V. Food: needs and supply

Table of Contents

• Facts and Figures
• Cited Literature and Links

Facts and Figures

1. World population 1997: 5.848 billion
Number added 1996-1997: 80.95 million (FAOSTAT)

2. Gross energy and protein needs per individual (Loomis and Conner, 1992)

• Approximate average food energy requirement per individual: 10.5 MJ per day or 3.8 GJ per year
  (4186J= 1 kcal; 10.5 MJ = 2500 kcal)
• Approximate protein requirement per individual: 50 g protein per day; 18.3 kg per year

Food needs vary with gender, age, weight, activity and health. Energy needs calculated by Bender (1997) and shown in Table 1 below take account of these factors for different populations. See also FAO (1996) Health Canada, 1990 and on-line data available from FAOSTAT, for more informaton on variation in food needs between individuals and populations.

See Taube's estimates for daily influx of energy carriers and different structural materials for the average human

3. The global supply

Table 1: Global food needs, total food energy supply, Dietary Energy Supply (DES), dietary protein and fat and estimated efficiency factors. The dietary conversion factor is the ratio of total food available to food available in retail markets; it reflects food "lost" in feeding grain to livestock. The End-use efficiency factor is the ratio of food available in markets to food requirements, and reflects food wasted due to losses in storage (high in developing countries) or wasted at the end-use level (high in middle and high income countries).

Measure	World	Industrialized Co.	Developing Co.
Total food available1	3939 kcal (16.5 MJ)	6964 kcal (29.2 MJ)	3007 kcal (12.6 MJ)
Daily per caput DES1 (food available in retail markets)	2693 kcal (11.3 MJ)	3255 kcal (13.6 MJ)	2520 kcal (10.6 MJ)
Physiological food requirements1	2179 kcal (9.1 MJ)	2231 kcal (9.3 MJ)	2169 kcal (9.1 MJ)
Dietary conversion factor1 (ideal: 1.5)	1.46	2.14	1.19
End-use efficiency factor1 (ideal: 1.3)	1.24	1.46	1.16
Daily per caput protein2 (% from animals)	71 g (22%)	102 g (51%)	62 g (10%)
Daily total fats per caput 2 (% from animals)	69 g (28%)	125 g (68%)	51 g (12%)

(Source: ¹Bender, 1997²FAO 1996a)

These statistics indicate that in total, there is currently sufficient food for good nutrition of every human being. However over 800 million people, or more than 13% of the global population, are chronically undernourished , eating too little to meet minimal energy requirements; millions more suffer acute malnutrition during transitory or seasonal food insecurity (FAO, 1995). On the other end of the scale, diseases of imbalance and excess are common in the more affluent countries or sectors of societies.

4. The Standard Nutritional Unit (SNU):

This unit has been proposed by Loomis and Conner (1992) as a means of relating population number to production of food at the farm level.

1 SNU = 23 MJ cap^-1 day ^-1 = 8.4 GJ cap^-1 y^-1

The difference between the 23 MJ figure and the 10.5 MJ figure cited above allows for losses in harvest, storage, distribution, and food preparation, as well as for variations in production, seed supplies and diet diversity (including some livestock products).

Grain provides approximately 51% of both energy and protein globally (FAO, 1995), and the protein and energy of other foods can be expressed in grain equivalents. Hence it is convenient to express the annual SNU as "grain equivalents. 1 SNU = 500 kg grain based on energy content of 17 MJ/ kg^-1. Thus each tonne of a system's production expressed in grain equivalents can be equated with the generous nutrition of two humans (Loomis and Conner, 1992) and perhaps very modest, but possibly adequate nutrition of 4 humans.

5. Global grain production & supply/needs relationships

• In recent years, world grain production per person has averaged approximately 300 kg/year (Brown 1997); at 60% of diet*, that indicates an average of 500 kg grain equivalent per year for every human being, i.e. approximately 1 SNU . This suggests, as do the figures in V.2 and V.3 above, that there is suffficient food produced globally to provide a generous diet to every humans being. Actual annual grain consumption per person (including grain fed to livestock fed to humans) varies between countries from about 100 kg for Haiti to 974 kg for Canada (Postel, 1994).

  *See Table 1 above; cereals provide approx 51% of DES directly; the 60% figure takes into account, approximately, DES derived from livestock that is based on the grain component of their diet.

• Non-intensive grain production under temperate conditions produces 1.5-3 t/ha; intensive production 5-7 t/ha, and the most intensive production, circa 10 t/ha; under the more favorable of tropical conditions, the equivalent figures would be circa 3, 7 and 12 tonnes grain or grain equivalents per hectare per annum (Instructor's estimates).
• Actual yields of crops can be found at FAOSTAT
  e.g. for 1997, paddy rice yields (average) were 6.6 t/ha for USA, 4.4 t/ha for Indonesia, 1.4 t/ha for Chad; wheat yields were 2.1 t/ha for Canada, 1.6 t/ha for Brazil, 2.7 t/ha for USA and 7.5 t/ha for UK. Canadian yields are low because most wheat is produced in water limited, semi-arid regions, UK yields are high because most wheat is produced under intensive management with little or no water limitation.
• Rough estimates of the amount of land required to provide food to support a population at a specific nutritional level can be made accordingly. For example, if 60% of land were cultivated, and produced the equivalent of 4 t grain per hectare annually, this could support
  

  (4 t ha^-1 x 0.6 ha cultivated/ha land )/0.5 t cap^-1= 4.8 cap ha^-1 or 0.21 ha cap^-1. at a generous nutrition level.

6. Livestock conversion efficiencies.

Table 2: Feed converison efficiency by animal populations (Spedding 1979). Efficiencies are estimates of ceiling values for: (energy or protein in product)/(energy or protein in feed)*100. Values were calculated for breeding units of one female plus progeny plus the relevant proportion of feed intake of the male.

Animal Product	Energy Efficiency (%)	Protein Efficiency (%)
Cow’s milk	12-16	40
Rabbit meat	8.0	23-40
Beef (suckler)	3.2	9
Lamb	2.4-4.2	6-14
Hen’s eggs	11-12	24
Broilers	14.6	25-26
Pig meat	23-27	17-22

Livestock can and do consume food wastes and food that is inedible by humans (such as grass and tree leaves, culls), effectively upgrading it for consumption by humans. Thus the extent to which livestock actually compete with humans for food depends on what the livestock are fed, how that feed is produced, and on whether it would be more economical and ecologically sensible to produce human edible food on land that is producing human-inedible feed for livestock.

Below are some estimates of feed conversion efficiencies that take into account differences in the human edibility of livestock feed for systems in California. A value greater than 1 indicates that producing the particular livestock item increases the net supply of of food for humans, while a value less than 1 indicates that it reduces it.

Table 3: Estimated ratios for Output of Human-edible food-to-Input of Human-edible food for livestock systems in California (data cited in deHaan et al., 1997)

Animal Product	as Energy	as Protein
Milk	1.01	1.82
Beef	0.85	1.20
Pork	0.58	0.86
Poultry	0.31	0.75

Question: how can values for cows milk and beef be close to or greater than 1?
Question: what other factors should be taken into consideration when examining the question of whether livestock beneficial or detrimental for (a) the land, (b) food supply?

Contents

Cited Literature and Links

• Bender, W.H. 1997. How much food will we need in the 21st century?. Enviornment 39(2): 7-11; 27.
• Brown, L.R. 1997. Facing the prospect of food scarcity. In: Linda Starke (ed.) Worldwatch Institute State of the World. W.W. Norton and Company, New York, N.Y., 1997: 23-41.
• de Haan, C., H. Steinfeld, and H. Blackburn. 1997. Livestock and the Environment. Finding a Balance. European Commission Directorate-General for Development; WRENmedia, Fressingfield, Eye, Suffolk, IP21 5SA, U.K.
• FAO. 1995. Dimensions of need. An Atlas of Food and Agriculture. FAO, Rome.
• FAO. 1996. Sixth World Food Survey. FAO, Rome
• FAOSTAT
  (http://apps.fao.org/) Food and Agriculture Organization, Spons.(1999, January 1; Viewed 30 Jan. 2001)
• Health Canada. 1990. Nutrition Recommendations. The Report of the Scientific review Commitee 1990. Minister of Supply and Services, Ottawa.
• Loomis, R.S., and D.J. Conners. 1992. Crop Ecology: Productivity and Management in Agricultural Systems. Cambridge University Press, Cambridge, U.K.
• Postel, S. 1994. Carrying capacity: earth's bottom line. In: Linda Starke (ed.) Worldwatch Instutute State of the World. W.W. Norton and Company, New York, N.Y., 1994, 3-21.
• Spedding, C.R.W. 1979. An Introduction to Agricultural Systems. Applied Science Publishers, London.