[ethbro]

Variety has a non-aesthetic value as well -- more complex ecosystems have greater resilience to shock (e.g. climate change or invasive species introduction).

A broader variety of species allows for the loss / decrease in a particular function to be more quickly replaced by a similar species. As opposed to a simpler, more limited ecological system, where there may only be a single species fulfilling a given role. A single species that might be highly vulnerable to a new toxin / predator / fungus / virus / different average temperature.