Final answer:
Soil conservation has a positive effect on an ecosystem by improving soil fertility, water retention, and biodiversity.
Step-by-step explanation:
The example that has a positive effect on an ecosystem is Soil conservation. Soil conservation refers to practices and methods used to prevent soil erosion and degradation, and promote the sustainable use of soil for agricultural purposes. It helps improve soil fertility, water retention, and biodiversity, thereby benefiting the overall health and productivity of the ecosystem.
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