An action is what people did. Evidence of success is what was measured afterwards. This lesson teaches you to keep them apart so your evaluation answers “did it work?” and not only “what was done?”
It belongs to effects and management of resource extraction. If you have not traced an effect chain yet, start with tracing an environmental effect from an extraction case.
What counts as evidence of effort and what counts as evidence of effect?
Effort evidence counts what was done: trees planted, ponds built, money spent. Effect evidence measures the harm the action targets: soil lost, sediment in water, species counted.
Ask of every figure: does this measure the harm, or only the work? Only the first can show that the action worked.
Worked example: replanting a quarry slope
The numbers here are made up for illustration. A fictional quarry planted 2 000 saplings on a bare slope to reduce muddy runoff. After 18 months the records show:
- Saplings alive: 1 340.
- Sediment in runoff: 240 mg per litre in the year before planting, 150 mg per litre in the year after.
- Rainfall: the year before was much wetter than the year after.
Survival rate is 1 340 ÷ 2 000 = 67%. The fall in sediment is 240 − 150 = 90 mg per litre, which is 90 ÷ 240 = 37.5%.
| Figure | What it measures | Shows the action worked? |
|---|---|---|
| 2 000 saplings planted | Effort | No |
| 67% survival | Whether the action is still in place | Partly |
| Sediment down 37.5% | The harm the action targets | Possibly, but rainfall differed |
The sediment fall is the best evidence, but the wetter year before means rain alone might explain a lower reading after.
The mistake that loses marks
The common slip is to write: “The quarry planted 2 000 saplings, so the slope is now protected.” This states an action and claims a result in the same sentence, with no measured outcome.
A stronger answer reads: “Sediment in runoff fell from 240 to 150 mg per litre, a fall of 37.5%, and 67% of saplings survived. However, the year before planting was wetter, so the fall cannot be credited to the planting alone. A comparison with an unplanted slope in the same years would settle it.”
This answer leads with the measured outcome, uses the survival figure as support, and names a rival explanation and a way to test it.
How do I word the verdict?
Use the same ladder as in the correlation lesson: “fell after” is safe, “is linked to” needs a pattern, and “worked because” needs rival explanations removed. For this case the wording “fell after planting, which suggests the action helped” fits the evidence.
The claim, evidence and explanation revision desk lets you practise adjusting the strength of a verdict. The wording ladder is explained in correlation is not a proven cause.
Check yourself
Original data: a fictional tin-mining pool is fenced and a silt trap is built. The trap cost RM85 000.
Water cloudiness was 62 units before and 41 units after, with similar rainfall in both years. Did the silt trap work? Use two figures.
Answer
The cost of RM85 000 is effort, not effect. The effect figure is cloudiness: 62 − 41 = 21 units lower, which is 21 ÷ 62 = about 34% lower.
Rainfall was similar, so the rival explanation is weak. A verdict: “Cloudiness fell 34% after the trap was built under similar rainfall, so the trap appears to have worked. One year of data is short, so the result needs to be repeated.”
What to study next
Next, evaluating a conservation proposal with a stated limitation applies the same thinking before an action begins.
To have a teacher test your evaluations against a new case, see online one-to-one Geography tuition.