Green revolution Study Guide

📖 Core Concepts Green Revolution (GR) – “Third Agricultural Revolution”; 20th‑century technology transfer that lifted worldwide cereal yields via a package of high‑yielding varieties (HYVs), irrigation, mechanization, synthetic fertilizers, pesticides, and coordinated management. High‑Yielding Varieties (HYVs) – Semi‑dwarf wheat, rice, and corn bred for greater nitrogen use and resistance to lodging; key genes: wheat Rht, rice sd1, GA‑biosynthesis mutants. Package of Inputs – HYVs only reach potential when paired with reliable water (irrigation), ample nitrogen fertilizer, pest control, and mechanized planting/harvesting. Key Figures – Norman Borlaug (wheat, Nobel Peace Prize 1970) and Yuan Longping (hybrid rice). Institutional Backbone – CGIAR (est. 1971) created a global network of research centers that generated and disseminated GR technologies. 📌 Must Remember Global cereal yields ↑ ≈ 44 % (1965‑2010). Cereal production in developing nations doubled (1961‑1985). Synthetic nitrogen fertilizer now fuels ≈ 50 % of the world’s food supply. Infant‑mortality fell 2.4–5.3 pp after HYV adoption (baseline 18 %). Delaying GR by 10 yr would cut GDP per‑capita in developing countries by ≈ 17 %. Major dwarfing genes: Rht (wheat), sd1 (rice), GA‑20‑oxidase / ga1 (Arabidopsis) – reduce stem elongation → more photosynthate to grain. Environmental side‑effects: ↑ nitrous‑oxide (N₂O) emissions, groundwater depletion, loss of agrobiodiversity. 🔄 Key Processes Breeding HYVs Select for semi‑dwarf stature → higher N uptake without lodging. Introgress disease‑resistance (e.g., rust‑resistant wheat). Input Integration Irrigation → stable water supply → allows intensive fertilizer use. Fertilizer (N) → fuels rapid leaf/ear growth in dwarf plants. Pesticides → protect high‑density stands from pests/weed competition. Farm‑Level Management Schedule irrigation → match critical growth stages. Apply fertilizer in split doses → maximize N use efficiency. Use mechanized planting/harvesting → reduce labor bottlenecks. 🔍 Key Comparisons HYV Wheat vs. Traditional Wheat – dwarf → less lodging, higher N response → 2‑3× yield. IR8 “Miracle Rice” vs. Local Rice – requires fertilizer/pesticide → 3–4× yield, but higher input cost. Green Revolution vs. Evergreen Revolution – GR = yield boost with high inputs; Evergreen = “perpetual productivity” + ecological sustainability. ⚠️ Common Misunderstandings GR solved famine permanently – It averted large‑scale famines but did not eliminate food insecurity; distribution/policy still matter (Amartya Sen). Higher yields = better nutrition – HYVs often have lower protein and micronutrient density than traditional varieties. All regions benefited equally – Africa’s adoption was limited by infrastructure, governance, and ecological constraints. 🧠 Mental Models / Intuition “Package Deal” Model – Think of HYVs as a high‑performance car; without premium fuel (fertilizer), good roads (irrigation), and regular maintenance (pest control), the car cannot reach its speed. Dwarfism = “Resource Re‑allocation” – Shorter stems = less carbon spent on stalk, more diverted to grains → higher harvest index. 🚩 Exceptions & Edge Cases Land‑use reduction – Despite intensified input use, GR actually reduced total cultivated area (2021 analysis). Hybrid Rice in China – Achieved food security without expanding cropland but at the cost of heavy groundwater extraction. Second Green Revolution – Yield gains are plateauing; newer methods (SRI, marker‑assisted selection) aim to restore growth with fewer inputs. 📍 When to Use Which Choose HYVs when: Reliable irrigation & fertilizer supply exist. Market access justifies higher production costs. Opt for Agroecology / Evergreen approaches when: Water or fertilizer scarcity limits input use. Biodiversity conservation or long‑term soil health is a priority. Apply System of Rice Intensification (SRI) in water‑limited or low‑input settings to boost rice yields with less seed, water, and chemicals. 👀 Patterns to Recognize Yield spikes coinciding with: introduction of a new dwarf variety + fertilizer subsidy + irrigation project. Health‑risk red flags: mentions of pesticide exposure without protective equipment → likely exam distractor about “safe” practices. Environmental critique cues: nitrous‑oxide emissions, groundwater depletion, biodiversity loss → points toward GR’s negative externalities. 🗂️ Exam Traps “GR eliminated hunger worldwide.” – Over‑statement; famines persist due to distribution, not just production. “HYVs require no fertilizer.” – False; dwarf varieties are designed to exploit high N rates. Confusing dwarfing genes: attributing sd1 to wheat (it belongs to rice) – a common mix‑up. Assuming all pesticide use is harmful – The exam may ask for nuance: appropriate, regulated use can protect yields, but misuse (no protective gear) creates health risks. “Evergreen Revolution = same as Green Revolution.” – Incorrect; Evergreen adds explicit ecological sustainability.