To assess an environmental model, you take a claim about resources and production, test it against a table of evidence, and decide how far it holds. The skill is reading the table in full and then judging. This lesson belongs to the development, population and environment module.
How do you assess a model step by step?
- State the claim in your own words.
- Check the evidence across the whole range, not only the first rows.
- Calculate one helpful measure, such as catch per boat.
- Say where the model holds and where it does not.
- Name what the evidence cannot show, such as another place or a longer period.
Worked example
Lake Ordin is a fictional lake. A claim says: “Adding more fishing boats always increases the total catch.”
| Boats | Total catch (tonnes a year) |
|---|---|
| 10 | 100 |
| 20 | 180 |
| 30 | 220 |
| 40 | 200 |
Total catch rises from 10 to 30 boats (100, 180, 220), then falls to 200 at 40 boats. So the claim fails beyond 30 boats.
Catch per boat is total catch divided by boats: 100 ÷ 10 = 10, 180 ÷ 20 = 9, 220 ÷ 30 ≈ 7.3 and 200 ÷ 40 = 5 tonnes. It falls at every step, so each extra boat adds less.
Extra catch from each added group of ten boats: +80, +40, then −20 tonnes.
Judgement: “The claim holds only up to about 30 boats. Beyond that, extra boats reduce the total catch, which suggests the fish stock is being used faster than it can recover. The table covers one lake and does not show fish numbers or time, so more evidence would be needed to explain why.”
Note the careful wording: “suggests”, not “proves”.
The mistake to watch for
Mistaken answer: “The model is correct, because catch went up from 100 to 180 to 220.”
It stops reading at the third row and ignores the fall to 200.
The correction is to read the full table and check the trend at each step. A model can be right in one range and wrong in another, and a good answer says exactly where it changes.
Check yourself
1. In Lake Ordin, 50 boats would catch 150 tonnes. Find the catch per boat.
Show answer
150 ÷ 50 = 3 tonnes per boat. It continues the falling trend (5 at 40 boats).
2. Name one extra piece of evidence that would help explain why the catch falls beyond 30 boats.
Show answer
For example: the number of fish in the lake over time, or how fast the fish stock replaces itself each year. Either would show whether the stock is being used up.
3. Does the Lake Ordin table prove the same pattern would occur in another lake? Give a reason.
Show answer
No. It shows one lake. Another lake may have a different fish stock, a different recovery rate or different fishing methods, so more evidence would be needed.
Where this leads next
Next, identify a missing distributional detail. If the idea of a government response interests you, public finance and economic instruments explains tools such as taxes and rules. The ratio interpretation tool helps with per-unit figures.
If you can calculate the measures but find the judgement sentence hard to word, our teachers work on that directly in online one-to-one Economics tuition.