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23 August 2016

Domesticated Ruminants: Climate Change Hero or Villain?

Geoffrey Craggs, JP Research Analyst Northern Australia and Landcare Research Programme

Summary

There is considerable debate about ruminants as a major source of food and the role they play in

increasing levels of atmospheric greenhouse gas (GHG) through their emission of methane. This

paper seeks to examine both sides of this debate.

Cattle are being increasingly acknowledged as contributors to climate change through methane gas

emissions. But, through research scientific analysis is proving they can work with nature and play a

significant and vital role in reducing levels of atmospheric carbon.

In developed countries the importance of livestock, in particular ruminants, goes far beyond the

function of food production. In low-middle income countries cattle are a source of draught power,

Key Points

The role of domesticated ruminants in global societies extends far beyond

food production. They are significant in the social, cultural and economic

lives of millions of people.

World food security is at present heavily dependent on meat and other

products from ruminants.

It is estimated that on average over two billion tonnes of methane are

released by ruminants into the atmosphere each year.

With appropriate stewardship domesticated ruminant herds have the

potential improve pastoral soils, sequester atmospheric carbon and assist

in the mitigation of wildfire effects.

Leaders in government, private enterprise and academia must consider the

sponsorship of research into a range of competing factors relating to

reducing greenhouse gas emissions from ruminants.

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manure for soil fertility and crop production ensuring food security and fuel for domestic use. By

minimising the use of non-renewable energy and fossil fuels, livestock make a positive contribution

to local socio-economic development. As well, cattle and their by-products form an important

economic resource for farmers and poor rural communities.

Analysis

Ruminants

Ruminants are defined as mammals that are able to acquire nutrients from plant-based food by

fermenting it in a specialised stomach prior to digestion, principally through microbial actions. The

process typically requires the fermented material known as cud, to be regurgitated and chewed

again. The process of re-chewing the cud to further break down plant matter and stimulate digestion

is called rumination. There are roughly 150 species of ruminants with the majority being

domesticated cattle, sheep and goats. The large herds of wild ruminants such as the bison of North

America and the plains species of Africa have been diminished and replaced by agricultural

production. Prior to domestication, ruminants co-evolved with native grasslands which, once

covered approximately 40 per cent of the Earth’s land surface. Roaming in large herds, across

savanna’s and open plains, they would consume vast amounts of native grasses and other herbage.

Their feeding patterns and length of time spent in any given area would have been determined and

governed by the availability of forage, fire, geology and climatic conditions (snow and ice). Over time,

ruminants adapted to grazing and consuming different types of grasses and plant species dependent

upon on location, climate and availability.

In the process of grazing, ruminants knock down and consume the plant matter above the soil

surface, in turn producing manure. This manure or dung is rich in minerals and nutrients and in the

process of decomposing, builds up the soil organic matter also containing fixed carbon

(sequestration). Importantly the plants consumed above ground direct their growing energy below

the soil surface to promote roots development and re-growth, in turn enhancing soil structure and

fertility.

Human habitation and early farmers converted those grasslands to crop production for human

consumption or for commodities such as fibres used for making cloth. Coinciding with evolving

agriculture, roaming ruminants, in particular cattle, horses, sheep and goats were domesticated to

provide food, fibre, labour and comfort. Archaeological and studies of DNA suggest cattle were

domesticated from wild oxen common in Europe and Asia approximately 10,500 years ago, a period

of time that coincides to not long after the invention of farming.

Ruminants Role in Food Production

For thousands of years, mankind has depended on livestock as an important component of the

agricultural economy. Today, in both developed and in developing countries, livestock are closely

linked to the social and cultural lives of millions of resource-poor farmers for whom animal ownership

ensures varying degrees of sustainable farming, economic stability and food security.

Whilst the importance of livestock in food production is obvious. There are, however, negative

effects. For instance, increasingly scarce land must not only produce fodder for ruminants but must

also be used for cereals and grains as well as vegetables and other foods.

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Figure 1: A bull-cart in a rice paddy near Heret, Ethiopia. Source: Alex Treadway

From an environmental viewpoint, the need for livestock as a source of food, in particular cattle, have

resulted in environmental damage through deforestation (and continues to do so particularly in

lesser-developed countries) to convert land to cropping and pasture use. This coincides with

annexation of land for use as feedlots to rest and fatten cattle before they are sent to market. In

Australia environmental impacts attributable to feedlots relate to odour, noise, dust and waste

disposal. In addition, water quality can be impacted, where plans for concentrating grazing animals

do not consider hydrology factors. This can lead to runoff water containing antibiotics, heavy metals,

pathogens, pesticides, and ammonia, resulting in contamination of ground and surface waters.

According to the Food and Agriculture Organisation of the United Nations (FAO) populations of

ruminants have grown at about half the rate of the human population since the mid-1990s. An added

fact is the world’s population is expected to increase to approximately 8.9 billion within the next two

decades, mainly in developing countries. This increase in human population, and the resulting

increase in pressure on land and decrease in composition of the livestock population, will have a

major effect on both available natural resources and future food demands which will consequently

determine the type of livestock feeding and production systems to be adopted.

Meat consumption tends to be much higher in developed countries as t is comparatively expensive

to produce. In developing countries, particularly in Africa and Asia, ruminants continue to play

important cultural and social roles in addition to enriching soils, improving food security and

increasing incomes. In Uganda, for instance, a dairy project has successfully developed milk

production and, in the Niger River region of West Africa, small cheese-making units have provided

several hundred women with jobs and income in both production and marketing. In India, Operation

Flood promotes dairy development amongst small farmers and has established a modern and

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efficient dairy industry in that country where it has been estimated that for each 6 to 10 kg of

additional milk processed per day in India, one working day is added for feeding and care. These

activities bring money to a family and consequential enhancements to community incomes, the

addition of soil enrichments, thus and ensuring food security.

Figure 2: Women’s dairy project in Uganda. Source: Heifer International

Cattle dung is highly valued as fuel for cooking and heating in low-middle income countries, thereby

reducing reliance on timber or fossil fuels. In India alone, 300 million tonnes of dung are used for fuel

every year. Akin to milk production, the collection and drying of dung for cooking generates income

for women.

The FAO reports 52 per cent of the cultivated area in developing countries (excluding China) is farmed

using only draught power from cattle by pulling ploughs, pumping irrigation water or forest clearing.

Further, there has been a 23 per cent increase in the number of cattle and buffaloes used for draught

purposes during the past ten years. Animal power is a renewable energy source. Compared with the

use of tractors around the world, 90 per cent of which are produced in developed countries, draught

animals remain the most cost-effective power source for small and medium-scale farmers.

Correspondingly, power from draft animals avoids the drain of foreign exchange involved in the

importation of tractors, spare parts and fuel, not to mention fossil fuel savings in machinery

manufacture and from shipping costs.

Ruminants as Soil Improvers

Carbon is critical to soil health. Soil organic carbon (SOC) refers to the carbon stored (sequestered) in

the top soil, the upper, outermost layer of soil, usually from five to eight cms in depth. SOC is an

important contributor to soil fertility as it helps to resist erosion, improves water retention and

promotes soil biodiversity.

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The topsoils in most developed countries are generally well managed. By comparison, lesser-

developed countries support heavy land use in degrading soils and engage in intensified use and

heavy crop rotation, over-tillage, use of fire (which destroys organic matter), use of chemical

fertilisers and other poor land management practices. Additionally, through deforestation, soils

quickly become degraded as a result of compaction, loss of structure, nutrient degradation, salinity

and erosion leading to nutrient loss; soil heath and SOC levels leading to carbon loss are significantly

affected.

One approach to utilising cattle to increase SOC levels is currently in operation in villages and

communities in Karnataka, India: the Kolar Biogas Project is reducing local methane emissions from

cow dung to produce a biogas used as a fuel for cooking and heating, as opposed to the traditional

burning of fossil fuel and wood. An important bi-product of the biogas production process is carbon

and nutrient-rich fertiliser which is used as a soil improver and as a plant fertiliser.

A strategy becoming increasingly common in practical soil-regeneration practice is to integrate

managed programmes of rotational cattle grazing, designed to stimulate plant roots and develop sub-

soil biological communities. By introducing grazing livestock to forage on cover crops for short

durations, breaks plants down and re-directs the growing energy to producing organic matter in soil.

This allows new plants to emerge and adds green manure to the soil. The biological activity in the

decomposing organic waste matter enhances plant protection against pests and diseases further

resulting in improved soil fertility.

Ruminants and the Control of Wildfires

There is an increasing body of research evidence that supports the view that climate change is

contributing to an increased frequency, extent and intensity of wildfires. In addition to the

destruction caused by wildfires they also release tonnes of greenhouse gas (GHG) into the

atmosphere. With this increased frequency and intensity of burning, wildfires may be out-stripping

natures capacity to extract these GHG from the atmosphere and store it in vegetative regrowth.

Domesticated, pastoral ruminants, particularly cattle, can be used as a tool to lower wildfire risk by

reducing the amount, height and distribution of fuel. Careful and planned stewardship of the

agricultural landscape with controlled livestock grazing can reduce wildfire related GHG emissions in

two ways. Firstly, when wildfires do occur their intensity is reduced by the limited amount of available

fuel and secondly, the need for preventative “burning off” of fuel, which also releases GHG, is

avoided. Fire management strategies incorporating ruminants are being effectively used in the

tropical and subtropical savannah of Northern Australia.

Ruminants as Producers of Greenhouse Gas (GHG)

Methane is a primary GHG which, combined with water vapour, carbon dioxide, nitrous oxide and

other gases, absorbs and emits radiation within the thermal infrared range, the fundamental cause

of which is the ‘greenhouse effect.’ The effect of increasing the heat in the atmosphere, through the

emission of higher levels of greenhouse gases will ultimately contribute to global warming. Methane

is 23 times more potent than carbon dioxide in trapping heat in the atmosphere.

A major source of methane gas is animal waste; in particular cattle produce methane gas in their

ruminant digestive system which is then expelled through burping, flatulence and in their dung.

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According to the Food and Agriculture Organization of the United Nations (FAO) ‘livestock are one of

the most significant contributors to today’s most serious environmental problems, requiring urgent

action to remedy the situation.’

Globally, the increasing levels of methane gas is the subject of intensive research to identify and

implement reduction strategies to a point where the environmental threat diminishes to manageable

levels. Ruminant methane reductions, however, will be difficult to achieve considering the cultural

importance and reliance placed on cattle in less-developed countries.

Supporting research aimed at reducing domesticated livestock methane emissions through feed

modification is also being conducted. For example in Wales, cow feed has been supplemented with

garlic and at Denmark’s Aarhus University, scientists are investigating whether oregano has a positive

effect on the bacteria in a cow’s rumen that produce the methane. Elsewhere, researchers have

introduced maize silage and fermented the outer covering of corn in an effort to reduce methane

emissions by as much as 30 per cent.

While attempts are being made to reduce methane levels through dietary changes or supplements

in cattle, in Colorado scientists are investigating whether medicines are having an adverse effect on

a cow’s digestive system. There, antibiotics are also routinely administered in the belief that they

also enhance microbial actions, thus increasing the amount of methane produced in the gut and

emitted by an animal. The consequences of this research will be to attempt to identify and develop

natural medicines as alternatives.

Figure 3: Dung beetle (Family Scarabidae). Source: mPascalJ

Research conducted by the Australian Dung Beetle Project identified methane levels produced by

cattle grazing in paddocks can be significantly reduced by dung beetles (Family Scarabidae). Dung

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beetles are important to the ecosystem - they capture and bury dung in the ground to be used as the

medium in which they lay their eggs. When hatched, the dung beetle larvae consume the dung and,

microbial action in the soil further breaks the plant matter, completing the cycle by producing

nutrients and nitrogen needed for plant growth. The soil microbial processes breaks down the buried

dung and the carbon becomes sequestered in the soil.

The Australian Dung Beetle Project records dung beetles will remove the biomass of a dung pad in as

little as 24 hours, thereby stopping the continued microbial action in the fresh dung pad and the

consequential release of methane to the atmosphere. Given one kilogram of cow dung produces up

to 250 grams of methane in a 24-hour period, depending on the feed consumed; dung beetles are an

important strategy to managing methane produced by cattle. Additional benefits of the work of dung

beetles are improved soil from the increased nitrogen and nutrients and the consequential

introduction of SOC.

Conclusion

Domesticated ruminants are inextricably linked to human life on earth. The role of ruminants,

however, is attracting some controversy as we regard an increasingly warmer globe. On the one hand,

meat remains an important source of food with nearly a billion head of cattle in the world today. On

the other hand, it is estimated that these cattle release about two billion tonnes of methane every

year.

Ruminants can improve soil health and methane levels can be reduced by certain farm management

practices. Soils can also be improved by increasing SOC through the decomposition of dung which

also sequesters carbon from the atmosphere. Ruminants can also consume vegetative ground cover

and thus ameliorate the frequency, extent and intensity of wildfires.

At the heart of the ruminant debate is our incomplete body of research surrounding the competing

issues. There is an increasingly pressing requirement of directed and coordinated research into

impact and sustainability of certain farming practices with the potential to increase food production

but do not contribute to atmospheric GHG levels.

*****

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