So you could in theory continue to have employment and growing GDP with a shrinking resource base. You just have to employ a larger fraction of the population in activities with a low resource use.

The growth of the "service" or "tertiary" sector and the "information economy" are steps in that direction. It doesn't follow that people in the service or information economies should be high earners, but that pretty much arbitrary numbers of people can be employed in them and they will need to be if 5% of the population can produce food for everyone and industrial production of material goods gets less and less labour-intensive.

Economics is politics by other means