James Lovelock's Gaia hypothesis is the background for this surviving-the-apocalypse scenario. You might detect an unusual conflict between the themes of environmental concern and the more traditional 'are the aliens for us or against us'.
Then he realized that Darlene's craziness was driving him to defend the Tesslies, and he threw the brown gunk - it still looked like shit! - harder than necessary onto the soy. Or whatever it was. 'High-protein, dense-calorie plants,' Jenna had told him once. McAllister was teaching Jenna and Paolo all the science she knew from Before, so it wouldn't be lost. The other Survivors had done the same, but they hadn't known nearly as much. 'We must save everything we can,' she always said.