But to really make the world understandable, that challenge is remaining.”
Old-growth Amazon tree canopy in Tapajós National Forest, Brazil. A new NASA study shows that the living trees in the undisturbed Amazon forest draw more carbon dioxide from the air than the forest’s dead trees emit. Image credit: NASA/JPL-Caltech
Between Thorn Bushes and Claws 