"Let nature take its course"
Permaculture design aims to make best use of renewable resources to create, manage and maintain high yielding systems, even if some non-renewable resources are needed to establish the system in the first place.
As societies we need to value 'ecosystem services' such as water purification much more highly. Currently we are destroying natural ecosystems that would provide us with many thousands of years good service if we were to treat them with more respect.
Permaculture makes use of natural processes and animal behaviours as part of a design.
We need to understand the renewable resource we are using to ensure appropriate use, e.g. how many trees can we take from a woodland without damaging it? Harvesting of wild plants and animals can be part of the overall yield of a system.
Wind, sun and waves are key renewable resources that can help us move towards sustainability. Recreating forests and soils are two of the most important tasks of the twenty first century.