In a dying world, the Offset ceremony has been introduced to counteract and discourage procreation. It is a rule that is simultaneously accepted, celebrated and abhorred. But in this world, survival demands sacrifice so for every birth, there must be a death. Professor Jac Boltanski is leading Project Salix, a ground-breaking new mission to save the world by replanting radioactive Greenland with genetically-modified willow trees. But things aren't working out