--- title: "Food security: what limits yield and what it costs to raise it" description: "Crop yield can be limited by pests, diseases, water or nutrients. Raising yield can use more water or harm soil, rivers and wildlife. Food security also depends on whether people can obtain safe, nutr" canonical: https://lightmysky.com/learn/science/food-security-what-limits-yield-and-what-it-costs-to-raise-it-mt_SprRvGuyrK source: https://lightmysky.com/learn/science/food-security-what-limits-yield-and-what-it-costs-to-raise-it-mt_SprRvGuyrK.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Food security: what limits yield and what it costs to raise it Crop yield can be limited by pests, diseases, water or nutrients. Raising yield can use more water or harm soil, rivers and wildlife. Food security also depends on whether people can obtain safe, nutritious food. Subject: Science · Area: Organisms & Life Processes · Ages 15 to 16 Page: https://lightmysky.com/learn/science/food-security-what-limits-yield-and-what-it-costs-to-raise-it-mt_SprRvGuyrK ## Ready when they can - Identify threats to harvests and explain how climate change can increase some risks - Explain why feeding human-edible crops to animals usually leaves less food energy for people than eating those crops directly - Evaluate one intensive farming method by what it gains and what it costs ## Lesson: More food from the same field Food security means everyone can reliably obtain enough safe, nutritious food. A large harvest does not give everyone access if food is unaffordable or cannot reach them. Pests, diseases, drought, floods and soil damage can reduce harvests. Climate change can increase heat stress and change drought or heavy-rain risks. Warmer winters can let some crop pests survive. People with fewer resources may find it harder to cope. Plants store sunlight energy in food. Animals use food energy for respiration and release heat. Energy in uneaten or undigested material can pass to decomposers. Only some feed energy becomes new tissue. In calculations here, assume 10% becomes edible animal tissue. Ten percent is one tenth, found by dividing by 10. Real efficiencies vary. Compare food energy before human digestion. **Example.** A harvest has 4000 energy units in grain people can eat. At 10% transfer, edible animal tissue holds 4000 ÷ 10 = 400 units. The difference is 4000 - 400 = 3600 units. Eating the edible grain directly avoids the transfer through animals, which releases heat and leaves energy in waste or inedible parts. Grass and some by-products are not human food, so this comparison does not fit every farm. *(drawing: Food-energy units in the stated model: 4000 in edible grain and 400 in edible animal tissue.)* Fertiliser can raise yield when mineral nutrients limit growth. Dissolved nutrients can enter rivers and contribute to eutrophication, as in the previous topic. Irrigation supplies water when water limits growth. Pumping groundwater faster than it is replaced can lower the water table. Choose a method that addresses the crop's limit, then compare its yield gain with its money, water and environmental costs. Pesticides can protect yield by reducing pest damage. Some pests already resist a pesticide. If they survive spraying and reproduce, repeated use can make resistance more common. Pesticides can also harm non-target organisms, including species exposed through polluted water. To evaluate a pesticide, compare the crop damage it prevents with its cost, resistance risk and possible harm to other species. **Recap.** Food security needs reliable access to safe, nutritious food. Compare crop and animal food using stated assumptions, and judge farming methods by both yield gains and costs. *Lesson, questions and study cards written for this dataset. Energy-flow textbook records were consulted for scientific background; no source passages or illustrations are reproduced.* ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Fertilisers, Leaching and Eutrophication](https://lightmysky.com/learn/science/fertilisers-leaching-and-eutrophication-mt_9lTF20DWOZ) ## Optional connections - [Photosynthesis and Limiting Factors](https://lightmysky.com/learn/science/photosynthesis-and-limiting-factors-mt_PDn831oIih)