Agroecological zones (AEZs) are geographical areas sharing similar climate characteristics (e.g., rainfall and temperature) with respect to their potential to support (usually rainfed) agricultural production. Because of the general similarity of production conditions, many agricultural technologies, practices and production systems tend to behave or respond consistently within a specific AEZ. AEZs therefore provide a useful spatial framework for identifying the potential area extent of applicability of given innovations and, futhermore, the likely potential for production related innovations to "spillover" from one country (or continent) to another. AEZs provide an ecology-based division of geographic space as opposed to administrative or political boundaries within which environmental conditions could vary significantly.

In HarvestChoice we often use the AEZ spatial framework to summarize and report important agricultural measures such as production, population, extent of cultivation, and market accessibility. Specifically, we often use AEZs to identify land suitable for rainfed cultivation and for the production of specific crops. For example, our HarvestChoice crop allocation model (Spatial Prodcution Allocation Model, SPAM) utilizes input data on crop suitability surfaces developed by IIASA/FAO (Fischer, et al. 2001) that are based on agroecological zones, soils and other terrain variables. HarvestChoice has developed primers on both the assessment of Agricultural Potential and on Geographical Targeting/Segmentation and Development Domain.

Summarizing statistics by AEZs can also help highlight areas within countries where farmers may face greater challenges related to the adoption of new technologies or in dealing with adverse climate conditions. For example, based on our tabulation of cropped area by AEZ for Sub-Saharan Africa, nearly 45% of cultivated area in the tropical region falls in the more challenging arid or semi-arid zones, and only 13% of the total cropped area is in the more humid highland regions where conditions both for human populations and crop production are more favorable. The tabulation of rural population by AEZ for Sub-Saharan Africa indicates that just over 36% of the rural population lives in the more extensive arid or semi-arid zones, whereas 23% live in the more favorable, but less extensive moist highland regions.

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