The loss of biodiversity in a region may not lead to -

The correct answer is Option (3) → Decline in plant production but increase in animal populations

An ecosystem with more species is more stable and productive. So when a region loses biodiversity, the whole ecosystem suffers. The book names three results of the loss.

Option (1) Decline in plant production — A result of biodiversity loss. Fewer plant species produce less biomass, as Tilman’s experiments showed.

Option (2) Lowered resistance to environmental perturbations such as drought — A result of biodiversity loss. With fewer species, the ecosystem recovers less well from disturbance.

Option (3) Decline in plant production but increase in animal populations — Not a result of biodiversity loss. Animals depend on plants for food. When plant production falls, animal populations cannot rise; they fall too. The book lists no such increase.

Option (4) Increased variability in certain ecosystem processes such as plant productivity, water use, and pest and disease cycles — A result of biodiversity loss. These processes become less steady when fewer species keep them in balance.

NCERT Extract:
Loss of Biodiversity –