Final answer:
The least controllable cause of wetland loss is droughts due to their natural occurrence.
Explanation:
Causes of Wetland Loss:
- Droughts: People have little control over natural occurrences like droughts that can lead to wetland loss.
- Draining and filling: This is a human activity that significantly contributes to wetland loss.
- Discharge of pollutants: Humans play a direct role in polluting wetlands, leading to their destruction.
- Overgrazing: While human-related, overgrazing can be controlled to a certain extent compared to the other causes.
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