What describes the ecological outcome when purple sea urchins dominate their habitat?

• A. Kelp forests are replaced by urchin barrens.
• B. urchins create coral reefs.
• C. Kelp forests flourish.
• D. The habitat becomes a desert.

Answer: (A)

Dominant herbivory by purple sea urchins reshapes the habitat by removing kelp that forms the forest-like structure. When urchins graze heavily, kelp beds shrink and cannot recover, so the area becomes an urchin barren—rocky or sandy bottom with few plants and little biodiversity. The shelter and food kelp provides disappear, changing the whole community. Coral reefs aren’t created by urchin grazing, so that option isn’t correct. A kelp forest flourishing would mean kelp remains abundant, which contradicts heavy grazing. Calling it a desert isn’t the standard term here, since the key idea is the barren, urchin-dominated state.