- Slides: 72
Grazed and confused? Ruminating on cattle, grazing systems, methane, nitrous oxide, the soil carbon sequestration question – and what it all means for greenhouse gas emissions Tara Garnett*, Cécile Godde*, Adrian Muller, Elin Röös, Pete Smith, Imke de Boer, Erasmus zu Ermgassen, Mario Herrero, Corina van Middelaar, Christian Schader, Hannah van Zanten Food Climate Research Network – University of Oxford Eating Better meeting - 27 November 2017
Why did we do this research? What did we find? What are our frustrations with the way it’s been (mis)interpreted?
4. 2 mill views
We asked these questions: Can we (grassfed) eat our way out of the climate problem? Isn’t soy for pigs, poultry and vegans really driving land use change? Can cattle grazed right sequester carbon? What is the role of grazing ruminants in the net GHG balance? Doesn’t their dung help fertilise the soil? Can they sequester more than they emit? Is methane really a problem?
Nutritional qualities of grass fed Jobs, livelihoods & traditions Biodiversity and grazing systems We DIDN’T ask these ones Water use & impacts Zoonotic disease & other risks Animal welfare?
And we DON’T COMPARE grassfed vs intensive This is a really important point!!!!!!!! And the source of a lot of misinterpretation
And btw… we’re not in the pay of Monsanto https: //www. alternet. org/food/universityoxford-has-disturbingly -cozy-connectionmonsanto:
How & who? • How? Extensive literature review (academic & non academic). 2 years. • Who? Researchers from University of Oxford (Food Climate Research Network) University of Cambridge University of Aberdeen Commonwealth Scientific & Industrial Research Organisation (CSIRO), Australia Centre for Organic Food and Farming (EPOK), the Swedish University of Agricultural Sciences (SLU) • Research Institute of Organic Agriculture (Fi. BL) in Switzerland • Wageningen University • • • Mixture of: soil scientists, LCA people, land use modellers, livestock scientists, organic food systems researchers, and generalists
Grassfed & climate change Source or salvation? First we tried to define the bones of the dispute AS IT RELATES TO CLIMATE
Balance of GHG emissions vs removals Controversies over the other GHGs Argument Counterargument Ruminants generate high Good management – sequesters carbon in grasslands – GHG emissions – especially partially or entirely compensates for emissions methane and nitrous oxide Methane & nitrous oxide are very potent GHGs Methane has a short life span. CO 2 from burning fossil fuels is more important – intensive systems more culpable here Historically wild ruminants roamed on many grasslands, producing CH 4. Livestock recycle nitrogen and make it more available for plants to take up, fostering new plant growth. Land use change & Ruminants use lots of land Many grasslands are the natural climax vegetation and the CO 2 implications have historically driven not suited to cropping. deforestation. Crop production - for human food &intensive animal feed - increasingly drives land use change, & encroaches onto carbon-storing pastures.
But first… What is ‘grassfed’? What are grasslands?
What’s grassfed beef from a grazing system? • Hard to define! • FAO definition: the animals get most of their feed from grass. BUT • This varies over life course • The grass may ben ‘improved’ – i. e. fertilised & pretty monocultural • In mixed systems animals eat grass but also byproducts & sometimes grains • No official certifications - informal certifications vary in stringency
Important points to remember • NB: this was a GLOBAL study (i. e. not UK; not a particular farm X or farm Y managed by farmer Z). • There is HUGE variation (of which more later) – ‘grassfed’ encompasses the good, the bad & the ugly • We don’t know v accurately how much grassland we actually have (affects the estimates for any sequestration potential) • Grass = 20 -47% earth’s surface • 26%? grazing (pastures & rangelands) compared with 12% for crops • Many grasslands were once forest • We could use some of it for something else (arable; nature conservation; bioenergy) with diff implications for a. carbon; b. biodiversity; c. food & d. jobs (more later)
Grass-only systems don’t contribute much food** ** although high localised importance ** they could produce more ** more still when byproducts & residues are considered (more later) For year 2013 - FAO (2016). FAOSTAT [online]. http: //www. fao. org/faostat/en/#data/FBS
Dispute 1: The balance of GHG emissions vs removals Do ‘grassfed’ animals sequester more than they emit?
How do ruminants contribute to the climate problem? Data used in G&C report 7. 1 GT CO 2 eq Gerber, P. J. , Steinfeld, H. , Henderson, B. , Mottet, A. , Opio, C. , Dijkman, J. , Falcucci, A. and Tempio, G. (2013). Tackling climate change through livestock – A global assessment of emissions and mitigation opportunities. FAO, Rome
Some updated figures New FAO data (2010 ref period) • Livestock 8. 1 GT CO 2 eq* • Ruminants 5. 9 GT CO 2 eq (78%) • Monogastrics 1. 65 GT CO 2 eq Old FAO data (2005 ref period) • Livestock 7. 1 GT CO 2 eq • Ruminants 6. 2 (82%) GT CO 2 eq • Monogastrics 1. 35 GT CO 2 eq • Overall output up by 12% - ruminants slight decline so all from monogastrics • Ruminants’ share protein total: 55% • Ruminants’ share protein total: 49% • Monogastrics’ share protein total: 51% 45% • Emissions intensities fallen all species http: //www. fao. org/gleam/results/en/ Emissions growth driven by monogastrics … … but what wd the growth have been if driven by ruminants?
(How) do ruminants help reduce GHG emissions via soil carbon sequestration? • There are many ways of sequestering carbon • They don’t all involve an animal • E. g. afforestation, rewilding, conservation agriculture • All come with cost and benefits
How does soil carbon sequestration work? • Growing plants take carbon out of the atmosphere • Plants die AND • IF plant matter (roots and shoots) is buried • And IF left undisturbed • And IF climatic, soil & other conditions are right • The carbon converts into more stable forms = removal of carbon from the atmosphere
How do animals help? • Their nibbling stimulates plant growth… • …Can cause them to put down deeper roots • i. e. carbon containing biomass • Their manure moves nitrogen & carbon already in the eaten plants into the soil • BUT soil & climate conditions need to be right A few variables…
Agro-ecological factors Climate, rainfall, landscape & elevation Variables that have an effect on soil carbon stores and sequestration rates • • Temperature, rainfall, extreme weather events (e. g. drought), seasonal fluctuations Slope of land Fire risk Increased atmospheric CO 2 (CO 2 fertilisation effect) Soil type & quality • • • Soil type and texture Current soil carbon stock Starting conditions – degraded or in carbon equilibrium Drainage qualities & p. H level Presence or absence of earthworms, fungi, microbes etc. Organic matter input Nitrogen and phosphorus inputs & levels Atmospheric N deposition effects Native plant & animal species composition • • Presence of legumes Whether species have C 3 or C 4 photosynthetic pathways (affects what happens to their root structures when animals graze them). Baseline climax vegetation (might afforestation be a better option? ) Presence of wild herbivores and whether they compete for food or water Land area available • • Animal numbers/ha/yr. Animal type or species mix (influences grazing and trampling patterns). Timing of grazing. Goal: mgt for biodiversity, for sequestration, for livestock productivity or for profit. Feed supplementation or housing? and housing.
Soils stop sequestering carbon after a while Also problems of reversibility –by humans or changing climate
Historically both arable & grazing have a terrible track record Sanderman, J. , Hengl, T. , & Fiske, G. J. (2017). • • • Higher percent SOC losses on cropland But more than 2 X more land is grazed so slightly higher total losses from grazing land. Hotspots of SOC loss coincided with some major cropping regions as well as semiarid grazing regions Other major agricultural zones showed small losses and even net gains in SOC. There are identifiable regions which can be targeted for SOC restoration efforts.
Estimates of the grazing potential vary ‘Savory’ style claims much higher than academic estimates
The higher the stocking rate, the higher the sequestration needs to be to counter the methane emissions More animals / ha; assume lower sequestration rate Few animals/ha ; assume high sequestration rate NB: these are modelled relationships Nitrous oxide emissions not included
How do some of the ‘carbon ranching’ type claims come up with such high estimates? The example of Allan Savory: • Takes a high end estimate of overall (uncertain) grazing land area Takes a very high estimate of annual sequestration rates • Rolls these out globally regardless of climate, soils, etc. • Assumes these very high rates can continue for 40 years • Doesn’t factor in the animals’ emissions
The sequestration potential, the emissions… and where we need to be
This is not going to be easy
Dispute 2: Methane & nitrous oxide
Does methane matter?
Carbon dioxide Yes Different scales Methane
Some additional thoughts • Addressing methane without addressing CO 2 is a waste of time • But the closer we get to decarbonisation, the relatively more important methane becomes • Need to address consumption patterns now… bec v long lead times. . • Livestock’s most enduring climate impacts via LU and LUC. . Of which more later
Some important info about nitrogen Grass needs nitrogen to grow… so The sequestration potential is limited by nitrogen availability All nitrogen sources (fertilisers, legumes, manure) lead to N 2 O emissions Manure adds NO NEW nitrogen to the system – it (usefully) redistributes what’s already in the grass either on or off site (in which case lots of land needs to be available. . • Therefore: • • • There are trade offs between carbon sequestration and nitrous oxide emissions • Manure can be a source of nitrous oxide … • In a land limited world there isn’t enough manure to meet our fertiliser needs AND CARRY ON CONSUMING THE WAY WE DO
Dispute 3 The land use change question Isn’t soy now the problem?
What has historically caused land use change? • Many grasslands were once forest • Ruminants have historically driven deforestation • Directly: clearing forest for pasture • Indirectly: clearing forest & Cerrado for feed grains & soy • Causing CO 2 to be released (trees burnt; pastures ploughed up)
Area proportion of deforestation driver in some countries of South America from 1990 to 2005 (%) De Sy et al. 2015
There are new threats now • Cereal & oilseed production for intensive pigs, poultry & ruminants (beef & milk) • But grazing ruminants remain a problem • Land use change • Grazing land intensification
Fig shows the area devoted to cropland (left) and pasture (right) in 2013 (hectares in boxes), & what the vegetation cover on this land was in 2001. i. e. it shows what the crop and pasture land in 2013 was taken from based on the situation in 2001. e. g. top bar, the Latin American average, shows that most new cropland in 2013 came from pasture, although a small proportion was from forest or shrub land. Most new pasture land was from forest, with a small proportion from what was originally cropland, or from shrub. The overall pasture area is over three times larger than that of crops – so the impact is significant.
New FAO assessment BUT doesn’t include soil carbon losses from: • Pasture → arable conversion • Soil degradation in arable & pasture lands • Why not? Actually really hard to do – land goes bk and forth between uses. Attribution of responsibility?
Future trends in land use depend on various factors
Factors influencing arable land demand Higher demand for arable land Lower demand for arable land • High meat demand • More intensive (grain demanding) production systems (beef, milk, pork, poultry) • Lower levels of yield improvements • Less productive animals • Absence of land use controls • More biofuels and BECCS • Low meat demand • More grass based systems (but see next slide) • Higher levels of animal and crop productivity • More productive animals • Land use controls • Fewer biofuels and BECCs
Factors influencing grassland demand Higher demand for grassland Lower demand for grassland • Higher demand for ruminant products • Lower demand for ruminant products (beef, sheep meat, milk, etc) • Less productive animals • More productive animals • Higher demand for bioenergy • Lower demand for bioenergy production on grassland
The future is (obviously) uncertain Alexander et al. 2017
Impacts of diff livestock types on LUC if demand for ASF increases
Priorities are to • Halt deforestation • Halt further soil carbon losses by: • No more natural land to agriculture • No more pasture to arable • Farming in ways that maintain soil carbon • Build soil carbon where possible & where in line with other environmental goals
‘What if? ’
A ‘livestock on leftovers’ scenario • What if we… • Confined production to land unsuited to cropping • Plus byproducts • Plus food waste • How much would we get to eat?
We reviewed 3 studies which varied in: • Assumed grazing productivity • Human diets (e. g. projected or healthy – dictates quantity & type of agri byproducts available • Whether waste is fed (e. g. legality) • Success in meeting SDG on food waste reduction • Decisions to direct feed into ruminants vs into pigs • Whether supplementary grains were fed to maintain nutritional balance (pigs)
How much would we get to eat? grams animal protein / person /day 70 60 * ‘leftovers’ differ between studies: all include pastures and byproducts; most include food waste at differing levels; highest estimate includes some human-edible grain fed to pigs 57 50 40 27 30 21. 5 20 10 0 31 13 Ruminant products from pastures & byproducts All animal products from 'leftovers'* Current global average animal Projected global average animal Current high income animal protein in 2050 protein max min average From grassland only: ~ 7 g protein (better than current)
What is 21 g animal protein? • Approx 100 g of raw bonefree meat/person/day (about 65 -80 g cooked) but no milk • or 50 g of meat & 300 ml of milk • or 300 ml milk & 50 g cheddar • etc • BEFORE allowing for losses and waste.
For comparison. . We would need to reduce by more than half
Plus some important caveats • Grasslands aren’t ‘leftovers’!! • There are often alternative possible uses… • …with environmental & other costs and benefits • Improving grazing system productivity optimising grazing for sequestration • Optimising grazing system productivity optimising grazing for biodiversity
What if we got rid of more intensive systems, switched to grassfed … but KEPT current trajectories of demand? • Disaster! LUC & deforestation • So impossible to talk about ‘better’ without talking about ‘less’ (which you know)
We have choices Different costs and benefits How we juggle depends on our values And our assessment of what the counterfactuals might be
More arable land; more rewilding poss more fertilisers (but what if we dcarbonised? ) More fossil fuel use, more rewilding… but if we decarbonised? Possible livestock futures – what does ‘good’ look like? *** Less arable land, more pasture land, more methane… what if we didn’t curb demand? Overgrazing? More fossil fuel use, more arable land use, but more pasture land sparing. . And what if we decarbonised? ***Environmentally speaking 56
Some livestock futures: implications for land use Technically – but would be a bad idea Röös E, Bajželj B, Smith P, Patel M, Little D and Garnett T (2016). Protein futures for Western Europe: potential land use and climate impacts in 2050. Reg Environ Change
And GHG emissions
My personal ‘what if? ’ question What if…. We adopted a biodiversity first approach? • Which grassland best left to rewild? • Which grasslands best to be reared with animals? • How much grassland ok for grazing? • How much animal protein would you get? • What would be the implications for food availability? • What compromises might need to be made? • Other things we might need to do with the land (BECCS)
A quote from the report: Land constraints and population growth mean we can no longer rear animals in traditional ways while also continuing to fulfil an ever-growing demand for animal products. That reality has triggered the development of new production systems that may be more environmentally efficient in some respects but that also generate a whole new set of problems…. it does not follow that intensive production systems offer a better alternative. The shift to intensification changes the nature of the problems, and by some measures, makes things worse.
To summarise • • We have limited land… and many environmental problems We need to halt land conversion & stop destroying species We need to feed ourselves effectively (nutritiously) • What’s the ‘least bad’ way of using land?
Understanding the role of grazing is needed to help answer this question • Lots of environmental & non environmental considerations • We looked just at climate change • And we didn’t compare across systems
Some conclusions • Current trends in meat & dairy demand (all kinds, all systems) are not sustainable • Current consumption patterns and also switching to grassfed would be catastrophic • Intensive production generates its own problems & is not a solution • ‘Livestock on leftovers’ (requiring reduced consumption) might be an option, but with trade offs – and GHG emissions will still be high • High consumers need to cut back on meat - of all types • & dairy products
The terrifying power of dichotomous thinking • ‘If grassfed aren’t the solution…* • …Then somehow we’re in favour of intensive monogastric production. *and we didn’t ask what ‘the solution’ was… we only looked at the GHG balance
My personal view • Getting land use right is at least as important for food as GHGs • Biodiversity of paramount importance • What ‘getting land use right’ means requires exploration of lots of counterfactuals & a genuinely open mind
Read the report at: www. fcrn. org. uk/projects/grazed-and-confused Thank you taragarnett@fcrn. org. uk
Using GTP Persson M et al 2015 Environ. Res. Lett. 10 034005
Some reminders What this report looked at • “The purpose of this report is to investigate …the role of ruminants in grazing systems in the net GHG balance. Do ‘grassfed’ systems hold potential to help address our climate problems, or is their overall contribution damaging? There are of course many other ethical, nutritional and livelihood related arguments that can and should be explored to gain understanding of the benefits and costs of grazing systems (see Box 2), but this report limits itself just to the question of GHG emissionsand removals since the climate question is central to discussions on the sustainability of food systems – and complex enough as it is
Framing conditions You eat very little – i. e. you’re not driving a marginal increase in demand leading to increase in production Decision to eat grassfed ( for climate) You know exactly how it’s been produced – inputs, stocking rate, mgt The land being used wouldn’t be better off rewilded*