- Tree cover on agricultural land is strongly related to climate zone, with some regional variation
- Agroforestry allows for a gradual transition from subsistence to market-oriented land use
- Tropical commodity production is highly concentrated, with the top 1, top 3 and top 10 countries accounting for about one-third, two-thirds or 90%, respectively, of global production
- Agroforestry farmers face different and changing forest-policy and property-right regimes in countries and regions
- Progress in developing land-use policies supportive of agroforestry is uneven, with opportunities for inspiration and learning from frontrunner countries
- Upscaling agroforestry practices requires developing options tailored to varying, local, socio-ecological contexts and enabling environments
There are many ways to classify and describe agroforestry practices based on the spatial and temporal arrangement of trees, the type of trees in relation to economic value, the non-tree components (crops, livestock, fish) or the balance between retained, spontaneous and planted trees (compare with Chapter 2). The simplest way that is compatible with existing global data sets may well be the classification of tree canopy cover on agricultural land because it allows a direct comparison across regions and countries. In this chapter, we present data, experience and lessons from the six regions in which World Agroforestry is currently active. Together, they cover 66.8% of global agricultural land and 72.9% and 78.8% of such land with at least 10% and 30% tree cover, respectively. Across all regions, tree cover on agricultural land is positively related to rainfall (scaled by potential evapotranspiration in Figure 6.1).
Central America stands out as the region with the highest, relative, on-farm tree cover in any climatic zone, with relatively small differences between other regions, once climate is accounted for. From existing data, it appears that increases in soil carbon storage in agroforestry systems relative to open-field cropping (on average 19% for the 0–100 cm depth layer) are only partially related to aboveground carbon storage in trees across four different agroforestry practices (homegardens, alley cropping, windbreaks, silvopastoral systems), but do correlate with tree age.
Agroforestry is an important mode of production for some of the tropical commodities but has in others been replaced by monocultures. For these commodities, the top 1, top 3 and top 10 countries account for about 33%, 66% and 90% of global production, respectively.
However, there are some differences, with oil palm and coconut most concentrated, and coffee and tropical timber least geographically concentrated.
We will here give a brief characterization of the tree-cover data at country scale, the main development issues that agroforestry can contribute to, and the types of agroforestry research and development of the past four decades, with a focus on research performed by World Agroforestry and partners. Each of the six regions is ‘represented’ by single case studies in subsequent chapters (8–13), therefore, we will contextualize the examples here. As a generic group of settings with special consequences for agroforestry, Chapter 14 will focus on ‘small islands’ around the world.
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