Climate Change: Opportunities and Threats for Dairy Farming

September 6th, 2010 by Andrew Casebow

There were less than 3 billion people in the world when I was born 60 years ago, but now there are more than 6.7 billion people and it is anticipated that the population will rise beyond 9 billion before 2050.  This is the main driving force of increasing ‘Greenhouse Gas’ (GHG) emissions and the phenomenon of ‘global warming’ that is already having a dramatic effect on the natural world.  Coupled with this is the huge change in the way we live our lives.

The ‘balance of nature’ that has evolved slowly in the past is no longer in balance.  In Guernsey, as elsewhere in the world, we have seen temperature rises over the past 60 years that cannot be explained by natural occurrences, by volcanic action, sunspots, or any of the other phenomenon that have caused changes in the climate in the past.

The changes in climate are not just happening in distant countries, to people with whom we have little contact.  In Guernsey where records have been kept since 1843 we have experienced an average temperature rise over the past 30 years of well over 1°C (1.80 F) and a significant reduction of rainfall during the summer months, with higher rainfall in the winter.  This is affecting all manner of wildlife.

We have recorded wild plants flowering earlier in the spring, not by two or three days but with spring flowers opening on average some 3 weeks earlier now than they did only 25 years ago!  Birds are breeding earlier.  Some birds no longer migrate to Southern Europe or Africa during the winter but overwinter in the island.  Insects and moths are surviving over-winter.  They are flying and breeding earlier in the year, whilst some diseases of livestock are spreading northwards from Southern Europe and Africa.  Sea levels are rising due to thermal expansion as well as the melting of glaciers.  We are now growing field crops that could only be grown further south, or in a greenhouse, but summer droughts are changing the ways that we manage the cows.

Agricultural developments during my lifetime have been really spectacular, driven by the breeding of better crop varieties and improved livestock.  Better farm management, the use of mechanisation, fertilisers, pesticides and scientifically formulated livestock rations have more than doubled production of cereals and milk, so that fewer people are now engaged in agriculture and sufficient food has been produced from a reducing area of land.

Improvements in agricultural production in recent decades has ensured that the increasing population can be fed, which in itself is amazing as the number of mouths to feed has more than doubled.  However, the increasingly affluent ‘middle-class’ population in developing countries is no longer satisfied with rice and grains as their staple diet but increasingly want a meat and milk based diet that takes more energy to produce. Livestock consume cereals and produce more waste and greenhouse gases.

People are also migrating in greater numbers to the cities. The rural poor are becoming the urban poor, but in the coming decades they will become the new middle classes. They will have more money to spend on their new energy using urban lifestyles, driving cars instead of riding bicycles and eating meat rather than rice and vegetables. The larger number of people and more demanding lifestyle will use even greater quantities of energy and emit higher quantities of greenhouse gases into the atmosphere. Agriculture will have to become even more intensive and great care will need to be exercised if this is not to lead to unacceptable contamination of the environment.

Global demand for food is expected to increase by 70% by 2050 (FAO, 2009). Given the fact that livestock production is thought to be responsible for 18% of greenhouse gas emissions and that milk production alone causes 4% of global warming, how can we feed a burgeoning world population without dramatically increasing GHG emissions and making climate change far worse? Moreover, as governments strive over the next 40 years to reduce emissions of carbon dioxide equivalent gases by up to 80%, livestock production will stand out as the major contributor of greenhouse gases unless major changes are brought about in the way that we produce food in the future and the quantity of meat and milk that is consumed.

Climate change

Climate change is not unusual. Our planet has been much hotter and also much colder at different times in the distant past. We are currently in a long ice age that started about 2 million years ago. Throughout that period changes in the movement of the earth around the sun (known as Milankovitch cycles) has meant that every 100,000 years or so the ice recedes and North America and Northern Europe ‘enjoy’ a brief warm period (a summer) of about 10,000 years before the climate starts to become colder again and the glaciers slowly reform.

The last ice age reached its coldest period about 20,000 years ago just before the climate suddenly started to warm up, melting the glaciers that covered much of North America and Northern Europe and causing the oceans to rise. So much water is held in the ice that at the peak of the last glaciation (ice age) the sea level fell by about 120 metres, but then as the ice melted it rose again to the level it is today. This happened during each succeeding warm period. The UK was joined to continental Europe during each successive ice age and Guernsey Island was only separated from the French mainland some 6,000 years ago as the seas rose. As the climate warmed the trees, plants and animals (including man) migrated northwards to the areas that had been tundra or covered in ice.

So climate change is not an unusual phenomenon. What is new is ‘global warming’ (or anthropomorphic climate change) because it is not caused by the natural cycles of the earth around the sun, by sun-spots or by volcanic action although all these do influence the climate. It is called anthropomorphic climate change because it is caused by mankind’s use of fossil fuels to generate power. The use of these fuels generate emissions, including carbon dioxide and other gases, that reduce the loss of heat to space from the Earth’s surface, thereby causing a gradual warming of the climate.

Few would argue that rapid climate change is not now occurring and most climate scientists are in no doubt that this is caused by the increase in greenhouse gases in the atmosphere. The rising levels of greenhouse gases (GHG’s) are linked to increasing world temperatures and the warming increases water vapour that can be held in the atmosphere, acting as a ‘feedback’ mechanism by which surface temperatures are driven up even further. Global warming has once again started the climate to change in the same way that it did at the end of the last ice age.

A one degree Centigrade (1.8 degrees Fahrenheit) increase in temperature represents about 100km (or 60 miles) northward movement (in the northern hemisphere) so that, for instance, in Guernsey, we are already experiencing the type of climate that was typical of Northern France only a few years ago and within the next 100 years it is likely that our climate will be very similar to the climate in southern France today. This means that our weather will be much hotter and drier and the types of plants and animals that thrive in the South of France are likely to be typical in the island.

Since the industrial revolution the main greenhouse gases (GHG’s), Carbon Dioxide, Methane and Nitrous Oxide have been increasing, driven up by the huge growth in human populations and the desire of many people throughout the world to achieve a ‘western lifestyle’.

The increasing human population require more food and, as they become more affluent, they want a diet that is based more on meat and dairy products and less on cereals and other crops. The animals that produce the meat and milk consume large quantities of animal feeds and water, and produce quantities of methane, ammonia and nitrates that affect the air, soil and water resources. Greater areas of land have to be cleared of forest to make way for agriculture. In their turn the crops that are used to feed the livestock require sufficient water to grow and use large quantities of the earth’s resources of land, oil and fertilisers, which are all in increasingly short supply!

Greenhouse Gas (GHG) Emissions

The presence of greenhouse gases in the atmosphere acts like a blanket around the globe, reducing the radiation of heat from the surface of the earth out into space. If there were no carbon dioxide or methane in the atmosphere the earth would be much colder and inhospitable, but if there is too much then it could become unbearably hot. It is necessary to maintain the existing ‘balance’.

Since the beginning of the Industrial Revolution one of the greenhouse gases, carbon dioxide (CO2), has increased by nearly 40% from 277 parts per million (ppm) to 387 ppm, whilst methane has increased from 600 parts per billion (ppb) to 1728 ppb and Nitrous Oxide from 290 ppb to 318 ppb. What makes these gases important is the fact that methane has a ‘global warming potential’ 23 times that of carbon dioxide, and nitrous oxide is 296 times as potent as carbon dioxide. Their joint effect is usually expressed as carbon dioxide ‘equivalents’. Whilst the burning of fossils fuels produce carbon dioxide, food production is one of the main contributors of methane and nitrous oxide.

A report called ‘Livestock’s Long Shadow’ prepared by the UN Food and Agriculture Organisation (FAO) concluded that the global anthropomorphic (man-made) greenhouse gas (GHG) emissions from the livestock sector was between 4.1 and 7.1 billion tonnes of carbon dioxide ‘equivalents’ per year, or between 15% and 24% of total man-made GHG emissions.

A subsequent FAO report on ‘Greenhouse Gas Emissions from the Dairy Sector’ quantified the major greenhouse gases associated with dairy farming. This concluded that the global dairy sector (milk and meat from the dairy herd) contributes some 4% of the total annual global anthropogenic GHG emissions, when meat production from calves and culled cows was included; or 2.7% when only the emissions associated with milk production, processing and transportation were included. Most (93%) of these emissions occur at the farm level. Interestingly, the report also highlighted regional variations showing that North America and Europe had the lowest emissions per litre of fat and protein corrected milk. This suggests that lower emissions per litre of milk were associated with more efficient, higher production of milk per animal and more intensive farming systems.

With all the emphasis on carbon dioxide the role of methane and nitrous oxide are often overlooked but they are most important on the dairy farm. Methane accounts for over 50% of the GHG emissions from milk production and is particularly high in grassland systems, whilst nitrous oxide emissions range from 27% to 38% of total emissions depending on the type of grazing and manure storage systems employed. However, in a world that is becoming short of food, we should not overlook the fact that grazing animals convert forage produced on poorer quality land into high quality meat and milk and the animals also produce organic manures that can enrich soils and provide nutrients for crop production.

In Ireland, two researchers, Casey and Holden , quantified the GHG emissions from the average Irish milk production system. For instance, they calculated that manure management produced 11% of the GHG emissions (methane or nitrous oxide), whilst fertiliser use on dairy farms generated 21% of GHG emissions, of both carbon dioxide and nitrous oxide. However, most GHG emissions were methane from ruminant digestion.

Click graph to expand

Some people suggest that we should stop eating meat and consuming milk and adopt a vegetarian or vegan diet instead. However, whilst it might be beneficial for some people to reduce the quantity of food they eat for their own health benefits, it is not as simple as it might seem. What is obvious is that the human diet will have to change, or methods of production will need to change. For instance, within 50 years there will be over 50% more people on the planet to feed and many of those will demand the type of diet that only the wealthier people are able to afford now. Clearly if the quantity of meat and milk production double then, unless some very radical changes have been made in livestock diets and management, the increase in GHG emissions will be unsustainable.

If, by that time, personal action, government incentives and new technology have reduced the GHG emissions from transport, electricity generation and heating, etc., then livestock farming might be the largest producer of greenhouse gases, again clearly an unsustainable position for farmers and consumers! Therefore, it is likely that people in today’s richest countries might have to reduce the quantity of meat and milk that they consume, if others are to attain the improved nutrition that they desire.

Professor Beddington, the UK Government’s Chief Scientist, has suggested that the world is approaching what he called a ‘Perfect Storm’ within the next 20 years. He has suggested that by 2030 there will be demand for 45% more energy, although oil supplies will be reducing and therefore much more expensive, water demand will have increased by 30% with many more countries experiencing severe drought and reduced agricultural production, and there will be a 50% increase in the demand for food. Remember, this is not by 2050, or the end of the century, but within the next 20 years: so well within our own lifespan and that of our children.

Beddington has said that the challenge for agriculture is to produce 50% more food, on less land, with less water, using less energy, fertilisers and pesticides, whilst not increasing greenhouse gas emissions . It seems almost impossible but we know that it must be accomplished. We also know that this is just the start, as the human population of the world and the burgeoning ‘middle classes’ in many developing countries, are likely to increase far more over subsequent decades.

What can dairy farmers do?

Mitigation or Adaptation?

There are two ways that have been suggested that scientists and farmers can approach the problem of global warming. The first is to slow down climate change by reducing the emissions of greenhouse gases (known as mitigation), whilst the second is to take action to adapt to the higher temperatures and reduced rainfall that is likely to occur.

Agriculture’s problem is the greater because we also have to produce 50% more food within the next 20 years as well as satisfying the greater demand for meat and dairy products, whilst at the same time reducing emissions.


There are three main approaches to mitigating GHG emissions:

1. Improved efficiency by continually managing the farm and the herd better. By adopting ‘best farming practices’ for fertiliser and manure application, improved genetics and feeding practices;

2. Bio-tech solutions, such as the introduction of micro-organisms to change digestion / gut function, using genetically manipulated crops and livestock;

3. Dietary change, including novel forages and additives that manipulate digestion.

The farm management changes include all the small changes that can make improvements in the efficiency of farming, which is another way of saying that they are actually the same changes that save us money and improve the profitability of farming. They include changing to minimum tillage techniques and reducing fertiliser applications to take account of the nutrients in organic manures and applying fertilisers at the most appropriate time for crop growth.

It is common sense in business to be as efficient as possible and to reduce input costs as much as possible, and yet some farms do waste fuel, fertiliser and feeds. Part of this may be caused by not taking sufficient account of the nutrients in manures produced on the farm, but it is also caused by using excessively high protein concentrate feeds that may not be justified.

On average less than 50% of the nitrogen fertiliser applied to the land is taken up in crops, whilst over 70% of the nitrogen that is eaten by dairy cows in their animal feeds (mainly as protein) passes out at the back end! Reducing nitrogen fertiliser applications, making full use of the nitrogen in animal manures, spreading manure at the correct time for plant growth and reducing protein feeding will all reduce the emissions of nitrous oxide. There may also be a place for anaerobic digestion of animal manures to remove methane and use it as a fuel for electricity generation. I have farming friends in Germany who do just this and now make more money from the sale of electricity than from the sale of milk from the herd!

Breeding better cows that produce milk more efficiently will also make substantial improvements. Our current breeding goals are exactly right when we aim to develop cows that convert food to milk more efficiently, over a longer life with more lactations. Cows that are healthier, more fertile, with better udders and legs, have a longer productive life in the herd. It is also known that some individual cows produce less methane than others and so there could also be a genetic means by which cows can be bred that produce less methane. There is an obvious role here for genomics. The first step in this process will be to quantify the methane emissions from individual cows and a post doctoral researcher in the Animal and Poultry Science Faculty here at the University of Guelph has recently devised a method to do just that.

There is a possibility that methane emissions can be reduced by manipulating cattle diets to reduce enteric emissions from digestion. In a review article, McAllister and Newbold noted that “The microbial ecology of the rumen ecosystem is exceedingly complex and the ability of this system to efficiently convert complex carbohydrates to fermentable sugars is in part due to the effective disposal of H2 (Hydrogen gas) through reaction with CO2 (Carbon Dioxide) to methane by methanogens. However, although methane production can be inhibited for short periods, the ecology of the system is such that it frequently reverts back to initial levels of methane production through a variety of adaptive mechanisms”.

Many different feed additive chemicals have been used to reduce the production of methane in the rumen, but the reduction is small with less than 5% reduction at the present time. Improvements can also be short lived as bacteria in the gut get used to the changed conditions. The antibiotic ‘monensin’ which is used in the USA has also been shown to reduce methane emissions but the use of monensin is not allowed in animal feeds in Europe and in any case benefits may be transient and disappear after a few weeks.

Probiotics in the form of yeast cultures have been used in ruminant diets. These products have been used to enhance production but they can also reduce methane production. Similarly plant extracts, such as garlic, could be used to manipulate rumen fermentation and improve efficiency of nitrogen utilisation.

A number of research scientists have been investigating chemical additives, micro-organisms and plant extracts, with varying degrees of success. Bodas et al screened 450 plant extracts for their ability to inhibit methane production and found that 35 plant extracts reduced methane production by more than 15% and some by much more.

However, a note of caution was emphasised by Professor Reggie Lo recently when he said that “It is unlikely that we can change or modify what evolution and natural selection have accomplished over millions of years. There is a balance (an equilibrium) between a host and its commensal microbes that is not likely to be changed easily.”

As a longer term solution, researchers are developing new strains of perennial ryegrass with higher levels of water soluble carbohydrate (sugars), which might reduce methane emissions. A study by Miller et al showed that dairy cows fed a high sugar strain of ryegrass not only produced higher yields but also excreted less nitrogen than cows fed ordinary grass. Later, Moorby et al showed that feeding these improved grasses increases the capture of nitrogen into microbial protein in the rumen, which might decrease nitric oxide emissions from dung and urine.

To summarise, we can make a number of changes that can reduce the emissions of greenhouse gases from dairy farming. We can improve the efficiency of milk production by managing cows better, by changing the feeding of dairy cattle and modifying their rationing, by improved breeding for higher production, with improved lifetime efficiency and improved longevity and fertility. We can improve our manure storage and handling.

The actions that we are already taking to breed and select cattle for health and lifetime efficiency will also reduce GHG emissions. Most of our discussions during this conference have been about taking action to improve the genetics of our dairy cattle. In the future we will need to continue breeding animals that are the most efficient producers of milk but we will also need to consider breeding cows that produce less methane as well, so are better for the environment!

Most of the strategies to manipulate cow diets are best described as future or ‘speculative’ mitigation methods but there are some measures that we can take now that will make savings. These include making full use of the nitrogen that is available in slurry and animal manures, spreading manures only at appropriate times and in suitable conditions and ensuring that excess protein is not fed to dairy cows. These measures can all reduce nitrous oxide emissions now and save farmers money too. So it makes good business sense. At the same time many farmers, especially in Germany, are now looking at anaerobic digestion of livestock manures to produce methane gas that can be used for electricity generation.

Taking just one or two steps will have very limited impact but if we improve on all fronts then the greater efficiency will make our farms more profitable and also significantly reduce emissions. In many cases if we aim to improve the efficiency of our farming we will also be achieving most for the environment!

Finally, I know of two computer based emissions calculators that are being used successfully by dairy farmers. I would commend their use to you:

• The Calm Calculator is available from the UK Country Land and Business Association. It is a free business based calculator that measures the emissions of carbon dioxide, methane and nitrous oxide from land based businesses and balances these emissions against carbon sequestration in soil and trees.

• A new Cool Farm Tool has been developed by Jon Hillier at the University of Aberdeen in collaboration with Unilever Sustainable Agriculture. The tool is focused on farmers interested in quantifying their carbon footprint and finding practical ways of reducing it. The Cool Farm Tool will also be used in a multi-company project on agricultural climate mitigation coordinated by the US based Sustainable Food Lab, including Unilever, PepsiCo, Marks & Spencer, Pulse Canada, Yara, Sysco and others.


Adaptation is perhaps what happens when all else fails. It is how we continually change and adapt to our changing environment. How can our farming adapt to inevitable climate change?

Let us be clear, climate change is happening and even if humanity starts to reduce emissions immediately we are still on course for an average 2°C rise (some scientists believe an average 4°C increase) in world temperatures during the course of this century. This is due to the emissions of GHG that have already been released into the atmosphere and the fact that it has a continuing effect on the climate for many decades.

We are already witnessing hotter temperatures throughout the year and reduced summer rainfall in many parts of the world. In Guernsey we have longer and more frequent summer droughts than were previously normal which means that we need to feed cows on silage during the summer months. Similarly, heat stress that limits milk production is also becoming more important in hot arid climates and water availability is becoming scarce in some areas.

Heat stressed cows are more likely to break down to cattle diseases such as BVD and IBR. They can develop acidosis as sweating cows lose salts that would be valuable for rumen buffering. Their immune systems can be impaired and fertility reduced. The University of Arizona has produced a useful ‘livestock weather safety index’ that combines temperature and relative humidity into a graph that indicates when cows are likely to become stressed.

In Europe we are witnessing a northward spread of livestock diseases, such as Bluetongue (in cattle, sheep and goats), that were previously limited to Africa and the Mediterranean area. In many countries research is continuing on crops that can grow and yield successfully whilst requiring and using less water.


The world population is increasing and there will be greater demand for food, including more meat and milk in the future.

During the 21st century the global average temperature is projected to rise between 2°C and 6°C depending on the level of carbon dioxide emissions. This will affect the world’s weather systems, potentially increasing the likelihood of torrential rainfall, droughts and storms in vulnerable areas. Sea levels will rise and there is an increasing risk that low lying land will be flooded. Vulnerable people and wildlife will be adversely affected.

Global warming is caused by anthropogenic greenhouse gas emissions. Dairy farming produces large quantities of methane and nitrous oxide, so we have a considerable part to play in the reduction of emissions. There are numerous ways that emissions can be reduced but there is no ‘golden bullet’ so it is likely that we shall need to make many small improvements that will cumulatively have a large impact. Many of the improvements in efficiency could also improve the profitability of farming.

By our emissions we are not just affecting the climate today. Greenhouse gases remain in the atmosphere for many hundreds of years so the consequences of our emissions will last for many hundreds, if not thousands of years.

We are the cause of the problem so we are the solution. We need to take action now.

[1] Livestock’s Long Shadow: Environmental Issues and Options. Food and Agriculture Organisation (FAO), 2006.

[1] Greenhouse Gas Emissions from the Dairy Sector: A Life Cycle Assessment. Food and Agriculture Organisation (FAO), 2010.

[1] Casey, J.W.’ and Holden, N.M. Analysis of Greenhouse Gas Emissions from the Average Irish Milk Production System.  Agricultural Systems, 86 (2005), 97 – 114.

[1] Professor John Beddington:  ‘Key Issues in Agricultural Science’. The Frank Parkinson Lecture, Oxford Farming Conference, 5th January 2010.

[1] McAllister, T.A., and Newbold, C.J., (2008).  Redirecting rumen fermentation to reduce methanogenesis. Australian Journal of Experimental Agriculture 48, 7-13.

[1] Bodas, R., Lopez, S., Farnandez, M., Garcia-Gonzalez, R., Rodriquez, A.B., Wallace, R.J., and Gonzalez, J.S. (2008).  In vitro screening of the potential of numerous plant species as antimethanogenic feed additives for ruminants. Animal Feed Science and Technology 145, 245-258.

[1] Professor Reggie Low, Molecular and cellular biology faculty, University of Guelph: Personal communication.

[1] Miller, L.A., Moorby, J.M., Davies, D.R., Humphreys, M.O., Scollan, N.D., MacRae, J.C., and Theodorou, M.K. (2001).  Increased concentration of water soluble carbohydrate in perennial ryegrass: milk production in late lactation dairy cows.  Grass and Forage Science 56, 383-394.

[1] Moorby, J.M., Evans, R.T., Scollan, N.D., MacRae, J.C. and Theodorou M.K. (2006).  Increased concentration of water soluble carbohydrate in perennial ryegrass: evaluation in dairy cows in early lactation.  Grass and Forage Science 61, 52-59.

[1] Calm Calculator.

[1] The Cool Farm Tool.

[1] R J Collier (2007); D Armstrong (1994). Livestock Weather Safety Index, University of  Arizona.

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