Intended and unintended consequences
A pesticide kills the pests — and some of the insects that were eating them. A furnace warms a house — and adds carbon dioxide to the air. Every technology in Science 7 does what it was designed for and something else as well, and deciding whether it is worth it is a question science cannot answer on its own.
Why look past what something was meant to do?
Because the effects nobody planned are often the ones that matter most, and they are easiest to deal with before anything is built. Once a highway is paved, a valley is flooded or a new species has escaped, undoing it costs far more than thinking it through would have.
The idea gives you a method. Name what the technology was meant to do — the intended consequence. Then hunt for the others — the unintended consequences — by asking what else lives nearby, what happens downstream, what happens years later, and what happens if everyone does it. Then weigh them, and say whose point of view you are weighing them from.
Where it turns up
- The cane toad — Australia released cane toads in 1935 to eat beetles damaging its sugar cane. They did little to the beetles, spread across much of northern Australia, and poison native animals that try to eat them
- Leaded gasoline — lead was added to gasoline from the 1920s to make car engines run smoothly. It spread lead through the air, which harms the brain, especially in children, and Canada banned it from car fuel in 1990
- The ozone layer — CFCs were used in fridges and spray cans because they are not poisonous and do not burn. They turned out to destroy the high-altitude ozone that blocks harmful ultraviolet light; the Montreal Protocol of 1987 phased them out, and the ozone layer is slowly recovering
- Environmental impact assessments — before many large projects in Canada — a mine, a dam, a pipeline — are approved, their likely effects are studied, and the public, including affected First Nations and Métis communities, can respond
- 1. The words, first
- 2. Finding the consequences nobody planned
- 3. Every unit has one
- 4. Weighing them, and whose view counts
- 5. Keeping the benefit, shrinking the cost
The words, first
The idea: An unintended consequence is not always bad. It is just one that nobody planned.
| Word | What it means |
|---|---|
| Technology | A tool, machine, material or method that people make to solve a problem: a pesticide, a furnace, a bridge. |
| Consequence | A result of an action or decision. |
| Intended / unintended consequence | The result something was meant to have / a result nobody planned, good or bad. |
| Trade-off | Giving up some of one thing to get more of another. |
| Point of view | How a person or group sees a decision — a farmer, a town, a First Nation, a business — shaped by what they need and value. |
| Environmental impact assessment | A study done before a big project, to predict its effects on the environment and plan how to reduce them. |
Finding the consequences nobody planned
The idea: The intended consequence is easy to see: it is the reason the thing was made. The others turn up when you ask four questions.
- What else lives or works here? A spray meant for one insect can reach others.
- What happens downstream or downwind? Fertilizer spread on a field can wash into a lake many kilometres away.
- What happens later? Insect pests sprayed year after year can become resistant to the spray.
- What happens if everyone does it? One wood stove makes a little smoke. A whole valley of them on a still winter night makes smog.
Worked: an insecticide on canola.
| Question | Consequence |
|---|---|
| What was it meant to do? | Kill the flea beetles eating young canola, so the crop survives |
| What else lives here? | It also kills ladybugs, wasps and other insects that eat pests, and can harm bees if it is sprayed while they are feeding on flowers |
| Downstream? | Spray drifting or washing into a slough, a small prairie pond, can harm the insects that live in the water |
| Later? | Pests sprayed again and again can become resistant |
| If everyone does it? | Across a whole region, fewer of the insects that keep pests down |
None of this means spraying is wrong. It means the full list is longer than the one reason for spraying — and integrated pest management, in Unit B, is how farmers shorten it.
Every unit has one
The idea: Each Science 7 unit has a technology that solves a real problem and causes another. Once you see the pattern, the next one is easier to spot.
| Technology | Intended | Unintended |
|---|---|---|
| A · Ecosystems: a highway through a national park | Fast, safe travel | Wildlife killed on the road; habitat split in two |
| B · Plants: fertilizer | Bigger harvests | Runoff that feeds algae in lakes |
| C · Heat: a natural-gas furnace | A warm house all winter | Carbon dioxide in the air; carbon monoxide if it is faulty |
| D · Structures: a new bridge | A shorter trip across the river | More traffic and building on the far side; work in the river can disturb fish habitat |
| E · Planet Earth: a coal mine | Coal and jobs | Rain washing through piles of waste rock can carry selenium into streams, where it harms fish |
Some unintended consequences are good. Rows of trees planted on prairie farms to slow the wind also shelter birds and small animals. When a bridge in Austin, Texas, was rebuilt in 1980, the narrow gaps under its deck turned out to suit bats, and over a million now spend each summer there — a tourist attraction nobody planned.
Weighing them, and whose view counts
The idea: Science can predict the consequences. Which ones matter most depends on who is asking, so a good answer names the point of view.
Once both lists are written, you are weighing a trade-off. Four questions help with each consequence. How big is it? How likely? How long does it last — a season, or a century? Can it be undone, or made smaller?
Then ask who gets the benefit and who pays the cost. They are often different people, in different places or at different times. A dam's water may go to farms downstream while a valley upstream is flooded. A mine's jobs arrive now, while its waste rock may affect streams for generations.
Worked: a proposed reservoir. A dam is proposed on a river in southern Alberta, to store spring runoff for irrigation. Different people will weigh it differently:
| Point of view | What they might say |
|---|---|
| A farmer downstream | Reliable water in dry summers means a crop every year. |
| A town downstream | The dam could hold back floodwater in a wet spring. |
| A biologist | Fish that swim upstream to spawn would be blocked, and the river's flow below the dam would change. |
| A First Nation whose traditional land is in the valley | Places used for generations for hunting, gathering plants and ceremony would be under water. |
| A taxpayer | Who pays to build and look after it, and is it worth that much? |
Every one of these is reasonable, and science alone cannot say which matters most. What science can do is make each prediction accurate: how much land would flood, which fish would be affected. A strong answer gives the consequences from more than one point of view, then makes a choice and gives the reason for it.
Keeping the benefit, shrinking the cost
The idea: The choice is rarely all or nothing. Most good decisions keep the intended consequence and find a way to shrink the unintended ones.
| Problem | A way to shrink it |
|---|---|
| Wildlife killed on a highway | Fences, with overpasses and tunnels for animals (Unit A) |
| Spraying kills helpful insects | Integrated pest management: count first, spray only when needed (Unit B) |
| Heat escaping from a house | Insulation and a thermostat turned down at night, so the furnace burns less (Unit C) |
| A structure failing | A margin of safety, and regular inspection (Unit D) |
| Land torn up by a mine | Reclamation — reshaping and replanting the land when mining ends — which Alberta law requires (Unit E) |
And sometimes the answer is no. CFCs were not made safer; they were replaced. Leaded gasoline was not filtered; it was banned. When an unintended consequence is serious and cannot be made smaller, the technology itself has to change.