Guest post by Jason West and David Briske
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 a blog 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.
95
dhogaza says:
10 Nov 2013 at 12:16 PM
“Scott Strough:
Proven to work? Do you have any reference that backs up the claims of massive increases in carbon sequestration, actual measurement and observations over a significant period of time, or is your “proof” merely based on Savory’s claims. Which apparently many professionals believe to be overblown, even without taking into consideration his claims regarding carbon sequestration.”
Sure. There are plenty. First I recommend going to my first post #53 and check those reference links thoroughly. Then for real world examples, try contacting people like Joel Salatin, Dan Dagget, Chris Kerston, Greg Judy, Bill Mollison, Gabe Brown, Greg Reding etc. Some of these guys proved it on their own land and others have proved it by helping others time and time again all over the world. If you really want some good raw data, I suggest you contact Jay Fuhrer, District Conservationist with the National Resource Conservation Service (NRCS) in Bismarck, North Dakota. He has a wealth of information, not only about rotational grazing systems, but innovative ways they can be integrated with conventional crop rotations and multi species cover crops, and their effect on soil carbon long term.
I would like to point out that this really is nothing new. Just the cutting edge. The Haughley experiment, started in 1939, although using a different rotational system and includes crops as well, does have the longest running data on soil properties including soil carbon, moisture and temperature.
I’ll leave you with a prophetic warning offered way back in 1947. Pity it has taken us over 60 years to hear that warning.
“As the small trickle of results grows into an avalanche — as is now happening overseas — it will soon be realized that the animal is our farming partner and no practice and no knowledge which ignores this fact will contribute anything to human welfare or indeed will have any chance either of usefulness or of survival.”-Sir Albert Howard
I have always discounted Savory’s claim of Carbon Sequestration and agree with your calculations. However his claim of reversing desertification seems real and worthy of widespread pursuit.
If all we need to do is enforce grazing patterns that mimic natural grazing in the presence of fearsome top carnivores, that is a small price to pay for the benefits in slowing or reversing desert expansion.
Only nuclear power will allow us to reverse the damage combustion has wrought. Solar and wind could protect US lifestyles, but to bring the abject poor out of poverty and provide for 11 billion humans on half as much topsoil will require more industrialization and more energy. But that can take way less space and make more room for nature if food production is nuclear powered and in greater part, indoors.
There is no reason for gloom and doom, or false claims of carbon sequestration trough photosynthesis. There isn’t enough surface area on Earth for 8% efficient photosynthesis to sequester our carbon pollution. But with advanced nuclear power, such as LFTR or LENR or any one of 15 other safe fusion and fission schemes, we can solve it.
11 billion people can have a middle class life style while making more room for biodiversity and nature, thanks to clean safe nuclear power.
Trouble is, there is no nuclear power industry to speak of working with innovative designs like LFTR or LENR. And the industry of the future doesn’t have lobbyists. So progress is excrutiating. Most people’s idea of nuclear power is what we were building in 1967…. a slightly modified bomb plant. And then they complain that it’s not safe. duh…
sj, we try to stay away from banging our collective heads against the nuclear wall around here. I’ll just point out that, since its inception, the next generation of nuclear plants have always been promoted as the great savior of all mankind. So far, that hasn’t worked out quite as advertized.
But to move away from the nuke issue in particular, is it really a great idea to provide humans with vast new sources of energy of any sort? We have had enormous amounts of virtually free energy just from fossil “death” fuels for the past couple hundred years, and what have we done with it? Even leaving aside their GW effects, ff’s subsidized massive destruction of ecosystems, destruction that is still going on (again, even setting aside the GW effects). Is there any indication that humans (and modern industrial capitalist society in particular) will use any vast new sources of energy any more wisely that we have used the ff and nuclear we have already expended?
We all have to get past the idea of limitless growth, and of expanding human power over the earth. Those are among the fundamental mindsets driving the whole calamitous mess in the first place. Our main job clearly has to be how to limit humans, particularly our most destructive activities. (I see now reason, though, to limit art, dancing, philosophizing…as long as those aren’t done in the facilitate or legitimize destructive levels of material consumption.)
Sue Jones: “Only nuclear power will allow us to reverse the damage combustion has wrought. Solar and wind could protect US lifestyles, but to bring the abject poor out of poverty and provide for 11 billion humans on half as much topsoil will require more industrialization and more energy.”
Ill-informed and, with all due respect, blatantly false statements like the above beg for a response based on actual facts about the present reality and near-future potential of solar and wind energy — not only in industrialized countries like Germany, Japan, Australia, and the USA, but in particular to meet the needs of the developing world, where these technologies are already enabling a revolution in rural electrification.
Off-grid solar is already providing electricity to communities in rural Africa, India, the Caribbean and elsewhere who will never get access to grid power from nuclear or any other form of large, centralized generation, because the resources to build either the grids or the giant power plants do not exist, nor do those communities have the wealth to purchase grid power. Instead, they are getting the ability to generate their own power, in perpetuity, from the sun and wind.
However, such a response would necessarily imply rebutting the “only nuclear power” claim in Sue’s comment, and would thus run afoul of this site’s prohibition on “debating” nuclear power, so I’ll stop there.
I would add that feeding “11 billion humans on half as much topsoil” has pretty much ZERO to do with generating electricity, which is all that nuclear power (or wind turbines or solar panels) are good for, so that is a complete non sequitur.
#97 Scott Strough says:
Hey, bud. Psst. I’ve got this perpetual motion machine I want you to take a look at, over here in the corner…
But just for the lolz, how many hectares of grassland would we need to have working at 100% efficiency employing the Savory method (whatever that is exactly. There seem to be an awful lot of variants on it) to draw down 6ppm of CO2 per year? And how many years would it take to ramp up to that capacity?
Photosynthetic efficiency for most plants is more like 1 to 2 percent.
Steve
@105 Steve Metzler,
That figure is based on roughly 5 billion hectares worldwide. If for whatever reason you can’t convince the managers of roughly 5 billion hectares world wide to change, it obviously will only work on land it is used. As far as the training goes, it will take time. It isn’t instant. There is a learning curve. Not everyone gets the hang of it first try either. Some land starts recovering in one year. Other lands may take longer. But it is doable.
Here is an example and the potential turnaround in one year from the most meager of resources one could imagine.
http://www.youtube.com/watch?v=pIMmIvY5m2o
wili wrote: “… is it really a great idea to provide humans with vast new sources of energy of any sort?”
Well, let’s hope it is a good idea.
Because given the vast amount of solar energy available to us, and given the rapidly increasing efficiency and even more rapidly plummeting cost of solar technology, and given the extreme simplicity and ease of manufacturing that technology anywhere from abundant and recyclable materials, it’s going to be hard to stop people everywhere from getting their hands on a vast new source of energy.
Of course, stopping that from happening is the point of “the other denialism”: the anti-solar propaganda which proclaims that solar power can never do what it is already doing.
And in fact, I do think it would be a good idea for the billions of people all over the world who have never had access to electricity to have access to cheap, efficient, mass-produced off-grid solar power — power they can generate for themselves, without being beholden to big utilities. So they can replace kerosene lamps with LEDs. So they can have cell phones and computers and satellite communications and Internet access and refrigeration and medical equipment. All of which will drastically improve their lives and expand their opportunities, and all of which can easily be powered by small-scale PV and batteries.
Here’s another along the same lines as the original story:
http://www.nytimes.com/2013/11/12/business/an-accidental-cattle-ranch-points-the-way-in-sustainable-farming.html
The description sounds a lot like Salatin’s Polyface Farm:
SA, I get that you are a promoter of the solar industry. Note that I said nothing against it, in particular.
You said: “let’s hope”
Is that all we are left with. What is the basis of your hope that modern industrial civilization will suddenly change its stripe and use all energy supplied to it to do only things that don’t endanger ecosystems?
Most honest people admit that everything has upsides and down sides. Are you claiming that solar is the one thing in the universe that only has up sides? If not, what would you be willing to admit are its down sides? (And don’t say “the it is still to expensive and not wide spread enough”. I obviously mean what are the downsides to this technology being geared up to run modern industrial society?)
Hank, thanks for the comment (#109) on TomKat Ranch. Granted that the “farmer” is a hedge-fund billionaire, it may bring some high-profile attention to the potential for carbon-rich farming. Notice the variety of animals and crops supporting each other in the ranch and connected enterprises: this is the value of an ecological approach. When you put a ton of carbon in the soil, it supports a web of organisms that exponentially grow and sequester more every year.
see also Polyface Farm
wili wrote: “Most honest people admit that everything has upsides and down sides. Are you claiming that solar is the one thing in the universe that only has up sides?”
Not at all. I am saying that like it or not, for better or worse, ultra-cheap ultra-efficient photovoltaic materials are already plentiful and readily available all over the world, and there is every reason to expect that trend to continue, with the technology becoming rapidly more powerful and less expensive and easier to produce.
Which means an era in which all of humanity will have access to an unending supply of abundant, low-cost energy. Indeed, the time may come when discussions of energy issues will revolve around the implications of electricity that has become, in the words of that old saw, “too cheap to meter”.
Of course that will have “upsides and down sides” — not only environmental, but social and economic, and some people will experience more of the upside (e.g. rural villages in Africa and India benefiting from off-grid PV) and some will experience more of the downside (e.g. investors in large, centralized fossil fuel or nuclear power plants that will not be able to compete with dirt-cheap PV).
Fortunately, in the context of global warming, solar (and wind) energy have a very crucial upside, which is their ability to very quickly replace fossil fueled electricity generation, which is not only a major source of current GHG emissions, but threatens to become an even bigger source of GHGs if developing countries like China continue to build coal-fired power plants.
I’ve said this before: global warming is certainly not our only big environmental problem, but it is an urgent crisis that must be fixed immediately, if we are going to buy the time to address the other problems. And the only way to do that is with technical fixes that can be applied as quickly as possible — evolutionary changes in the way that human beings relate to the rest of the Earth’s biosphere cannot possibly have any impact in the very short time frame that is required to prevent the worst outcomes of global warming.
Eliminating all GHG emissions from electricity generation is one of those short-term technical fixes, and we have the means to do it at hand, NOW.
OOOkaaay, so the only downside to solar power it to its competitors. Thanks for your honest assessment. 8-0
Any thought on what humanity is likely to do with all this too-cheap-to-meter energy?
I believe the correct position answer of the impact of holistic management of grasslands is somewhere between the comment in this article and Savory’a claim.
Per the article: 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.
Where do these numbers come from? To do a simple calculation:
1) Per http://en.wikipedia.org/wiki/Carbon_cycle There are 720 Gt = 720Pg of C in the atmosphere. Divide this by 395 ppm gives each ppm of CO2 in the atmosphere equating to 2.43Pg of C.
2) The last three years Mauna Loa data http://www.esrl.noaa.gov/gmd/ccgg/trends/ show an average 5.71 drop in the ppm of CO2 in the atmosphere between May and October each year. This is due to vegetation growth in the Northern Hemisphere sucking down carbon faster than the average 2.06 increase in C in the atmosphere. Therefore for these five months growth in the Northern Hemisphere exceeds decay in the Southern Hemisphere by 5.71 + 2.06*5/12 = 6.57 ppm. Multiply this number by the 2.43Pg C per ppm and you get 16Pg.
Please can West and Briske explain how their annual 2.6Pg for carbon uptake by vegetation relates to this 16Pg for 5 month excess of vegetation growth in the Northern Hemisphere over Southern Hemisphere. Presumably the answer is the annual overall decay of vegitation. The issue is thus how to keep the C out of the atmosphere rather than have the vegetation decay and this is where Savory may have a point – albeit not one with as substantial an impact as he suggests.
@115
J Robert Gibson says:
15 Nov 2013 at 9:41 PM
“Please can West and Briske explain how their annual 2.6Pg for carbon uptake by vegetation relates to this 16Pg for 5 month excess of vegetation growth in the Northern Hemisphere over Southern Hemisphere. Presumably the answer is the annual overall decay of vegetation. The issue is thus how to keep the C out of the atmosphere rather than have the vegetation decay and this is where Savory may have a point – albeit not one with as substantial an impact as he suggests”
I am not West or Briske, but I’ll be happy to take a stab at it. I doubt West or Briske will, because at even a superficial level, the issue you pointed out shows a glaring Math error in the original article. Since I know these scientists are significantly smarter than me, a simple farmer, one can only guess their use of the improper figures was purposeful. But I apologise in advance if their error was a simple mistake.
~2.6 +/- 1.2 PgC/yr is the NET annual uptake into vegetation. In addition, there is ~1.1 +/- 0.8 PgC/yr NET EMISSIONS from land use change, largely from agriculture, deforestation and/or desertification of land that has had all or part of the vegetation killed.
The actual estimate for the total GROSS uptake by vegetation is ~ 123 PgC/yr. So yes, annually that much larger figure can actually account for the seasonal flux you are measuring.
Thus the statement,
“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.”
is completely false and misleading. To properly put this figure in perspective, the gross figure 123 PgC/yr should have been used, if it is compared to the gross fossil fuel emissions of 8 PgC/yr. Then you are looking at a much more manageable increase of 123 to 131. Or less than 10% improvement, not the 300% increase the bad math using the net figure leads you to believe.
Now what Savory is advocating is to use land that is currently a net emissions source due to land use change resulting in desertification, and add that newly restored land to the Gross uptake of Carbon by all vegetated lands. Since that land is actually a net emissions source due to land use changes, what Savory is saying is probably highly conservative. There is also land considered vegetative that better management could improve. We could probably do very much better than 10% if we include the efforts by conservationists to reforest and improve agricultural management practices in addition to Savory’s method of restoring desertified ground and improvement of rangeland. Then apply new technologies in solar, geothermal etc… to attack the emissions side. In other words take a more holistic approach to all our land and energy use, and not just desertified land. I highly suspect you won’t get much argument from Savory there, but that is my own honest opinion, I haven’t spoken to Savory about it. I have spoken to Peter Holter, CEO of Holistic Management International, and we are in agreement in principle.
The problem doesn’t seem so overwhelmingly huge when you use proper figures and math. A 10%+ worldwide improvement is far more reasonable goal than the 300%+ worldwide improvement implied by the article. Actually convincing people of the importance and getting the social and political changes needed to implement these changes seems to me to be the much bigger hurdle. This highly biased article is certainly not helping there. It is already being used by the deniers who are resisting change.
Thanks, Scott Strough (comments 53 and 116). As you say, even a conservative reading of Savory’s ideas shows he is making realistic claims for restoring lands which otherwise would be a total liability to environment and climate.
I think restoring grasslands needs much greater attention from the public and policy community. When the damage done by industrial agriculture is reversed, the living web of organisms in the soil become an extremely powerful carbon pump. The benefits are not only in the CO2 sequestered from the atmosphere, but also in restoring hydrology which can directly cool the climate.
Scott Strough:
“Since I know these scientists are significantly smarter than me, a simple farmer, one can only guess their use of the improper figures was purposeful.”
This fits well with the mindset that the only thing keeping Savory’s ideas from being widely accepted is the existence of a professional conspiracy against them.
Which, of course, immediately raises questions in the minds of those who are skeptical of extraordinary claims that fly in the face of accepted science …
“To properly put this figure in perspective, the gross figure 123 PgC/yr should have been used, if it is compared to the gross fossil fuel emissions of 8 PgC/yr. Then you are looking at a much more manageable increase of 123 to 131. Or less than 10% improvement, not the 300% increase the bad math using the net figure leads you to believe.”
How do you get a gross increase of 10% uptake with 100% efficiency?
It is the net figure that is important, not the gross. You’re claiming that a 10% increase in the gross will yield a net increase of 300%, which seems a bit mind-boggling to me.
@118
dhogaza says:
16 Nov 2013 at 1:00 PM
“Which, of course, immediately raises questions in the minds of those who are skeptical of extraordinary claims that fly in the face of accepted science …”
True enough, except the extraordinary claim that flies in the face of accepted science is “To put these emissions in perspective, the amount of carbon taken up by vegetation is about 2.6 Pg per year.” That is false. [edit]
The accepted figure is around 123 Pg per year. [edit]
[Response: Please dial it down. You may be convinced that gross uptake is the issue, but I am with the authors above in concluding that the only thing that matters is net uptake. Increasing gross uptake without considering concomitant increases in respiration is only half the issue. However, you are more than welcome to argue for the opposite, but not by casting aspersions on the integrity of the authors here. – gavin]
I’ll tell you something else too. Who said this article is the “accepted science” anyway? Briske says his own research is the accepted science? If you are the skeptic you claim to be I suggest you apply the same skeptic thinking to this article you seem to be applying to Savory. Look at that “accepted science” and not just Briske’s own claims backed up by his own paper.
[Response: This line of argument is pretty much a waste of space. Please argue on the merits of the case, not about semantic arguments about definitions. Thanks. – gavin]
” Who said this article is the “accepted science” anyway?”
While the argument is pretty much a waste of space, the argument pretty much hinges on the notion that Savory is turning accepted science on its head. If this weren’t the case, there’d be nothing revolutionary about the claims he makes for his grazing regime …
It certainly isn’t accepted science that changes in grazing methodology can miitgate against current and foreseen human CO2 emissions. If it were thought possible by a significant number of mainstream scientists, you’d find it in AR4 or the upcoming AR5, for instance …
#120 Gavin response
Of course, it is about net uptake; however, the 2.6 number was put out there without really explaining it was the net update.
Also it is clear that reforestation or restoration of grassland will increase respiration also but we would hope not as much since in both efforts we are taking land that is sequestering small amounts (in some cases with destroyed grassland perhaps almost no amount) of carbon to land that would sequester substantial amounts.
On a related note, this is an interesting resource:
http://www.umdrightnow.umd.edu/news/umd-leads-1st-local-global-mapping-forest
With the amount of forest loss we are having I am surprised the balance between decay/fire and update hasn’t already tipped to the negative net balance.
Ok I will try this again with a more neutral POV. The fundamental flaw in the article is in inducing the reader to believe that it would require tripling the gross vegetative uptake of the entire planet to offset the net carbon atmospheric increase, while using figures for the net vegetative uptake and the gross emissions. They also ignored the processes involved, including, but not limited to, the differences in properties of grazed lands compared to woodlands, the effect of the ocean and other sequestration sinks, and the fact the while undergoing deterioration and desertification, poorly managed grasslands are an emission source instead of a sequestration sink due to land use changes. These errors of omission combined with the dance of sloppy figures leads the reader to a conclusion orders of magnitude different than anything Savory is claiming. To be fair, that doesn’t necessarily prove Savory correct, all it proves is that this misleading article by West and Briske doesn’t apply to anything Savory is saying.
#123
Fundamentally I agree with this. Sorry I kept writing “update” instead of “uptake” in 122.
It goes back to the glass half full glass half empty I talked about earlier.
If you look at net, you think the problem is impossible to solve with grassland restoration and reforestation.
On the other hand, once you realize that there is an enormous amount of vegetative uptake already (123 Pg) and you look at the amount of destruction of forest and grassland is occurring today, you will realize that if stop the destruction and begin the restoration a significant contribution could be made. Not a complete solution but it is something we need to be doing anyway.
“If you look at net, you think the problem is impossible to solve with grassland restoration and reforestation.”
If you don’t look at net, you’re just fooling yourself. Because the only number that counts is ppm CO2 in the atmosphere, and that increases or decreases by the net amount, not the gross.
Basic inability to do arithmetic (this is not “math”, BTW) does little to instill confidence in the validity of the claims being made.
DEFICIENCIES IN THE BRISKE ESTIMATES OF CARBON SEQUESTRATION ON RANGELANDS
By Richard Teague
Professor, Ecosystem Science and Management, Texas A&M University
Senior Scientist of the Borlaug Institute
Associate Resident Director, Texas A&M AgriLife Research
P.O. Box 1658, Vernon, TX 76385
E-mail: rteague@ag.tamu.edu
Most research related to grazing management, and thus carbon sequestration potential, on rangelands cited by Briske et al. [1,2,3] has been short-term and has examined the issue from a reductionist viewpoint that ignores the critical influences of scale, and does not use adaptive multi-paddock grazing to achieve sound animal production, resource improvement, and socio-economic goals under constantly varying conditions on rangelands [4]. Superior results in terms of range ecosystem improvement, productivity, soil carbon and fertility, water holding capacity and profitability have been regularly obtained by ranchers using multiple paddocks per herd with short periods of grazing, long recovery periods and adaptively changing recovery periods and other management elements as conditions change [4,5].
The references cited by Briske et al. [1,2,3] concentrate only on differences in rangeland productivity without meaningfully taking into account negative impacts on the environment that can lead to misleading extrapolations. These conclusions cloud, rather than enhance, knowledge about sustainable grazing management and are not relevant to practical grazing management. Multi-paddock grazing research from Australia, Southern Africa, Argentina and USA [4,5] that was: i) conducted at the scale of ranching operations, ii) adaptively managed as conditions changed to achieve desired ecosystem and production goals, and iii) measured parameters indicating change in ecosystem function, have arrived at the opposite conclusion. These published data were omitted in the reviews by Briske et al. [1,2,3].
Many ranchers around the world have used adaptive, multi-paddock grazing management to restore ecosystem services and productivity on degraded rangelands in areas with less than 10 and up to 80 inches of annual precipitation. Many of these ranches in drier areas were initially so bare of vegetation that they would have been classified as desertified. By ignoring such successful restoration examples, Briske and other scientists with the same limited experience are grossly underestimating the potential of management to increase carbon sequestration on the rangelands of the world. Consequently, the inferences and conclusions made by Briske et al. [1,2,3] do not represent the subject adequately because conclusions have been selectively chosen so as to exclude published data showing superior results at commercial ranch scale from adaptively managed multi-paddock grazing. The studies referenced underestimate positive benefits to soil and ecosystem function, so they almost certainly underestimate the potential of rangelands to sequester carbon. The accumulated body of small-scale grazing systems research promoted by Dr. Briske and partners needs to be evaluated in light of the discrepancies with larger-scale studies, and perhaps should be largely set aside as being of little relevance to any discussion of grazing distribution on commercial ranches.
The majority of conservation awards to ranchers operating on native rangelands have overwhelmingly gone to ranchers using multi-paddock grazing of one form or another. These ranchers operate in extensive, heterogeneous landscapes, where they are confronted with the adverse effects of uneven grazing distribution, and their collective ecological and management knowledge using multi paddock grazing indicating the necessity of using adaptive, multi-paddock grazing management to achieve superior outcomes. The articles in the Rangelands October 2013 issue, a journal of the Society for Rangeland Management, support this.
In calculating the potential of rangelands to sequester carbon to offset global climate change and improve ecosystem function we cannot ignore the superior outcomes achieved by conservation award winning ranchers, those who have restored ecosystem function and productivity on degraded rangeland using adaptively managed multi-paddock, time-controlled grazing, or published research that does not refute the results achieved on these ranches.
References
1. Briske, D., Derner, J., Brown, J., Fuhlendorf, S., Teague, R., Gillen, B., Ash, A., Havstad, K., Willms, W., 2008. Benefits of Rotational Grazing on Rangelands: An Evaluation of the Experimental Evidence. Rangeland Ecology and Management 61, 3-17. http://www.srmjournals.org/doi/abs/10.2111/06-159R.1
2. Briske, D.D., Sayre, N.F., Huntsinger, L., Fernandez-Gimenez, M., Budd, B., Derner, J.D., 2011. Origin, persistence, and resolution of the rotational grazing debate: integrating human dimensions into rangeland research. Rangeland Ecology and Management 64, 325e334.
3. David D. Briske, Brandon T. Bestelmeyer, Joel R. Brown, Samuel D. Fuhlendorf, and H. Wayne Polley, 2013. The Savory Method Can Not Green Deserts or Reverse Climate Change. A response to the Allan Savory TED video. Rangelands 35(5):72-74. 2013
doi: http://dx.doi.org/10.2111/RANGELANDS-D-13-00044.1
4. Richard Teague, Fred Provenza, Urs Kreuter, Tim Steffens, Matt Barnes, 2013. Multi-paddock grazing on rangelands: Why the perceptual dichotomy between research results and rancher experience? Journal of Environmental Management, Volume 128, 15 October 2013, Pages 699-717, ISSN 0301-4797, http://dx.doi.org/10.1016/j.jenvman.2013.05.064.
5. Teague, W.R., Dowhower, S.L., Baker, S.A., Haile, N., DeLaune, P.B., Conover, D.M., 2011. Grazing management impacts on vegetation, soil biota and soil chemical, physical and hydrological properties in tall grass prairie. Agriculture Ecosystems and Environment 141, 310-322.
http://www.sciencedirect.com/science/article/pii/S0167880911000934
I don’t think it is wise to confuse what I see as two issues of debate running down this thread of late. Farming practices most likely will be able to transform certain barren lands into verdant pastures. Also creating a verdant pasture will absorb carbon that a previously barren land would not. The two issues concern the significance of the transformation and the significance of the absorbing – is either of them significant on a global scale?
Concerning the transformation issue, can this be significant? I do wonder how it can be a subject of debate if the results on the ground are so spectacular. How ever simple a farmer is, would he not adopt the methods of his neighbour with the evidence so obvious? That he appears not to – that is enough to make anyone sceptical of such long-lived claims.
Concerning the absorbing issue which is the main subject of the post, I was not impressed by the numbers presented in the post but the argument that a vast increase in grasslands across the globe would reverse the atmospheric CO2 rise is surely bizarre.
Net or gross numbers? One is caused by incremental CO2 increases, the other by winter. Is there a better number to bandy around? There has been no mention of the 15PgC figure, a figure that has increased 15% over the last 60 years. While the ‘gross’ 126PgC estimates the flux in/out of the biosphere annually, the 15Pg figure is a measure of the effect that flux has on the atmosphere, as measured at MLO. (Of course it depends where you measure it. In size & increase, it is zero in Antarctica & double in the Arctic. MLO thus appears a useful global average.) The 15PgC figure is interesting as our annual emissions from all sources are not so far below 15PgC. (The 8PgC figure for FF quoted up-thread dates back to 2005.)
So can a grand increase in pasturage absorb sustainably year-on-year something like than 15PgC & prevent CO2 levels rising higher? Can it be more significant to the global biosphere than winter?
Here is a question for those who think it may be. What was the impact on atmospheric CO2 when the Sahara turned from grassland to desert? There was a 43Pg increase in atmospheric CO2 over the 8,000 year period (+20ppm). With any emissions being 80% absorbed by biosphere & ocean, that would represent 213PgC. Assuming the source was all the desertification of the Sahara (a very brave leap of faith given the HN cooling over the period), that would make the total desertification of the Sahara, a plot of land of not inconsiderable size, worth 14 years of our emissions. So remind me – how big is this here ranch we’re gonna transform?
To MARodger, #127: This here ranch we’re gonna transform is roughly 12 billion acres, the extent of worldwide grasslands mostly degraded or desertified.
Our scientific sample set of soil carbon storage capacity is severely skewed because so much of it is comprised of croplands that have been mangled far beyond their original state. In general biological conditions on land in the holocene have been blurred by human activity. IOW, it can be hard to discern how the extraordinarily complex systems that are soils would behave in optimal conditions – conditions that we have a pretty good idea of how to re-create should we decide to do so.
There are good reasons to believe that soil carbon sequestration potential is far greater than we currently acknowledge. No matter, eco-restoration of grasslands has such remarkable and widespread benefits – for carbon and water cycles, for biodiversity, for food production (especially in poorer countries) – that we should proceed full speed ahead regardless of carbon-number specifics.
” No matter, eco-restoration of grasslands has such remarkable and widespread benefits – for carbon and water cycles, for biodiversity, for food production (especially in poorer countries) – that we should proceed full speed ahead regardless of carbon-number specifics.”
Which is not the issue under discussion. It is hard to imagine anyone being opposed to improved rangeland management.
The subject of the original post, and the subsequent discussion is whether or not improved rangeland management can fully mitigate human CO2 emissions, as claimed by Savory. Some of us, to put it mildly, are skeptical.
Richard Teague’s post also dodged the issue.
He summarizes by saying “In calculating the potential of rangelands to sequester carbon to offset global climate change and improve ecosystem function we cannot ignore the superior outcomes achieved by conservation award winning ranchers, those who have restored ecosystem function and productivity on degraded rangeland using adaptively managed multi-paddock, time-controlled grazing, or published research that does not refute the results achieved on these ranches.”
This boils down to him saying that even if Savory is wrong about the magnitude of CO2 sequestration, improved rangeland management is a good thing.
It appears that a few people here are attempting to defend Savory’s claim by essentially ignoring it, and changing the question to something else entirely (“are there other benefits to improved rangeland management?”. Yes. Duh!).
I agree with Dhogaza that improving agricultural soil fertility is very important, but when talking about 12 billion acres I would like to know where the water would come from. It takes a lot of water to raise food for grazers and water for the grazers themselves, and easily accessible fresh water is rapidly becoming scarce worldwide. Has this been figured in?
Steve
Adam D. Sacks @128.
Your comment sort of leads back to my own comment @127. You tell us there is potential for this transformation to apply to lands equal to a third of global land area. Yet, although this work by Savory dates back to the 1960s, and you tell us “that we should proceed full speed ahead regardless of carbon-number specifics” (which sounds quite an emphatic endorsement to me), you rather pull your punches by saying that we do have a pretty good idea of what to do “should we decide to do so.”
Why is this decision so difficult to make? If this is such a win-win-win situation, what the blazes is stopping it?
I do not know the merits of Savory’s approach. What bothers me about the article by West and Briske is that the authors seem to dismiss the importance of soils in the carbon cycle. That is completely unjustifiable. The authors do not mention the amount of carbon stored in the soil, and the extent to which release of soil carbon (due to erosion, drought, development, agricultural mismanagement, overgrazing etc.) contributes, and has historically contributed, to GHG emissions. The authors: “the amount of carbon in vegetation is currently estimated at around 450 Pg, most of that in the wood of trees.” They fail to mention that the amount of carbon stored in the soil is multiple times that stored in vegetation.
The authors state: “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.”
Where the 20% number comes from and what it means is mysterious (it cannot refer to “global carbon stocks” because that would include the deep ocean and so on.) References would have been helpful (this is supposed to be the voice of science right?) Btw where can I find the most current and reliable figures for the carbon cycle? The figures that I find by a simple google search diverge are quite a bit from those given by the authors.
In any case, “only 20%” is a weird formulation. There is no doubt that grasslands are a big issue in the carbon cycle. 30-40% of the global land surface, that’s huge, and it contains a lot of carbon. Proper management methods can have a hugely beneficial impact on many dimensions (soil carbon, water, desertification etc.). The question should be what the best practices are. To dismiss the importance of adopting better practices is widely misleading.
OK, so ‘this here ranch’ is 12 billion acres. I note that land under direct Savory management so far is 200,000 acres, so there’d clearly be a scaling question here…
But 8 Pg translates (if I haven’t slipped up) to 8 billion tonnes of carbon. So once we got all 12 billion acres under Savory’s grazing regime, we’d need to see nearly 700 kg of carbon sequestered per acre, per year, for as long as we keep burning fossil carbon at anything like current rates. (Which, of course, are still accelerating…)
Taking it from the other end, I haven’t seen (in some desultory looking about) any quantitative estimates as to carbon uptake in a Savory-style scheme that I could compare to the target number, but absent any actual estimates, I’m feeling pretty darn skeptical about the TED talk claims made. (Though, qua grazing method, the Savory model may be perfectly wonderful.)
#128 – For comparison, the area of the Sahara is around 2.3 billion acres, or in the region of one-fifth of the 12 billion acres claimed as improvable grassland and potential grassland. According to the numbers given in #127, this translates into the possibility of absorbing roughly 70 years’ worth of emissions.
Thanks for this article, I really wanted to read up on this but have been lacking the time. I never thought it the silver bullet it was claimed to be, but an intriguing possibility to add to the toolbox of climate mitigation. People looking for the one true solution are likely to be misguided when faced with any complex problem.
> “Dan H.
C’mon, show us you can at least be honest enough to correct yourself and withdraw your claim that vegetation aborbs 50% of our carbon emissions.
Or don’t. It’s your reputation, not mine or hank’s, that is at stake.”
My standard disclaimer to all readers, especially new readers, of Real Climate is simply to skip over comments by Dan H. He will never lead one towards a greater understanding of the science or climate, he only serves to distract. The easiest way to make sure you are getting valid information is simply read the main articles and comments from the RC contributors.
It’s been maybe a year or so since I have had any time to comment here, but Dan H is doing the same nonsense as he was back then. He has no reputation to defend, and I do not expect him to claim ownership for his statements. If you spend enough time reading the comments you eventually see his patterns of obfuscation.
Perhaps a few comments would be useful here to address some questions and apparent confusion about our post. The post was in response to a specific claim made by Alan Savory and then championed in a variety of forums: that his method (however defined) applied to half of Earth’s grasslands (here one must assume arid and semi-arid grasslands) could return atmospheric CO2 levels to those prior to the Industrial Era.
Since it is difficult to understand what exactly is meant by Holistic Management® in this context, and there is no scientific literature that we are aware of that supports a significant net gain of soil carbon across environments in response to his method, we did not attempt to assess what a realistic global number might be. We took a different approach using the available literature and a basic understanding of the global C cycle. Here, what is relevant is the size of the C stocks in the atmosphere, the magnitude of the ongoing additions from fossil fuel burning and cement production, and a simple “order-of-magnitude” assessment of what may be expected from the grassland component of the biosphere. Of course long-term biosphere storage of C is in soils, but any net gain of soil C must first have been fixed by photosynthesis. Again, since photosynthesis and respiration nearly completely offset, what is relevant as a starting point is the apparent net C gain of terrestrial ecosystems. It’s really possible to stop the argument there. The terrestrial C cycle is currently in a significant disequilibrium resulting in an annual net C uptake at a global scale that is still only a fraction of the annual additions to the atmosphere. It is a tall order to make the case that managing grasslands would somehow result in multiples of the current global terrestrial C uptake. However, one can further think about the total biomass of vegetation and ask how many multiples of that must be incorporated into soil (permanently – or at least for “thousands of years”) to draw down atmospheric CO2 appreciably. Recognizing that grasslands are a fraction of the total terrestrial biosphere, and that only a fraction of productivity is incorporated into soil organic matter annually, this results in a very large gap between a plausible expectation and the claim made in the Savory talk. It seems unreasonable to expect that any land management scheme applied to these grasslands is likely to have such an outsized impact on atmospheric CO2.
We did not engage in a detailed discussion of the carbon cycle within grasslands, life-cycle analysis of various management schemes, and several other issues simply because we believe it’s not necessary to address these given the large gap between the problem (elevated atmospheric CO2) and the purported solution (altered management of arid/semi-arid grasslands). Our intent was simple: to place the claim made in the context of the global C cycle.
It seems obvious, then, that any argument made to support the claim should provide evidence that it is possible. This evidence would consist of research published in the scientific literature that has, at a minimum, had the benefit of peer review.
Perhaps an additional comment should be made about other ongoing debates about what is understood to be the Savory Method or Holistic Management®. This post was not about those debates and we think it is important to separate the climate impacts statement from any other claims made in the TED talk or elsewhere.
Some commenters here have argued that the claim was made with the premise that all fossil fuel consumption would stop. We believe this is not at all made clear in the talk and take the quoted statements at face value.
Of course there are many exciting areas of ongoing C cycle research at an incredible range of scales and systems worldwide. We again encourage all readers and commenters here to read Chapter 6 from the recently released Fifth Assessment Report (http://www.ipcc.ch/) for a rich analysis of much of that work.
We look forward to ongoing discussion here and again will look for opportunities to comment here and inline.
Jason West & David Briske
> Chapter 6
(the IPCC main page will always point to the current document, and that will change; at the moment their link points to
http://www.climatechange2013.org/images/uploads/WGIAR5_WGI-12Doc2b_FinalDraft_Chapter06.pdf
Better rangeland management does not affect surfaces temperatures simply by carbon sequestration, but by altering the skin surface. The metamorphosis of grasslands to barren soil can raise maximum skin surface temperatures by 10 to 20C degrees. Since grasslands cover 30-40% of the land surface increasing the vegetation could have a major cooling effect on global land surface temperatures.
Read Mildrexler,D.J. et al., (2011) Satellite Finds Highest Land Skin Temperatures on Earth. Bulletin of the American Meteorological Society
Repairing grasslands provides tremendous economic and biological benefits and controllingour carbon footprint can never heal these habitats. This rant against Savory seems more concerned with saving a CO2 theory than saving threatened environment.
On face value, Briske and West are correct. Savory’s claim is unreasonable. The terrestrial biosphere only nets 3 Gt C/an. How could we possibly expect another 5 or more Gt to be sequestered annually? Consider that most arid land is degrading. Not much uptake there. Consider that there are ranchers who have been successful at transforming depleted, brittle landscapes for some time. How much soil carbon in these cases? There are some who manage well over a ton of C/acre/an. There are some who manage 4 tons per acre, and there have been “outrageous” examples of more than that. Not all sites will take in 4 tons per year, but can we, with good management, average a ton or two? That doesn’t seem unreasonable. The challenge is to get the land to be managed holistically, and that will take more managers, and more animals. Of course, in a wilderness situation with predation, nature becomes the manager. Chris Gill at http://www.circleranchtx.com regenerates his desert by using cattle or a Yeomans subsoil plow to break the crust of the earth and allow water to penetrate and seeds to germinate. After managed grazing with livestock, rewilding occurs. There are, of course, many benefits to HM beyond the scope of the narrow topic here. Regenerated landscapes, as has been pointed out, produce less heat from sunlight through cooler surfaces, and also improves the water cycle. The important thing is to get back into the more natural, more perennial, covered ground approach that built the prairies, savannas, and forests in the first place. That’s what got us here. That’s what will get us out of this mess.
Jason West @136,
Thank you for the clarifying ‘addendum’. What is still missing in all this is a figure for the carbon sequestration potential of regenerating grasslands Savory-style. Without nailing that down, many will remain unconvinced/unsatisfied by this account of the impracticality of Savory’s carbon sequestration claims.
Adam D. Sacks @128 tells us the land available for such regeneration totals approx 5 billion hectares, although it appears way too large an estimate in my view. Savory talks of “about half the world’s grasslands” so perhaps a figure of 2.5 billion hectares should be used. Taking that figure, just to sequester last year’s FF+cement carbon emissions would thus require an uptake of about 4 tC/ha. (CDIAC have just published 2012 preliminary emissions estimates = 9.67GtC.)
Indermuhle et al 1999 suggest a conversion from desert to grass/scrub/savannah would sequester 23-37tC/ha, providing sequestration for ~8 years-worth of emissions from 2.5 billion ha. There may be newer estimates that revise this figure. As it stands, a desert-to-grassland conversion appears fall far short of Savory’s claims, even when such large land areas are involved. And this assumes Savory starts from desert.
There are also proposals for forestation schemes which suggest photosynthesis supported by suitable irrigation is capable of sequestering from 5 tC/ha/year to 25 tC/ha/year and inbetween, the last even with a TED conversation. The big difference with Savory’s proposal & these forestation schemes is the size of the plants, forest wood can be harvested to allow sequestration to begin again and they do require serious amounts of irrigation, and investment.
I would appreciate it if those knowledgeable about agricultural carbon sequestration could document how much of this carbon is retained in the soil over time. In other words, does managed grassland that sequesters 4 tons C/acre annually, increase its total C content by 400 tons/acre over a 100 year period?
Steve
Re Comment by Jim Steele — 19 Nov 2013 @ 10:39 PM
I presume that you and others who have commented on the cooling effect of plant transpiration are aware that this process is very local and actually absorbs more heat into the atmosphere from sunlight that a bare desert. Just in terms of radiation physics, converting desert to grassland increases global warming.
Steve
#123
The key is in the next sentence in the paragraph which gives the context for the figure: “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.”.
So the number is a net figure to be compared to the net emissions (the human part of the gross emissions which includes the emissions from vegetation).
This is a rough estimate so the authors ignored lots of things.
The big difference is that they have rough numbers while Savory has an unsupported (in the video) opinion.
Just a quick note to let folks know about a nice source of easily-accessible information on the carbon cycle:
http://www.globalcarbonproject.org/
This is the latest release from an active and over ten year old effort to “establish a common, mutually agreed knowledge base supporting policy debate and action to slow the rate of increase of greenhouse gases in the atmosphere.”
Check it out, explore and visualize data, and share with your friends!
@ #143 I have no fundamental problem in using the net figures. My objection is in using them in a misleading manner IMHO. It is well known that the majority of carbon stored in vegetation mostly returns to the atmosphere through the processes of decay, fire, and/or slow oxidation. There is however a difference in the way grasslands and forests function in respect to the carbon cycle.
In a grassland the net vegetative uptake that stays in the plant is nearly zero like forests, but the difference doesn’t necessarily return to the atmosphere, a significant % can be sequestered in the soil. The % that stays in the soil does vary according to the biology and/or management.
This is why the figures used by West and Briske are wildly and hugely misleading. Instead of tripling the entire vegetative absorption of the planet as Briske implies, What Savory is really talking about is a relatively smaller % increase in total vegetation uptake, combined with a relatively smaller change in the % of that gross vegetative carbon being sequestered into the soil. (when viewed on a global scale)
Just to give you a truer picture of the realistic scales involved, if you increased the total vegetative uptake just 10% and increased the % of that gross uptake that is sequestered instead of re-released into the atmosphere by 10%, you would decrease the gross atmospheric carbon by roughly 13.5 PgC/year in addition to the 2.6 PgC/year given in the article. Our gross FF emissions are around 8 PgC/year. So around a 5 PgC/year net decrease in addition to the what vegetation is sequestering now.
Now I am not necessarily saying Savory’s methods can accomplish either one of those benchmarks. But it gives you a much more realistic and useful benchmark to compare and study to either prove or disprove. I am fairly sure in an already reasonably managed grassland, it probably wouldn’t show that full 10% increase. But in a desertified area, it might show a much higher rate. Same thing goes for forests. If the wood is allowed to decay, a mature forest is nearly a net zero in the carbon cycle. But harvest the mature trees and plant new, in other words managed well, that wood could potentially last for hundreds of years. Just a 10% net increase is all we need, taken on a global scale.
The West and Briske figures presented are useless in understanding the scale of the problem or the potential agricultural/vegetative solutions. Considering the new information I have been seeing for months on methane and CO2 releases from thawing both in tundra and in the oceans, I personally don’t think we have any other option but to try.
[Response: The numbers speak for themselves and are far from misleading. We have no information about expected effects of Holistic Management® on soil carbon on which to base an assessment of its likely impacts. Fictionally large changes in terrestrial uptake can be imagined if you simply make up a number (e.g., as you have here with 10%) and apply it to the estimated gross terrestrial fluxes of the planet, but this is clearly inappropriate. If you look at the estimated global terrestrial sink it has varied from near +4 to around -1 Pg C yr-1 since about 1960 (see slides available here: http://www.globalcarbonproject.org/carbonbudget/13/presentation.htm). This compares reasonably well with global land models. What conceivable mechanism could justify an imagined terrestrial sink that’s some multiple of the currently understood flux? Remember that the gross flux of C uptake is photosynthesis, something that is highly constrained by precipitation in the areas Savory is talking about. Also remember that when we talk about the global C sink, this is an aggregation of large spatial variation in regional sinks. It may be useful here to take a look at the outputs from land models available at http://www.globalcarbonatlas.org. The grasslands we’re talking about are in areas that (as we’ve said) are weak C sinks or weak C sources (check atlas output against Savory’s map outlines). These are not systems that are likely to shift radically to strong sinks in response to any management activity. The net figures are far from useless and accurately reflect the scale of the problem. In thinking about impacts, it’s important to use existing scientific understanding to guide any discussion and there is no science to support your assertion that our figures are misleading. -Jason and David ]
Re- Comment by Scott Strough — 21 Nov 2013 @ 1:24 PM
When a tree is cut down the carbon it contains is released as CO2 and CH4 very quickly on a forest growth time scale. The new growth of the forest will just store up approximately the same amount that was previously released, but it will take longer. Negative benefit.
Steve
How grasslands sequester carbon: grasses tend to keep root systems in proportion with top growth, so when livestock graze on high grasses then that land is allowed to rest, the roots slough off the excess growth and their carbon becomes available to microbes as food, polymerizing it into humus. That humus improves soil structure and holds moisture, so there is potentially an exponential increase in growth. That is how the net sequestration can be considerably greater than what the mass of vegetation is at any one time.
“Just in terms of radiation physics, converting desert to grassland increases global warming.” My understanding is that Intensity = Emissivity x Stefan-Boltzmann Constant x Surface Absolute Temperature ^4. Bare earth is considered blackbody, with little albedo, so T^4 is the dominant factor. I have some data from a sunny days, a random sample of which shows leaf temp = 299K and bare soil = 319K, a 33% increase in IR re-radiation. Ground cover and topsoil also mean more water in soil and vegetation. Trees transpire moisture and send cloud and water droplet nuclei into the atmosphere –> rain. Evaporation cools the surface, and the absorbed heat in the water vapor re-radiates when it condenses in the upper troposphere in all directions, including upward toward space –> net cooling. Figure 10’s of millions of acres of desertification per year. That’s an enormous amount of soil carbon released each year. I see no net climate benefit for bare soil.
” The new growth of the forest will just store up approximately the same amount that was previously released, but it will take longer. Negative benefit.” This depends. Well managed woodlots may contain 70-90%, my estimate, the carbon of mature forests, but can allow for healthy regrowth while sequestering carbon in stable, long lived wood products, and converting waste to biochar, etc. Coppicing also has rapid regrowth.
The carbon balance shows that terrestrial biomass and soil nets an extra 3 Gt C per year, so only 60-70% of emissions remain, ~6 Gt C, as ghg’s and ocean acidifying H2CO3. The terrasphere only sinks a net of 2.4% of its 123 Gt productivity, about a 40:1 ratio. It is hard to imagine adding another 246 Gt of productivity to get another 6 Gt sequestered. But that’s not necessarily how it works.
Existing mature forests, for example, are at steady state, with new growth balanced by decay. What if more land were used for forestry? That would mean more growth and less decay until mature. Tropical forests have rapid growth. Hardwood forests are slower, but can e managed for more productivity, and there is more soil carbon in temperate and boreal forests.
Soils can sequester carbon rapidly and can be especially carbon stable. Soil carbon is often under-reported, but this needs to change. One ton C per acre per year is not uncommon, and three or more tons is very doable, with some farmers frequently exceeding this amount. Most soil scientists discount these results, but farmers are doing this.