Deforestation reduces biodiversity in rainforests

Steps:

• Recognize that tropical rainforests support diverse ecosystems with many species.
• Note that felling hardwood trees removes habitats for numerous plants and animals.
• Understand that replacing with a single crop like palm creates a monoculture, limiting species variety.
• Conclude the primary environmental impact is loss of biological diversity.

Why D is correct:

• Biodiversity, defined as the variety of life in an ecosystem, decreases when diverse rainforest species are replaced by one crop type, per ecological principles of habitat destruction.

Why the others are wrong:

• A: Removing trees increases runoff and flooding by reducing water absorption and root systems.
• B: Soil structure degrades and nutrients deplete faster without tree cover to maintain fertility.
• C: Soil erosion increases as tree roots no longer protect against wind and rain.

Final answer: D