Option (D) is correct because conservation of biodiversity is important for all organisms. Biodiversity includes animal species, plant species, genes, ecosystems and landscapes. Conservation of biodiversity is important for all organisms to maintain stable ecosystems.

Option (A) is not correct because conservation of biodiversity is not important for only animals as it includes plant species, microorganisms, genes, ecosystem such as coral reefs, forests, deserts etc. Ecosystem will not be stable if conservation of biodiversity is important for only animals.

Option (B) is not correct because biodiversity conservation is the practice of protecting and preserving the wealth and variety of plant species, animal species, microorganism, ecosystem etc.

Option (C) is not correct because biodiversity boosts ecosystem productivity where each species, no matter how small, all have an important role to play.