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Outlook on Agricultural Changes and Its Drivers | 283

Figure 4-20. Projected landuse changes for (a) agricultural land and (b) forest land from selected scenarios (indexed to year 2000)

Notes: Agricultural land is an aggregate of cropland and grazing/pasture/grassland land types. The following scenarios were redrawn from Alcamo et al., 2006: GSG xx = Global Scenarios Group (Raskin et al., 2002) scenarios from the PoleStar model (MF = Market Forces, PR = Policy Reform, FW = Fortress World, GT = Great Transition); GEO-3 xx = Global Environment Outlook 3 (UNEP, 2004) scenarios using the PoleStar model (MF = Market First, PF = Policy First). The other scenarios were assembled from various sources: SRES (Special Report on Emissions Scenarios) = IPCC, 2000; IMAGE-EMF21 = van Vuuren et al., 2006 scenario from EMF-21 Study; IMAGE-MA-xx = MA, 2005 scenarios from the IMAGE model for four storylines (GO = Global Orchestration, OS = Order from Strength, AM = Adapting Mosaic, TG = TechnoGarden); AgLU-0.5% = Sands and Leimbach, 2003 scenarios with 0.5% annual growth in crop yield; GTM-EMF21 = Sohngen and Sedjo, 2006 global forest scenario from EMF-21 Study; GCOMAP-EMF21 = Sathaye et al., 2006 global forest scenario from EMF-21 Study; GTM-2007 = Sohngen and Mendelsohn, 2007 global forest scenario; GRAPE-EMF21 = Kurosawa, 2006 scenario from EMF-21 Study.


rect drivers act in addition to global (indirect) drivers. For example, in cultivated systems, cultural,  socioeconomic, and educational background as well as expectations, per­ceptions, preferences, and attitudes toward risk of farmers and farm households can play significant roles in shaping land use choices.
     Tropical deforestation depicts the connectedness of mul­tiple drivers. In the humid tropics, deforestation is primarily the result of a combination of commercial wood extraction, permanent cultivation, livestock development, and the ex­tension of overland transport infrastructure (e.g., Strengers et al., 2004; Verbist et al., 2005; Busch, 2006; Rounsevell et al., 2006). However, regional variations exist. Deforestation driven by swidden agriculture (see 4.5.1.2) is more wide­spread in upland and foothill zones of Southeast Asia than in other regions. Road construction by the state followed by colonizing migrant settlers, who in turn practice slash-and-burn agriculture, is most frequent in lowland areas of Latin America, particularly in the Amazon Basin. Pasture creation for cattle ranching is causing deforestation almost exclusively in the humid lowland regions of mainland South America. Expansion of small-scale agriculture and fuelwood extraction for domestic uses are important causes of defor­estation in Africa (Geist and Lambin, 2002; FAO, 2006b) and Latin America (Echeverria et al., 2006). Recently, two new land use types that are partly related to new drivers have emerged: bioenergy production (see 4.4.5.4) and soy­bean expansion driven by international markets, but also by the development of GMOs has rapidly become a major threat in Latin America (see Box 4-3).

 

The range of combinations of factors is not infinite, al­though single-factor causes are rare (Reid et al., 2006). A sig­nificant share of land use changes involves lifestyle choices and shifting consumption patterns; governance; global mar­kets and policies. Underlying causes often have a strong influ­ence on local land use and cover changes. In the same way, land use alters in multiple ways agricultural production and AKST.
     Global forces are the main determinants of land use change, as they amplify or attenuate local factors (Lambin et al., 2001). Less visible but of no lesser importance is the build-up of small impacts at lower levels of the spatial and temporal scales to generate impacts at higher levels; cumu­lative impacts are caused by incremental impacts at the in­dividual level and are felt usually after some period of time at the regional or even the national level. The issue of scale is implicated in these and similar instances and makes the use of "scale-sensitive" analytical approaches imperative. Multiscale efforts bring global, regional, and local studies together (e.g., MA, 2005a).
     Many recent scenarios include land cover and land use changes, and many of those include explicit information on the main land use drivers. The scenarios also acknowledge the complexity of environmental, social, and economic driv­ers of land use change. However, due to lack of data, a lim­ited subset of drivers is included in the modeling efforts. The dynamics of land use (and thus of land cover) are largely governed by human (e.g., policy and socioeconomic) fac­tors, that are well-documented as indirect drivers (see 4.2), but poorly represented as direct drivers. Important drivers
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