An explained impact has three parts: a point, evidence from the data, and the process that links them. This lesson shows the pattern with an original dataset.
It belongs to environmental management. The idea of separating what you know from what the data show continues in separating local evidence from generic claims.
What is the pattern?
- Point: state the impact in one clause.
- Evidence: quote and compare figures.
- Explanation: give the process that makes the evidence happen.
- Link: tie the paragraph back to the question.
Keep each paragraph to about three sentences. A marker can then see each part at a glance.
Worked example: clearing mangrove for ponds
The numbers here are made up for illustration. On a fictional coast, 30 ha of a 120 ha mangrove belt was cleared for shrimp ponds. The data supplied are:
| Measure | Intact section | Cleared section |
|---|---|---|
| Shoreline retreat (m per year) | 0.6 | 2.4 |
| Young fish per net haul | 46 | 18 |
The cleared area is 30 ÷ 120 = 25% of the belt. Retreat in the cleared section is 2.4 ÷ 0.6 = 4 times faster. The fish difference is 46 − 18 = 28, which is 28 ÷ 46 = 61% fewer to the nearest whole number.
A paragraph on coastal erosion: “Clearing mangrove increased shoreline erosion. The cleared section retreated 2.4 m a year, four times the 0.6 m of the intact section. Mangrove roots slow wave energy and hold sediment, so without them waves remove the shore faster. This shows that clearing 25% of the belt exposed the coast to greater erosion.”
Here the point opens the paragraph, the evidence is a comparison, the explanation names the process, and the last sentence links back.
The mistake that loses marks
The listed impact reads: “Mangrove clearing causes erosion, fewer fish and loss of habitat.” Each item is true and each is a label only. Nothing shows how or by how much.
| Listed | Explained |
|---|---|
| Fewer fish. | Young fish per net haul fell from 46 to 18, 61% fewer, because mangrove roots shelter juveniles and cleared ground offers no cover. |
| Erosion. | Retreat was 2.4 m a year against 0.6 m, four times faster, because roots no longer slow the waves. |
The explained version is longer, and each clause has a job: the figure shows how much, the because-clause shows how.
Which process words should I use?
Use the process that matches the activity: roots hold soil, canopy slows rain, wetlands store water. If you do not know the process for the case, say “this is likely to” and stay with the data.
Do not add facts the data do not give. The claim, evidence and explanation revision desk lets you practise adding the because-clause to a bare claim.
Check yourself
Original data: a fictional hill slope with 70% tree cover has soil loss of 4 tonnes per hectare a year. A cleared slope has soil loss of 14 tonnes per hectare a year. Write a point, evidence, explanation paragraph on soil erosion.
Answer
The soil loss ratio is 14 ÷ 4 = 3.5 times. The difference is 14 − 4 = 10 tonnes per hectare a year.
Model answer: “Clearing trees increased soil erosion. The cleared slope lost 14 tonnes per hectare a year, 3.5 times the 4 tonnes lost on the tree-covered slope. Leaves slow raindrops and roots hold soil, so bare ground is washed away more easily. Clearing therefore raised the loss by 10 tonnes per hectare a year.”
What to study next
Next, practise reading raw data in interpreting fieldwork data, then test the skills in the environmental management practice set.
To have a teacher add evidence and process to your own impact answers, see online one-to-one Geography tuition.