Which of the following ecosystem is most productive in terms of net primary productivity ?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Tropical rain forests
Net primary productivity is the biomass left after plants use part of what they make in respiration (NPP = GPP − R). It is highest where light, warmth and water are all plentiful through the year.
Option (1) Deserts — Incorrect. Lack of water keeps plant growth, and so productivity, very low.
Option (2) Estuaries — Incorrect. Estuaries are productive, but they cover small areas; the answer expected is the land ecosystem with the most plant growth.
Option (3) Tropical rain forests — Correct. High temperature, rainfall and light all year give the fastest plant growth.
Option (4) Oceans — Incorrect. Oceans are huge, but their productivity per unit area is low; they give only about 55 billion tons a year despite covering 70 per cent of the surface.