It’s not just the total number of species preserved that matters, it’s the number of key species.
In a study on a US saltmarsh, scientists found that preserving optimum health of the ecosystem came down to the number of key species, rather than the total number of species.
The study suggests that the ability of nature to perform well at multiple levels may depend not just on the overall number of species present, but on having many distantly related species, each of which performs a particular task that keeps an ecosystem healthy and allows it to provide the multiple benefits humans value.
The loss of key species can have profound impacts on the overall performance of an ecosystem.
Read more at Duke University