Apr 22, 2016

Ruminant livestock and greenhouse gases

By Alan Broughton 

Within the climate change action movement there is a stream that places priority on reduction in livestock numbers as the key strategy to reduce greenhouse gases. I believe this is mistaken. The choice to not eat meat or other animal products should be regarded as a personal choice, not an ecological choice. There is no ecological justification for advocating a drastic reduction in livestock numbers as part of climate change mitigation. Efforts would be better spent in focusing on the real issues: energy generation, transport and the sustainability of farming systems. 

Livestock production can become an effective carbon sink with great potential to modify the greenhouse gas effect. The obstacle is not livestock but how the animals are managed. This essay addresses the ability of well managed grasslands to sequester the methane produced by grazing ruminant animals and some of the carbon dioxide in the atmosphere produced by industry. 

Livestock greenhouse gas contributions

The anti-livestock arguments cover the following issues (Mahony 2013, Earth to Philly 2012, Goodland & Anhang 2009, Russell 2015 and 2016, and the movie Cowspiracy): livestock contribute 51% of greenhouse gases, greenhouse gas accounting systems vastly underestimate the contribution of livestock, holistic grazing management as advocated by the Savory Institute is no better than other forms of grazing, and land used for livestock should be converted to forest and biofuel production. In the background lies the vegan belief that humans should not use animals for any purpose and that eating meat and other animal products is unnecessary. 

There are many estimates of the contribution of livestock to greenhouse gases. A commonly quoted figure is 18% (FAO, 2006, in Steinfeld Livestock’s Long Shadow). In a subsequent report the FAO reduced the estimate to 14.5% (Gerber, Tackling Climate Change Through Livestock, 2013). The 51% figure used by the anti-livestock lobby includes livestock respiration of carbon dioxide which most other researchers see as illegitimate (Fairlie 2010, Herrero 2011), savannah burning and foregone forestation. For a brief critique of the 51% figure from a vegan perspective see Chivers (2016). Ripple (2014) uses the lower FAO figure of 14.5% but also finds that livestock numbers need to be greatly reduced. 

Fairlie (2010) analysed the 18% figure and concluded that it was actually much lower. The FAO assumed that land clearing in Brazil would continue at its 2004 rate of 2.7 million ha/year, whereas it had reduced to 0.7 million by 2008. The FAO also assumed that all this land clearing was done for cattle raising, but much has been for biofuel production, though cattle were used initially to help prepare the ground for cultivation. The rate of clearing fell consistently from 2004 to 2008 while the number of cattle remained the same (Pinjuv 2011). The FAO also allocated a large proportion of livestock related greenhouse gases to nitrous oxide release from fertilisers, but admitted there would be extra nitrate fertiliser use if livestock land was converted to cropping to provide the food deficit that reduced livestock would cause. Therefore, Fairlie (2010) concluded, the true figure for livestock contribution was no more than 9.6%, and the ruminant methane component about 5%. 

The World Resources Institute in 2005 provided the following figures for human caused greenhouse gas emissions (from Fairlie 2010): transport 14.3%, electricity and heating 24.9%, other fuel 8.6%, industry 14.7%, fugitive emissions 4.0%, industrial processes 4.3%, land use change 12.2%, waste 3.2% and agriculture 13.8%. Of the agriculture component, soils emitted 5.2%, livestock and manure 5.4%, rice production 1.5% and other agriculture 1.7%. 

Teague (2016) reported total human caused GHG emissions of 13.57 billion tonnes. Of this, cropping and fertiliser (including pesticides and fuel used in agriculture) made up 6.3%, cropping and rangeland soil erosion 7.4% and domestic ruminants 11.6%. 

None of the 14.5%, 18%, 51% or other figures take into account carbon sequestration in grasslands – they are gross figures, not net figures, for livestock contribution to greenhouse gases. The argument that converting pasture land to trees in order to sequester massive amounts of carbon dioxide cannot be used if the carbon sequestration of grasslands is ignored. The argument too that reducing livestock numbers would free up food for the 800 million hungry people is also irrelevant because many countries where hunger occurs are already net food exporting countries – hunger is an economic and political issue, not a production issue. 

Net greenhouse gas contribution of grazing

It is meaningless to consider methane in isolation – well managed grasslands provide a significant carbon sink. The carbon balance can vary widely from high net carbon release to high net carbon capture, depending on the circumstances (Webster 2013). 

Grasslands can store 260 tonnes of carbon per hectare (Neely 2009). Teague (2016) argues that well managed pasture and livestock can sequester significantly more carbon in the soil than ruminants emit: “Ruminant livestock are an important tool for achieving sustainable agriculture” (Teague 2016). Methods needed to develop this kind of sustainable agriculture include no-till cropping, cover crops between cropping rotations, minimising the use of feedlots for cattle, more perennials, more diverse rotations, ley cropping (pasture with livestock as part of cropping rotation systems), and regenerative grazing (Teague 2016). Reintroducing pasture as part of cropping rotations, and grazing it, is also recommended by Conant in a FAO report (2010) as a method of increasing soil organic carbon. 

Soussana (2010) calculated the net greenhouse gas impact of grazed pastures in Europe, finding soil carbon sequestration exceeded methane emissions from ruminants and nitrous oxide emissions from fertiliser use; these calculations were for conventionally grazed animals on pastures year round. In the study the emissions from year-round grazed beef cattle amounted to 167 carbon dioxide equivalents per year due to methane and nitrous oxide production, compared to pasture sequestration of 471 carbon dioxide equivalents per year, leaving a sequestration net balance of 320 CO2 equivalents. 

Under existing management most temperate grasslands worldwide are net carbon sinks (Jones & Donnelly 2004). Sequestration in North America is 0.2 to 0.58 tonnes/ha/year of carbon; Australian estimates are 0.28 to 0.6; European figures are 0.52. The sequestration rate depends on rainfall, soil type and management (Jones & Donnelly 2004). Management is of key importance: pasture species, irrigation, soil fertility, legume content, earthworm introduction and intensification of grazing all increase sequestration; rotational grazing has the greatest potential for increasing sequestration (Jones & Donnelly 2004). 

Liebig (2010) compared grazing systems on the Northern Great Plains of the US: moderately grazed native pasture, heavily grazed native pasture, and heavily grazed introduced fertilised pasture, for net carbon dioxide equivalent emissions. The emissions included ruminant methane and emissions from fertiliser production and usage; this was balanced against soil organic carbon changes over 44 years. There was no detail about the grazing method, just the intensity. All of the three grazing systems increased soil organic carbon and all were minor methane sinks. Only the fertilised pasture showed a net carbon dioxide equivalent loss because of nitrous oxide emissions from the fertiliser; the other two were net sinks (Liebig 2010). 

The carbon sequestration potential of well managed grazing is greater than ruminant and manure methane emissions, according to a FAO report (Neely 2009). The report continues, saying that improved rangeland management could potentially sequester more carbon than any other practice. Another FAO report (Conant 2010) says that while continuous excessive grazing is detrimental to soil organic carbon and plant communities, changed grazing management can rebuild soil organic carbon, without reducing grass production and while restoring productivity of the grassland. 

Soil carbon sequestration is one of a few strategies available on a large scale and with low cost to supplement a necessary decrease in greenhouse gas emissions from fossil fuels (Paustian 2016). Techniques include reduced tillage, better livestock management, more perennial plants, reduction in nitrate fertiliser use and better crop rotations (Paustian 2016). The overuse of nitrate fertilisers is a major destroyer of soil carbon, in addition to emitting nitrous oxide into the atmosphere (Philpott 2010). 

Sheldon Frith’s online book Letter to a Vegetarian Nation (2016) concludes: “It turns out that livestock, when properly managed, are not only good for the environment, they are essential to maintaining civilization in the absence of industrial-chemical agriculture” (p.166). 

Soil organic carbon (SOC) formation processes 

Soils contain 1,500 billion tonnes of organic carbon in the top metre of soil and 2,400 in the top two metres, which is three times the amount in the atmosphere (Paustian 2016). An increase of 1% in soil organic carbon in the top 10 cm of soils would take up all the carbon produced by all US cropland (Follett 2001). 

Of the earth’s carbon, 770 billion tonnes is in the atmosphere, mostly as carbon dioxide; 40,000 billion tonnes is sequestered in the oceans; 500 billion tonnes is in terrestrial vegetation; and 1,500 billion tonnes is in the soil (McCarl 2007). In the last 200 years about half the soil organic carbon (SOC – the term organic carbon is used to exclude the carbon in limestone and other rock carbonates) in managed ecosystems, that is, land not in its natural state, has been lost. McCarl (2007) estimated a potential for sequestering 80 billion tonnes of carbon in agricultural soils via improved agricultural practices, including rotations, no-till, improved water and nutrient management and higher residue producing plants.

Grasses release carbon into the soil from dead roots, sloughing from living roots, and root exudates. More than one third of the carbohydrates produced by photosynthesis in the leaves above ground are exuded through the roots into the soil to feed microbes which in turn release minerals to the plant (Follett 2001). In addition decomposing litter and animal dung is deposited on the soil surface, though most of this is short term labile carbon, to be consumed by soil microbial life, releasing the carbon dioxide to the atmosphere and nutrients to the soil. Underground released carbon is much more stable than surface carbon, capable of lasting hundreds or thousands of years. 

In the US short grass prairie ecosystem, 1% of the total organic carbon is above ground in the grass, 10% is below ground in living plants and decomposing matter, and the remainder is stored in the ground, mostly in a recalcitrant form lasting from 200 to 1000 years (Follett 2001). Root biomass increases with the age of the grasslands, and with grazing; exclusion of grazing results in a loss of SOC (Acharya 2012). SOC also declines with over-grazing, infrequent grazing, and invasion of unpalatable species (Acharya 2012). 

Many studies show that SOC is greater in grazed grasslands than ungrazed, irrespective of the grazing system, and greater under grazing than mowing (Follett 2001). Root mortality increases SOC, and trampling of standing matter by stock results in greater decomposition; dead grass not in contact with the soil does not decompose but oxidises (Follett 2001). Net photosynthesis is greater on grazed plants compared to ungrazed. Grazing removes standing dead matter allowing its decomposition, and allowing light to stimulate new growth (Follett & Reed 2010).

Removal of livestock causes immobilisation of carbon in excessive plant litter and an increase in annual pasture species which sequester less carbon than perennials because of their smaller and less fibrous root systems. Conversion of grazing land to cropping can cause a 60% loss of SOC because of soil disturbance, while converting cropping land to pasture greatly increases SOC (Jones & Donnelly 2004). There are many examples of soil organic carbon being greater in grazing land compared to cropping, at least double (Follett 2001). Converting grassland to cultivation can result in a loss of 0.3 tonnes/ha/year of SOC (Follett 2001). In the first year there can be a sudden decrease in SOC of 20-30% (Acharya 2012). 

The greatest potential for decreasing loss of SOC is controlling erosion (Follett 2001). Erosion prevention depends on canopy cover and species composition and by using less disturbing cultivation practices and grazing systems that maintain full ground cover (Follett 2001, Teague 2016). About 20% of erosion-displaced soil organic matter reverts to carbon dioxide each year (Follett 2001). Perennial vegetation reduces erosion; it also reduces nitrogen loss and increases SOC (Janzen 2011).

Approximately 27% of SOC is glomalin, only produced by mycorrhizal fungi from the plant root exudates it feeds on (Comis 2002). The volume of root exudates depends on the level of available nitrogen and phosphorus in the soil (low levels increase exudation) (Singh 2013). The activity of mycorrhiza is suppressed by phosphatic and nitrogenous fertilisers, some herbicides and fungicides, and cultivation (Bünemann 2006, Paula & Zambolin 1994). 

Bekku (1997) measured root exudates from two annual wild plants, Digitaria adscendens (crab grass, summer grass) and Ambrosia artemisiifolia (ragweed) and found 3.1% of carbohydrates manufactured by photosynthesis were exuded into the soil from the Digitaria and 6.9% from Ambrosia. In other studies cited by Bekku (1997) exudation ranged from 7% to 30% for annual crop plants (wheat, corn). Whipps and Lynch (1983) found 20-25% in wheat and barley trials. Dawson (2000) reported 40% for perennial ryegrass (Lolium perenne) and 12% for red fescue (Festuca rubra) on low nitrogen soils; in high nitrogen soils the figures were 1% and 2% respectively. Rates can be up to 85% for some plant species (Tresder & Allen 2000). Glomalin production is higher in grassland than cropping soil; no-till cropping increases levels (Singh 2013). Dawson (2000) also reported that exudates increase with grazing. 

Glomalin is extremely important for long term sequestration of carbon in soils. Providing ideal conditions for mycorrhiza and glomalin production should be a priority in farming. 

Ruminant methane emissions

There are three broad sources for methane emissions (Kirschke 2013): biogenic, thermogenic and pyrogenic. Biogenic emissions are produced by methanogenic bacteria in wetlands, rice fields, dams, landfill, manure and the digestive system of ruminant animals and termites. Thermogenic emissions come from fossil fuels, both natural emissions and emissions from the extraction of coal, gas and oil. Pyrogenic emissions arise from incomplete combustion of biomass in bushfires and biofuel burning, and from the burning of the fossil fuels oil, gas and coal. 

According to Kumar (2009), ruminants are the single greatest producers of methane, greater than landfill, rice fields, swamps, industry, etc. However this is not backed up by the evidence. Here are the figures used by Topp & Pattey (1997): 25-75 million tonnes/year for landfills, 60-200 from natural wetlands, 95 from rice fields, 60-100 from ruminants, 15-45 from biomass burning, 25-45 from coal mining, 30-110 from gas and oil production and transport, 5-15 from termites, and 20 from other sources. These figures attribute about 16% to livestock ruminants. 

Backman’s (2009) figures for non-natural methane emissions are similar: fossil fuels 74-106 million tonnes, landfill and waste 35-69, ruminant livestock 76-92, rice growing 31-112, and biomass burning 14-88. Wild ruminants contribute about 15 million tonnes per year (Backman 2009). Australia’s share of ruminant methane emissions is 3.1 million tonnes (Reay 2010). It is possible that methane emissions from the drilling, processing and distribution of natural gas (methane) are underestimated, as some researchers have measured up to 9% leakage from gas wells in the US (Jellofson 2013), and some large regional methane hotspots corresponding to oil and gas extraction have been un-noticed (Gass 2014). Therefore the proportion allocated to rumination is likely to be on the lower side of the above range of figures. 

Nearly three quarters of ruminant emissions come from cattle and the remainder from sheep, goats, camels and buffalos (Mirzaei-Aghsaghali 2015). Crutzen (1986) estimated the following figures for 1983: cattle 54 million tonnes per year, buffalos 6.2, sheep 6.9, goats 2.4, camels 1.0, pigs 0.9, horses 1.2, mules and donkeys 0.5, humans 0.3, wild ruminants 2-6, invertebrates 28 (mainly termites), and rice fields 70-130. Coal mining and natural gas leaks amounted to about 37 million tonnes per year. Total annual methane production in 1983 was 300-500 million tonnes per year. 

Plant crops also emit methane, though the amount is unclear. Recent research found that plants may contribute 63-236 million tonnes per year of methane, similar to that of natural wetlands (Fairlie 2010). Houweling (2006) considered 85 million tonnes per year to be more accurate. However these figures are contested; Kirschbaum (2007) found emissions of methane from plants were insignificant compared to the carbon sequestration ability of plants, and Kirschke (2013) reported that the original study showing high emissions from plants has not been confirmed. The question remains unresolved (see Duerk & van der Werf 2008 for a discussion).

Methane emissions rose strongly between 1930 and 1990, largely due to leakage from gas pipelines, but there was little change in the following 20 years (Quirk 2010). According to Quirk (2010) this means there is no justification for penalising agriculture. On the other hand carbon dioxide and nitrous oxide emissions have continued their steep rise curve (Backman 2009). Indeed, atmospheric methane levels did not increase between 1999 and 2008 despite a 70% increase in world ruminant numbers (Savory 2013). Any correlation between ruminant numbers and methane emissions ended by 1999 (Fairlie 2010). There is also no correlation between areas of concentration of ruminants and areas of global methane distribution (Glatzle 2014). A Joint FAO/IAEA (2010) paper also stated: “Currently there is no relationship between increasing ruminant animal population and changes in atmospheric methane concentrations”. 

Methane levels started rising again in 2007, probably due to an increase in natural wetland emissions because of higher temperatures and higher rainfall, and from increased fugitive emissions from the coal, oil and gas industries (Kirschke 2013). During the 2000’s net methane emissions were low: total emissions were 548 million tonnes per year and sinks 540, leaving a very small net increase. In the 1990’s there had been a net annual increase of 17 million tonnes, and 34 million tonnes in the 1980’s (Kirschke 2013). 

There is great variation in the amount of methane released per animal, ranging from 2-15% of ingested energy (Kumar 2009). Diet is the chief factor – high roughage diets result in more methane production, concentrates reduce it. Thus feedlot cattle emit lower amounts of methane; however greenhouse gas accounting needs to offset this with the high carbon footprint of concentrate production (corn, soy, etc), nitrate fertiliser production and use, and methane and carbon losses from the manure produced. Methane emissions from dung are much lower for pasture raised animals compared to feedlots (Broucek 2014). Nitrogen loss from pasture deposited dung is also much lower - about half the nitrogen ingested by feedlot cattle is lost to the atmosphere as ammonia (Janzen 2011). Legumes in a pasture feed mix allow better utilisation of the feed by animals. Animal genetics also play a part in determining methane emissions (Cassandro 2013). Condensed tannin content of pasture, for example Lotus, also reduces methane emissions (Mirzaei-Aghsaghali 2015). Interestingly, cattle grazed on fertilised pasture have been found to emit more methane than on unfertilised – 223 gm/day compared to 179 gm/day (Broucek 2014).

DeRamus (2003) found a considerable reduction in methane emissions under planned grazing systems compared to continuous grazing. This was put down to the improvement in pasture quality leading to a better diet. However not all researchers have reached this conclusion (Mirzaei-Aghsaghali 2015). 

Recent CSIRO studies found that methane emissions from cattle are 24% lower than previous estimates (Charmley 2016). This difference comes to 12.6 million tonnes CO2 equivalent and thereby reduces the estimate of 15% agriculture contribution to greenhouse gases in Australia, of which 70% has been attributed to ruminants. 

Therefore it is likely that the methane emissions from livestock are lower in proportion to total emissions than most estimates place them, and the coal, oil and gas field proportion higher. However ruminant methane emissions can be controlled without reducing livestock numbers. The next section shows that well managed pasture soils can reduce net emissions to zero. 

Methanotrophic ability

Methane is a short lived gas, with a life of 8.9 years in the air (Wuebbles 2002). Approximately 90% is destroyed in the troposphere (the lowest 12 km of the atmosphere) by hydroxyl radicals (OH) from water vapour, 5% in the stratosphere by hydroxyl and chlorine radicals, and 5% in the soil by methanotrophic bacteria (Wuebbles 2002). 

Soil is an important sink for methane by way of methanotrophic bacteria, measuring 30 million tonnes per year compared to 40 million tonnes by oxidation in the stratosphere and 506 million tonnes in the troposphere (Cassandro 2013). 

According to Topp & Pattey (1997), oxidation of methane in soils accounts for 10% of global methane production. There are some required conditions for maximising methane oxidation in soils (Topp & Pattey 1997, Topp 1993). Nitrogenous fertilisers are very inhibitive (this is backed up by many studies, eg. Le Mer & Rogers 2001, Kravchenko 2005), soil must be aerobic, compaction and tillage are detrimental, and the following chemicals are known to be restrictive: nitrapyrin (a nitrification inhibitor used to reduce the conversion of nitrate fertiliser to nitrous oxide), bromoxynil (a herbicide) and methomyl (an insecticide). The effect of bromoxynil and methomyl is short lived, less than 3 weeks, while nitrapyrin lasts at least 7 weeks (Topp 1993). Topp (1993) found no significant inhibitory effect from another 27 herbicides and insecticides tested, including the herbicide 2,4-D, however other researchers have found a strong negative effect from 2,4-D (Syamsul Arif 1996), the insecticide and miticide dimethoate, the herbicide isoproturon used for grassy weeds in wheat crops, and the fungicides propiconazole and fenpropimorph (Priemé 2011). 

Soil fumigants also suppress the activity of methanotrophs (Spokas 2007). The following three were tested: 1,3-dichloropropene (1,3-D), methyl isothiocyanate (MITC), and chloropicrin. All three were suppressive in soils that had not been previously fumigated with the particular chemical (Spokas 2007). Nanoparticles as pollutants from automotive equipment, pesticides, fertilisers, soil remediation, irrigation and deposits from air pollution could also harm methanotrophs (Rajput 2013). 

Best pH range for methantrophic activity is about neutral. There is no known methanotrophic bacteria activity in soils with a pH below 5.0 (Hanson & Hanson 1996. Syamsul Arif (1996) found a limited pH range of between 5.9 and 7.7. Moisture is needed but temperature has little effect and there is only small variation between night and day (Hanson & Hanson 1996), and the bacteria even continue operating under a cover of snow (Dunfield 2007). Castro (1995) noted that both dry and wet soils inhibit oxidation. Inhibition of methanotrophic bacteria by nitrate fertilisers is severe and long lasting (Hanson & Hanson 1996), but organic nitrogen fertilisation does no harm (Dunfield 2007). 

Estimates of the amount of methane soils sink varies from 26-43 million tonnes per year (Backman 2009) to 40-60 million tonnes (Hanson & Hanson 1996). Rates depend on soil, vegetation and land use: deciduous forest soils 0.5 to 5.5 kg/ha/year, tropical forest soils 0.5 to 2.9 and subtropical woodlands 4.6. Wheatfield soils have been found to oxidise only 25% the rate of adjacent grasslands. Desert soils are significant methane sinks, 7 million tonnes per year. 

New Zealand research (Walcroft 2008) found the following results for soil oxidation of methane: NZ beech forest soil 10.5 kg/ha/year, pine forest soil 4.2 to 6.4, shrub land 2.3, cropping 1.5, dairy pasture 0.5 to 0.6, sheep pasture 0.6 to 1.0, and ungrazed pasture 0.85. 

King (1992) reported the following soil oxidation rates (converted to kg/ha/year): tundra 9.9 to 12.0, temperate forest 1.1 to 12.8, tropical forest 1.8, grassland (in Colorado) 0.4 to 2.2, and African savannah 4.4. 

The following figures are from Le Mer & Roger (2001): cultivated soils 2.0 kg/ha/year, grassland 2.4, uncultivated upland soils 3.0, forest 3.6, and wetland 62.8. It is thought that forest soils have higher oxidation rates because of higher methane emissions from the leaf litter – there is a direct correlation between local emission levels and local oxidation levels (Le Mer & Roger 2001). 

Professor Adams of University of Sydney calculated 8.76 kg/ha/year methane sequestration in alpine soils in Australia (originally reported as 8.76 tonnes – Gocher 2009). The world’s highest rate of 50 kg/ha/year was found in Indian tropical forest soils (Dunfield 2007).

Dunfield (2009) reported that oxidation rates for cultivated soils are very low. Dobbie (1996) calculated a 60% decline in soil methane oxidation when forest or grassland soils were converted to arable or fertilised pasture in northern Europe (0.6 million tonnes per year to 0.23 million tonnes per year), and cite similar results for conversion of prairie to cropping in the US. These results were backed up by Kravchenko (2005), finding a severe reduction in methane oxidation and soil organic carbon when forest was converted to cropping. Soil compaction can reduce oxidation by 52% and nitrate fertilisers by 50%, producing a combined reduction of 78% (Dobbie 1996). The inhibitory effect of nitrogenous fertilisers has been found to last for up to 8 years after a single application (King 1992). 

Research in grazing land in China, where 313 million hectares are grazed, showed that using improved management systems, including reseeding, irrigation, fertilisation, rest from grazing in early spring, and avoided overgrazing, but not including holistic planned grazing and with no information about fertilisation methods, resulted in net methane sinks (Wang 2014). The methane oxidation in the soil was around 5 kg/ha/year, exceeding methane emissions from ruminants. The improved methods also increased carbon sequestration. The authors concluded that methane oxidation in soil was often underestimated and methane emissions by ruminants overestimated, and that there was tremendous potential for totally mitigating ruminant methane emissions. 

Methanotrophic bacteria have also been found on some plants – buds and leaves of linden and spruce, stems of corn plants (Reay 2010), and on the roots of rice and other aquatic plants, providing a major mitigation effect on rice field produced methane (King 1992). More than 90% of methane emitted from freshwater wetlands is oxidised on the sediment surfaces (King 1992), which calls into question the contribution of swamps and rice fields to atmospheric methane. The contribution of termites is also in question because very high levels of methane oxidation by methanotrophic bacteria have been detected in tropical savannahs in South Africa adjacent to termite mounds (King 1992). Methane is also oxidised by some fungi, for example Graphia species, and several yeasts (King 1992). The majority though is oxidised in the troposphere.

Grazing systems

There are many terms for systems of non-continuous grazing (also called set stocking), with various meanings attached to each one, and this has muddied the discussion about the efficacy of grazing systems in managing greenhouse gases. These terms include cell grazing, rotational grazing, time controlled grazing, management intensive grazing, regenerative grazing, high intensity low frequency grazing, short duration grazing, multi-paddock grazing and rational grazing, among others. I will be using the term “planned grazing” to refer to a grazing system in which large numbers of animals graze a small area in a short time and do not return to that area until the pasture has recovered. It is an adaptive system without fixed timelines. Times of grazing and rest depend on soil, pasture species, climate, seasonality and farm goals. The positive greenhouse gas footprint of this system has been adequately demonstrated, whereas that of more inflexible rotational systems is variable (McCosker 2000). 

Planned grazing in the modern era was initiated by André Voisin in the 1950’s (Voisin 1959) and further developed by Allan Savory (Savory 1988), though it had been traditional practice before fences were in place, and still is in parts of the world where livestock are housed at night and taken out to graze or browse for the day. 

The following explanation of its features is from Terry McCosker, an Australian advocate: “It is based upon ‘time control’ pasture management, which requires the following practices: Monitoring the rate of growth of pastures and resting (or spelling) of pastures to allow for the regeneration of grasses and herbage; calculating stocking rates to match the carrying capacity of the pasture; planning, monitoring and managing the whole system very closely; utilising short grazing periods to increase animal performance; stocking cells at maximum density for short periods; encouraging a diversity of animals and plants to improve ecological health; and ensuring that there are large cattle numbers to encourage ‘herding’ behaviour” (McCosker 2000, p. 208).

Grasslands and grazers have evolved over tens of millions of years. Studies of the Serengeti in East Africa explain (Frank 1998) that this co-evolution has produced sustainable systems in the following ways: grazing removes old growth and promotes new growth by increasing light to the new shoots, it improves soil moisture and water use efficiency, enhances mineral availability by nutrient recycling, and stabilises nitrogen to prevent leakage either via leaching downwards or volatilisation upwards. Animals are continually moving, so while grazing is very intense it does not last long. Wildlife exclusion trials in the Serengeti find that grass production was halved without grazing. 

Humans have transformed about 20% of the world’s natural grasslands into cropping and most of the rest is used for livestock. Livestock grazing systems often are very different to natural grazing systems; the goal of planned grazing is to try as much as possible to mimic the actions of wild grazing animals in grazing management. Bison co-evolved with the North American prairies from about 5 million years ago, preventing forest re-development and creating the tremendous topsoil depth and carbon content of the prairies. The bison grazed as huge herds, close together for protection from predators, eating everything non-selectively and constantly moving. Selective grazing favours weed development. 

It is not possible to accurately determine historic wild populations of methane emitting animals. Hristov (2012) calculated that for the contiguous United States methane emissions from ruminants before European settlement was 86% of current levels (if the medium estimate of 50 million bison numbers was used) or 23% above (using the higher estimate of 75 million bison), and stated that estimates for the rest of the world are not available. Perhaps a more reliable estimate of bison numbers is 60 million bison (The Bison Herd 2014), which means little change in ruminant methane emissions. 

Some estimates of historic ruminant numbers are available for the 1500’s, particularly for Africa, but not for the millions of years before that (Mahony 2003, Subak 1994). Subak estimated African ruminant methane emissions now to be triple the 1500 level. Ruminants also inhabited Europe, Asia and South America, but not Australia. 

Livestock can cause stress on land or they can be beneficial; shifting the net effect to beneficial is necessary so that livestock can be ecologically justified (Janzen 2011). Poorly managed livestock causes a significant amount of greenhouse gas because of land degradation, land use change for livestock feed production and for grazing, methane from feedlot dung, fossil fuel use to produce fertilisers, and nitrous oxide emissions from manure and nitrogenous fertilisers, but these are all avoided in holistic planned grazing management (Savory 2013). 

Gill (2009) gives the following definition of over-grazing: exposing plants to grazing for too long, or grazing too soon, with little regard to livestock numbers. Both over-grazing and under-grazing can occur at the same time – if stocking density is low some plants will be continuously grazed to their detriment while less favoured plants will senesce also to their detriment (Weber & Horst 2011). Therefore low stocking density can be as damaging to the grassland as total stock exclusion (Weber & Horst 2011). 

Planned grazing detractors

The anti-livestock lobby (for example Mahony 2013) relies on a couple of papers that purport to show conclusively that grazing animals are detrimental to the environment no matter how they are managed, including by Savory Institute planned grazing (Briske et al 2008, Holechek 2000, Carter 2014). 

The contentions in these articles have been very well refuted by several researchers (see Itzkan 2013), who say that the research cited in those articles does not reflect holistic planned grazing as advocated by Allan Savory. This research data was based on trials using predetermined stocking rates and grazing timing, not “adaptive grazing” that is governed by plant recovery time. Plant recovery time depends on the local environment, the season and the year, not a certain number of days or months. Briske and Holchek disregarded research done on rangelands that were using the methods promoted by the Savory Institute and instead focused on unrepresentative paddock trials (Itzkan 2013). 

Teague (2013) gives a detailed critique of the Briske paper covering the above, adding that trials were conducted on paddocks much smaller than common holistically grazed ranch sites which meant that continuously grazed paddocks were not as selectively grazed as larger paddocks would have been, that the trial times were often too short, the stocking rate was higher in the rotationally grazed paddocks than the continuously grazed paddocks, and the recovery times for the rotationally grazed paddocks was too short. Allan Savory responded thus: “All papers cited referred to derivations of the work in which the holistic planned grazing process was converted to a grazing rotation system to fit research criteria and the Holistic Decision-Making Framework was never used in any of those studies” (Savory 2013).

Briske acknowledged the discrepancy between experiment and experience in a later paper (2011), and admitted there was confusion about grazing terms. He also noted that excluding adaptive decision making would affect outcomes: “The capacity for management to adapt to variable ecological conditions and desired outcomes at the local scale was excluded in order to maintain uniformity and consistency in experiments across time and place”.  

Stinner talks about two different research systems for agriculture, sciential and praxis. Sciential research is quantitative, focused, precise and controlled so that it is disassociated from the complexities of farming. Praxis on the other hand is qualitative, in a context and holistic, taking account of the complexities of agricultural ecosystems. Scientists often reject the praxis system because the variables are not controlled, but it can be argued that understanding individual parts of a system fails to provide understanding of the whole. Therefore there is a body of scientific opinion that the praxis approach is quite legitimate for ecosystem analysis, and correspondingly a body that dismisses the evidence of holistic grazing because it has not always used the sciential approach. 

Evidence supporting planned grazing

Gill (2009) reported that the results of planned grazing on his farm were completely different to that found by Briske; cattle numbers increased four fold because of the higher pasture production. 

Stinner (1997) conducted a study of holistic resource management practitioners in the US, using questionnaires. The farmers reported the following results: more spare time, return of native grasses, increased carrying capacity with fewer inputs resulting in higher profitability, faster decomposition of manure, more earthworms, reduced erosion, rejuvenation of springs and creeks which commenced flowing after decades of being ephemeral, reduction in weediness, a longer growing season and more perennial grasses. 

Teague (2011) compared multi-paddock grazing with both light and heavy continuous grazing in the tall grass prairie in Texas, concluding that multi-paddock adaptive grazing was significantly superior because of less bare ground, more stable and less compacted soil, less erosion, higher soil organic carbon, greater herbaceous biomass, higher cation exchange capacity and a much higher ratio of fungi to bacteria. He concluded that the Briske (2008) comparisons were not valid for ranch-size adaptive grazing. 

Wang (2015) compared light continuous grazing, heavy continuous grazing and multi-paddock grazing in Texas, finding that multi-paddock grazing gave the highest SOC stocks and carbon sequestration exceeded methane emissions, making it a net GHG sequester. The authors recommended conversion of continuous grazing to rotational systems in order to reduce GHG emissions.

Earl and Jones (1996) compared planned grazing (using the Savory system) and continuous grazing on the Northern Tablelands of NSW. Over a two year period the most desirable and palatable species remained the same or increased under planned grazing but decreased under continuous grazing (by 65-70%), while the least desirable species remained unchanged under continuous grazing but declined greatly (by 45%) under planned grazing. Ground cover increased with planned grazing. Continuous grazing causes cumulative root pruning that reduces the ability of the plant to access water and nutrients and to recover from grazing. 

Shane Joyce (2000) reported the following on his central Queensland property: increases in ant and earthworm numbers and a doubling of the number of bird species, reduced bare ground percentage that lessened nutrient and sediment runoff, an increase in pasture diversity including native grasses and legumes, reduction in weediness, elimination of the use of fire to control unpalatable vegetation, and a doubling of stock carrying capacity. 

Robin Sparke (2000) of Moura in Queensland adopted planned grazing in 1994; over the following four years he reported an increase in desirable pasture species (bluegrass and legumes), increased ground cover, a pasture yield increase from 1,800 kg/ha to 3,500 kg/ha, a reduction in the cost of production from 90 cents/kg for beef to 40 cents, and an increase in return on assets from 2% up to 8%. 

Weber and Gokhale (c. 2009) found a significant increase in soil moisture levels after three years of planned grazing (high density for 6 days once a year) compared to a low density 30 day grazing period once a year, and total stock exclusion, in a high semi-arid region in Idaho. There was also increased litter on the soil. 

Sherren (2012), who conducted a study of the attitudes to landscape of holistic resource management farmers and conventional farmers in the Lachlan catchment of NSW, concluded: “We conclude that HM grazing should be encouraged so as to adapt the industry to climate change”.

For more peer reviewed references to the success of holistic planned grazing see the Savory Institute Holistic Management Portfolio (Savory Institute 2014).

My own experience confirms the positive benefits of planned grazing (Broughton 2015). Between 2009, when the grazing system at “Strathfieldsaye Estate” on the shores of Lake Wellington in eastern Victoria changed, and 2015, ground cover rose to 100% and has been maintained at that level. The percentage ground cover of the unpalatable plants sorrel (Acetosella vulgaris), Poa tussock (Poa labillardieri), buckshorn plantain (Plantago coronopus) and Australian salt grass (Distichlis distichophylla), and the less desirable plants couch (Cynodon dactylon) and capeweed (Arctotheca calendula) declined significantly. Perennial species increased at the expense of annuals, carrying capacity improved, birthing difficulties became insignificant, and the farm became profitable. At the same time soil organic carbon increased from a reading of 2.7% in the top 10 cm to 3.2% and from 0.4% to 0.9% at the 40-50 cm level. Cost of conversion was minimal – paddocks were subdivided and cattle contained with single wire moveable electric fencing, no extra watering points were needed as single wire laneways allowed access in subdivided paddocks, and there was no extra work involved in moving stock as they were being checked twice a day previously.

However not all studies have found SOC to rise under planned grazing (eg. Sanderson 2015). Sanderson, comparing grazing systems in South Australia, did find a small increase in SOC, much less than expected, and speculated that more time may have showed a more significant increase. 

The Savory Institute (2013) argues that many of the items attributed to livestock production in the FAO reports do not apply to holistically planned grazed livestock, in which land degradation is reversed, there is no deforestation for feed production or grazing, no concentration of manure that emits methane and nitrous oxide, no chemical fertiliser use, so no fossil fuel use in its manufacture and no emissions of methane and nitrous oxide as it breaks down. As long as nitrogenous fertilisers are not used, all methane produced by ruminants is oxidised in the soil by methanotrophic bacteria. Therefore any greenhouse gas footprint from livestock is fully dependent on their management, and holistic planned grazing makes no contribution to greenhouse gases.

Pastures that are stocked continuously with few animals are less productive than with intensive rotational grazing (Follett 2001). Non-intensively managed grasslands have an average SOC increase of 50-200 kg/ha/year; improved intensive grazing can double or triple that rate (Follett 2001). Properly grazed grassland can gain 0.3 tonnes/ha/year SOC compared to ungrazed enclosures (Follett 2001). Cattle under low intensity stocking do not graze evenly, changing the vegetation to less palatable species; under high intensity they are much less selective (Follett 2001). 
Distribution of dung is also important in soil carbon sequestration, enhanced by planned grazing (Follett 2001). 

Teague (2011) found that over time an additional 30 tonnes/ha SOC is sequestered in “restorative grazing” compared to heavy continuous grazing, with greater water holding capacity. 

Itzkan (2004) calculated that semi-arid grasslands could sequester 25-60 tonnes/ha SOC over a ten year period under planned grazing, doubling the amount of SOC, at a rate of 1-2.4 tonnes/ha/year, converting the landscape to tropical savannah and perennial grassland. If 25-60 tonnes/ha could be achieved overall in grasslands, this would take out 41-99 ppm carbon dioxide from the atmosphere (Itzkan 2004). This is equivalent to the estimated SOC loss of 30-60 tonnes/ha from agricultural activities (grazing and cropping) since agriculture commenced, which reflects the potential for re-sequestration (Itzkan 2004). 


There is no doubt that feedlot raising of livestock is ecologically detrimental, because of very high energy use (35 kj fossil fuel produces 1 kj of beef), competition with humans for grains, and the production of manure as waste product that emits 18 million tonnes of methane per year, plus nitrous oxide. Manure deposited on pasture does not produce significant amounts of methane, according to the FAO (Savory 2013). 

Condemnation of the feedlot livestock industry should not lead to a condemnation of livestock in general. Of the world’s cattle and buffalo numbers, an average of 90% of the diet is from pasture; for sheep and goats it is 98% (1981 figures, Hendy 1995). In Australia about 2% of the national cattle herd is in feedlots at any one time; average stay is 50-120 days (ALFA 2015). 

Even in the US where feed lotting is well established, all beef animals spend at least their first 8 months on pasture until weaning, and many spend much longer, up to 16 months, to be finished in feed lots for 4-8 months (Gurian-Sherman 2011). Their mothers spend their entire life on pasture. Gurian-Sherman calls for a reduction in the grain feeding period to reduce the carbon footprint and produce healthier beef (grain causes acidosis leading to liver abscesses and other illnesses in cattle, and higher saturated fats and lower omega-3 fatty acids in the meat). Also advocated is better quality pastures including the use of legumes in pasture mixes, and managed rotational grazing to increase the growth rate on pastures and lower the methane production levels. 

In Australia and many other parts of the world many of the horrors depicted in the movie Cowspiracy (Anderson & Kuhn 2014) do not exist. Housed dairy cattle are not found in Australia; feedlots for beef production are used just for the last few weeks before sale, not for the life of the animal. The film gives the false impression that maltreatment of livestock is the norm – this is not the case and such treatment is not necessary. 

Maltreatment of livestock can be prevented by legislation. We already have Codes of Practice for the Welfare of Animals that are enforceable; these can be extended to more closely match the standards applicable under organic certification. Organic standards do not permit feedlots and intensively housed pig and poultry raising, dairy cattle must have access to pasture for at least half the year (the full year in Australia, where ground is not covered by winter snow), and clearing of native vegetation is disallowed (NASAA 2016). The organic standards recognise the importance of animals in ecosystems, as no natural ecosystem on earth is devoid of animals, and insist that farmers need to include livestock in their agricultural systems.

Grassland and forest

Grasslands comprise the largest ecosystems on earth, 26-40% of the world’s land, holding 20-35% of SOC; of the 3,500 ha of grasslands grazing takes up 2,900, the remainder cropping (Itzkan 2004). More than half of the world’s land surface is grazed (Follett & Reid 2010). Rangelands (where animals graze) make up 70% of Australia’s land mass (Richards & Lawrence 2009). In many areas of the world animals are the only option (Webster 2013). There is 1,500 billion tonnes of carbon stored in soils compared with 600 in vegetation; this is three times as much as in the atmosphere (Follett 2001). Between 10 and 30% is in grasslands, and grasslands are sequestering 500 million tonnes of carbon per year, with a potential of up to 2 billion tonnes/year (Scurlock & Hall 1998).

More SOC is stored in grasslands than forests (in forests more carbon is stored above ground). Temperate grassland stores about 236 tonnes/ha of SOC while temperate forests store 147; tropical grasslands store a similar amount of SOC to tropical forests (Itzkan 2004

Barson 2000 provides the following figures for land cover in Australia. Prior to colonisation 9% was forested (defined as more than 30% foliage cover), 21% was woodlands (10-30% foliage cover), 21% was open woodlands (less than 10% foliage cover), 40% was shrublands (including acacia and mallee, heaths and saltbushes), and 7% was grasslands. By the 1980s 5% was forested, 14% woodland, 25% open woodland, 37% shrublands and 16% grasslands. This represents a loss of 31 million ha of forest, 54 million ha of woodland and 23 million ha of shrubland, and a gain of 31 million ha of open woodland and 69 million ha of grassland (grassland includes cropland). Until the 1950s most land clearing was for cropping; in the period 1990-1995 there was large scale land clearing in Queensland for grazing (924,000 ha) plus continued clearing for cropping in WA and Queensland. Land clearing has been successfully ended in most states of Australia and can be in other parts of the world. A better strategy for increased food production is the restoration of the huge amount of degraded land in the world.

Trees and grazing are not mutually exclusive. A commonly reported figure for tree and other woody vegetation cover that does not diminish livestock carrying capacity is 10%. However there are examples greater than this – Richard Weatherly in western Victoria believes 11% tree cover plus 7% wetland creation has increased carrying capacity (Francis 2014), and Shane Joyce in central Queensland reports 40% revegetation as valuable for pasture production (Joyce 2000). Shade, wind protection and bird and insect habitat are cited as factors in increased profitability. It has been found that total carbon capture in pastures with scattered trees is about twice that of treeless paddocks (Webster 2013). 

Agroforestry, the integration of trees with cropping or pasture, is practised on about 1 billion hectares in the world by more than a billion farmers, mostly in developing countries (Nair 2010). There is great potential to expand agroforestry in industrialised countries with a resulting increase in carbon sequestration. Current estimates of carbon sequestration by agroforestry range from 0.29 to 15.2 tonnes/ha/year above ground, and 30-300 tonnes/ha/year below ground (Nair 2010). Pinjuv (2011) includes agroforestry as a major method of reducing greenhouse gas emissions in the Brazilian Amazon. 

There has been large scale loss of carbon and biodiversity from land clearing which should not continue. Some of this loss has been for grazing, some for crop production. There is tremendous potential for reversal by partially revegetating grazing land without reducing livestock numbers. Re-greening the world is already happening (Liu 2015).

Effect of ruminant removal

What would happen if ruminant livestock were removed from grasslands? 

Conversion of grazing land to biofuel production is one of the major changes that the anti-livestock proponents advocate (Goodland & Anhang 2009), arguing that ethanol use reduces greenhouse gases because while the emissions from oil extraction, processing and use are similar to those for the production, processing and use of ethanol, carbon dioxide sequestration in the plants results in a net decrease in GHG. 

However, as Searchinger (2008) points out, this does not take into account the land use changes that biofuel production requires – when forest or grassland is cultivated there is a loss of about 25% soil organic carbon, plus the above ground biomass. Thus Searchinger (2008) estimates that converting grassland to biofuels results in a net doubling of GHG over a 30 year period. Emissions of nitrous oxide, nearly 300 times more powerful than carbon dioxide as a greenhouse gas, from nitrogenous fertiliser use to grow biofuel crops like canola, corn and sugar cane more than negates reduction in carbon dioxide emissions from fossil fuel savings, resulting in higher greenhouse gas emissions, not lower (Crutzen 2008). Proponents of biofuels can quite rightly argue though that diverting corn and soy from livestock feed to biofuels is a net GHG improvement, as is happening to some extent in the US.

When livestock are removed from grasslands often wild ruminants take their place. This happened in Scotland where deer replaced sheep, and in the Serengeti where wildebeest numbers greatly increased once cattle were removed (Fairlie 2010). In these cases there was no change in methane emissions. In Australia kangaroo numbers would be likely to increase (though not if the watering points were removed with the stock), significantly lowering methane reduction as kangaroos produce negligible amounts of methane. However cattle and sheep might be replaced by camels, goats, deer, horses or buffalos (a horse produces methane even though it is not a ruminant – Fairlie 2010). Would mass sterilisation be used to control numbers? 

Wildlife without predators leads to degradation of the environment (Fairlie 2010). 

Crops would have to be protected from the additional wildlife, such as wild boar, deer, squirrels, elephants, kangaroos. 

Some land would become forested, which is what anti-livestock activists are counting on, but other grassland areas cannot support trees because rainfall is too low, including the North American prairies, the steppes of Central Asia and large parts of Australia and South America (Jones & Donnelly 2004). Much grazing land cannot be used for another purpose. Soils may be too shallow or the rainfall too low for trees. One billion people in the world depend on livestock, often in dryland areas where there is no alternative (Neely 2009). 

Despite continued forest destruction in Indonesia and the Amazon, tree cover in the world increased by 4 billion tonnes of carbon between 2003 and 2012, due to reforestation of abandoned farmland in Russia, tree planting in China and increased vegetation in savannahs and shrublands in Africa, Australia and South America (Liu 2015). However Liu points out that in Australia much of this gain can be destroyed in a single bushfire. 

Wildfire in the ungrazed grass would ensure minimal tree seedling survival, and forest above ground is not permanent if it is destroyed by fire. Grassland sequesters carbon underground where it is protected. Grazing reduces grassfire potential. It is likely that there would be a need for increased amounts of grassland burning in order to reduce the likelihood of wildfire. Burning is a greenhouse gas contributor. Currently burning of grasslands sends 1.6 billion tonnes of carbon into the atmosphere, compared to fossil fuel burning of 5.5 billion tonnes. Burning also releases methane, nitrous oxide and carbon monoxide gases, and hardens soil, reduces water holding capacity and kills micro-organisms (Neely 2009). In Australia an average of 500,000 square kilometres per year is burnt, producing 3% of Australia’s net greenhouse gases (Wahlquist 2012). Grazing can control excess grass, obviating the need for burning and the risk of wildfire. 

Significant reduction in ruminant numbers would necessitate an increase in cropping to provide the extra food. Cropping is more energy intensive and would lead to an increase in carbon dioxide emissions (Fairlie 2010). Conversion of grazing land to cropping is a major cause of greenhouse gas emissions – an average of 60% below ground carbon is lost (Neely), a figure of 0.5 to 2 tonnes of carbon per hectare per year until equilibrium is reached (Paustian 2016). 


Effective action on any issue involves both personal decisions and political decisions, with political decision being of paramount importance. The cigarette smoking rate did not decrease because of personal decisions alone – it was because of a massive government-led campaign and a cessation of tobacco promotion. Ending the fossil fuel industry will not be due to people switching off their lights – government approval or non-approval of new coal mines and gas fields is what matters. Personal decisions can only have a marginal effect. Thus spending energy on promoting veganism is a diversion from the real campaign to reduce greenhouse gases, which is the substitution of fossil fuel energy by renewable energy. Focusing on livestock is misguided because livestock can and should be part of the solution to climate change. Fossil fuel phase-out is possible; ending the use of livestock is not. 

Between 1970 and 2004 carbon dioxide emissions from fossil fuels doubled, nitrous oxide emissions increased by 50% and methane by 40% (Fairlie 2010). Methane levels stopped increasing in 1999 and recommenced in about 2006 with increased coal and gas mining. Targeting ruminant methane shifts the focus away from fossil fuels, the main culprit. 

Pasture based livestock can be, and often already is, carbon neutral, as methane emissions are offset by carbon sequestration in grasslands. To optimise carbon and methane sequestration it is necessary to adopt sound ecological farming systems that foster the production of glomalin, increase the ability of methanotrophic bacteria to function, allow pastures to recover after being grazed, minimise soil disturbance, maintain year-round soil cover, include animals in cropping systems, and include trees in both grassland and cropping land.

Many of the legitimate arguments against livestock – cruelty, poor conditions of life, waste of resources, carbon footprint - can be resolved with management and legislation changes. It is a myth that animal agriculture is the biggest cause of global warming, responsible for 51% - there is no scientific basis for that figure or anything like it. 

Farmers are already bringing about management change. Government and public support would assist. Holistic planned grazing is a solution for ruminants. Pastured poultry and pigs is a viable option. Organic cropping using no-till can become normal. Nitrogenous fertilisers can be phased out. 

Turning a personal moral opinion into an ecological issue is not legitimate when there is no sound basis. Those really concerned about global warming should be targeting the fossil fuel industry and campaigning for sustainable agriculture as an alternative to GHG producing chemical agriculture. Concentrating on ruminant livestock is a diversion from this task.

ALFA, 2015, About the Australian Feedlot Industry, Australian Lot Feeders’ Association, http://feedlots.com.au/industry/feedlot-industry/about/ (retrieved 13/4/2016).
Andersen, K. and K. Kuhn, 2014, Cowspiracy: The Sustainability Secret (film 2014), Awaken Consciousness, https://vimeo.com/148406267 (retrieved 15/4/2016).
Acharya, B. S., J. Rasmussen & J. Eriksen, 2012, “Grassland carbon sequestration and emissions following cultivation in a mixed crop rotation”, Agriculture, Ecosystems and Environment 153 (2012) 33– 39. 
Backman, L., 2009, “Methane – Sources and Sinks”, HENVI Seminar, February 19, 2009, www.helsinki.fi/henvi/research/presentations09/Backman.pdf  (Retrieved 15/3/16).

Barson, M., L. Randall & V. Bordas, 2000, Land Cover Changes in Australia, Bureau of Rural Sciences, 2000.

Bekku, Y., M. Kimura, H. Ikeda & H. Koizumi, 1997, “Carbon input from plant to soil through root exudation in Digitaria adscendens and Ambrosia artemisiifolia”, Ecological Research 12, pp. 305-312.

Boyce, J., 2001, 1835: The Founding of Melbourne and the Conquest of Australia, Black Inc, Collingwood.

Briske, D.D., J. D. Derner, J. R. Brown, S. D. Fuhlendorf, W. R. Teague, K. M. Havstad, R. L. Gillen, A. J. Ash, and W. D. Willms, 2008, “Rotational Grazing on Rangelands: Reconciliation of Perception and Experimental Evidence”, Rangeland Ecology & Management, 61(1):3-17.  

Briske, D.D., N. F. Sayre, L. Huntsinger, M. Fernandez-Gimenez, B. Budd, and J. D. Derner, 2011, ”Origin, Persistence, and Resolution of the Rotational Grazing Debate: Integrating Human Dimensions Into Rangeland Research”, Rangeland Ecology & Management, 64(4):325-334.

Broucek, J. (2014) “Production of Methane Emissions from Ruminant Husbandry: A Review”, Journal of Environmental Protection, 5, 1482-1493.

Broughton, A., 2015, Report of the Strathfieldsaye Estate Grazing and Pasture Improvement Project, Australian Landscape Trust (unpublished, available from madelinew@alt.org.au; an earlier 2011 version is available at http://www.wgcma.vic.gov.au/for-landholders/gippsland-soil-trials/strathfieldsaye-estate-extended-grazing-trial, retrieved 17/4/2016). 

Bünemann, E.K., G.D. Schwenke & L. Van Zwieten, 2006, “Impacts of agricultural inputs on soil organisms – a review”, Australian Journal of Soil Research, Vol.44, pp. 379-406, CSIRO Publishing.

Carter, J., A. Jones, M. O’Brien, J. Ratner & G. Wuerthner, 2014, “Holistic Management: Misinformation on the Science of Grazed Ecosystems”, International Journal of Biodiversity, Volume 2014. 

Cassandro, M., M. Mele & B. Stefanon, 2013, “Genetic aspects of enteric methane emission in livestock ruminants”, Italian Journal of Animal Science, volume 12:e73.

Castro, M.S., P.L. Steudlear, J.M. Melillo, J.D. Aber & R.D. Bowden, 1995, “Factors controlling atmospheric methane consumption by temperate forest soils”, Global Biogeochemical Cycles, Vol 9, No. 1, pp.1-10.

Charmley, E., S.R.O. Williams, P.J. Moate, R.S. Hegarty, R.M. Herd, V.H. Oddy,
P. Reyenga, K.M. Staunton, A. Anderson & M.C. Hannah, 2016, “A universal equation to predict methane production of forage-fed cattle in Australia”, Animal Production Science, 56, 169–180.

Chivers, D., 2016 “Cowspiracy: Stampeding in the opposite direction”, Climate and Capitalism, 13/2/2016, http://climateandcapitalism.com/2016/02/13/22449/ (retrieved 15/4/2016). 

Comis, D., 2002, "Glomalin: Hiding place for a third of the world's stored soil carbon", USDA Agricultural Research magazine, 50:9. 

Conant, R.T., 2010, Challenges and opportunities for carbon sequestration in 
grassland systems: A technical report on grassland management and climate change mitigation, Plant Production and Protection Division, Food and Agriculture Organization of the United Nations (FAO), Rome, http://www.fao.org/fileadmin/templates/agphome/documents/climate/AGPC_grassland_webversion_19.pdf (Retrieved 19/2/16). 

Crutzen, P.J., I. Aselmann & W. Seiler, 1986, “Methane production by domestic animals, wild ruminants, other herbivorous fauna, and humans”, Tellus (1986), 388, 271-284.

Crutzen, P.J., A.R. Mosier, K.A. Smith & W. Winiwarter, 2008, “N2O release from agro-biofuel production negates global warming reduction by replacing fossil fuels”, Atmospheric Chemistry and Physics, 8, 389–395.

Dawson, L.A., S.J. Grayston & E. Paterson, 2000, “Effects of grazing on the roots and rhizosphere of grasses”, Grassland Ecophysiology and Grazing Ecology (eds G. Lemaire, J. Hodgson, A. de Moraes, C. Nabinger & P.C. de F. Carvalho), CAB International 2000.

DeRamus, H.A., T.C. Clement, D.D. Giampola, & P.C. Dickison, 2003, “Methane Emissions of Beef Cattle on Forages: Efficiency of Grazing Management Systems”, Journal of Environmental Quality, 32:269–277 (2003).

Dobbie, K.E., K.A. Smith, A. Priemé, S. Christesen, A. Degorska & P. Orlanski, 1996, “Effects of land use on the rate of methane uptake by surface soils in northern Europe”, Atmospheric Environment 30:7, pp. 1005-1011.

Duerk, T. & A. van der Werf, 2008, “Are plants precursors for methane?”, New Phytologist, Vol 178, Issue 4. 

Dunfield, P.F., 2007, “The soil methane sink”, in D. Reay, C.N. Hewitt, K. Smith & J. Grace (eds), Greenhouse Gas Sinks, CABI, Wallingford, UK. 

Earl, J.M. & C.E. Jones, 1996, “The need for a new approach to grazing management: Is cell grazing the answer?”, Rangelands Journal, 18(2), 327-50. 

Earth to Philly, 2012, “Livestock and climate: Whose numbers are more credible?”, Philadelphia Daily News, March 2, 2012, http://www.philly.com/philly/blogs/earth-to-philly/Livestock-and-climate-Whose-numbers-are-more-credible.html (retrieved 14/4/16).

Fairlie, S., 2010, Meat: A Benign Extravagance, Chelsea Green Publishing Company, White River Junction, Vermont USA. 

Follett, R.F., J.M. Kimble, and R. Lal, (eds.), 2001, The potential of U.S. grazing lands to sequester carbon and mitigate the greenhouse effect, Lewis Publishers, Boca Raton, USA, http://eco.ibcas.ac.cn/group/baiyf/pdf/gxzy/9_The_Potential_of_U.S._Grazing_Lands_to_Sequester_Carbon_and_Mitigate_the_Greenhouse_Effect.pdf  (Retrieved 19/2/2016).

Follett, R.F. & D. A. Reed, 2010, “Soil Carbon Sequestration in Grazing Lands: Societal Benefits and Policy Implications”, Rangeland Ecology and Management, 63:4–15.

Francis, P., 2014, “Existing knowledge should underpin NLP on-farm project funding policy”, http://www.moffittsfarm.com.au/2014/08/21/existing-knowledge-should-underpin-nlp-on-farm-project-funding-policy/ (retrieved 18/4/2016). 

Frank, D.A., S.J. McNaughton & B.F. Tracy, 1998, “The Ecology of the Earth's Grazing Ecosystems”, BioScience, Vol. 48, No. 7, pp. 513-521.

Frith, S., 2016, Letter to a Vegetarian Nation: Why We Need Livestock for Sustainable Food Production and Environmental Restoration, published online, available from http://sheldonfrith.com/Book.html

Gammage, B., 2011, The Biggest Estate on Earth: How Aborigines Made Australia, Allen & Unwin. 

Gass, H., 2014, “How scientists overlooked a 2,500 square mile cloud of methane over the Southwest”, Christian Science Monitor, October 10th 2014, http://www.csmonitor.com/USA/USA-Update/2014/1010/How-scientists-overlooked-a-2-500-square-mile-cloud-of-methane-over-the-Southwest-video (retrieved 15/4/2016). 

Gerber, P.J., H. Steinfeld, B. Henderson, A. Mottet, C. Opio, J. Dijkman, A. Falcucci & G. Tempio, 2013, Tackling climate change through livestock – A global assessment of emissions and mitigation opportunities, Food and Agriculture Organization of the United Nations (FAO), Rome.

Gill, C., 2009, “Doing what works”, Range Magazine, Fall 2009.

Glatzle, A., 2014, “Questioning key conclusions of FAO publications ‘Livestock's Long Shadow’ (2006) appearing again in ‘Tackling Climate Change Through Livestock’”, Pastoralism: Research, Policy and Practice, 4:1.
Gocher, K., 2009, “Soil can store methane”, ABC Rural, Friday, 07/08/2009.
Goodland, R. & J. Anhang, 2009, “Livestock and climate change”, World Watch, Nov/Dec 2009, https://www.worldwatch.org/files/pdf/Livestock%20and%20Climate%20Change.pdf (retrieved 18/4/2016).
Gurian-Sherman, D., 2011, Raising the steaks: Global warming and pasture-raised beef production in the United States, Union of Concerned Scientists, February 2011, http://www.ucsusa.org/sites/default/files/legacy/assets/documents/food_and_agriculture/global-warming-and-beef-production-report.pdf (retrieved 16/4/2016).
Hanson, R.S. & T.E. Hanson 1996, “Methanotrophic Bacteria”, Microbiological Reviews, June 1996, p. 439–471 Vol. 60, No. 2.
Hendy, C.R.C., U. Kleih, R. Crawshaw & M. Phillips, 1995, Interactions between Livestock Production Systems and the Environment, FAO & Natural Resources Institute, UK, 1995, http://www.fao.org/wairdocs/lead/x6123e/x6123e00.htm (retrieved 13/4/16).

Herrero, M., P. Gerber, T. Vellinga, T. Garnett, A. Leip, C. Opio, H.J. Westhoek, P.K. Thornton, J. Olesen, N. Hutchings, H. Montgomery, J.-F. Soussana, H. Steinfeld & T.A. McAllister, 2011, “Livestock and greenhouse gas emissions: The importance of getting the numbers right”, Animal Feed Science and Technology 166– 167 (2011) 779– 782.

Holechek, J.L., H. Gomes, F. Molinar, D. Galt & R. Valdez, 2000, “Short-Duration Grazing: The Facts in 1999”, Rangelands 22 (1). 

Houweling, S., T. Röckmann, I. Aben, F. Keppler, M. Krol, J. F. Meirink,
E. J. Dlugokencky & C. Frankenberg, 2006, “Atmospheric constraints on global emissions of methane from plants”, Geophysical Research Letters, Vol. 33.

Hristov, A.N., 2012, “Historic, pre-European settlement, and present-day contribution of wild ruminants to enteric methane emissions in the United States”, Journal of Animal Science, 90:1371-1375.

Itzkan, S.J, 2004, “Upside (Drawdown): The Potential of restorative grazing to mitigate global warming by increasing carbon capture on grasslands”, Planet-TECH Associates, http://www.planet-tech.com/sites/default/files/Upside%20%28Drawdown%29%20-%20A%20New%20Narrative%20on%20Grassland%20Carbon%20Capture%20-%20Itzkan%202014%20-%20V0.9.6.pdf (Retrieved 19/2/16).

Itzkan, S.J., 2011 “Regarding Holechek and Briske, and rebuttals by Teague, Gill & Savory: Correcting misconceptions about the supposed discrediting of Savory’s approach”, Planet-TECH Associates, 2011 (updated 2013), http://planet-tech.com/sites/default/files/Itzkan%202011,%20RegardingHolechekSavory%20v4_0.pdf (Retrieved 28/2/16).

Itzkan, S.J., 2013, “Talking Points Regarding Savory”, Planet-TECH Associates, March 2013, http://planet-tech.com/blog/talking-points-regarding-savory (retrieved 14/4/2016).

Janzen, H.H., 2011, “What place for livestock on a re-greening earth?”, Animal Feed Science and Technology 166– 167 (2011) 783– 796.

Joint FAO/IAEA Programme, 2010, “Methane, ruminant, livestock”, http://www-naweb.iaea.org/nafa/aph/stories/2010-methane-ruminant-livestock.html (retrieved 14/4/2016). 

Joyce, S., 2000, “Change the management and see what happens: A producer’s perspective”, Tropical Grasslands, Vol 34, pp.223-229.

Jones, M.B. & A. Donnelly, 2004, “Carbon sequestration in temperate grassland ecosystems and the influence of management, climate and elevated CO2”, New Phytologist.

Kaiser, C, M.R. Kilburn, P.L. Clode, L. Fuchslueger, M. Koranda, J.B. Cliff, Z.M. Solaiman & D.V. Murphy, 2015, “Exploring the transfer of recent plant photosynthates to soil microbes: mycorrhizal pathway vs direct root exudation”, New Phytologist (2015) 205: 1537–1551.

King, G.M., 1992, “Ecological aspects of methane oxidation, a key determinant of global methane dynamics”, Advances in Microbial Ecology, Vol. 12, edited by K.C. Marshall. Plenum Press, New York.

Kirschbaum, M.U.F., Ü. Niinemets, D. Bruhn & A.J. Winters, 2007, “How important is aerobic methane release by plants?”, Functional Plant Science and Biotechnology, Global Science Books.

Kirschke, S. et al, 2013,Three decades of global methane sources and sinks”, Nature Geoscience, September 2013. 

Kravchenko, I.K., V.M. Semenov, T.V. Kuznetsova, S.A. Bykova, L.E. Dulov, D. Pardini, M. Gispert, P. Boeckx, O. van Cleemput, & V.F. Gal’chenko, 2005, “Physicochemical and biological factors affecting atmospheric methane oxidation in gray forest soils”, Microbiology, Vol. 74, No. 2, 2005, pp. 216–220.

Kumar, S., A. K. Puniya, M. Puniya, S. S. Dagar, S. K. Sirohi, K. Singh & G.W. Griffith, 2009, “Factors affecting rumen methanogens and methane mitigation strategies”, World Journal of Microbiology and Biotechnology, September 2009.

Le Mer, J. & P. Roger, 2001, “Production, oxidation, emission and consumption
of methane by soils: A review”, European Journal of Soil Biology,  37 (2001) pp. 25−50.

Liebig, M.A., J.R. Gross, S.L. Kronberg, R.L. Phillips & J.D. Hanson, 2010, “Grazing Management Contributions to Net Global Warming Potential: A Long-term Evaluation in the Northern Great Plains”, Journal of Environmental Quality, 39:799–809.
Liu, Y., A. van Dijk & P. Canadell, 2015, “Despite decades of deforestation, the Earth is getting greener”, The Conversation, March 31st 2015, http://theconversation.com/despite-decades-of-deforestation-the-earth-is-getting-greener-38226 (retrieved 14/4/2016). 
McCarl, B.A., F. B. Metting & C. Rice, 2007, “Soil carbon sequestration”, Guest Editorial, Climatic Change (2007) 80:1–3.

McCarthy, M., 2015, “Cows off the hook as scientists downgrade impact of beef and dairy cattle on Australia's methane emissions by 24pc”, ABC Rural 15th December 2015.

McCosker, T., 2000, “Cell grazing – The first 10 years in Australia”, Tropical Grasslands, #34, pp. 207-218.

Machmuller, M.B., M.G. Kramer, T.K. Cyle, N. Hill, D. Hancock & A. Thompson, 2015, “Emerging land use practices rapidly increase soil organic matter”, Nature Communications, April 2015.

Mahony, P., 2013, “Do the math: There are too many cows!”, Terrastendo, July 26th, 2013, http://terrastendo.net/2013/07/26/do-the-math-there-are-too-many-cows/ (Retrieved 26/2/16). 

Mirzaei-Aghsaghali, A., N. Maheri-Sis, S.A. Siadati & N. Jalilnejad, 2015, “Factors affecting mitigation of methane emission from ruminants: Management strategies”, Ecologika Balkanica, 2015, Vol 7, Issue 1, June 2015, pp.171-190.

Nair, P.K.R., V.D. Nair, B.M. Kumar & J.M. Showalter, 2010, “Carbon sequestration in agroforestry systems”, Advances in Agronomy, Volume 108.

National Association for Sustainable Agriculture Australia Ltd., 2016, NASAA Organic and Biodynamic Standard, http://www.nasaa.com.au/data/pdfs/NASAA%20Organic%20Standard%20Feb%202016.pdf (retrieved 19/4/2016).

Neely, C., S. Bunning and A. Wilkes, 2009, “Review of evidence on drylands pastoral systems and climate change: Implications and opportunities for mitigation and adaptation”, FAO Land and Water Discussion Paper No 8, 2009. 

Paula, T.J.D. Jr. & L. Zambolim. 1994. “Effect of fungicides and herbicides on the establishment of the vesicular-arbuscular mycorrhizal fungus Glomus etunicatum on Eucalyptus grandis”, Fitopatologia Brasileira #19:2, pp.173-77.

Paustian, K., J. Lehmann, S. Ogle, D. Reay, G.P. Robertson & P. Smith, 2016, “Climate-smart soils”, Nature, 7th April 2016.
Philpott, T, 2010, “New research: synthetic nitrogen destroys soil carbon, undermines soil health”, Grist, 24/2/2010, http://grist.org/food/2010-02-23-new-research-synthetic-nitrogen-destroys-soil-carbon-undermines/ (retrieved 15/4/2016).
Pinjuv, G., 2011, “Gigaton analysis of the livestock industry”, Carbon War Room, April 2011, http://carbonwarroom.com/sites/default/files/reports/Carbon%20War%20Room-%20Livestock%20Report_2_0.pdf (retrieved 15/4/2016).
Priemé A. & F. Ekelund, 2011, “Five pesticides decreased oxidation of atmospheric methane in a forest soil”, Soil Biology & Biochemistry 33 (2001) 831-835.

Quirk, T., “Twentieth Century Sources of Methane in the Atmosphere”, 2010, 43rd Seminar on Planetary Emergencies, World Federation of Scientists (Erice, Sicily, August 2010), pp 365-374,

Rajput, P., R. Saxena, G. Mishra, S.R Mohanty & A. Tiwari, 2013, “Biogeochemical aspect of atmospheric methane and impact of nanoparticles on methanotrophs”, Journal of Environmental and Analytical Toxicology, Vol 3, Issue 7, 2013.

Reay, D., P. Smith & A. van Amstel, 2010, Methane and Climate Change, Earthscan, London & Washington DC.

Richards, C. & G. Lawrence, 2009, “Adaptation and change in Queensland’s rangelands : cell grazing as an emerging ideology of pastoral-ecology”, Land Use Policy, 26(3), pp. 630-639.
Ripple, W.J., P. Smith, H. Haberl, S.A. Montzka, C. McAlpine & D.H. Boucher, 2014, “Ruminants, climate change and climate policy”, Nature Climate Change, Vol. 4, January 2014.

Rumpel, C., A. Crème, P.T. Ngo, G. Velásquez, M.L. Mora & A. Chabbi, 2015, “The impact of grassland management on biogeochemical cycles involving carbon, nitrogen and phosphorus”, Journal of Soil Science and Plant Nutrition, 2015, 15 (2), 353-371.
Russell, G., 2015, “Halting climate change means more than cutting carbon”, New Matilda 25/11/2015, https://newmatilda.com/2015/11/25/halting-climate-change-means-more-than-cutting-carbon/ (retrieved 18/4/2016).
Russell, G., 2016, “Cowspiracy? Or is there a deeper problem?”, New Matilda, March 24th 2016, https://newmatilda.com/2016/03/24/cowspiracy-or-is-there-a-deeper-problem/ (retrieved 13/4/16).
Sanderman, J., J. Reseigh, M. Wurst, M. Young & J. Austin, 2015, “Impacts of rotational grazing on soil carbon in native grass-based pastures in southern Australia”, PLOS ONE, August 18, 2015, https://www.researchgate.net/publication/281852666_Impacts_of_Rotational_Grazing_on_Soil_Carbon_in_Native_Grass-Based_Pastures_in_Southern_Australia (Retrieved 19/2/16).

Savory, A., 1988, Holistic Resource Management, Island Press, Covelo, California, USA.

Savory, A., 2013, “Response to request for information on the “Science” and 
“Methodology” underpinning holistic management and holistic planned grazing”, http://savory.global/assets/docs/evidence-papers/The_Science_and_Methodolgy_of_Holistic_Planned_Grazing.pdf  (Retrieved 19/2/16).

Savory Institute, 2013a, “An exploration of methane and properly managed livestock through holistic management”, http://savory.global/assets/docs/evidence-papers/exploration-of-methane.pdf (Retrieved 15/3/16).

Savory Institute, 2013b, “Restoring the climate through capture and storage of soil carbon through holistic planned grazing”, http://savory.global/assets/docs/evidence-papers/restoring-the-climate.pdf (retrieved 13/4/16).

Savory Institute, 2014, “Holistic management: Portfolio of scientific findings”,

Scurlock, J.M.O. & D.O. Hall, 1998, “The global carbon sink: a grassland perspective”, Global Change Biology (1998) 4, 229–233. 

Searchinger, T., R. Heimlich, R.A. Houghton, F. Dong, A. Elobeid, J. Fabiosa, S. Tokgoz, D. Hayes & T. Yu, 2008, “Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land-use change”, Science, 29 February 2008, Vol 319. 

Sherren, K., J. Fischer & I. Fazey, 2012, “Managing the grazing landscape: Insights for agricultural adaptation from a mid-drought photo-elicitation study in the Australian sheep-wheat belt”, Agricultural Systems 106 (2012) 72–83.

Singh, P.K., M. Singh & B.N. Tripathi, 2013, “Glomalin: an arbuscular mycorrhizal fungal soil protein”, Protoplasma (2013) 250:663–669.

Soussana, J.F., T. Tallec & V. Blanfort, 2010, “Mitigating the greenhouse gas balance of ruminant production systems through carbon sequestration in grasslands”, Animal (2010), 4:3, pp 334–350.

Sparke, R., 2000, “Cell grazing – a producer’s perspective”, Tropical Grasslands, Vol 34, pp. 219-222.

Spokas, K., J. King, D. Wang & S. Papiernik, 2007, “Effects of soil fumigants on methanotrophic activity”, Atmospheric Environment 41 (2007) 8150–8162.

Steinfeld, H., P. Gerber, T. Wassenaar, V. Castel , M. Rosales & C. de Haan, 2006, Livestock’s Long Shadow: Environment Issues and Options, FAO, Rome 2006, ftp://ftp.fao.org/docrep/fao/010/a0701e/a0701e00.pdf (retrieved 17/4/2016).

Stinner, D.H., B.R. Stinner & E. Martsolf, 1997, “Biodiversity as an organizing principle in agroecosystem management: Case studies of holistic resource management practitioners in the USA”, Agriculture Ecosystems & Environment, · April 1997.

Subak, S, 1994, “Methane from the house of Tudor and the Ming dynasty: Anthropogenic emissions in the sixteenth century”, Chemosphere, 29:5, pp. 843-854.

Syamsul Arif, M.A., F. Houwen & W. Verstraete, 1996, “Agricultural factors affecting methane oxidation in arable soil”, Biology and Fertility of Soils, March 1996, Volume 21, pp 95-102.

Teague, W.R., S.L. Dowhower, S.A. Baker, N. Haileb, P.B. DeLaune & D.M. Conover, 2011, ”Grazing management impacts on vegetation, soil biota and soil chemical, physical and hydrological properties in tall grass prairie”, Agriculture, Ecosystems and Environment 141 (2011) 310– 32.

Teague, W.R., F. Provenza, U. Kreuter, T. Steffens & M. Barnes, 2013, “Multi-paddock grazing on rangelands: Why the perceptual dichotomy between research results and rancher experience?”, Journal of Environmental Management 128 (2013) 699e717.

Teague, W.R., S. Apfelbaum, R. Lal, U.P. Kreuter, J. Rowntree, C.A. Davies, R. Conser, M. Rasmus­sen, J. Hatfield, T. Wang, F. Wang & P. Byck, 2016, “The role of ruminants in reducing agriculture’s carbon footprint in North America “, Journal of Soil and Water Conservation, 71:2, 2016.

Tedeschi, L.O., J.P. Muir, D.G. Riley & D.G. Fox, 2015, “The role of ruminant animals in sustainable livestock intensification programs”, International Journal of Sustainable Development & World Ecology, 22:5, 452-465.
The Bison Herd, 2014, “A discussion on the interaction of the bison herd with earths' spheres”, October 1st 2014, https://thebisonherd.wordpress.com/ (Retrieved 28/2/16).
Tollefson, J., 2013, “Methane leaks erode green credentials of natural gas”, Nature, Vol 493, Issue 7430, 2/1/2013. 
Topp, E., 1993, “Effects of selected agrochemicals on methane oxidation by an organic agricultural soil”, Canadian Journal of Soil Science, 73,
Treseder, K.K. & M.F. Allen, 2000, “Mycorrhizal fungi have a potential role in soil carbon storage under elevated CO2 and nitrogen deposition”, New Phytologist (2000), 147, 189-200.

Tunstall, B. & Walter Jehne, 2005, “Possibilities for increasing and measuring soil carbon”, http://www.eric.com.au/docs/microbes/soil_health/eric_soil_carbon.pdf, 2005 (retrieved 15/4/2016).

Wahlquist, A., 2012, “Cattle and methane”, Ockham’s Razor, ABC Radio 12/8/2012, http://www.abc.net.au/radionational/programs/ockhamsrazor/12-august-2012/4182176 (retrieved 15/4/2016).

Walcroft, A., S. Price, K. Tate, R. Sherlock & D. Whitehead, 2008, “Soil methanotrophs: A novel methane mitigation technology?”, Landcare Research Contract Report LCO708/154, Ministry of Agriculture & Forestry, NZ, June 2008.

Wang, C. et al, 2014, “Sound management may sequester methane in grazed rangeland ecosystems”, Scientific Reports 4, Article number: 4444, 2014,  http://www.nature.com/articles/srep04444(Retrieved 19/2/16).

Wang, T., W.R. Teague, S.C. Park and S. Bevers, 2015, “GHG mitigation potential of different grazing strategies in the United States Southern Great Plains”, Sustainability 2015, 7.

Weber, K.T. & B.S. Gokhale, c.2009, “Effect of Grazing Treatment on Soil Moisture in Semiarid Rangelands”, Final Report: Forecasting Rangeland Condition with GIS in Southeastern Idaho, undated, c.2009, http://giscenter.isu.edu/research/techpg/nasa_oneal/pdf/ch15.pdf (Retrieved 19/2/16).

Weber, K.T. & S. Horst, 2011, “Desertification and livestock grazing: The roles of sedentarization, mobility and rest”, Pastoralism: Research, Policy and Practice 2011, 1:19.

Webster, J., 2013, Animal Husbandry Regained: The Place of Farm Animals in Sustainable Agriculture, Routledge, Oxon & New York.

Whipps, J.M. & J.M. Lynch, 1983, “Substrate flow and utilisation in the rhizosphere of cereals”, New Phytologist, #95, pp. 605-623.

Wuebbles, D.J. & K. Hayhoe, 2002, “Atmospheric methane and global change”, Earth-Science Reviews 57 (2002) 177–210.

Alan Broughton is a biological agriculture researcher and teacher at Strathfieldsaye Estate, Eastern Victoria, Australia.   He can be contacted at : matunda7 @hotmail. com