World agroecological regions

Story hook

1970s, FAO Rome. The Food and Agriculture Organisation faces a problem: how do you compare wheat from Kansas with wheat from Punjab with wheat from the Volga steppe? They are the same crop, same species (Triticum aestivum), but the growing conditions — length of growing period, temperature, soil moisture, frost incidence — are radically different. A single global "yield" average tells you nothing useful. A planner trying to figure out if sorghum will replace maize in the Sahel needs to know the agro- ecology, not just the crop name.

So FAO + IIASA invents the Agroecological Zone (AEZ) method, finalised in the 1978 FAO Soil Map of the World + 1981 Agroecological Zones Project. The world is divided into zones where climate × soil × terrain × LGP (length of growing period) combine to produce a specific suitability for specific crops. A million pixels are crunched. The output: a global map where every hectare carries a "wheat-suitable / maize-suitable / unsuitable / marginal" tag.

By 2024, the AEZ framework has evolved to GAEZ v4 (Global Agro-Ecological Zones) — running on FAO + IIASA servers with climate-change scenarios baked in. India's own National Agricultural Research Project uses an Indian AER (Agro- Ecological Region) classification — 20 regions + 60 sub-regions — to plan everything from MSP support to varietal release. UPSC asks you to know it.

Why this matters for UPSC

Syllabus location: GS-I — World Physical Geography (agricultural geography) + GS-III food security + GS-I Indian Geography. Prelims asked AER concepts in 2017 (LGP), 2019 (Köppen climates), 2022 (AER 4 — Gujarat plains). Mains 2018 + 2020 used AEZ language implicitly. The matrix logic — crop × climate × soil — underwrites every higher-level geography question.