IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group III: Mitigation of Climate Change

8.2 Status of sector, development trends including production and consumption, and implications

Population pressure, technological change, public policies, and economic growth and the cost/price squeeze have been the main drivers of change in the agricultural sector during the last four decades. Production of food and fibre has more than kept pace with the sharp increase in demand in a more populated world. The global average daily availability of calories per capita has increased (Gilland, 2002), with some notable regional exceptions. This growth, however, has been at the expense of increased pressure on the environment, and depletion of natural resources (Tilman et al., 2001; Rees, 2003), while it has not resolved the problems of food security and child malnutrition suffered in poor countries (Conway and Toenniessen, 1999).

Agricultural land occupied 5023 Mha in 2002 (FAOSTAT, 2006). Most of this area was under pasture (3488 Mha, or 69%) and cropland occupied 1405 Mha (28%). During the last four decades, agricultural land gained almost 500 Mha from other land uses, a change driven largely by increasing demands for food from a growing population. Every year during this period, an average 6 Mha of forestland and 7 Mha of other land were converted to agriculture, a change occurring largely in the developing world (Table 8.1). This trend is projected to continue into the future (Huang et al., 2002; Trewavas, 2002; Fedoroff and Cohen, 1999; Green et al., 2005), and Rosegrant et al., (2001) project that an additional 500 Mha will be converted to agriculture during 1997-2020, mostly in Latin America and Sub-Saharan Africa.

Table 8.1. Agricultural land use in the last four decades.

 Area (Mha) Change 2000s/1960s 
 1961-70 1971-80 1981-90 1991-00 2001-02 Mha 
1. World               
Agricultural land 4,562 4,684 4,832 4,985 5,023 +10 461 
Arable land 1,297 1,331 1,376 1,393 1,405  +8 107 
Permanent crops  82  92  104  123  130 +59  49 
Permanent pasture 3,182 3,261 3,353 3,469 3,488 +10 306 
2. Developed countries               
Agricultural land 1,879 1,883 1,877 1,866 1,838 -2 -41 
Arable land  648  649  652  633  613 -5 -35 
Permanent crops  23  24  24  24  24 +4  1 
Permanent pasture 1,209 1,210 1,201 1,209 1,202 -1  -7 
3. Developing countries               
Agricultural land 2,682 2,801 2,955 3,119 3,184 +19 502 
Arable land  650  682  724  760  792 +22 142 
Permanent crops  59  68  80  99  106 +81  48 
Permanent pasture 1,973 2,051 2,152 2,260 2,286 +16 313 

Source: FAOSTAT, 2006.

Technological progress has made it possible to achieve remarkable improvements in land productivity, increasing per-capita food availability (Table 8.2), despite a consistent decline in per-capita agricultural land (Figure 8.1). The share of animal products in the diet has increased consistently in the developing countries, while remaining constant in developed countries (Table 8.2). Economic growth and changing lifestyles in some developing countries are causing a growing demand for meat and dairy products, notably in China where current demands are low. Meat demand in developing countries rose from 11 to 24 kg/capita/yr during the period 1967-1997, achieving an annual growth rate of more than 5% by the end of that period. Rosegrant et al. (2001) forecast a further increase of 57% in global meat demand by 2020, mostly in South and Southeast Asia, and Sub-Saharan Africa. The greatest increases in demand are expected for poultry (83 % by 2020; Roy et al., 2002).

Figure 8.1

Figure 8.1. Per-capita area of arable land and pasture, in developed and developing countries.

Source: FAOSTAT, 2006.

Table 8.2: Per capita food supply in developed and developing countries

   Change 2000s/1960s 
 1961-70 1971-80 1981-90 1991-00 2001-02 cal/d or g/d 
1. Developed countries               
Energy, all sources (cal/day) 3049 3181 3269 3223 3309 +9 261 
% from animal sources  27  28  28  27  26 -2 -- 
Protein, all sources (g/day)  92  97  101  99  100 +9 8 
% from animal sources  50  55  57  56  56 +12 -- 
2. Developing countries               
Energy, all sources (cal/day) 2032 2183 2443 2600 2657 +31 625 
% from animal sources 8 8 9 12 13 +77 -- 
Protein, all sources (g/day) 9 11 13 18 21 +123 48 
% from animal sources 18 20 22 28 30 +67 -- 
Source: FAOSTAT, 2006.               

Annual GHG emissions from agriculture are expected to increase in coming decades (included in the baseline) due to escalating demands for food and shifts in diet. However, improved management practices and emerging technologies may permit a reduction in emissions per unit of food (or of protein) produced. The main trends in the agricultural sector with the implications for GHG emissions or removals are summarized as follows:

  • Growth in land productivity is expected to continue, although at a declining rate, due to decreasing returns from further technological progress, and greater use of marginal land with lower productivity. Use of these marginal lands increases the risk of soil erosion and degradation, with highly uncertain consequences for CO2 emissions (Lal, 2004a; Van Oost et al., 2004).
  • Conservation tillage and zero-tillage are increasingly being adopted, thus reducing the use of energy and often increasing carbon storage in soils. According to FAO (2001), the worldwide area under zero-tillage in 1999 was approximately 50 Mha, representing 3.5% of total arable land. However, such practices are frequently combined with periodical tillage, thus making the assessment of the GHG balance highly uncertain.
  • Further improvements in productivity will require higher use of irrigation and fertilizer, increasing the energy demand (for moving water and manufacturing fertilizer; Schlesinger, 1999). Also, irrigation and N fertilization can increase GHG emissions (Mosier, 2001).
  • Growing demand for meat may induce further changes in land use (e.g., from forestland to grassland), often increasing CO2 emissions, and increased demand for animal feeds (e.g., cereals). Larger herds of beef cattle will cause increased emissions of CH4 and N2O, although use of intensive systems (with lower emissions per unit product) is expected to increase faster than growth in grazing-based systems. This may attenuate the expected rise in GHG emissions.
  • Intensive production of beef, poultry, and pork is increasingly common, leading to increases in manure with consequent increases in GHG emissions. This is particularly true in the developing regions of South and East Asia, and Latin America, as well as in North America.
  • Changes in policies (e.g., subsidies), and regional patterns of production and demand are causing an increase in international trade of agricultural products. This is expected to increase CO2 emissions, due to greater use of energy for transportation.
  • There is an emerging trend for greater use of agricultural products (e.g., bio-plastics bio-fuels and biomass for energy) as substitutes for fossil fuel-based products. This has the potential to reduce GHG emissions in the future.