--- title: "People and Nature" book: "Primary & Middle School Biology" subject: biology language: en chapter: 35 exercises: 11 source: https://one-course.com/books/biology/1/en/chapter/35-people-and-nature --- # Chapter 35 — People and Nature From a hilltop, look down at the valley: fields in neat squares, a managed forest, straightened riverbanks, roads, roofs. Almost nothing in sight grew that way by itself. Humans are the one [species](https://one-course.com/books/biology/1/en/chapter/30-biodiversity#def-g5-biodiversity-species) that reshapes whole landscapes to its needs — and this chapter looks honestly at that power: what it gives us, what it costs, and how it can be used well. ## 35.1 Landscapes made by people **Proposition 35.1 (Most landscapes are managed).** Nearly every landscape around us is shaped by people: - *fields* are managed ground where one chosen [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) — wheat, maize, potatoes — is grown in place of the wild mixture; - most *forests* are planted, thinned and harvested like slow crops; - *meadows* exist because they are mowed or grazed — abandoned, they grow back to scrub and then woodland; - towns, roads and dams redraw the land itself. “Untouched” corners are the exception, and most are protected on purpose. **Proof.** *Admitted at this level.* ∎ **Example 35.2 (Reading the valley).** That hilltop view, item by item: the wheat field feeds the bakery; the spruce rows are a timber crop older than their forester; the flowery meadow is mowed each July — skip two summers and brambles take it; the river was straightened long ago to protect the fields from floods. The valley is a workshop — one that has been running for centuries. ![The view from the hilltop: fields, hedges, managed forest, straightened river, village — a working landscape, centuries old.](https://one-course.com/images/onecourse/chapters/biology-1/g5-people-and-nature/img-e00433fdc909.jpg) *The view from the hilltop: fields, hedges, managed forest, straightened river, village — a working landscape, centuries old.* **Remark 35.3 (Neither villain nor garden gnome).** It would be false to tell this story as pure destruction — farming feeds humanity, and hedged farmland can be rich in [species](https://one-course.com/books/biology/1/en/chapter/30-biodiversity#def-g5-biodiversity-species) ([Example 30.6](https://one-course.com/books/biology/1/en/chapter/30-biodiversity#ex-g5-biodiversity-orchard)) — and just as false to pretend reshaping costs nothing ([Proposition 30.8](https://one-course.com/books/biology/1/en/chapter/30-biodiversity#prop-g5-biodiversity-loss) listed the bills). The honest question is never “touch nature or not?” but “how to manage what we touch so it keeps working — for us and for the rest of the web?” ## 35.2 Managing well and managing badly **Example 35.4 (Two ways to farm a hillside).** Hillside A: one giant field, hedges grubbed out, soil bare all winter. Rain washes the loosened soil downhill; the helpers of [Example 30.6](https://one-course.com/books/biology/1/en/chapter/30-biodiversity#ex-g5-biodiversity-orchard) have no home; one pest can sweep the single crop unopposed. Hillside B: smaller fields with hedges kept, soil covered through winter, crops rotated year by year. The hedges hold the soil and house the pest-eaters; the rotation rests the ground. Both hillsides feed people — one still will in a hundred years. **Proposition 35.5 (The rules of lasting use).** Use of nature lasts when it respects three rules: 1. *take no faster than it renews* : harvest wood at the forest’s growing pace, [fish](https://one-course.com/books/biology/1/en/chapter/14-sorting-living-things#prop-g3-sorting-living-things-groups) at the shoal’s breeding pace — the overfishing of [Proposition 30.8](https://one-course.com/books/biology/1/en/chapter/30-biodiversity#prop-g5-biodiversity-loss) is this rule broken; 2. *keep the workers* : soil life, pollinators, pest eaters — the free services of [Exercise 30.11](https://one-course.com/books/biology/1/en/chapter/30-biodiversity#exo-g5-biodiversity-11) — need their homes kept; 3. *return what you borrow* : the compost loop of [Remark 22.5](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#rem-g4-what-plants-need-soil) , at every scale. **Proof.** *Admitted at this level.* ∎ **Example 35.6 (The forester’s arithmetic).** A well-run forest is the oldest proof that rule 1 works: foresters count what the forest grows each year, and cut no more than that. The forest then yields timber every year, forever — while remaining a forest, with its owls, deer and beetles. Some managed [forests](#prop-g5-people-and-nature-managed) in the world have been harvested this way for many hundreds of years without shrinking. ## 35.3 Cities, and making room again **Example 35.7 (Nature in town).** A city looks like nature’s opposite, yet it is a [habitat](https://one-course.com/books/biology/1/en/chapter/11-where-animals-live#def-g2-where-animals-live-habitat) too — a strange rocky one. Swifts nest on “cliffs” of concrete, foxes patrol the bins, wild [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) split the asphalt seams. And town-dwellers can widen the welcome: parks, green roofs, balcony [flowers](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) for the bees, the school pond of [Example 11.8](https://one-course.com/books/biology/1/en/chapter/11-where-animals-live#ex-g2-where-animals-live-schoolpond). The methods of [Method 30.9](https://one-course.com/books/biology/1/en/chapter/30-biodiversity#met-g5-biodiversity-help) work between buildings too. **Example 35.8 (Giving a river its bends back).** The straightened river of the valley ran fast and flooded badly downstream; its [fish](https://one-course.com/books/biology/1/en/chapter/14-sorting-living-things#prop-g3-sorting-living-things-groups) and dragonflies had gone with the bends. Engineers now sometimes *re-bend* such rivers: restored curves and wet meadows slow the water, store the floods, and the storks of [Example 30.10](https://one-course.com/books/biology/1/en/chapter/30-biodiversity#ex-g5-biodiversity-storks) find their meadows again. Management can run in reverse — repairing is managing too. **Method 35.9 (Judging a use of nature).** Given any use of land or water — a farm, a fishery, a planned road, a garden: 1. ask what is *taken* , and whether faster than it renews (rule 1); 2. ask what *homes and workers* are kept or lost (rule 2); 3. ask what is *returned* — and what wastes are left (rule 3); 4. then judge: could this go on for a hundred years? What one change would most improve the answer? ## 35.4 Exercises **Exercise 35.1 ★.** Give four kinds of human-shaped landscape from [Proposition 35.1](#prop-g5-people-and-nature-managed), each with what it is managed for. **Solution of Exercise 35.1.** Fields, managed for one chosen crop; [forests](#prop-g5-people-and-nature-managed), managed for timber; meadows, kept open for hay or grazing; towns, roads and dams, built for living and moving. (Any four with their purposes.) **Exercise 35.2 ★.** What happens to a meadow that stops being mowed or grazed? **Solution of Exercise 35.2.** Left unmowed and ungrazed, it grows back to scrub within a few years, and then to woodland — the open, flowery meadow [habitat](https://one-course.com/books/biology/1/en/chapter/11-where-animals-live#def-g2-where-animals-live-habitat) disappears. **Exercise 35.3 ★.** State the three rules of lasting use. **Solution of Exercise 35.3.** Take no faster than it renews; keep the workers (the [species](https://one-course.com/books/biology/1/en/chapter/30-biodiversity#def-g5-biodiversity-species) whose free services the use depends on); return what you borrow (close the loops, leave no piling wastes). **Exercise 35.4 ★.** In [Example 35.4](#ex-g5-people-and-nature-twofarms), list three differences between the two hillsides, and what each difference changes. **Solution of Exercise 35.4.** Hedges grubbed out versus kept: A loses the soil-holders and the homes of pest-eaters. Bare winter soil versus covered: A’s soil washes downhill in the rains. One giant single crop versus rotation: A invites any pest of that crop to sweep the whole hillside, and never rests the ground. **Exercise 35.5 ★.** Explain the forester’s arithmetic. Which rule is it, and what does the forest yield in return — for how long? **Solution of Exercise 35.5.** Count what the forest grows in a year; cut no more than that. It is rule 1 — take no faster than it renews — and the forest yields timber every year, indefinitely, while remaining a living forest. **Exercise 35.6 ★.** Name three wild inhabitants of cities, and what feature of the city each uses as [habitat](https://one-course.com/books/biology/1/en/chapter/11-where-animals-live#def-g2-where-animals-live-habitat). **Solution of Exercise 35.6.** For example: swifts, nesting on concrete “cliffs”; foxes, patrolling bins and gardens; wild [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant), rooting in asphalt seams and wall [joints](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#prop-g3-bones-and-muscles-joints) (also pigeons on ledges, falcons on towers). **Exercise 35.7 ★.** What did re-bending the river restore — for people, and for the web? **Solution of Exercise 35.7.** For people: slower water and flood storage in the restored wet meadows — less flooding downstream. For the web: the bends’ [habitats](https://one-course.com/books/biology/1/en/chapter/11-where-animals-live#def-g2-where-animals-live-habitat) came back, and with them [fish](https://one-course.com/books/biology/1/en/chapter/14-sorting-living-things#prop-g3-sorting-living-things-groups), dragonflies and the storks’ hunting meadows. **Exercise 35.8 ★.** Try it: pick one view near home — street, field, park — and list everything in it that people manage, as in [Example 35.2](#ex-g5-people-and-nature-valley). Anything left unmanaged? **Solution of Exercise 35.8.** Open answer. Typical finds: mowed verges, pruned trees, planted beds, weeded pavements — with perhaps one unmanaged wall-top or ditch, which is often the wildest spot in view. **Exercise 35.9 ★★.** “Protecting nature means never touching it.” Discuss using the mowed meadow of [Proposition 35.1](#prop-g5-people-and-nature-managed) — a [habitat](https://one-course.com/books/biology/1/en/chapter/11-where-animals-live#def-g2-where-animals-live-habitat) that *disappears* without human touch — and [Remark 35.3](#rem-g5-people-and-nature-honest). **Solution of Exercise 35.9.** Never-touching would actually destroy some [habitats](https://one-course.com/books/biology/1/en/chapter/11-where-animals-live#def-g2-where-animals-live-habitat): the flowery meadow exists *because* of mowing, and grows shut without it. Protecting nature is not zero touch but good management — the honest question is how to touch: which rules the use respects, not whether hands were laid on at all. **Exercise 35.10 ★★.** Run [Method 35.9](#met-g5-people-and-nature-judge) on hillside A of [Example 35.4](#ex-g5-people-and-nature-twofarms): which rules does it break, and what one change would most improve it? **Solution of Exercise 35.10.** Rule 2 broken outright (workers evicted with the hedges), rule 3 partly (soil washed away is never returned), and rule 1 endangered (soil lost faster than soil forms). Most improving single change: replant the hedges — they hold the soil and rehouse the pest-eaters at one stroke. **Exercise 35.11 ★★★.** A fishing fleet doubles its catch for five splendid years; in the sixth, the shoals are gone and the fleet is idle. Explain the six years with rule 1 — why did breaking it *look* like success at first? Compare with the forester’s opposite arithmetic. **Solution of Exercise 35.11.** The doubled catch took [fish](https://one-course.com/books/biology/1/en/chapter/14-sorting-living-things#prop-g3-sorting-living-things-groups) far faster than the shoals bred — spending the breeding stock itself. Spending capital always looks splendid while it lasts: the holds were full precisely because next year’s [fish](https://one-course.com/books/biology/1/en/chapter/14-sorting-living-things#prop-g3-sorting-living-things-groups) were being landed this year. The forester harvests only the year’s growth and keeps the growing stock whole — same arithmetic, opposite sign, which is why the forest yields forever and the fleet stopped in year six.