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Livestock, Climate Change and the Environment  


 Peak Oil, resource depletion, global warming, financial stress and future world food and feed production

R A Leng

Emeritus Professor, University of New England, Armidale, NSW, Australia




The world appears to be at a most critical period in recent history, a financial crisis precipitated by simultaneous and interrelated/ interactive events including Peak Oil (the end of inexpensive energy),other global resource depletion and  climate change all of which are undermining  food security particularly in developing countries.   There is an urgent need to respond to these challenges in order to produce and deliver food to maintain the present world population, let alone the increased population predicted by 2030 of 8-10 billion people..


The primary underlying cause of world recession appears to be depletion in fossil fuel energy availability. The world has been using more fossil energy then is being discovered and it appears that the reserves of energy that can be cheaply mined are now at peak production (half these resources have been combusted). As oil reserves are depleted, prices will rise continuously with increasing scarcity and the extra demand now coming through the increased wealth in many emerging economies.


Nations have to prepare for a significant rate of depletion of oil reserves and large increases in costs of essentials relative to peoples purchasing power. World population expansion has been promoted by the availability of inexpensive oil, which has supported a “Green Revolution” by providing inexpensive inputs including fertilizers, insecticides, herbicides, traction power( lowering the need for labour and reducing the numbers of people in farming) and in places irrigation water. Inexpensive oil allowed food to be produced cheaply but this will change greatly as oil prices rise creating the potential for major disruptions in food availability and even famine. Failure to deal with increasing demand for oil, rising world temperature, failing water availability ( from snow melt, river flows and depleting aquifers) and reduced crop land fertility and  availability  through erosion, pollution, sea level rise   may cause  a slump in food production  leading to widespread world  famine 


Peak oil represents a massive change and will affect other resource availabilities. Agriculture has received inexpensive fertilizers on which high crop yields have been predicated including


The dependency of the industrialized countries on oil to drive agricultural production and the fact that most cannot meet their domestic requirements has seen development of alternative fuels including bio ethanol produced from sugar cane and maize mainly in Brazil and the USA respectively and development of bio diesel from oil palm largely in Asia. Cereal grain availability for industrial livestock production (pig, poultry, fish and feedlot beef and milk) will be highly restricted in the coming years and the short fall in meat/milk can only be replaced by expanding the production through forage-fed ruminants particularly by using crop by-products as bulk feed.  Ruminants are the logical animals for future meat and milk production but herbivores in general are likely to be used more extensively with time, particularly the rabbit with its dual capabilities of high reproduction rates and the capacity to utilize efficiently forage resources produced locally.


Water resources available for crop production have also been depleted. Many of the world’s large river systems are being drained for urban and industrial water supplies or for irrigation purposes before they reach their previous destination, a sea or a lake. Glacial melt is altering water availability, particularly where it supplies irrigation water in the dry season. Many of the world’s aquifers that were normally replenished annually by rainfall have also been drawn down with periodic loss of irrigation potential   The advent of Peak Oil with ultimate high cost of fuel has(will) curtail  pumping of deep water and  cut back crop production in many areas. Water depletion will eventually cause a return of vast areas of highly productive irrigated crop land back to rain fed cropping, pasture or desert   in the future with major loss of food productivity.


Expensive oil will undoubtedly force some farmers to return to draught power with considerable risks to decreasing the amount of land that supports multiple cropping which was a major factor in the increase in crop yields in SE Asia during the Green Revolution. Expensive inputs may derail the extensive land acquisition for industrial agriculture by foreign nationals in developing countries aimed at securing home land food security with repercussions for the local small farmers that are disenfranchised.   


Soil erosion and fertilizer run off from cropping systems are also major concerns as the present day cereal crops only tap the nutrients in the top few inches of soil and even the prairies of USA which were only cropped for about 100 years have depleted the top soil reserves with potential to decrease crop yields significantly. The response of crops to fertilizer application has been slowly diminishing now for 10 years 

Global climate change cannot be ignored in any discussion on future agriculture  Rising  sea levels will undoubtedly inundate  areas of fertile delta and weather patterns are predicted to  change, leading to at times more intense drought and or flooding rains with the potential to reduce crop production. Warming also carries with it the risk of decreased crop production as recent research has demonstrated that rice yields decrease by 10% for every o C rise in night time temperatures.

Each of the major global crises has the potential to lower world crop production by direct or various flow on effects. It is suggested the world an era where grain based animal production will become increasingly expensive as the competition for resources for food, feed and fuel, develops. The livestock revolution which suggested that by 2050, 900million tonnes of feed grain could be available for animal feed clearly failed to account for the resource decline and the inevitable flow on effects to crop production. However world demand for food of animal origin is likely to increase requiring a major shift to animal production industries based on herbivores exploiting a wide range of waste by-products of agriculture or pasture land not capable of being farmed for food or feedstock for biofuel production.  The scale of industrialised animal production is likely to be much reduced and small herbivores such as the rabbit are likely to play a much greater role in providing animal protein.


The enormous increase in inland aquaculture in China may indicate the way forward for producing more fish protein through integration of carp production using the manure from ruminant production to fertilize ponds for biomass production. The production of farmed fish in China now represents 0.3 of oceanic fish catch. Poly-culture of carp (herbivorous fish) integrated with ruminant and rabbit production appears to offer a major opportunity for making available inexpensive animal protein particularly in developing countries.


The high cost of fuel, decreased use of fuel in cropping,  pressure to produce biofuel, declining soil fertility, the high cost of chemical fertilizers, decreasing availability of  irrigation water and the loss of arable land to erosion, non agricultural purposes (such as roads and houses) coupled with likely overall decreases in crop production from global warming  appear to form “the perfect storm” that  will  make it  difficult for many nations to feed themselves in the future. The developing countries may be the most capable of supporting themselves through the maintenance of small farmer practices that integrate food and fuel production. The only way forward appears to be integrated farming systems that match the farming system with available local resources.


Key words: Animal production, aquaculture, development, energy, environment, farming systems, greenhouse gas, sustainable,


The objective of this presentation is to draw attention to the potential food crisis that is likely to occur in the next 10-20 years that will result from the present financial crisis and recurring recessions, depletion of critical agricultural resources and failure to limit the demand for fossil energy. A major question arises from this discussion in respect to future animal protein production systems - is animal protein production from cereal grain obsolescent?


Present day animal production can be categorised into the following  

  1. Intensive industrial systems (factory farming) including animals and fish based on concentrated protein and energy resources.
  2. Integrated cropping and animal production where animals, particularly ruminants utilise waste by products of agriculture or graze  pastures as part of a rotational crop /animal cycle  or native pastures  incapable of being economically cropped.
  3. Systems in densely populated areas of small farming enterprises where the animal is fed crop by products and is an integral component with out which a system can hardly operate and where the ruminant plays a key roles providing draught power, dung for energy or fertilizer and meat and milk or any combinations of these.
  4. Specialised or opportunity cost systems that take advantage of specialised crops such as ruminants integrated into tree  plantation management where they utilise the biomass undergrowth and  by-products of the crop.


Factory farming developed through the advent of inexpensive inputs such as feeds that were produced with inexpensive fossil fuels. It was further stimulated by increasing demand for animal protein as family incomes increased, the industrial revolution drew people into dense urbanisation and industrial cropping systems reduced the numbers of people required in food production. Specialised systems such as plantation grazing grew as pressure on fossil energy sources forced a move into potentially renewable fuel production systems.


Fossil fuels were massively exploited in the late parts of the 20th and early 21st centuries. The fossil energy provinces were so large and distributed so widely that competition and volume of production kept oil inexpensive. Inexpensive energy promoted industrialisation of just about every thing that people, including farmers and businessman, required. The availability of inexpensive food and medical advances allowed the world population to grow at unprecedented rates.  Prior to the age of abundant fossil fuel, world population was constrained below 1 billion people and the population growth was slow. Following the discovery of, first coal, but more importantly oil, it has increased almost exponentially from about 1.5 billion to 6.7 billion in a little over 100 years. Over this time, inexpensive energy supported enormous developments in industries, transport, trade, agriculture, medical progress and financial capital. Financial capital created by banks, fuelled what appeared to be, a never ending inexpensive source of energy as oil, coal or gas which appeared to provide adequate collateral, to support financial debt. The age of increasingly expensive energy appears to have arrived and will be marked by the decline of all that depends on it, including financial capital and peoples’ living standards particularly in the industrialised countries (see Youngquist 1997; Campbell 2005; McKillop 2009; Rupert 2009).


Deepening economic turmoil is prioritising resources in the industrialised world; the emphasis is on decreasing the ‘politically unacceptable’ loss of jobs by increasing consumption and therefore resource utilisation, in order to return countries to growth (or business as normal). But ‘kick starting’ economies and increasing development in emerging economies, without decreasing demand for fossil energy at its peak of production, may rapidly reverse economic recovery by increasing fuel prices (see Campbell, 2005; Rupert 2009; McKillop 2009). Historically, global economic growth has never occurred without a simultaneous increase in the use of fossil energy. Oil is fundamental to economic well-being.  World GDP growth & world oil production growth have tracked each other for decades (see Figure 1).


Figure 1. World GDP growth & world oil production growth have tracked each other for decades. Oil production data is from EIA, April 2007 International Petroleum Monthly. May 8, 2007.

GDP Market Exchange Rate data is from the IMF World Economic Outlook Database.  April 2007( after Hirsch 2009)


All nations of the world use oil, but for a few nations, coal is an important component of the fuel mix.  Unless economic policies ensure a decreased demand for fossil fuels relative to production, there seems little prospect of a permanent recovery from depression in industrialised countries and little chance of substantial growth in the underdeveloped  economies. The second half of the age of oil has major implications for all aspects of the world’s economy and world agriculture will be massively perturbed with implications for food production, in both industrialised nations and in the densely populated emerging economies, particularly of India and China.


Inexpensive oil led to industrialization of food production, land clearing and cropping on a scale that had never been seen in the history of the planet. Fertilizers, extracted from natural sources or in the case of nitrogenous fertilizers, by the manufacture of ammonia from nitrogen gas and methane, became abundantly available and inexpensive. Fertilizers increased crop yields and other crop inputs, including herbicides and insecticides, allowed potentially high yielding crops to be successfully and inexpensively grown. The Green Revolution supported a massive increase in the growth of the human population particularly in the Asian developing countries, although large tracks of Africa were largely untouched, seemingly because of the cost of seed and fertilizers even at that time. It created surplus grains, that provided incentive for factory farming of pigs and poultry in industrial countries and the incentive for a “Livestock Revolution” based on grain based feeding systems for meat, milk and fibre producing animals (see Delgardo et al 2002).


The changing availability of world resources particularly energy makes the potentially extravagant availability of meat and milk an unlikely outcome in the future. Increasing the availability of animal protein is not simply a matter of diversifying people’s diets, it also directly relieves the ill health of a large proportion of the resource poor people that rely on mainly cereal based diets that are deficient in essential micronutrients and essential amino acids. In this respect the requirement for animal protein in cereal based diets of the poor has been further strengthened with the recognition that green revolution cereal varieties contain substantially less micronutrients then traditional varieties (Ming-Sheng Fan 2008)  By 2000, 1.0 billion people were chronically undernourished (consume fewer than 2,000 calories per day), 100 million pre-school children have a vitamin A deficiency, and 400 million women between the ages of 15 to 49 have an iron deficiency leading to anaemia (Conway and Toenniessen 1999). Animal products, even in tiny quantities, support physical and intellectual development of young people (see Chapters 18 and 19 in Waterlow 1998) and improve the health of pregnant adults and development of the foetus in women consuming largely cereal based diets.


The changes that are likely to occur in the world’s livestock production systems are going to be complex and interactive making the task of predicting the future exceedingly difficult at the time of writing. However, the present food/financial crisis has brought out some highly informative recent publications (see Brown, 2009; Nellemann et al., 2009: Scherr and Sthapit, 2009; McKillop 2009).

Peak oil

The Hubbert Peak of oil resource exploitation

Prediction of oil availability and its use are dominated by principles originally proposed by Dr M King Hubbert, who introduced the concept that oil well exploitation could be described by a bell-shaped curve that indicated the early and late production rates from an oil field. Following discovery of oil and the establishment of facilities to manage the wells, the rate of extraction is increased until a peak production is attained and then the extraction rate falls (this is known as the Hubbert Peak). The peak extraction rate is always close to the mid point of depletion of the resource. Peak oil was also foreseen in 1957 by Rear Admiral Hyman G Rickover, who warned of the potential for the fossil fuel era to end rather abruptly with calamitous effects on food production (Rickover 1957). Many of his predictions are now happening.


 The Hubbert Peak has become a reality in those oil fields (that provide a high percentage of the total world oil) that have now passed their peak production and are depleting (see Duncan and Youngquist 1997). Oil discoveries world-wide, peaked in the mid 1960s (Figure 2) and have declined since; the total world production of fossil fuel has probably already peaked or will within 3 to10 years (Figure 3). At the present time for every new barrel discovered the world is currently using 4 barrels (the reader is directed to the ASPO website for a reasoned and unbiased discussion of Peak Oil. The Hubbert Peak concept appears to be now accepted and is being used to predict future world oil well exploitation and their likely depletion rates).



Figure 2. World oil discoveries and the trend in world utilization of oil (from Campbell 2005)


The pattern of reserves depletion for world fuels is validated by the pattern of production of oil from some of the giant fields (fields that yield more then 500 million barrels and are about 1% of the total number of oil fields) which dominate world oil production. Recent evaluation of these, especially those recognized to be in the phase of depletion      (e.g.  Cantarell in Mexico and the North Sea province) suggests that Peak Oil arrived in 2008 and that the average depletion rate of world oil resources will be 6% per annum and increasing (see Hook et al 2009). By 2030 the production from fields currently on stream could have decreased by over 50% (Hook 2009;  Figure 4). The International Energy Agency ( IAE) has disagreed with the predictions of Hook  et al 2009) see figure 4 but recent leaked documents suggests that this disagreement is political rather then real (Macalister 2009).


The world has been using oil at a greater rate than its discovery rate (Figure 2). Despite highly sophisticated and accurate methodology for identifying the geological formations where oil and gas would have accumulated in the past, few fields and no new mega fields have been found in recent times.


Figure 3. Forecast of future world oil production, including non-conventional oil, from the Association for the Study of Peak Oil, Released at Uppsala May 2002 First International Workshop on Oil Depletion, Uppsala University, May 2002.  


It appears that the advent of peak oil and the increasing demand for energy with increasing population and increasing wealth will ensure increasingly high priced fuels in the future (Campbell and Leherrere 1998: for more recent discussion see McKillop 2009), but with considerable variability over time, as periodic recessions lower demand and price, allowing both to rise again thereafter (Campbell 2005). High oil prices have great implications for the cost of many of the essentials of life. Interacting factors also indicate that food availability and food prices will be compromised directly or indirectly by flow on effects of oil depletion (see Leng 200, 2005, 2009), possibly the most important being the diversion of land from crop production to production of biofuel.



Figure 4. The historical world oil production along with crude oil forecast the reference scenario from IEA World Energy Outlook 2008. A constant decline rate of existing production of 6%, combined with an increasing share of fields in decline, is displayed as one possibility.  The IEA WEO 2008 forecast for fields in production (FIP) is compared to estimates made by Hook et al 2009. Using an increasing decline rate can mean 7 Mb/d less production capacity then predicted by 2030.



Interacting factors affecting world agriculture

Industrial biofuel production

The twin threats of peak oil and global warming have resulted in politically driven development of alternative liquid fuels resulting in massive development of industrialised ethanol production from sugar cane in Brazil, and maize in the USA. Both countries have huge importation costs for oil. Biofuel production from cereal grain with competition for food and feed has massive implications for human health and welfare and livestock production world wide and particularly for developing countries (see Runge and  Senauer 2007).


Manufacture of bio-ethanol from maize and other cereal grains is growing at a great rate and increasingly diverting crop land used to alcohol feedstock production. It is not the intention here to focus on the net efficiency gains in transport fuel from this strategy, however the amount of fossil energy used and energy returned in ethanol from growing maize and processing the starches through to alcohol is probably negative ( Patzek 2004; Patzek and Pimmentel 2006)


The Livestock Revolution coined by researchers from The International Food Policy Research Institute (Delgado et al 1999, 2002) was predicated on surplus world grain supplies and that the relative price of grain would not rise significantly in the next 50 years. It was theorised that grain (900 million metric tonnes), surplus to human requirements in most developed countries, would be used locally and also exported to developing countries as the basis of an industrialised pig and poultry industry to meet the growing world demand for meat /milk and also to meet the nutritional requirements for essential amino acids and other essential micro-nutrients for poor people on cereal-based diets.


Figure 5. US grain for ethanol and for export (adapted from Earth Policy Institute 2007; see Leng 2009)



The industrial production of biofuel, has already created major conflicts over food for humans, feed for animals and feedstock for liquid fuels.   By 2020, world alcohol production could remove conservatively 400 million tonnes of grain from world food - feed markets, either directly or by diversion of land from food crops to energy crops (Leng 2007). The balance between maize exports and maize used for ethanol in the US indicates the extent of the potential effects on world food supplies (see Figure 5, from Earth Policy Institute (Brown 2007)). Many countries in the world and even some that currently have chronic under and mal nutrition in their population, are planning biofuel programs. Inevitably these programs, whatever the source of feedstock, will remove land from food production.  The world grain stocks were depleting over the period 2000-2007,but good yields in 2008 ,particularly in Russia and the Ukraine have seen these reserves increase (Figure 6) and should more then offset the decline in world production that may come from the droughts plaguing a number of grain exporting nations (see de Carbonel 2009). However production and consumption are still critically balanced and expected future constraints are likely to result in major deficiencies (see below).   



Figure 6 World grain production and consumption has resulted in low world reserves (USDA Foreign Agricultural Servies 2009;


The world trade in all grains is around 240 million tonnes, of which around 80-90 million are exported from the USA. The acquisition of grain by the ethanol industry in the USA will thus have major impact on world grain availability and prices. Present world wheat and coarse grains reserves are 280 million tonnes, down from 450 million tonnes in 6 years. However, world demand for grain is increasing but carry over stocks from 2008 have regained some of the lost capacity up to that time. World grain surplus is narrowing and global per capita grain availability is also declining.


Many countries, particularly in South America (Brazil in particular) will clear forest land for cropping of   biofuel feedstock, which adds to global warming and ‘the new’ land quickly loses its initial high fertility. Following a short period of 2-10 years many of these highly fertile soils particularly planted to sugar cane require substantial fertilizer application to support adequate yields. The exception may be Palm oil integrated with cattle grazing (Devendra 2009). 

Global warming and climate change are also likely to reduce crop yields
The huge ethanol industries that are developing are compounding a number of other factors which are likely to reduce cereal grain availability in the future. The most significant effects of climate change on agriculture arise through changes in climate patterns. Increasing temperatures in tropical countries can have a slowing effect on photosynthesis and hence plant growth.  For example, rice yields in Asia are declining by 10% for every oC rise in night-time temperatures (Peng et al 2004).

A recent paper (CGIAR 2007), that focused on the effects of increased temperatures on wheat production in the South Asia Indo-Gangetic Plain, indicates a massive decrease in yields. This area produces 15% of total world wheat grain, about 90 million tonnes per annum. CIMMYT researchers are reported to have suggested that under climatic conditions expected to prevail in 2050, the wheat mega-environment will shrink by just over half, mainly through shortening of the growth period as a result of heat stress early and late in the wheat growing season. This threatens the food security of about 200 million people.

 The predictions on climate change are for increasing rain in some areas but less rain in others, thus it appears that rainfall patterns will become more variable (Stern 2007) and storms more intense, which will lead to increasing crop failures, particularly in the event of a return to draught power (Leng 2009). Conversely, warming will open up new land for grain production in the Northern Hemisphere but far away from the main centres of population. These lands will possibly be more attractive for biofuel crops

 Recent models of the effects of global warming suggest that flow-on effects are likely to reduce world agricultural output by between 16 and 3%. However the effects will not be spread evenly with productivity in the tropical, developing countries likely to be reduced disproportionately by  21-9%.(Cline 2007) The spread of estimates is brought about by the uncertainty surrounding the benefits of  increased atmospheric carbon dioxide on plant growth (carbon fertilization)..

Other resource depletions with implications for agriculture

Over the last century, and particularly the early part of the 21st century, inexpensive energy enabled unprecedented growth in rates of extraction of many resources. Many of these resources appear now to be in depletion, as they begin to reach or have reached peak extraction rates. They will therefore become more expensive as availability is reduced.  Some resources will become expensive simply because the world’s reserves are being depleted, others because the mining, processing, delivery to the farm and application are dependent on the use of fossil energy. The resource depletions that are likely to impact on crop yields are discussed below.


Water is the most potent resource for plant growth and without water, plant growth ceases. Two-thirds of the available fresh water is used for irrigation in agriculture (Revenga et al 1998) and water availability is a major factor limiting food production (Revenga et al 2000). The total amount of water withdrawn or extracted from freshwater systems has risen 35-fold in the past 300 years (Revenga et al 1998) and, since 1960, has increased by 20% per decade. Agriculture accounts for 70% of human water use. World-wide, groundwater is being withdrawn faster than it can be recharged, depleting a once renewable resource (Revenga et al 1998). Water use in many other industrialized processes is increasingly competing with water for agricultural purposes. The ethanol industry has a large appropriation of water and so has many industrial mining systems.


There is a growing body of opinion that water may ultimately limit world food production (Postel 1999). A number of significant rivers, that have provided irrigation water, now do not reach their destination, either to the sea or to lakes, because of water extraction and this is curtailing water use in food production (eg: the Murray-Darling river in Australia, the Amu Darya that feeds the dying Aral Sea, the Ganges and Indus rivers which barely make it to their natural destination). The World Wild Life Fund recently released a major report concerning the many risks that the world’s river systems face world (Wong et al 2007).


Water flows are decreasing in rivers when unprecedented quantities of water are being added to river systems through melting ice due to global warming. However, with time, as the ice and snow reserves are reduced, river flows will decline further. In a number of “food bowls” the timing of the decline in water flow occurs when irrigation is most needed with reduction of multiple cropping of land. Rain-fed agriculture will be affected mainly by changing weather patterns but these will also influence river flows. Irrigated crop production accounts for an enormous proportion of the total world food production. In twenty years time, the Himalayan glaciers will have been reduced from 500,000 square kilometers to 100,000 square kilometers (see Anthwal et al 2006, for a discussion on the rate of glacial melt). In the areas that are fed from these rivers, present rainfall occurs mainly in the winter and it is only the melting glaciers that supply water for irrigation and other purposes in the hot summer months placing over a billion people at risk.


Water tables are reported as dropping in nearly all countries (Brown 2005, 2009) as farmers over-use aquifers normally replenished from rain. For example, the water table in the huge Ogallala aquifer occupies 174,000 square miles at shallow depths beneath parts of eight states of the United States. It used to be the source of irrigation for 13 million acres of land but this area is steadily reducing (down by 370,000 acres in 1992; Postel 1992), owing to over-use for agriculture. Aquifer depletion results in reduced irrigation in certain areas and increased energy cost in all areas as the depth to reach water increases. With the advent of expensive oil the depth from which it can be pumped has an economic limit.  The world's irrigated land was 48 million hectares in 1900 and about 220 million hectares in 1990. About 75% of all irrigated land is in the developing countries and around 60% of cereal grain is produced under irrigation. Irrigated land accounted for approximately 15% of the cultivated land but produced 36 percent of the world's food in 1990 (Jensen et al 1990). Using data from major aquifers in China, India, Saudi Arabia, North Africa, and the United States where water tables are dropping - in some places precipitously - Postel (1999) calculated the annual over pumping of aquifers at 160 billion tonnes. On the basis that it takes 1,000 tonnes of water to produce 1 tonne of grain, Brown (2001) calculated that a 160 billion tonne water deficit is equal to 160 million tonnes of grain that cannot be produced, or around 10% of total world grain production, but more importantly, 66% of the world’s currently traded grain.


With the enormous pressures coming onto land for food, feed and feedstock for biofuel, the world’s water deficit can only get worse. Recently the International Water Management Institute has warned that pursuing biofuel production in water-short countries will put pressure on an already stretched resource and will turn green energy into a major threat to resources. The Comprehensive Assessment of Water Management in Agriculture report shows that at a global average, the biomass needed to produce one liter of biofuel evaporates between 1000 and 3,500 liters of water, under prevailing conversion techniques (de Fraitur et al 2007). India and China, even though they both are presently importing considerable staples and  facing severe water limitations for irrigated agriculture have initiated programs to boost biofuel production. The governments of water deficient countries in Asia should examine extremely carefully their priorities when mandating or promoting biofuel production through subsidies.

Peak land availability and soil fertility

Over 5% of the world’s cropland is highly susceptible to erosion by wind and water and all cultivated land is subject to loss of top soil with inevitable loss in fertility. Cereal crops in particular grow in the top few inches of soil where the nutrients are concentrated and loss of top soil leads to loss of productivity and /or an increased requirement for fertilizers. In addition to losing cropland to severe soil erosion, salination and desert expansion, the world is also losing cropland to many non farm uses, including construction of roads, houses, affluent pleasure facilities such as golf courses and industrial buildings.


The enormous twentieth-century expansion in world food production pushed agriculture into highly vulnerable land in many countries and these will surely start to produce at reduced levels as off-take of commodities and erosion reduces productivity. The mining of highly fertile, newly cleared forest land is a case in question. When first cleared, fertility is high but diminishes with time and the fertility can only be reclaimed with fertilizer use, leading to increased costs. This scenario appears to be playing out particularly in land cleared for sugar cane production for bioethanol in Brazil and land clearing for palm oil production in SE Asia and South America. Another serious effect of forest clearing is the removal of carbon sinks enhancing global warming. At the same time increasing temperatures are increasing the loss of a major carbon sink, the soil carbon which is more rapidly depleted as soil temperature increases (Carney et al 2007).


The conundrum is also made more complex if melting snow and ice influence sea levels. Most of the world’s most productive land is in delta areas that will flood or be inundated should sea levels rise as predicted, for instance, by Stern (2007).   


 In industrialized countries, and increasingly in the emerging economies, crops grown for food, feed, biofuel or other commodities are produced with large inputs of oil for ploughing, direct drilling, seeding, cultivation, fertilizer, pesticide application and the work of harvesting, processing, storage and transport


The fertilizers used are mainly sources of N, P, K and S. These have been the catalysts that allowed crop yields to be increased, supported in part by the discovery of high yielding grain varieties that could take advantage of the improved nutrient availability in the soil. This resulted in the great leap forward in agricultural production that was termed the Green Revolution. However, fertilizer use will be constrained in the future depending on: i) the cost of manufacture of nitrogenous fertilizers; ii) depletion of reserves of P, K and S; and iii) the cost of mining and delivery to the farm gate. Depletion of micronutrients (such as selenium, zinc, cobalt) and increasing cost of extraction are also becoming of major importance. The high yielding varieties of cereals appear to have lower requirements for microelements such as zinc as they contain only some 70% of the levels in the older long straw varieties  


Nitrogen is one of the most abundant elements on Earth, and is the critical limiting element for growth of most plants due to its unavailability as salts in the soil (Smil 1999). Prior to 1930, the N cycle on Earth was in dynamic equilibrium (Frink et al 1999). Grain crop yields until the 1930s were about 0.5 to 1.0 tonnes per hectare, with N supplied primarily from crop rotations and manures.  The advent of inexpensive energy allowed the production of ammonia based on the use of natural gas  Inexpensive fertilizers particularly ammonia and/or urea allowed large increases (up to 10 fold) in cereal grain production from high yielding grain varieties. This led to surplus world grain and massive investment in intensive animal production based on confinement of animals fed energy and protein-rich feeds. Whilst Asia accepted the high yielding varieties and the use of inputs many parts of Africa were unable to take up the strategy and many governments are now looking for a new Green Revolution in Africa similar to the one that occurred in Asia, perhaps offsetting some of the decline foreseen for global food production. In Asia the Green Revolution was enhanced by inexpensive oil which will not be the case in Africa. Despite this, land for growing crops in Africa and other developing counties using industrialised methodology, is being purchased by foreign interests, to support their own food security (Knaup  and von Mittelstaedt 2009)


N fertilizer manufacture is almost entirely dependent on the use of natural gas. The Haber -Bosch process of production uses 1% of all energy consumed by humans (Smith 2002) and its cost will follow fuel prices linearly. The availability of nitrates in soils is increased by leguminous plants that fix atmospheric nitrogen and this is probably the alternative source of nitrates when oil prices make artificial N fertilizers too expensive. Phosphorous on the other hand is either not available in soil or unavailable because of extensive binding in the soil matrix. The growth of mycorrhizal fungi on and in plant roots dramatically increases the surface area of roots available for soil exploration of nutrients, particularly P, but also N (Marschner and Dell, 1994). Whilst these associated fungi  may increase  P uptake it is clearly difficult to find food crops with this attribute sufficiently developed and P is likely to be limiting in the future for food production. Growing crops remove soluble phosphates and other nutrients from the soil. Most of the world's farms do not have adequate amounts of phosphate for plant growth and plants that grow on P deficient soils are low in P and do not meet animal and human requirements for this element. It has been shown that P resources are limited and soil P availability is being depleted (Steen 1998).


Just as with oil, human population growth was not possible until phosphorus deposits were found and inexpensive energy was available to extract, concentrate the ore into fertilizer, transport it to farms and add it to the soil. Future generations ultimately will face problems in obtaining enough phosphorus to exist. Recent studies have drawn analogies between Peak Oil and Peak P (see Dery and Anderson 2007).


In the same way that Hubbert showed the production and depletion characteristics of fossil fuels, the characteristics of P fertilizer production and depletion (see IFIA 1997 for data on world P reserves) follows the same bell-shaped curve. Using what is now called Hubbert Linearization, which is used to fit a bell shaped curve to fossil fuel extraction and depletion, the same bell shaped prediction of reserve availability can be seen for P (Figures 6 and 7). 



Figure 7:
Actual production of rock phosphate

Figure 8: Fitting the Hubbert curve to the  production of  rock phosphate, showing likely dates of depletion                 



 It seems that Peak P was reached around 2000. Dery and Anderson (2007) justify the use of this modelling by showing that deposits of phosphates on Nauru were depleted in precisely the same pattern and that the large deposits in the USA are being depleted similarly.


Peak P has immense implications for peak food production, with mounting problems with the cost and availability of phosphate fertilizers. Fortunately both P and N can be recycled and the conservation of nutrients within the farming system is still possible and will become what used to be considered a prime objective of agriculture- that is, the recycling of nutrients back to the farm. Whilst nutrient recycling within a farm can be effective, nutrients exported from the farm are less easily recycled. The problem is often that the food is consumed at some distance from the site of production and recycling then is costly in returning the nutrients to its origin because of water and fuel costs. It will be particularly expensive to do this from the huge point pollution sources in mega cities and from those that will arise, particularly in USA and Brazil, in the industrial production of alcohol.


Estimates of the world’s potash resources vary widely ranging from about 160 to 250 billion tonnes as K2O. Canada’s potash resources are conservatively projected at 60 billion tonnes, while US resources are estimated at 6 billion tonnes... enough to produce at current levels for several thousand years (see Roberts and Stewart 2002). However, the reserves are concentrated in a few countries and cost of potash increases with fuel costs.


The reserves of sulphur are almost undefinable. Bardi and  Pagani (2007) examined the world production of 57 minerals reported in the database of the United States Geological Survey (USGS). Eleven cases were found where production has clearly peaked and is now declining. Of these, selenium, phosphate rock and potash (contradicting earlier suggestions of ample amounts) were of immediate concern to agriculture. 

The serious consequences of expensive fertilizer, particularly P and N are illustrated by the fact that half the N and P incorporated in world crops arise from fertilizers (see May 2007)

Animal traction, human resources and inundation of land 

World feed reserves and production are still balanced with consumption but per capita availability has declined. The world cereal grain stocks are shown in Figure 6. The tripling in the world grain harvest since 1950 was due to the ability of farmers, with modern seed varieties and access to fertilizers, pesticides and mechanized conservation technology, to increase the number of harvests produced per year in Asia. Examples of this are the double or triple cropping of rice in southern China, southern India, and Southeast Asia. (Brown 2009)  A gradual return to draught power can be expected in these areas as fuel becomes expensive with world depletion. This will also signal the need for more labour in agriculture. The potentially lost harvest is difficult to predict but annual production of cereals in SE Asia could be halved by 2030. In addition it appears that by 2050 significant sea level rise will inundate some coastal lands and river deltas, often the most productive cropping areas. The amount of land “consumed” by the sea or made too saline for crop production also cannot be predicted, given the uncertainties of global warming scenarios. However, these appear to represent greater threats to world food production (9) than those considered by other authors.



Figure 9. Possible ranges of cropping land losses and reduction in crop yield by 2050 (adapted by Leng 2009 from Nelleman 2009). Note the values for effects of land inundation and return to draught power


If drought, such as the world is experiencing in a number of countries at the present time (de Carbonnel 2009), returns in the next 20 years and the reduction in food production is super imposed on the other potential contractions of crop yields (Figure 9), famine is likely to affect more people in more countries and the developing countries will not be the only ones affected.


It is clear that as agriculture was progressively industrialized the numbers of people employed were reduced but the energy costs of food production were substantially increased. It was observed in Cuba, when fuel price increased when the Soviet Union stopped the supply of inexpensive oil in 1991, that industrialized food production particularly meat and milk quickly became too expensive and there was an abrupt change  to organic farming, with a major increase of people moving into food production activities. The extinct animal traction industry was revived and over a short interval of time most traction was supplied by animals (over a period of less than 5 years 600,000 oxen had been deployed into agriculture) crop yields declined because of the lack of application of expensive inputs such as fertilizers. The relationship between energy use per person and the percentage of the population in agriculture has been documented by Pimentel (2001) (see (Table 1 ). The lower fossil fuel availability the greater the need for increased populations of agricultural workers to produce the food requirements of the population. 


The question to be asked is a hard one. Will it be possible to move the numbers of people needed into agriculture from their preferred work and life style, particularly in the developed countries, and will it be possible to train them to a new agriculture that will be less dependent on fossil energy? A society that needs to de-industrialise will have major problems with availability of material resources but also will have to accommodate the resistance of the privileged non manual labour force to change their work ethos. This is where those countries that have not industrialised their agriculture may be better prepared and therefore more able to survive in a fossil fuel declining environment.


The future impacts of peak oil, global warming, resource depletion and an on-going financial crises are difficult to predict and  cannot  be realistically incorporated into any quantitative model, as none exist that assesses agriculture using an holistic approach and

that takes into account future constraints (foreseen and unforeseen). Possible future reductions in cropping areas and crop yields have been tentatively predicted by Nellemann et al (2009) and Leng (2009). These data are presented in Figure 9.  


Table 1. Comparisons of developed and developing country consumption of commercial energy [1012 kcal] and the percent of the population engaged in agriculture [Pimentel 2001].


Solid fuel

Liquid fuel

Natural Gas

Hydro & nuclear energy

Total energy

Energy use per person

[106 kcal]

Population in agriculture



































 Crop Residues Must Become a Major Resource for Livestock Production in the Future   

The foregoing discussion suggests a major depletion in cereal grain availability with time and an increasing price for this commodity, which will seriously limit the availability of feed for livestock. The world produces around 2 billion tonnes of cereal grains which is accompanied by about the same yield of straw. Straw has a number of uses; it is fed to ruminants, mostly without appreciation of production responses that could be achieved with treatment and supplementation; it may be burned to facilitate multiple cropping practices and it is, in places, harvested for other commercial purposes or ploughed back into the land. Much speculation has centred on the prospects for producing second generation cellulosic ethanol fuel from straw. However the logistic constraints of moving the huge amounts of straw to centralised processing plants appears to be a formidable barrier. This is fortunate because it appears to be one of the few feed resources available to increase animal protein production in the future. There is a major case to be made to retain straw organic matter as soil carbon. However, the major long term action of straw on soil carbon is through its least digestible component - lignin. This is 100% excreted by the animal and therefore if manure is returned to the land there is little reason why straw and other cellulosic biomass (eg: Palm fronds) cannot be fed to livestock as long as the land is not exposed to erosion by maintaining a low cover of biomass. 

Crop Residues can Support Surprisingly High Levels of Ruminant Production

Crop residues particularly straw  can support moderate to high levels of production in ruminants provided efficient means of treating the straw to enhance  digestibility and  deficiencies of nutrients in the diet are corrected. If additional bypass protein is then provided, levels of production and efficiency of use of biomass for growth and milk production are greatly improved (see Preston and Leng 1987; Leng 1991, 2004).   The improvement in utilisation of straw by ruminants by adhering to these simple principles is now well demonstrated. In India, milk production, largely from cows fed straw has escalated by the application of good nutritional principles (see Banarjee 1994). In the northern wheat belt of China cattle growth rates on straw, with enhanced digestibility and appropriate supplementation approached 0.9kg per day or 75% of the rate that could be achieved with similar animals fed grain based feed lot diets (see Cungen et al 1999). At these growth rates the numbers of animals that can be fattened on the same quantity of untreated straw increases 10-13 fold (see Leng 2009). In multiple cropping areas, the wet season rice crop of straw is mostly wasted but with preservation methods that also improve digestibility, this rice straw is now being harnessed to efficiently feed ruminants. The advances in straw utilisation have been made with primitive technology and productivity could be enhanced further by improved technology as is being applied in the embryonic cellulosic ethanol industries.   


At the present time there is enormous need to implement the known treatment and nutritional strategies to improve straw use by ruminants, particularly applying these technologies to the dairy herd. All countries, must quickly begin to put in place the known technologies to use crop by-products efficiently for ruminant production and at the same time relieve the pressure on over-grazed pastoral lands. Mechanization of straw treatment/preservation is the first step with development of supplementation strategies. Cheap grain removed the stimulus for massive application of roughage-fed ruminants but with good support farmers can fill the coming vacuum of animal protein supply by directing the available resources into the efficient feeding of ruminants. The vast majority of ruminants, which number some 1800 million large ruminant equivalents, are low producing and can be upgraded to moderate to high levels of production with modern technology. There are 2 billion tonnes of straw that could be converted into animal products with a feed conversion ratios of about 10:1 This could produce 200 million tonnes of live animal product annually which could support 4 billion people at 25 kg/year.. Devendra (2009) has recently discussed the potential of integrated ruminant production and Palm oil production. There is tremendous scope for development using the same principles that have been applied to the utilization of straw, to the use of under story and by-product biomass of palm plantations. Thus with information transfer and political will, ruminant production systems could be the major development for production of animal protein in the future, but this would be localised and close to markets and feed resources.


Concluding comments


Figure 10. The relationship between live weight gain (LWG) of cattle and methane production per kg of gain (after. Kurihara et al 1997, Klieve. and Ouwerkerk 2007, Howden  and Reyenga  1999)



The bottom line is that present economic theories and policies have become outdated because they ignored the depletion of natural resources and the cost of environmental pollution. The depletion of fossil energy will be a primary factor in how the world’s financial structures survive (see McKillop 2009; Rupert 2009). Without a massive effort to decrease fossil energy utilisation it appears that the world faces economic obsolescence and all the problems associated with dysfunctional economies. The greatest threats are to food supplies and therefore the potential for famine.  Governments should be urgently putting in place new economic policies based on ecological principles that will be advantageous to food production systems, particularly where these are environmentally friendly. The oil protocol as drafted by Dr Colin Campbell would go a long way to resolving many painful future events but the developed countries  appear to be unable to unbridle themselves and accept lowered growth in their economies or take a step back in their national standard of living   

The arguments for a new paradigm in economics have recently been discussed by Hall and Klitgaard (2006) who state (sic) “that no resource can be viewed as truly sustainable at present rates of production, consumption and growth because all are subsidized by cheap petroleum” and that the value of a resource should be based on their EROI which stands for “energy return on investment”, and refers most explicitly to the ratio of energy delivered to society from one unit invested in getting that particular energy.


Ecological, bio-diverse, local agriculture is part of the solution to global warming and food scarcity. Under these conditions even the developed countries will recognize that priority must be given to ruminants and other herbivores that transform biomass into food resources with minimum jeopardy to the environment. The industrialised production of meat and milk  based on the use of cereal and high quality protein meals will become obsolete as fossil energy  becomes scarce and a number of events as discussed above come together to reduce world crop production.

In the same way that arguments are developed to support future ruminant industries the supply of animal protein can be enhanced using the forage-fed rabbit (Lukefahr 2008). Their major attributes include ability to utilize cellulosic biomass efficiently, coupled to a high fertility with ability to breed every 6 weeks producing multiple offspring.

Herbivorous fish have a major role to play as the manure from increased ruminant production can be processed through biodigestors for methane production that will supply local energy requirements. The nutrients in the effluents from biodigestors can be used to produce algae and support aquatic plant growth particularly for the production of carp in polyculture systems. China has developed aquaculture to the extent that protein from inland fisheries has surpassed that from poultry. Carp production has increased substantially from about 1 million tonnes to some 16 million tonnes over the last 30years and now China’s farmed fish production (32 million tonnes) is about 0.3 of world oceanic harvest (FAO, FISHSTAT 2007). An integrated system of crop residues and high-protein forages fed to ruminants and rabbits, plus farmed herbivorous fish, seems to be the most likely basis for future animal protein production. Research needs to be concentrated on natural resource management and sustainable production to keep these systems viable.



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