The direction of the various expected impacts on consumers and on farm income is summarized in Table 4.2. Farm income is defined as returns to land, labor, and capital. The net effect on food security depends on local conditions.
Table 4.2 General Impacts of Rising Concentrations of Greenhouse Gases on Factors Affecting Food Security
Greenhouse Gas Phenomenon
CO2 fertilization Climate change Extreme weather events Sea level rise
Impact on Food Availability
Quantity Price + -
Impact on Local Farm
Consumers Income +??
Higher levels of CO2 in the atmosphere tend to increase plant growth. However, increases in agricultural productivity due to this fertilization effect will vary considerably from one location to another. First, some crops benefit more than other crops. The response of maize, millet, sorghum, and sugarcane (known as C4 crops) to increases in atmospheric CO2, for example, is expected to be relatively small compared to other crops (Kirschbaum et al., 1996). Also, crop responses to atmospheric CO2 are positively correlated with the level of nutrients available. If nutrients are limited, the response is negligible (Acock and Allen, 1985). Hence, productivity increases are likely to be smaller in low-income countries that rely heavily on C4 crops and where the availability of fertilizers is a limiting factor in agricultural production.
CO2 fertilization increases agricultural production and reduces food prices (Rosenzweig et al., 1993; Reilly and Hohm-ann, 1993; Tsigas et al., 1997; Darwin and Kennedy, 2000). This benefits consumers, but tends to reduce farm income (Darwin, 2003). Reductions in farm income are due to reduced revenues and the reallocation of resources (e.g., land, labor, and capital) from agriculture to other sectors that is expected after a decline in agricultural prices. The net effect on food security is not readily apparent. It will depend on the extent to which agriculture is a source of income in the country, and the ease with which alternative nonagricultural sources of income can be tapped by excess agricultural factors of production, particularly labor. Low-income countries that depend on agriculture for a large share of their income or that have few alternative sources of income are at greater risk of increasing food insecurity than other countries.
Climate change refers to average changes in meteorological patterns. Global mean temperature and precipitation are increasing. The distribution of changes, however, is far from uniform. Temperature and precipitation are declining in some areas (Folland et al., 2001). Climate change affects the quality and quantity of land and water resources available for production in agriculture and other climate-dependent sectors such as forestry and fisheries (Darwin et al., 1995, 1996; Darwin, 1999; Fischer et al., 2001, 2002). Increases in agricultural production are accompanied by reductions in food prices and vice versa. Lower or higher prices would respectively benefit or hurt consumers. They tend to have the opposite effect on farm income (Darwin, 1999, 2003).
Some data suggest that extreme weather, such as drought, heavy precipitation, and high winds, are increasing (Folland et al., 2001). Because of their detrimental effects on food production, storage, and delivery systems, extreme weather events tend to reduce food quantities and raise food prices, all of which, in turn, hurts consumers. Farm income is also likely to decline for farmers impacted by them, because, in addition to destroying crops or livestock, extreme events also generate substantial losses in physical and natural capital. Extreme events, for example, are often characterized by increases in water and wind erosion. The increased incidence of extreme events would also make it more difficult for farms to remain economically viable, because savings generated in good years may not be adequate to offset losses during bad years.
Sea levels are projected to rise by about 0.4 m during the 21st century (Church et al., 2001). Rising sea levels are associated with increased flooding, land loss, and salt water intrusions into freshwater aquifers in coastal areas. This increases the value of and competition for land and water resources in noncoastal areas. And resulting decreases in food supplies and increases in food prices hurt consumers. The impact on farm income is less certain. Farm income falls for those whose land is submerged or damaged. Farm income will tend to rise, however, in adjacent areas.
Was this article helpful?