Genetic rescue & de-extinction. The Genetic Rescue Foundation https://www.geneticrescue.science/ and Revive & Restore http://longnow.org/revive/ have research projects that are advancing the scientific techniques required to do this. Having YC Research also take an interest in this would help to expand a field that already has the attention of some pretty talented individuals e.g. George Church.

Human beings are now the curators of planet earth. This is the Anthropocene era. We can either continue to intentionally and unintentionally destroy the earth's biodiversity; or through technology we can develop the means to preserve it.

We're not preserving biodiversity because panda's are cute and starving polar bear pictures make us sad. We're doing it because biodiversity is useful to humans and it takes a very long time to get it back when it's gone.