Sustainability vs Survivability

I have just discovered a new term in Yvon Chouniard's book "Let my people go surfing".
A concept I had never seen applied before, at least for the human race.

Survivability.

To those that have come to understand the philosophy of sustainability, our greatest fear is that this term, could evolve into a more complex and irreversible situation, much beyond unsustainability.
This more "complex situation" has just been presented to me as: Survivability.