Conservation evidence is data about whether protecting a species or place has made a difference. To evaluate it, state what the figures show, say how far they support the claim, name the limitations, and reach a judgement. Questions often use the words “assess” or “how far” to ask for this balance.
This lesson follows explaining a disturbance with a causal chain, because protection is a response to a disturbance and the evidence has to be read carefully.
How do you evaluate step by step?
- Describe the change with the start and end values and the time period.
- Calculate the change and the percentage change.
- Compare with a control site if one is given.
- State what the evidence supports in cautious terms.
- Name limitations, then say how each one weakens the conclusion.
- Judge and say what extra evidence would help.
Worked example
All figures are invented for practice. A reserve protected a bird species. Counts were made once a year, in the same month, over five years.
| Site | Year 1 count | Year 5 count |
|---|---|---|
| Protected reserve | 120 | 150 |
| Similar unprotected site | 110 | 118 |
Protected reserve. Change = 150 − 120 = +30. Percentage change = 30 ÷ 120 × 100 = +25%. Check: 25% of 120 is 30.
Unprotected site. Change = 118 − 110 = +8. Percentage change = 8 ÷ 110 × 100 = +7.3% (to 1 decimal place). Check: 7.3% of 110 is about 8.
Compare. Both sites rose, but the reserve rose by about 17.7 percentage points more (25 − 7.3). The control site suggests that part of the rise may come from other causes, such as a good breeding season.
Limitations. The period is short at five years. One count a year can be affected by weather on the counting day. The data comes from one reserve and one comparison site, so it may not apply elsewhere. The table does not show why numbers rose.
Judgement. The evidence suggests that the protection may have helped, because the reserve rose more than the control site. It does not prove it, and more years, more sites and records of habitat change would make the case stronger.
The mistake to watch for
A common answer is: “The population rose by 25%, so the conservation worked.”
Mistaken answer: a rise after protection proves the protection caused the rise.
The same period also saw a rise at the unprotected site, so other factors were at work too.
The correction is to ask “compared with what?”. Use the control site, then write “suggests” or “is consistent with” instead of “proves”.
Check yourself
1. A seabird colony rose from 400 pairs to 480 pairs. Give the percentage change.
Show answer
Change = +80. 80 ÷ 400 × 100 = +20%. Check: 20% of 400 is 80.
2. Name two limitations of one count made in one month each year.
Show answer
Weather on the counting day can change the result, and one month may miss the movement of animals in and out. Both reduce how well the count represents the whole year.
3. What extra evidence would make the reserve conclusion stronger?
Show answer
Counts over more years, more reserves and comparison sites, and records of habitat or food supply. Each one checks a different alternative explanation.
Where this leads next
Next, look at how places and people are described in avoiding ecological or demographic stereotypes. The statistics and distribution explorer helps with the percentage work and the food-web and energy-flow explorer helps you link a result back to the ecosystem.
Many students only describe the figures and never weigh them. A teacher in online one-to-one Geography tuition can read your evaluation and show where the judgement is missing.