We don't, and probably can't, know the ripple effects from each individual lost species. Some will have an important place in the incredibly complex food web. So we'll lose other species in other parts of the food chain. Some may turn out to be critical to something we find important. Once they're lost, no matter how critical they turned out to be, it's too late.

At the other extreme, we do know the problems associated with extensive monocropping. We've seen the effects of monocrop agriculture and forestry through the 20th century. The more healthy biodiversity we can keep in all species, the better for us.