An environmental effect is a chain, not a single jump. This lesson shows how to write the chain from the activity to the final change and tag each link with the evidence behind it.
It is the first lesson in effects and management of resource extraction. To handle a pattern in data carefully, see correlation is not a proven cause.
How do I build the chain?
Start with the activity and the final change. Then ask “what happens next?” until the two ends meet, writing one short step each time.
For each step, look in the data for a figure. A step with a figure is supported. A step with no figure is an assumption, and you should say so.
Worked example: sand mining on a river
The numbers here are made up for illustration. A fictional company removes sand from the bed of the Sungai Lenta. The data supplied are:
- Dredged area: 1.2 km of riverbed.
- Riverbed depth in the dredged section: 1.5 m before, 2.4 m after.
- Bank retreat: 0.4 m a year for three years before dredging, 1.2 m a year after.
- Notes: the bank had a line of farm plots 6 m from the edge.
The chain is:
- Sand is removed from the bed, so the bed lowers. Supported: depth rose from 1.5 m to 2.4 m, a change of 0.9 m.
- A deeper channel lets water flow faster against the banks. Assumed: no flow speeds are given.
- The bank wears away faster. Supported: retreat rose from 0.4 m to 1.2 m a year, which is three times as fast (1.2 ÷ 0.4 = 3).
- Farm plots lose land. Supported only as a risk: at 1.2 m a year, the 6 m strip lasts about 5 years (6 ÷ 1.2 = 5), but no plot loss is recorded.
Step 2 is a link that geography knowledge supplies. It fits the data, but the data do not show it.
The mistake that loses marks
The one-jump answer reads: “Sand mining destroys farmland.” It is short and confident, and it skips the middle of the chain. No marker can credit an explanation that is missing.
| One jump | Chained |
|---|---|
| Sand mining destroys farmland. | Dredging lowered the bed by 0.9 m, which is likely to speed the flow, and the bank retreat tripled to 1.2 m a year, putting the plots 6 m from the edge at risk within about 5 years. |
The chained answer is longer, and every part of it can be checked against the data.
Which links need the most care?
Links that depend on a process you know but cannot see in the data, such as faster flow, need a hedge word such as “likely” or “would be expected to”. Links with a figure can be stated directly.
Do not add links the question does not need. A chain about bank erosion does not need a sentence on tourism. The graph evidence and fair-comparison lab helps you check which steps the numbers carry.
Check yourself
Original data: a fictional quarry cut a hillside. Stream sediment was 40 mg per litre before and 130 mg per litre after. No rainfall figures are given.
Write a three-link chain from blasting to fish, marking each link as supported or assumed.
Answer
- Blasting and stripping expose loose soil on the hillside. Assumed: no soil data are given.
- Rain washes the soil into the stream, so sediment rises. Supported: sediment rose from 40 to 130 mg per litre, an increase of 90 mg per litre. The rainfall is missing, so the wash-in is likely, not shown.
- Muddy water reduces light and clogs fish gills, so fish numbers may fall. Assumed: no fish count is supplied.
What to study next
The next lesson, separating a mitigation action from evidence that it worked, uses the same habit of tagging claims by evidence.
If you want a teacher to check your effect chains against a past-year style question, see online one-to-one Geography tuition.