Because many people worry we will run out of or be unable to access non-renewable resources like oil, a lot of attention has shifted to alternate energy sources like solar power.
As the vampire apocalypse progressed and human blood became a scarce, non-renewable resource, the loathsome bloodsuckers were forced to turn to four legged mammals for sustenance.
The non-renewable resource was of critical concern to the team as they were focusing on the long term viability of the strategy.