Multifunctionality and sustainability would require indicators of both local and scientific knowledge.

1.2.4 Agrifood systems, agricultural products and services

Agricultural systems, outputs and services. The major outputs generated by the multiple agricultural systems worldwide may be referred to as "provisioning services" (MA, 2003):

• Food consisting of a vast range of food products derived from plants, animals, and microbes for human consumption;
• Feed products for animals such as livestock or fish, consisting of grass, herbs, cereals or coarse grains and othercrops;
• Fiber such as wood, jute, hemp, silk, and other products;
• Fuel such as wood, dung, biofuel plants and other biological materials as sources of energy;
• Genetic resources including genes and genetic information used for animal and plant breeding, and for biotechnology;
• Biochemicals, natural medicines, and pharmaceuticals including medicines, biocides, food additives, and biological materials;
• Ornamental resources including animal products such as skins and shells, and ornamental plants and lawn grass; and
• Freshwater from springs and other sources, as an example of the linkage between provisioning and regulating services.

Agricultural systems are highly complex, embracing economic, biophysical, sociocultural and other parameters. They are based on fragile and interdependent natural systems and social constructions. Agriculture has a potential to play positive roles at different scales and in different spheres (Table 1-3).

Diversity of agricultural systems

Globally, agricultural systems have been changing over time in terms of intensity and diversity, as agriculture undergoes transition driven by complex and interacting factors related to production, consumption, trade and political concerns. There are a multitude of agricultural systems worldwide. They range from small subsistence farms to small-scale and large commercial operations across a variety of ecosystems and encompassing very diverse production patterns. These can include polycultures or monocultures, mixed crop and livestock systems, extensive or intensive livestock systems, aquaculture systems, agroforestry systems, and others in various combinations. In Africa alone, there are at least 20 major farming systems combining a variety of agricultural approaches, be they small- or large-scale, irrigated or nonirrigated, crop- or tuber-based, hoe- or plough-based, in highland or lowland situations (Spencer et al., 2003).

     Agricultural systems are embedded in a multiplicity of different economic, political and social contexts worldwide. The importance of the agricultural sector in these economies, or the type of agricultural policy enforced will therefore depend on the national economies. It is thus crucial

to gain a clear knowledge of the state of agriculture in the different ecological and socioeconomic contexts to be able to assess the potential for further development of this sector in relation to development and sustainability goals. The different contexts have led to economic disparities within and among regions, countries and especially between industrial and small-scale farmers (FAO, 2000). Apart from differences in labor productivity, examples of disparities are average farm sizes (121 ha in North America vs. 1.6 ha in Asia and Africa, see von Braun, 2005; 100,000 ha in Russia, Ukraine and Kazakhstan, see Serova, 2007) and the crop yield gap between high- and low-income countries.

     The last 50 years have seen a tremendous increase in agricultural food production, at a rate more rapid than human population growth. This was mainly due to the increase in area productivity, which differed between the regions of the world, while cereal-harvested area stagnated almost everywhere (Cassman, 2003).

     In all regions of the world, however, a decrease in the economic importance of the agricultural sector at different stages of economic development can be observed. But there is insufficient recognition of the fact that, in a monetized economy, the central functions of agriculture support the performance of other sectors. The regulating and supporting functions of global ecosystems are insufficiently understood. The findings of the Millennium Ecosystem Assessment (MA, 2005b) show the key role of agriculture not only in productive and social aspects but also in preserving or endangering ecosystem functions.

The crops component of agriculture

World crop and livestock output growth fell in 2005 to the lowest annual rate since the early 1970s, and well below the rates reached in 2003 and 2004, with a strong decline in industrialized countries as a group and negative 1.6% growth in 2004 (FAO, 2006a). This was mainly due to a decrease in output growth in the crops sector from 12% in 2004 to negative 4% in 2005 in industrialized countries. But with growing resource scarcity, future food production depends more than ever on increasing crop yields and livestock productivity (FAO, 2006a). The positive and negative effects of technological progress have raised uncertainties. Two groups of crops are cited here as examples.

Cereal crops. World cereal production, after several years of stagnation, increased sharply in 2004/2005, reaching 2,065 million tonnes, a 9% increase from the previous year, and global utilization continued an upward trend (FAO, 2006a). However, cereal yields in East Asia rose by an impressive 2.8% a year in 1961-2004, much higher than the 1.8% growth in industrialized countries, mainly due to widespread use of irrigation, improved varieties, and fertilizer (Evenson and Gollin, 2003).

     The green revolution doubled cereal production in Asia between 1970 and 1995, yet the total land area cultivated with cereals increased by only 4% (Rosegrant and Hazell, 2001) while in sub-Saharan Africa it changed little in the same period.

     Slowing down expansion of cultivated areas through intensification benefited the environment by preserving the forests, wetlands and biodiversity. But there are negative