Table 4-4. Population projections in different assessments.

to rise to 5 billion persons by 2030 (UN, 2005a). At the same time, the rural population of the world is expected to decline slightly from 3.3 billion in 2005 to 3.2 billion in 2030. The share of urban population of the world, which was nearly 30% in 1950, is expected to reach more than 60% in 2030. The most changes are likely to happen in developing regions. The share of urban population in 2030 is expected to increase gradually to about 82% in devel­oped countries, but increases from only 40% to 57% in less developed regions (UN, 2005b). As urbanization advances, this will have important consequences for agricultural sys­tems; foremost will be feeding urban dwellers according to their changing diets (4.4.1) while also providing sufficient access to other resources such as clean water and other basic services. Urbanization can also increase pressure on crop areas as expansion of cities and industrial areas often occurs on good agricultural land. Finally, urbanization is likely to affect access to labor (see 4.4.6).

     An important dominant demographic trend is the ag­ing of population. During the 20th century, the proportion of older persons (60 years or above) continued to rise; this trend is expected to continue well into this century. For ex­ample, proportion of older persons was 8% in 1950, 10% in 2005 and is projected to reach about 22% by the middle of the current century (UN medium scenario). This implies that by 2050, the world is expected to have some 2 billion older persons; a tripling of the number in that age group within a span of 50 years. These trends in the UN medium scenarios are similar to those in other scenarios. The pace of population aging is much faster in the developing countries than in the developed ones. Hence, developing countries will have less time to adjust to the adverse impacts of aging. Moreover, population aging in developing countries is tak­ing place at much lower level of socioeconomic development than that which has occurred in industrialized countries.

     Trends in life expectancy are projected to continue in all scenarios. Using the UN medium scenario as an exam­ple: global average life expectancy (47 years in 1950-55) increased to to 65 years in 2000-2005 and is projected to increase to 75 years by mid-century. The UN projections as­sume that life expectancy may not increase beyond 85 years; some demographers believe this age represents an intrinsic limit to the human life span. Another important demo-

graphic trend is the decline in mortality in most countries, (including infant and under 5 years old mortality), because of better public hygiene and education, improved nutrition and advances in medical science (Lee, 2003). However, the mortality rate has increased in countries with deteriorating social and economic conditions and in those affected by HIV/AIDS epidemic.

4.3.1.4 Demographic change and its impact on agriculture
Although population projections have slowed from past es­timates, a large absolute increase in population raises serious concerns about the capability of the agricultural production and associated natural resource base (Pimentel and Wil­son, 2004). A key question is whether agriculture can feed the expanding global population in the ensuing decades. A key issue involves the effects of increased urbanization on transport of agricultural products into urban areas, with as­sociated development of infrastructure and markets. Direct consequences include a more distant relationship between consumer and producer and an increasingly important role for actors involved in food distribution and markets (e.g., supermarkets).

4.3.2 Economics and international trade

4.3.2.1 Future trends and scenarios of economic growth and the agricultural economy
Economic change is a primary driver for future agricul­tural systems. The most employed indicator for economic change, GDP per capita, is used as a driver in most scenario studies.

     Historically, GDP has grown substantially. Between 1950 and 2000 world GDP grew by 3.85% annually resulting in a per capita income growth rate of 2.09% (Maddison, 2003). Global GDP growth decelerated over time from 2.1% per year in the 1970s, to 1.3% per year in the 1980s, and to 1.0% annually in the 1990s (Nayyar, 2006), but this may have been a consequence of particular events such as the transi­tion process in countries of the Former Soviet Union. Projec­tions of future economic growth vary considerably. In many environmental assessments, GDP projections are not an outcome—but an assumption (e.g., in SRES, GEO and the MA). All studies expect economic growth to continue. The World Bank short-term outlook, for instance, uses values that are comparable to historic rates (around 2%). The four scenarios in SRES show a wide range of global annual economic growth rates from 1 to 3.1% (van Vuuren and O'Neill, 2006) (Figure 4-4 and 4-5). Many other studies use a somewhat smaller range.

     All assumptions are that growth in industrialized coun­tries will be slower than those in developing economies (Table 4-5). Among the developing regions, Asia, particu­larly East Asia will continue to have higher growth rates. Different outlooks exist with respect to sub-Saharan Africa. Most recent assessments assume that institutional barriers will result in slower (though positive) economic growth than in other developing regions. Other current work (OECD, 2006a), however, projects Africa to grow faster than Latin America, and slowing growth to 2030, except for MENA and sub-Saharan Africa. For the Asia region, alternative per capita income growth projections (GDP per capita) for the