One way of looking at biodiversity is by considering the extreme case of a single species: us. If we become the sole species left, then that would not be sustainable, obviously. There would be nothing to produce oxygen, among other dire consequences.

Scaling up from imagining that it’s just us, we can see that there is some limit on the number of species that will result in sustainability of ourselves, as well as other species. (Please forgive my being so ego-centric. It’s part of being human, and it helps make the point.)

At the other end, picture a vast web of interrelated species, plants and animals living in a kind of equilibrium. That’s what we (and other species) need, and that’s why biodiversity is so important. There are lots of mathematical equations for expressing biodiversity, but I think looking at these extremes helps put things in perspective. We sure don’t want to be at the extreme end of one.