Film director, Peter Byck, responds to criticism and sets out the science-basis for the hit film series, ‘Roots So Deep’.
This article first appeared on LinkedIn. It is reproduced in full below, with kind permission.
BYCK WRITES: Esther Remmelink recently posted this criticism of Roots So Deep (you can see the devil down there) after attending a screening in Rotterdam on June 14, 2024. We think this is a fantastic opportunity to dig into some common criticisms and misconceptions of regenerative grazing.
We have copied Esther’s text in full and made it italics so it’s easy to see her text, and our replies.
We appreciate the dialogue. We invite everyone to visit the Roots So Deep website to read the 11 papers published to date – we will have another 6-8 papers published in the hopefully not-too-distant future (13). Thank you to the members of the Roots So Deep team who contributed to this article.
Background
My team and I were led to AMP/regenerative grazing through our hunt for solutions to climate change – and in these 17 years of investigation, via doc filmmaking and helping to lead this large science team over the past decade, AMP grazing is the most productive system we’ve found in building soils, rewilding farmland, getting farmers out of debt, greatly improving the water cycle – and – creating a GHG sink, when accounting for carbon dioxide, methane and nitrous oxide. AMP enables farmers to double or triple their forage production when compared to their conventional neighbors – all that extra forage increases the Carbon drawn down (cooling) that greatly counterbalances the warming of the methane and nitrous oxide.
Our research was conducted in the Southeast US – and we are strong proponents for the need for much more research to be conducted in regions around the world. We replicated our measurements on 5 farm pairs – with AMP grazing on one side of the fence, and conventional grazing on the other. We started the design of this research in 2014, and hit the fields in 2018. In 2015 and 2016, we conducted numerous peer reviews of our research plan and our methods – and those peer-review sessions included some of the scientists in the papers you cite. (2, 3, 11).
All carbon numbers in the docu-series are given as Carbon, not CO2 – but for this reply, I’ll give both. As you know, 1 tonne of C means 3.67 tonnes of CO2 – that’s the math.
Our GHG flux work is not yet published; the data in the series was the most current analysis Dr. Nuria Gomez-Casanova, our lead GHG scientist, could give pre-peer-review.
Our GHG data
We found that AMP grazing produced a GHG sink of 3.3 tonnes of Carbon equivalent per hectare per year – C equivalent means accounting for the warming of the methane, the warming of the nitrous oxide and the cooling of the C drawdown. So again, that is a Carbon equivalent (Ce) sink/cooling of 3.3tCe/ha/yr – in CO2 equivalent (CO2e), it is 12.1tCO2e/ha/yr. AMP is not a less bad method of grazing, this is a beneficial method of grazing – the interaction of the animals and the pastures are creating cooling events. IF enough farmers adopted AMP across the world, and IF they got similar results, it could be very beneficial in helping to slow climate change. That’s a big IF.
Methods of measuring the GHG: we measured C emissions from the soil, from the atmosphere via Flux towers. We measured methane from the cows (enteric emissions), from the soil, and from the atmosphere via flux towers. We measured nitrous oxide from the soil and from the atmosphere, via open chamber equipment from Aerodyne.
We are all eager to complete the peer-review for this GHG work.
The issue of soil samples being only 30cm
We collected meter deep, 2” wide soil samples – over 500 of them, on the 5 farm pairs in our study. In a healthy grassland, there is a lot of carbon in the 31-100cm depth. Ignoring this fact is a weakness to Wang et al specifically (3). Wang et al does a meta-analysis of papers that contain only soil measurements down to 30cm. Carbon is drawn down to the depth of the living roots and microbes. In a sick system, 30cm may well be deep enough – but in a thriving, healthy system, that C is a meter or deeper. For example, in our study, 30-35% of the C in the soil samples was measured deeper than 30cm – from both the AMP and the conventional pastures. In the field, measuring to 30 cm is relatively easy – getting 1-meter-deep cores is a lot of work. We suggest folks beware of studies that only go down 30cm and make overarching claims of the earth’s soils’ ability/potential to house large amounts of C.
We have documented plant roots going as deep as 20 feet. It is routine in AMP grazing situations to find roots as deep as 10 feet or so. Roots, and the attached mycorrhiza fungi, carry C down much deeper into the soil.
A new paper highlighting the importance of measuring well below 30cm, please see this paper (Dietz et al) (14).
Now – to Esther’s post (in italics) and our reply:
ESTHER REMMELINK: Esther Remmelink | July 31, 2024 – Can cows be a solution to the climate crisis? According to the documentary Roots so Deep – You can see the devil down there –
PETER BYCK: Peter Byck | August 20, 2024 – They can. Please see the GHG data at top of this reply for why we say cows can be a solution.
REMMELINK: The 4-part documentary series follows a research project that spans almost a decade with the aim ‘to figure out if the way cows are being grazed could actually help solve climate change.’ Shots of lush green fields, free roaming cows –
BYCK: AMP grazing is not free roaming – that is conventional. AMP keeps the animals in a tight herd, grazing for a short period of time (hours to a day) and then moves the animals to the next paddock.
REMMELINK: and many different insects are mixed with, sometimes, deeply personal interviews with the farmers and the scientists. The result: YES, how farmers let their cows graze, can be a ‘huge’ part of the solution and WOOHOO, farmers are willing to make the ‘easy’ change if you show them the science, find common ground and show them it costs less. While it’s inspiring to see the biodiverse fields and hear the birds (calling for change?), does this team really have the data to ‘surprise those who think eating meat is bad for the planet’ as it claims it will? –
BYCK: Yes.
REMMELINK: The first episode introduces a group of ‘maverick’ scientists, brought together by the director Peter Byck. Their study aims to understand whether ‘AMP grazing can make the land better and make farmers more money’. They compare five pairs of farms in the South East of the US, where ‘one side of the fence’ is AMP (adaptive multi-paddock) grazed and the other side conventionally grazed. Data on soil carbon, biodiversity and methane emissions are collected, and they check the health of the cows and the financial health of the farmers. The result, or at least that’s what they claim, AMP grazing is better on all aspects. –
BYCK: We make all our papers available, and share as much pre-peer review data as we can – these data are research findings. Why do you use “claim”?
REMMELINK: Adaptive multi-paddock grazing is a form of rotational grazing where multiple fenced paddocks are grazed by many animals for short periods (hours to days, depending on the season), during which plant consumption is monitored (aimed to leave ~50% forage uneaten), followed by an adequate time of recovery after grazing to allow vegetation regrowth. Additionally, AMP practitioners seek to minimize the use of external inputs (i.e., fertilizers, herbicides, pesticides). –
BYCK: The AMP farmers in our study do not use synthetic fertilizers – the animals provide their fields’ fertilization.
REMMELINK: This form of grazing management is meant to regenerate the soil. By contrast, under conventional grazing management, cows are continuously left in a field. When left free to graze, the animals overgraze patches of the field, making it hard for the grass to grow back.
“We can cut all human carbon emissions by a third”
For over a decade, AMP grazing has been proposed as a way to get carbon (C) from the atmosphere into the soil (1). Grassland ecosystems account for ~40% of the Earth’s land surface excluding Greenland and Antarctica (2). If these land areas can be used to sequester carbon and at the same time produce food, that sounds like a win-win. However, there’s ongoing debate about how much C can be stored in the soil, if it can keep on storing more and more forever (see below) or whether there’s a plateau (see below) (3).
Besides that, for it to really help solve the climate crisis, carbon needs to be stored permanently. –
BYCK: Completely disagree: nothing is permanent in nature. Carbon is meant to cycle and MUST cycle for life to exist on this earth. If all C is stored permanently, then all life ceases to exist. The idea of permanence is a paradigm problem – it’s paradoxically the wrong goal. We want more C working in the soil, at any given time, where it makes all life thrive. Analogy: don’t think of C like gold in Ft. Knox, where you lock it away – think of C like currency in an economy; as it’s invested and spent, it grows. The only thing that matters is that the total amount of C in the soil is increasing, at any given time. Then, by definition, it is no longer in the air.
On the issue of soil C amounts reaching a plateau – where no more C can be stored at that point in the pasture. First, since our soils are, across the world, vastly depleted of C, getting them to this theoret+ical capacity of C would be an incredible benefit for the planet. So even if the plateau theory were accurate – it will still take a lot of regenerative work to get soils to the point of C saturation. People seem to bring up this theory as if it were reason enough to not even try rebuilding the soils, or that the soils can only be a small part of the climate solution. We disagree.
Most of this debate about a plateau in soil carbon accumulation/saturation seems to conflate the saturation of a point, with the growth of a volume. It’s the difference between how wet can water in a swimming pool be and how much water a pool can hold. Carbon cycles in and out of the soil – in 3 basic time scales – days, decades and centuries. The decades decay is from decomposing roots, for example. The centuries decay is from decomposing microbes. Necromass is the key word here. Dead microbes (necromass), in a healthy soil system, can make up to 50% of the soil carbon. And, via this paper from our team (Soil microorganisms respond distinctively to adaptive multi-paddock and conventional grazing in the southeastern United States), we found that AMP grazing increased microbial abundance by 25% – more microbes equals more dead microbes, which equals more NEW soil (15). AMP/regenerative grazing builds new soil by building the soil microbial populations. So – if the actual volume of soil is increasing due to new soil production, why would the soil reach a place where it can house no more C as the plateau theory assumes?
Beyond necromass, if carbon were accumulating in soil in a manner that filled in the pores between mineral grains, the overall density of the soil would go up and the permeability to fluids would go down. But as all who study or even just observe soil know, the opposite actually happens. This is because the accumulation of carbon is a biological process wherein the original mineral grains move apart just like in an expanding universe. As there is no room for soil grains to move down or sideways, this means that the accumulation of carbon in soil involves soils whose surface grows upwards towards the sky where there is literally no limit. The real limit is root depth – the glories of which can be seen in a tallgrass prairie or a savanna where the roots grow ever deeper as the above ground vegetation grows taller.
In a grassland system with deep, dense and diverse roots, the overall interval into which carbon can be stored is much larger than a shallow 30cm sample. Sampling to 1m, as we did in this project, helps overcome this problem, but it really doesn’t put any limit on how much carbon we can hold in soils because as long as there’s a root to go deeper, the sky is literally the limit. The Great Plains had topsoils 10 to 15 feet deep – those soils are now inches deep; there is a huge opportunity for increasing soil C amounts.
On a planet where there is still roughly 3 times as much carbon in the top 2m of soil as in the entirety of our over-filled atmosphere, it doesn’t take much to put a very big dent in the imbalance problem.
We are suggesting regenerative grazing can help rebuild soils in a time scale of years and decades – which is what we need to slow down climate change.
REMMELINK: Plowing the land causes carbon to be released, so this permanence is threatened when a farmer, or the next farmer on the land, decides it’s needed. –
BYCK: We agree completely that plowing is destructive to soil and releases carbon. Plowing, or tillage, is very seldom used by livestock grazers as it is a significant cost and lowers productivity of pastures. The vast majority of tillage is done by the farmers who are growing plant-based foods. They routinely till and release huge amounts of C into the atmosphere. Tillage is also the major culprit in our enormous soil losses due to wind and water erosion and the subsequent harmful runoff. It is tillage that is creating the Dead Zone in the Gulf of Mexico each year. Tillage also greatly damages soil microbial life and overall biodiversity. You will almost always find more life where people graze than where monoculture crops are grown.
REMMELINK: The movie claims AMP grazed soils can be a global carbon sink of 3.3t of CO2e per year. –
BYCK: Incorrect: please see the earlier paragraphs that start with “Our GHG data:” We say the AMP-grazed soils in the Southeast US can be a Carbon equivalent sink of 3.3 tonnes of Carbon per hectare per year. You’ve written 3.3t of CO2 equivalent (CO2e) per year. Our data in its CO2e conversion is 12.1t/ CO2e/ha/yr.
REMMELINK: This roughly equals to 1t of C per year (1t C = 3.67t CO2). –
BYCK: While your math is correct, your numbers for our research are not. Our GHG sink numbers for AMP: 3.3tCe/ha/yr = 12.1tCO2e/ha/yr.
REMMELINK: It then goes on to say: “If we can draw down 1t of carbon in each of the 265 million hectares of US grazing land, this is equal to cutting US carbon emissions by 1/5th. If we can draw down 1t of carbon for all the 3.5 billion hectares of grazing land in the world, this equals cutting all human carbon emissions by a third.” –
BYCK: In the above paragraph from the series, we are not talking about the full GHG accounting #s, we are talking about C #s only.
REMMELINK: This sounds like we have found THE solution to getting us out of the climate crisis, but these numbers really need to be scrutinized. –
BYCK: Agreed, these numberss need to be scrutinized – you are conflating the CO2e numbers of the full GHG accounting, with C only numbers we are presenting at that part in the series.
REMMELINK: First of all, they underestimate total human carbon emissions. If 3.5 billion tonnes of carbon equals one-third of all emissions, this means they assume global emissions are 42.8 billion tonnes of CO2e. –
BYCK: No – you’re conflating C with CO2e (which we are not talking about in this part of the film). 3.5b tonnes of C is about 1/3 of human C emissions per IPCC 5. In this part of the film, we are only talking about C, not C + CH4 + N2O.
REMMELINK: Sadly, they were 53.9 billion tonnes in 2022, 1.3 times more. This means that if 1t of C can be drawn down yearly per hectare, this only covers one-fifth of all human emissions, not one-third. Still a considerable chunk though. –
BYCK: Again, you are conflating the C numbers discussed in the film, and your CO2e numbers in the above sentence.
REMMELINK: However, second, they overestimate the amount of hectares for which grazing can be optimized. There might be about 3.2 billion hectares of pasture on this planet (note: not 3.5!) but it makes no sense to assume that on all those hectares there is the same ‘conventional’ form of cattle management, nor that on all those hectares it’s possible to do AMP grazing. Also, soil carbon sequestration potential varies with climate and soil conditions, the amount of C already in the soil and the types of plants on the field (1,4). –
BYCK: We use Dr. Rattan Lal’s figures for the 3.5b hectares of grazing land (16). We know there is huge uncertainty in how much grazing land could be productive enough to draw down 1 tC/ha/yr. And we also see in our research a farm in Alabama drawing down 5t/C/ha/yr. We averaged it out to give a talking point for the C draw down potential of the world’s grasslands, if made healthy. There is a lot of currently desertified land that was healthy grassland just 150 years ago – see New Mexico, Arizona and the Karoo in South Africa. We are already seeing ranchers rebuild the soils on these degraded lands world-wide. How much of, and how fast can these regions be regenerated?
REMMELINK: Henderson (5) came to an ‘amenable’ area for optimizing grazing intensity of 712 Mha, almost 5x less. This means that if 1t of C can be drawn down yearly per hectare, this only covers 5% of all human emissions, not 33%. Not a considerable chunk anymore! –
BYCK: We find this Henderson paper problematic. In the first place – it claims the very areas we studied in the Southeast US are not “amenable” for optimum grazing.
“Amenable” is, in this case, just a word to say they ran Daycent/Century models over all of the world’s grazing land and found net potential positive results on ~20% of them. To give you an example of relevance, they estimate positive results on 9.4 million ha in all of North America or 23 million acres (of the ~250 million acres of grazing land). Aside from all the usual DayCent/Century or even general model questions, what they are effectively doing is encapsulating all of “improved grazing management” as either increasing or decreasing “grazing pressure” (i.e. stocking rate) to match modeled forage productivity.
And, none of those models account for AMP grazing’s dense herds, frequent moves and resulting long rest periods for the land – meaning, the concept of AMP does not exist in the Henderson paper.
Additionally, this is one of those papers where the additional practice of “seeding legumes in pastures” is the only other alternative practice (and the one that they say drives the most benefit). Seeding legumes alone, without incorporating it into a proper grazing strategy, can actually create negative effects and harm the C:N ratio in the soil and produce microbial imbalances. The seeding of legumes is a poor way to improve pastures and often makes them less productive.
These range of practices are a) limited and unrelated in any material way to AMP grazing, and 2) we already know there are WAY more acres where AMP can make a difference, across the world… including, again, the area we did our study, which is labeled as a 100% non-amenable region per this paper.
REMMELINK: Third, and most misleading, they leave out the fact that cows contribute to global warming by producing greenhouse gasses. –
BYCK: We ABSOLUTELY studied and communicated clearly in the series that cows emit methane and that farms emit nitrous oxide – THERE IS NO MISLEADING here as you claim – please see the GHG paragraphs at the top of this reply. We are very clear about the warming effects of methane and nitrous oxide from grazing farmland – and we show the cooling effects of the large C drawdown on that same land. In our study, the cooling of the C drawdown far eclipses the warming of the methane and nitrous oxide – AMP grazing produces a GHG sink when accounting for these 3 GHGs.
ALL ruminants emit methane as they digest their food. They always have and always will. If they failed to do so, they would die. So, we have had methane emissions by ruminants for eons. There were far more wild ruminants once roaming the earth than we have today. How would you rectify this? Where are the methane spikes in ice core samples from, as an example, 1491 and back? In addition, methane emissions in North America have increased in the past 4-5 years, while we are at record lows in cattle numbers. How can we have more methane from ruminants with fewer cattle? Look at the recent videos from NASA showing key sources of methane release in the US.
REMMELINK: Cows burp out methane (CH4), produced in their rumen when fermenting their food, and their manure releases nitrous oxide (N2O) as well as methane. While there’s debate on how to compare methane to carbon dioxide (it’s a more potent greenhouse gas but also stays in the atmosphere for a much shorter period of time), it’s not a gas that can be ignored. A 2023 Nature paper by Wang et al. (3) used a climate model instead of a conversion factor (i.e. GWP100 or GWP*) to compare ruminant emissions to the potential of grasslands to sequester carbon and found that carbon stocks in global grassland would have to increase by 135 gigatonnes (Gt) of C to offset the continuous methane and nitrous oxide emissions from the ruminant sector worldwide. This is nearly twice the current global carbon stock in managed grasslands and almost equal to all soil organic carbon (SOC) loss due to agriculture in the past 12000 years. Clearly, this seems unfeasible. –
BYCK: Please see the above paragraph that starts: “The issue of soil samples being only 30cm.” We believe this is a fatal weakness of the Nature paper you cite here (3) and by only using samples measuring 30cm in depth, instead at least a meter down, this paper is missing enormous amounts of both existing and potential soil C stocks worldwide.
REMMELINK: In the last episode, Jonathan, an agroecologist, mentions that ‘the potential for AMP generating positive results doesn’t asymptote out, it always keeps going up’, but he doesn’t give an explanation of what proves that and their study wasn’t set up to study this. –
BYCK: First, you didn’t include Jon’s first line on this: ‘There’s never been a perfect study that’s ever been conducted. Science is not black and white. Science is gray. But right now all signs are pointing to this works.’ Second, this is a montage of 3 well-regarded scientists giving their opinion of what they learned from the data – acknowledging that we do not yet know how much soil regeneration can be accomplished by AMP grazing, and regenerative agriculture.
REMMELINK: The team ignores the current scientific consensus that carbon levels in the soil plateau (3,6) and as Wang explains, it’s unrealistic to assume that we can undo all soil carbon losses that happened over centuries. –
BYCK: First, we do not ignore it – we see the science evolving. The study of necromass is relatively new (last 10-15 years), and the study of regenerative soil systems is woefully unrepresented in the literature. This is a new frontier. (Please see above paragraph starting with: “On the issue of soil C amounts reaching a plateau…”
And re: Wang et al’s “unrealistic” claim – we also disagree. Humans have done huge damage to the world’s soils – who’s to say we cannot repair these soils? We observe phenomenal things happening on regenerative farms across the world; we can see the land heal – grow much more forage, feed many more animals – and create havens for wildlife. We want to do more science, for sure. We consider our studied observations on these farms around the world as important data as well.
REMMELINK: Earlier in the year, Australia’s most known carbon-neutral beef farm reported it can no longer offset its own emissions. –
BYCK: In reading this Guardian article, it appears these cattle farmers were using eucalyptus plantations (which sounds like a mono-crop, but we’d need more info) as a large source of their carbon drawdown equation. We’d need to speak with the farmers to learn more about their grazing operation – and we would also like to learn more about the current massive droughts’ affects on this cattle station’s ecosystem.
REMMELINK: The movie does claim AMP grazing can lower methane emissions, with 10% for one of the farmers, however, even if this would be true for all the AMP farmers, this is still only 10%. –
BYCK: Context: this is clearly stated that the 10% refers only to the enteric emissions and not the soil or atmospheric methane measurements.
Here’s the dialogue – Peter Byck: “We have the methane going on your all’s property with Jason Rowntree. There’s 10% less methane coming out of your animals (AMP side) than coming out of your all’s animals (conventional side). So that could be a big deal when you’re talking about methane, you’re talking about greenhouse gases and things like that. So that was a real interesting just slice of information. We need to do more.”
REMMELINK: Also, other research finds no difference in greenhouse gas (CO2, CH4 and N2O) fluxes between AMP and conventionally grazed pairs of farms and explains the fluxes were regulated by specific conditions, such as prior cultivation history, cattle stocking rate, soil moisture content, and bulk density (7). –
BYCK: Thank you for bringing this paper to our attention. They are using in-ground chambers only, for only specific months of the growing season, over a 3 year period – but they have no data collected in the fall/winter/early spring months. We wonder if the accuracy of our eddy covariance flux towers, and the fact that we gathered samples every 30 seconds for 2 years would affect the vast difference in results re: GHG. We found that the full picture of the GHG flux wasn’t complete without this constant, year-round flux data to couple with the in-ground chambers and enteric measurements.
Also, it is questionable to use static chambers to try to quantify net ecosystem exchange (NEE). NEE is equal to gross primary productivity (GPP) minus ecosystem respiration (Re). But an in-ground soil chamber is just measuring Re. And indeed, in healthier soils Re can be (paradoxically to most) higher – exactly what they’re seeing here. But they’re blind to GPP (carbon uptake by photosynthesis), so are missing the bigger and more important variable – the chambers aren’t seeing the net uptake of C into plants before the C goes into soil. So, beyond the problem of not getting year-round data, they have the inherent limitation of relying solely on in-ground chambers. Flux towers are an essential tool to get the full GHG cycling picture of the whole ecosystem, not just a component.
Please note members of our science team advised the Alberta team during their methods development and had strong concerns about the specific selections of the ranches – that ranches this paper refers to as AMP were not practicing frequent, multi-paddock herd moves per the method’s definition.
Here’s a note from Steve Apfelbaum, one of our lead scientists, in thinking about the Alberta work’s chambers-only approach as compared to our Southeast US work with multiple measurements for all the GHG:
“I believe the SE work, including the additional and redundant testing of different flux tower units, and the green feed station measurements (enteric emissions) are exemplary and provide high confidence in our results because of the multiple levels of redundancy compared to most other GHG measurements I have read about. I also think David Johnson’s insitu soil respiration work is truly important and may provide some of the best soil respiration understandings I’ve seen in the literature (17). The alignment between bacterial biomass, soil respiration, and GHG measurement of photosynthesis, decomposition and microbial activity, as independent measurements all supported strong and compelling understandings of the individual measurements and was further supported by the vegetation and standing crop biomass methods. The additional work that Aerodyne did with us on some of the farms to understand nitrous oxide emissions, also added to the redundancy, calibration, and value of the work. I was strongly impressed with how well the various independent data sets robustly supported the overall conclusions reached by the effort.”
REMMELINK: There is no mention of this being studied by the scientists in the documentary –
BYCK: The conditions mentioned above (such as prior cultivation history, cattle stocking rate, soil moisture content, and bulk density) are all very clearly studied and written up in Mosier et al (18), our soil C and N paper. There is no way to include all of our science in the documentary series. It would be a snooze-fest.
REMMELINK: and the results of the flux experiments are not published by the group yet. –
BYCK: Correct – please see the GHG paragraphs at the top of this reply.
REMMELINK: Without detailed information on all the greenhouse gas emissions, it’s impossible to determine whether carbon sequestration can even offset the methane and nitrous oxide emissions of the animals in this movie, let alone offset all emissions by all cows on this planet if they would all be AMP grazing. –
Please see the GHG paragraphs at the top of this reply.
REMMELINK: Moreover, if you want to make statements about the carbon sequestration potential of changing to AMP grazing from conventional grazing, you need to study this change and you need to study the amount of C in the soil over time. –
BYCK: In our study, the conventional side acts as the control – and the AMP side is the change. Both sides had been practicing their grazing methods for at least 7 years, most more than that – which gives us the apples to apples comparison of grazing methods as both sides had the same soil type and same rainfall.
REMMELINK: The team has only published the carbon storage results (8). They’ve received critique on this paper that ‘no conclusions regarding the grazing management treatment effects on soils could be made’ and rebutted this by writing: “We presented the differences between grazing managements and across farm pairs, but we did not attempt to attribute those differences to greater SOC sequestration rates in a given management.” However, in the movie it’s all about soil organic carbon sequestration rates and attributing it to management. Again, without details on the flux experimental design and results it’s presumptuous to make strong claims about the climate mitigation potential of AMP grazing. –
BYCK: In the series, we make clear distinctions between Mosier et al being about soil C and N stocks, a snapshot in time – and the temporal data sets for flux (i.e. changes in stocks) from the GHG team’s work. The critique paper you refer to said our soil C and N paper claimed temporal data – which it did not. The temporal data is our GHG work, clearly stated in the first paragraphs of this reply.
REMMELINK: So when there’s debate on whether carbon sequestration can offset ruminant emissions, whether there is a maximum amount carbon the soil can store and we know that not all soils are the same or have the same potential, it seems audacious to claim AMP grazing can cut human emissions by a third. –
BYCK: Please see the paragraph above that starts with “We use Dr. Rattan Lal’s figures for the 3.5b hectares of grazing land” (16).
REMMELINK: “Roots so deep”
This documentary is all about AMP grazing; when to move your animals to the next section of the pasture to allow as much grass as possible to grow. But does that on its own lead to carbon being sequestered?
It does not. The beneficial effects of grazing management that are showcased in this documentary are not just the result of AMP grazing, but are also dependent on the diversity of plant species on the AMP fields. Plants with deeper roots than ‘standard’ grass. (It depends on the climate what the most common aka ‘standard’ grass species is). It’s these deep roots that make the soil sequester carbon longer term and they only do so if there’s sufficient nitrogen. Nitrogen fixing legumes can aid in getting nitrogen from the atmosphere into the soil and in this way promote soil carbon sequestration. Sowing legumes has about the same sequestration potential as optimizing grazing intensity (9) and it’s the presence of C4 grasses and legumes that increased the carbon capture rates on degraded agricultural lands (10). –
BYCK: This whole section feels like a strawman argument. Of course plants are integral – and plant biodiversity is a driver for microbial, insect and bird biodiversity. Please see our plant paper and our bug paper (19, 20). Our Bird paper is in the final stages of peer review and should be published soon. If I’m understanding your line of argument, you’re saying that the benefits of AMP grazing that we have measured and reported in our documentary cannot all be attributed to the grazing alone. We address the interconnectedness of our work many, many times in the series, starting with this narration 8 minutes into the first episode:
Narration: “Our research had one main goal: to measure how nature worked on grazing lands. It’s called system science. It’s about carbon in the soil for sure. We also wanted to measure the diversity of soil microbes and bugs and plants and birds, the amount of methane from the cows and their health, and how well the farmers were doing.”
AMP grazing is a system – it’s much more than frequent animal movement – it’s a way of interacting with an ecosystem – where the farmer learns about the animal impact on the whole system of insects, birds, water infiltration, microbes, animal health and the farmers’ pocket book. AMP grazing is the tool, and a key differentiator with conventional grazing – its benefits are all naturally interconnected, because nature is interconnected and these farmers are aiming to work with nature – not fight nature. It could well be called Observational Grazing.
The AMP grazers in this study, and the plethora of AMP grazers we know across the continent and around the world, aim for plant diversity – as much as possible. They all report seeing plants express themselves once they change to AMP grazing – where seeds have been dormant in their soils until they applied the animal impact found with AMP/regenerative grazing. They call it the latent seed bank. Some farmers add to this diversity by inter-seeding desired plants.
Our ecologist Steve Apfelbaum always points out to the AMP farmers that they could increase their deep-rooted native species as well. That many of these plants are growing in the ditches along the roads next to the farms. We were just in South Africa, and they also have native species growing in the ditches along the roads outside the ranches.
So – AMP grazing is a tool – and it inspires the farmers to begin a lifelong conversation with nature on their land.
REMMELINK: One farmer in the documentary mentioned he planted species like clover, a legume, and cereal rye by direct drilling them into his field. Another AMP farmer ‘thought the different seeds were there anyway, they just had to come back up’. However, that’s about the extent of the details given in the movie on the different plant species on each pasture. –
BYCK: We didn’t want to put every bit of the science into the documentary – please see the Plant paper for these details (19).
REMMELINK: Why put ‘roots’ in the title of your documentary but go in so little ‘depth’ on them? Why is there no single mention of the plant species on the pastures in the scientific papers that have come out of this project? –
BYCK: Not accurate – see the Plant paper (19).
REMMELINK: You can’t attribute superior carbon storage to just grazing management without considering the plants that are required for this storage. –
BYCK: We do consider the plants – the diversity of the plants – the interaction of those plants with the insects and the insects’ increased diversity and balance of species – the ability of the plant roots to aid water infiltration – the ability of those plants to increase microbial abundance and activity.
REMMELINK: Establishing different legumes and perennials among ‘standard’ grass isn’t as easy and straightforward as the movie wants to make it look, at least not in more moderate climates like the UK. –
BYCK: What do you mean by “standard”? We don’t hide the challenges of farming in our film, or our research. Many farmers who’ve seen our series call out that fact – that they appreciate our not sugar-coating the challenges. That said, all of our AMP farmers say the management is very easy to do.
REMMELINK: You need to sow the right mix at the right time and carefully manage grazing to prevent weeds from coming and legumes need to be introduced steadily to prevent bloat, the build up of gas in the rumen, which can kill the animals. But more importantly, grassland that has been grassland for a long time, also called permanent grassland, shouldn’t be broken up because this will release carbon. –
BYCK: This is exactly why this section of your critique feels like a strawman – you’re bringing up so many things that we don’t propose – we absolutely agree that never-plowed grasslands should never be broken up – no one in our study is breaking up unplowed ground. Unfortunately, in the Southeast US – there is virtually no ground that hasn’t been plowed.
REMMELINK: The mention of ‘harrow to fine tilth’ in this ‘How to guide’ does not inspire confidence that C isn’t lost when farmers try to establish diverse pastures for AMP grazing. –
BYCK: No AMP farmer in our study, nor any of the 100s of AMP farmers we know would dream of harrowing to a fine tilth – I’m not sure, again, why you’re conflating AMP with plowing.
REMMELINK: Besides the lack of detail on grass species, there’s more that isn’t mentioned. To propose AMP grazing as THE way to use the land for climate mitigation, you need to study the alternative solutions and determine they are not as effective. –
BYCK: We say, very clearly in the 1st minute of the series that we are studying AMP grazing to see if it is “A” solution. We never say, or imply, it’s THE solution, ever. We are open to every solution out there – it’s just that, to date, from our research, this is the best way to rebuild soil that we’ve found. What are the other ways? Where are they? What have you found?
Dr. Greg Retallack, a prominent paleo soil scientist at the University of Oregon, has proposed that ruminant animals (like cattle) and grasslands have been working in tandem as an “engine for global cooling” for roughly 30 million of years due to the co-evolution of ruminants and grasses and the signature that left in ancient soils (ref: Retallack, 2013) (21). AMP grazing simply tries to mimic the dynamics of these natural ecosystems in Earth’s deep history. Retallack concludes: “Future global warming may be mitigated by commercial carbon farming using such techniques as new grass varieties, cell grazing, natural sequence farming, stubble burning, and pasture cropping” and our project’s results are consistent with that hypothesis.
REMMELINK: This team has not studied the effects of rewilding or reforesting the land, while reforestation is considered the natural climate solution with most potential (9). –
BYCK: All the farmers in our study know the value of trees (nutrient benefits, wind breaks for animals, beauty, homes for many wild animals and insects, erosion protection and more) and many plant consistently; wishing they had started decades ago. As for re-wilding, we consider birds as an indicator species for wildlife health. Our data shows the AMP farms are havens for grassland birds, many of which are endangered – they thrive on the AMP farms and are dying off on the neighbors’ farms across the fence. We measured the increased wildlife populations on the AMP farms – birds, insects, microbes – and the AMP farmers tell us their observations of mammal population increases as well.
REMMELINK: Interestingly, the subtitle of the movie “you can see the devil down there” refers to the roots of a tree. It seems like they are aware that trees are great for the soil and the climate, so why did they not study a field that’s been reforested? A paper from last year that assessed the carbon opportunity costs – the potential carbon sequestration that could occur on land if it were not used for production – in addition to beef production emissions and carbon sequestration potential from grazing, found that pasture-finished operations have a higher carbon footprint than grain-finished systems (11). So it turns out it’s very relevant to take into account that AMP grazing requires a lot of land and that this land can be used differently. The team also did not study the carbon sequestration potential of mixed farming where there’s both crops and animals grown on the farm. Basically, they did not study any forms of agriculture or land use that would reduce the number of ruminants. –
BYCK: This was a grazing study – very specific – very focused – very rigorous. It took us a decade to get this designed, funded and executed – and I’ve clearly mentioned we’re still in the peer-review process for some of the research. This complaint of what we didn’t study just shows the need for more research. We would love to study the folks who are stacking enterprises – growing many species of animals, with row crops and cover crops – this is important research that needs to be carried out.
Regarding opportunity costs – we look at it this way: What is the highest and best use of an acre of land to maximize the capture of incoming solar energy? Most US ranchland is a grassland, and it would be ecologically foolish to plant a forest on it, just as it would be foolish to cut down a forest to plant a grassland.
We can see the industrial approach of both the beef industry (not to mention poultry and pork) and the row crop industry are extractive and soil destroying. So we are interested in any food production method that creates soil health. Soil health is our north star as we look to share our research with farmers, and help all that want to adopt regenerative methods.
REMMELINK: Perhaps this is explained by who provided the money for this movie?
“I said to McDonalds I think we can make your main product, the hamburger, a health food”
A large part of the funding for this documentary and its research comes from McDonalds. –
BYCK: McDonald’s is our largest funder – $3.75m. The project cost $10m. All of the funding history is published on our site (22).
REMMELINK: In episode 3, Jonathan expresses his discomfort with this. –
BYCK: You should mention that you edited this section of dialogue between Jon and Peter.
REMMELINK: Jonathan: I’ve had long discussions about this issue, but almost everybody said: “Take this money and use it for good”. I hate having to take this money. I just know the end of the story.
Peter: You know the end of a story. We have to write a new one. I like taking the money from the corporations because my hope is that we affect them from the inside. I said to McDonalds I think we can make your main product, the hamburger, a health food. I think we can really affect climate change in a positive way in the doing of that. Not one of our funders has come in to ask “can you tweak this, can you change that”.
Jonathan: They haven’t needed to yet.
Peter: Well they haven’t changed how we’re doing it. The next step is, are they gonna change how we publish it. So right now they can’t. –
BYCK: You’ve chosen not to quote the narration that helps set up the scene with Peter and Jon.
Narration: “I knew people would dismiss our science out of hand because they would say a hamburger company is just paying for science that will prove it doesn’t have to change. That it was looking for an easy way out. My thoughts on that. If AMP proved to be great for farmers and the planet, then McDonald’s will have paid for its own intervention. Will have bought a ticket to its own hard way in. They will have funded the proof that they must help all their cattle farmers change. That did not sound easy to me.”
REMMELINK: But do they need to as long as nobody in this research or documentary is telling anybody to eat fewer hamburgers? Does McDonalds not just love all the good press beef is getting through this movie? There is absolutely no mention of changing our diets and consuming less meat in any of the episodes. –
BYCK: On this last point on diet, correct. Our data suggests that AMP-grazed cattle creates a GHG sink. And as you state below, very little beef in the US is produced regeneratively. We are not spokespeople for any of our funders – we spent years writing a proposal for a rigorous study comparing AMP and conventional grazing, and a small number of the funders we approached chose to fund the work. Re: classifying regeneratively produced beef as a health food, please see Dr. Stephan van Vliet’s work on nutrient density of beef – and his comparisons between regeneratively produced and feedlot produced beef (23). We have no agenda on whether people should or should not eat meat. Regeneratively-produced meat could be essential for some peoples’ health, while for others, maybe not.
REMMELINK: 70% of cows in the US are industrially farmed, where they don’t have access to a field where they can graze and are crammed together. That means we need to think about how to transition from CAFO’s (concentrated animal feeding operation) to grazing instead of focusing on the ~25% of cows that are currently conventionally grazing. And, more importantly, we need to calculate how much meat we can sustainably consume if we do so. –
BYCK: Per this link you’ve cited above (70% of cows) – it says the following of it calculated this %: “These estimates use the number of animals per farm as the best available proxy for whether the farm is a CAFO with the following premises: (1) All Large sized farms are CAFOs, (2) all Medium sized farms are CAFOs, and (3) for birds, the largest three quarters of Small sized farms are CAFOs, (4) for mammals, the largest half of Small sized farms are CAFOs, and (5) farms are evenly distributed among sizes within each range.”
This is absolutely false. We have very large ranches that have zero animals in a CAFO and those ranches are NOT classified as CAFO operations. If the cattle are on pasture, whether it be a large, medium or small operation, it is not a CAFO system. It seems it would be more accurate if they actually counted animals in the CAFOs. Conflating farms and ranches with CAFOs is not the truth on the ground.
REMMELINK: McDonalds started talking about sourcing “verifiable, sustainable beef” 10 years ago, but their scope 3 greenhouse gas emissions, the scope that encompasses on-farm emissions, have even slightly gone up since 2018. According to Jennifer Molidor, senior food campaigner at the Center for Biological Diversity, ‘there’s no such thing as sustainable beef at current rates of consumption and production.’ The planetary health diet proposes getting just 0.6% of calories per day from red meat, about 6 times less than the current rate of consumption in the US and 2 times less than in the Netherlands. Also, besides a climate concern, beef is considered a health concern. Not mentioning we need to reduce beef consumption is hampering progress towards a sustainable world, but saying it can be a ‘health food’ is ‘sickening’. –
BYCK: Again, re: health of regeneratively produced beef, please see Dr. Stephan van Vliet’s work (11).
REMMELINK: Grazed and misleading
Grazed and Confused (12), –
BYCK: Not a peer-reviewed paper, but wonderfully titled.
REMMELINK: a 2017 report exploring the role of grazing ruminants in climate change, stated: “Regenerative grazing, applied well and by motivated farmers, could well benefit soils, build organic carbon matter and as such perhaps help sequester some carbon. However the overall gains are likely to be modest, are not exclusive to rotational practices, and will be time limited – and the problem of the other greenhouse gasses, methane and nitrous oxide – do not go away. There is an important difference between arguing that good adaptive management can improve soil quality and increase soil organic matter – and concluding that it offers the solution to our climate crisis.”
We should acknowledge that AMP grazing in combination with diversifying the species on pastures has many benefits (e.g. improving water retention, biodiversity and grassland productivity) but claiming it can mitigate climate change can be dangerously misleading and might move us further away from taking the essential step: consuming less meat. –
BYCK: If concern about climate change is paramount, the data from our research could be received as good news – and cause for inspiring more research on AMP grazing around the world. We are showing, at least in one large region, AMP grazing is a GHG sink – 12.1t CO2e/ha/yr – we are also surprised that conventional grazing is a GHG sink, at 2.9t CO2e/ha/yr.
In regards to taking an essential step for mitigating climate change – we hope you are also looking at row crop production and the massive amount of soil carbon loss, wildlife deaths (birds, bugs, mammals of all sizes) and causes of flooding created by those industrial systems.
IF we want to significantly improve our environment, climate, soil health, biodiversity, and human health, then we must stop eating industrially-produced plant-based food – 95% of all plant-based food is industrial. The highest soil temps we have measured are not from pastures but from cropland and orchards/vineyards. The most degraded soils are not from pastures, but from cropland and orchards and vineyards. The greatest loss of topsoil and leaching of nitrates and phosphates is not from pastures, but from cropland. The billions of bare and exposed acres around the globe (for 2/3rds of the year) are not pastures but cropland soils.
Again, soil health is our north star. Ruminants and grasslands have had millions of years of R&D together, evolving together, creating incredibly vibrant habitats for wildlife by building the world’s best soils. Soils that are teeming with microbes that bring otherwise unavailable nutrients from the soil to the plants, producing nutrient-dense vegetables, fruits, nuts, legumes and meats.
AMP/regenerative grazing is a tool to rebuild our soils. Healthy soils work for everyone’s benefit.
We are always available for more discussion if you would like.
—–
This documentary was screened for the first time in mainland Europe in June, followed by a Q&A session with its director, Peter Byck. The event was organized by the crew behind Investing in Regenerative Agriculture and Food. Watching the full documentary is now also possible in the UK, Ireland and South Africa, in addition to the USA and Canada, by renting the episodes via the movie website.
ESTHER REMMELINK’S REFERENCES:
1. Stanley, P. L., Wilson, C., Patterson, E., Machmuller, M. B. & Cotrufo, M. F. Ruminating on soil carbon: Applying current understanding to inform grazing management. Glob. Chang. Biol.30, e17223 (2024).
2. Bai, Y. & Cotrufo, M. F. Grassland soil carbon sequestration: Current understanding, challenges, and solutions. Science377, 603–608 (2022).
3. Wang, Y. et al. Risk to rely on soil carbon sequestration to offset global ruminant emissions. Nat. Commun.14, 7625 (2023).
4. Bai, Y. & Cotrufo, M. F. Grassland soil carbon sequestration: Current understanding, challenges, and solutions. Science 377, 603–608 (2022).
5. Henderson, B. B. et al. Greenhouse gas mitigation potential of the world’s grazing lands: Modeling soil carbon and nitrogen fluxes of mitigation practices. Agric., Ecosyst. Environ.207, 91–100 (2015).
6. Smith, P. Do grasslands act as a perpetual sink for carbon? Glob. Chang. Biol. 20, 2708–2711 (2014).
7. Ma, Z. et al. Soil greenhouse gas emissions and grazing management in northern temperate grasslands. Sci. Total Environ.796, 148975 (2021).
8. Mosier, S. et al. Adaptive multi-paddock grazing enhances soil carbon and nitrogen stocks and stabilization through mineral association in southeastern U.S. grazing lands. J. Environ. Manag.288, 112409 (2021).
9. Griscom, B. W. et al. Natural climate solutions. Proc. Natl. Acad. Sci.114, 11645–11650 (2017).
10. Yang, Y., Tilman, D., Furey, G. & Lehman, C. Soil carbon sequestration accelerated by restoration of grassland biodiversity. Nat. Commun. 10, 718 (2019).
11. Blaustein-Rejto, D., Soltis, N. & Blomqvist, L. Carbon opportunity cost increases carbon footprint advantage of grain-finished beef. PLoS ONE (2023).
12. Garnett, T. et al. Grazed and Confused.
ROOTS SO DEEP REPLY REFERENCES:
13. “Published Research”. Roots So Deep. (2023). https://rootssodeep.org/amp-research/published-research
14. Dietz, C.L., Jackson, R.D., Ruark, M.D. et al. (2024). Soil carbon maintained by perennial grasslands over 30 years but lost in field crop systems in a temperate Mollisol. Commun Earth Environ 5, 360. https://doi.org/10.1038/s43247-024-01500-w
15. White, L. J., Yeater, K. M., & Lehman, R. M. (2023). Soil microorganisms respond distinctively to adaptive multi-paddock and conventional grazing in the southeastern United States. Soil Science Society of America Journal, 1–13. https://doi.org/10.1002/saj2.20573
16. Lal, R. (2022, January 20). Soil Health and Global Agricultural Productivity: Virginia tech cals global. Global Agricultural Productivity. https://globalagriculturalproductivity.org/soil-health-and-global-agricultural-productivity/
17. Johnson DC, Teague R, Apfelbaum S, Thompson R, Byck P. (2022). Adaptive multi-paddock grazing management’s influence on soil food web community structure for: increasing pasture forage production, soil organic carbon, and reducing soil res- piration rates in southeastern USA ranches. PeerJ 10:e13750 http://doi.org/10.7717/peerj.13750
18. Mosier, S., Apfelbaum, S., Byck, P., Calderon, F., Teague, R., Thompson, R., & Cotrufo, M. F. (2021). Adaptive multi-paddock grazing enhances soil carbon and nitrogen stocks and stabilization through mineral association in Southeastern U.S. Grazing Lands. Journal of Environmental Management, 288, 112409. https://doi.org/10.1016/j.jenvman.2021.112409
19. Apfelbaum, S. I., Thompson, R., Wang, F., Mosier, S., Teague, R., & Byck, P. (2022). Vegetation, water infiltration, and soil carbon response to adaptive multi-paddock and conventional grazing in southeastern USA ranches. Journal of Environmental Management, 308, 114576. https://doi.org/10.1016/j.jenvman.2022.114576
20. Schmid, R. B., Welch, K. D., Teague, R., & Lundgren, J. G. (2024). Adaptive Multipaddock (AMP) pasture management increases arthropod community guild diversity without increasing pests. Rangeland Ecology & Management, 94, 141–148. https://doi.org/10.1016/j.rama.2024.03.001
21. Retallack, G. J. (2013). Global cooling by grassland soils of the geological past and near future. Annual Review of Earth and Planetary Sciences, 41(1), 69–86. https://doi.org/10.1146/annurev-earth-050212-124001
22. “Funding sources for research and documentary”. Roots So Deep. (2023). https://rootssodeep.org/amp-research/funding-sources-for-research-and-documentary
23. Van Vliet, S. The Van Vliet Lab. https://stephanvanvliet.com/
Reproduced from LinkedIn with kind permission.