>If our greatest environmental efforts can at best end in failure

To date, this may be true.

But human cultivaiton _can_ result in an increase in biodiversity and ecological productivity vs non-intervention.

This generally looks like gardening instead of monoculture agriculture.

It may be the case that the biodiversity and ecological productivity of the amazon rainforest was greatly aided by human cultivation. See:

http://science.sciencemag.org/content/355/6328/925

https://en.wikipedia.org/wiki/Terra_preta

https://www.theatlantic.com/science/archive/2017/03/its-now-...