What does nature is not benign mean?
Here are some definitions of benign from Dictionary.com:
1. having a kindly disposition; gracious: a benign king.
2. showing or expressive of gentleness or kindness: a benign smile.
3. favorable; propitious: a series of benign omens and configurations in the heavens.
So, the statement "Nature is not benign" means that nature isn't kind and gentle. Nature includes predators and prey, storms and droughts, thorns and thickets.
4. (of weather) salubrious; healthful; pleasant or beneficial.