Is it possible that productivity and diversity of a natural community remain constant over a time period of,say $100$ years?

David Tilman suggested:

As biodiversity increases in an ecosystem,its stability $...$

Which of the following statements are true?
$I$. Species diversity provides stability to the ecosystem.
$II$. Communities with more species tend to be more stable than those with fewer species.
$III$. Ecosystems with higher biodiversity are more productive than ecosystems with lower biodiversity.
$IV$. Biodiversity is not essential for the maintenance and health of the ecosystem.
Choose the correct option.

What characteristics make a community stable?

More than $25\; \%$ of the drugs are derived from plants. What benefit does this describe?