Agricultural Challenges

Whether food production can keep pace with the demand for improved diets for a rapidly growing world population is a question that has been debated vigorously since it was raised by Malthus two centuries ago. Although much of mankind has experienced improvements in diets over the past century, expert views about prospects for the coming decades differ as sharply as ever (Bongaarts, 1996).

There is a rather optimistic group consisting primarily of economists and modellers in the neoclassical tradition. They note the relatively low crop yields, inefficiencies throughout the food production and consumption chain, and the ample reserves of potential arable land in many developing countries. They further hold the view that sounder government policies, wider application of green revolution technology, reduced inefficiencies, upgraded rural infrastructure, and greater investments in human resources and research will make much larger harvests possible and no insurmountable environmental constraints are foreseen (Alexandratos, 1999; Alexandratos, 1995; Pinstrup-Andersen and Pandya-Lorch, 1998; Rosegrant and Ringler, 1997).

The rather pessimistic group primarily belongs to the ecology and ecological economics communities focussing on the carrying capacity of the Earth. They point to the many signs of environmental stress and the increasing difficulties encountered in expanding agricultural land, water supply, crop yields, and in controlling pests. In their view a large expansion of agricultural output is not feasible, and they even doubt whether current levels of crop production can be sustained in a number of countries. Global warming would impose further stress on agricultural systems, and thus the prospects for increased food production would become even less favourable than they are at present. A major expansion of food supply would require a highly organized global effort by both the developed and the developing countries that has no historic precedent (Brown and Kane, 1994; Kendall and Pimentel, 1994).

In the debate about global food security over the next century there is a clear focus on supply-side effects and developments, i.e. technological change in agricultural production, limits to natural resource availability and resource quality, most of all agricultural land and water for irrigation. Surprisingly, the importance of changes in demand growth and demand structure have been studied to a lesser extent. In many scenarios, the current trend towards higher meat consumption at higher income levels is simply extrapolated over a wide range of countries on a global scale in the course of economic development. However, there may be significant scope for altering the relationship between income and food demand. For example, changes in dietary structures may evolve due to increasing knowledge and concerns about health impacts of alternative diets (Bender 1994). In addition to improved production efficiency and waste reduction, demand changes towards healthier diets could also significantly affect the outcome of long-term global food scenarios (Table 7.1).

Most scenarios and analyses on the development of the global food system cover the period up to 2025 at most (Alexandratos, 1999; Alexandratos, 1995; Pinstrup-Andersen and Pandya-Lorch, 1998; Rosegrant and Ringler, 1997). From a social science point of view the time span of one generation is already very long and it may be questionable whether model simulations and scenario analyses beyond two to three decades are possible and have any meaning (Smil, 1994). A few such analyses beyond the year 2050 have been conducted mainly with respect to the impact of climate change on agricultural production, as significant changes in the global climate system are not to be expected before the middle of the 21st century (Parry et al., 1999; Sands and Leimbach, 2003). Like long-term environmental changes, profound alterations in cultural habits and dietary preferences may also come about only within several decades, so there may be scope for longer-term analyses from this perspective as well.


Hermann Lotze-Campen et al.

Table 7.1

Conservative estimates of efficiency gains

in the global food system

achievable by the year 2050

Changes compared to 1990 practices

Gains equivalent to

global 1990 food

energy consumption (%)


Better agronomic practices (raise



average yields by 20%)


Higher fertilizer uptake (raise nutrient


use efficiency by 30%)

Reduced irrigation waste (raise water


use efficiency by 30%)


Post-harvest losses (lower by 20%)



End-use waste (lower by 20%)



(Limit fat intakes to 30% of total




Total gain


Source: Smil (1994).

Source: Smil (1994).

Food demand and dietary choices

World population growth is likely to come to an end in the foreseeable future. According to Lutz et al. (2001), there is around an 85% chance that the world's population will stop growing before the end of the 21st century. Furthermore, there is a 60% probability that the world's population will not exceed 10 billion people before the year 2100, with a median projection for the year 2050 of 8.8 billion. In any case this means that by 2050 about 50% more people have to be fed than currently.

Human diets are largely determined by economic factors, particularly prices and incomes. As income rises, people tend to consume more calories in total, and the share of animal calories increases, especially the consumption of animal fats. In Africa, people derive two-thirds of their calories from starchy staple foods and only 6% from animal products. In Europe, people derive 33% of their calories from animal products and less than one third from starchy staples. The average global diet falls somewhere in between these two extremes (Table 7.2) (Bender and Smith, 1997).

As most developing countries in the future are likely to follow the trends in rich countries, global meat consumption can be expected to rise strongly over the next decades, due to a combination of population growth, growth in per-capita income and a high income elasticity of meat demand. Annual growth rates of aggregate meat consumption until 2030 are estimated between 1.4 and 3.0%. This would imply an increase in average global meat consumption per capita from 32.6 kg/year to 44-54 kg/year, depending on growth assumptions (Keyzer et al., 2001).

Table 7.2 Major sources of food energy in industrialised and developing countries (1994, % share)

Product group








Meat and dairy products



Sweeteners and vegetable oils



Roots and tubers






Source: Adapted from Bender and Smith (1997).

Source: Adapted from Bender and Smith (1997).

Agricultural supply and resource use

In view of the described rapid developments on the demand side, it is heavily debated whether global food supply will keep up with this pace or whether farming activities will run into serious conflict with the concurrent goal of preserving local environmental conditions. In the past, agricultural production could rely on virtually costless water supplies as well as available land for expansion. Meanwhile, most of the potentially available arable land is already under cultivation and future production increases will have to be achieved mainly through more intensive production technologies on the currently used area of land. However, improper management and irrigation techniques have already caused serious land degradation on a large scale. In the future, agriculture will have to compete for water and land with other economic activities, like urban development, industrial use, forestry, and nature conservation (Kendall and Pimentel, 1994).

With respect to future yield increases, one can take an optimistic view and assume that past trends in agricultural productivity growth will continue for some time. Some model calculations show that even at conservatively reduced growth rates, global food supply will outpace demand up to 2020 and real prices for agricultural commodities are likely to continue to fall (Dyson, 1999; Rosegrant and Ringler, 1997). However, the assumption of exponential growth paths instead of logistic curves has been questioned. This distinction will become even more important in the very long run (Harris, 1996; Harris and Kennedy, 1999). The potential of biotechnology and genetic engineering for accelerating agricultural productivity growth is still very unclear and subject to strong public debate. Some initial trials show positive effects, but environmental consequences have to be further investigated and widespread social acceptance remains questionable (Qaim and Zilberman, 2003).

Land use

The amount of land necessary for the production of various food items differs widely, especially for animal products. Different animals have different feed requirements and feed conversion rates (Table 7.3) (Bender, 1997).

This directly contributes to the area of land required for certain food products (Table 7.4) (Gerbens-Leenes and Nonhebel, 2002). However, the required quality of land differs for various livestock production types. For example, ruminants like cows and goats are able to convert grass from permanent pasture land into valuable food for human consumption, but cattle can also be fattened on a feed mix with a large share of cereals. Pigs can be raised primarily on grains, but also on human food residuals. Hence, the amount and quality of land required for livestock production depends very much on the specific production systems.

Table 7.3 Conversion rates of grain to animal products (feed input per unit of output)

Animal product

Kg of feed/kg of output

Kcal of feed/kcal of output













Note: These conversions are very approximate, as the caloric density of both feeds and animal products can vary greatly. Furthermore, data units are often not specified or precisely comparable. Source: Bender (1997).

The total amount of land available for agriculture not only depends on biophysical conditions, but also on the demand for land for other economic and environmental purposes. Infrastructure development and urbanisation may reduce agricultural areas around the major population centres. In the course of a major energy transition there might arise a significant demand for bio-fuel production not only from fast growing forests, but also from agricultural crops. Moreover, a certain share of land may have to be set aside for nature conservation and biodiversity management, in order to maintain nature's basic life supporting functions (Goklany, 1998; Sands and Leimbach, 2003).

More intensive production systems may lead to land degradation, if they are applied year after year on the same area. The main types of land degradation are soil erosion from wind and water, chemical degradation (e.g. nutrient loss, salinisation, pollution), and physical degradation (e.g. compaction, waterlogging). Land degradation is a very important issue in some geographic regions, but it remains unclear whether it may become a serious threat to global food supply (Doos, 2002; Rosegrant et al., 1997). While in some parts of the industrialised world problems of fertilizer overuse, like nitrate leaching and eutrophication, are of considerable concern, in many developing regions, like Sub-Saharan Africa, inadequate replenishment of removed nutrients reduce soil fertility and increase erosion. Hence, in order to assure sufficient nutrient supply for more intensive production on a global scale, the demand for fertilizer will rise. Especially nitrogen requirements will increase significantly, according to some estimates to 50% above current consumption by 2050. What this means for sensitive environmental systems and the nitrogen cycle, which is as yet neither well observed nor understood, remains unclear (Gilland, 2002; Rosegrant and Ringler, 1997).

Table 7.4 Specific land requirements per food item per year in the Netherlands in 1990 (m2/kg)

Food item

Specific land requirement


Vegetable oil


Low fat spread







Chicken filet


Milk products and eggs

Whole milk






Cereals and other crops





Vegetables (average)


Source: Adopted from Gerbens-Leenes and Nonhebel (2002).

Source: Adopted from Gerbens-Leenes and Nonhebel (2002).

Water use

The resource base that may pose the most serious limitations to future global food supplies is water. Irrigated area accounts for nearly two-thirds of world rice and wheat production, so growth in irrigated output per unit of land and water is essential to feed growing populations. Since the development of traditional irrigation and water supplies is increasingly expensive and new sources like desalination are not expected to play a major role soon, water savings at every level are necessary. Crop output per unit of evaporative loss has to be increased and water pollution has to be reduced. However, the size of potential water savings in agricultural irrigation systems is unclear. While specific water uses can be made more efficient through better technology, especially in many poor countries, the potential overall savings in many river basins are probably much smaller, because much of the water currently lost from irrigation systems is reused elsewhere. Increasing water demand from households and industry will further exacerbate the challenge (Rosegrant and Cai, 2003; Wallace, 2000).

The specific water requirements for various agricultural products differs widely, from less than 200 litres per kg output for potatoes, sugar beets or vegetables, to more than 1000 litres per kg output for wheat and rice (Hoekstra and Hung, 2002). A typical diet with meat consumption at American levels requires about 5,400 litres of water for crop evapotranspiration, while a comparable vegetarian diet requires only about half the amount. In comparison, the daily amount of water required for drinking and sanitary purposes is almost negligible at less than 60 litres. The future global challenge with respect to agriculture and water implies that over the next 25 years food production has to be increased by about 40% while reducing the renewable water resources used in agriculture by 10-20% (Jaeger, 2001; Rijsberman, 2001).

Climate change

An additional influence on agricultural production in the long run, i.e. in the second half of the 21st century, is likely to occur through global climate change. A rise in atmospheric CO2-levels and a corresponding rise in global temperatures will not only affect plant growth and yields, but also alter the regional patterns of precipitation and water availability as well as land erosion and fertility. Sensitivity studies of world agriculture to potential climate changes have indicated that global warming may have only a small overall impact on world food production because reduced production and yields in some areas are offset by increases in others. However, regional impacts vary quite significantly, with tropical regions especially suffering from droughts. Moreover, the combined effects of various changes in the long run are still highly uncertain (IPCC, 2001).

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