Question

How can a large amount of biological diversity protect an ecosystem from environmental damage? Why are less biodiverse ecosystems at risk of suffering serious biological harm if subject to even small changes?

Answer 1

A less diverse ecosystem would mean that the organisms are similar to each other. Hence when can change occurs, however small it may be, but if it incurs significant adverse effect on the inhabitants then they may succumb to it. And since all/majority of them are similar the each other due to lack in diversity, a big chunk of the population would be affected. Had they been more diverse, the change would affect only those with a particular genetic make up. Others who are different stay unaffected or less affected and so the ecosystem is saved from the threat of extinction.