9.9. Food Yields and Nutrition
Background climate and annual weather patterns are key factors in agricultural
productivity, despite technological advances such as improved crop varieties
and irrigation systems. As temperature, rainfall, and soil moisture change,
plant physiology is affected; so too is the much less predictable risk of a
change in patterns of plant pests and pathogens. There are many social, economic,
and environmental influences on agricultural, horticultural, and livestock productivity.
Climate change represents an additional pressure on the world food supply system.
That system, which has yielded an overall increase in per capita food supplies
over the past 4 decades, has shown signs of faltering over the past decade.
There is ongoing scientific debate about the relative importance of economic,
technical, and ecological influences on current food yields (Waterlow et
al., 1998; Dyson, 1999). Optimists point to falling food prices; pessimists
point to falling soil fertility.
Modeling studies (reviewed in Chapter 5) indicate that,
under climate change, yields of cereal grains (the world's dominant food commodity)
would increase at high and mid-latitudes but decrease at lower latitudes. Furthermore,
this disparity would become more pronounced as time progresses. The world's
food system may be able to accommodate such regional variations at the global
level, with production levels, prices, and the risk of hunger relatively unaffected
by the additional stress of climate change. To minimize possible adverse consequences,
a dual development program is desirable. Adaptation should be undertaken via
continued development of crop breeding and management programs for heat and
drought conditions. These will be immediately useful in improving productivity
in marginal environments today. Mitigation strategies should be implemented
to try to reduce further enhanced global warming. However, recent work suggests
that the main benefits of mitigation will not accrue until late in the 21st
century (Parry et al., 1998).
The United Nations Food and Agriculture Organization (FAO) estimates that in
the late 1990s, 790 million people in developing countries did not have enough
to eat (FAO, 1999). The FAO report on food insecurity has identified population
groups, countries, and regions that are vulnerable. For example, nearly half
the population in countries of central, southern, and east Africa are undernourished.
Environmental factors, including natural factors and those that are a consequence
of human activities, can limit agricultural potential. These factors include
extremely dry or cold climates, poor soil, erratic rainfall, steep slopes, and
severe land degradation. The FAO report further states that undernutrition and
malnutrition prevail in regions where environmental, economic, and other factors
expose populations to a high risk of impoverishment and food insecurity.
Undernutrition is a fundamental cause of stunted physical and intellectual
development in children, low productivity in adults, and susceptibility to infectious
disease in everyone. Decreases in food production and increases in food prices
associated with climate change would increase the number of undernourished people.
Conversely, if food production increases and food prices decrease, the number
of undernourished people would fall, but populations in isolated areas with
poor access to markets still may be vulnerable to locally important decreases
or disruptions in food supply.
