The phrase "whole swathes" means a large or significant area or group of something. It refers to a wide or extensive coverage of a particular thing or concept. Full definition
They are about how we do our politics — particularly the way that we willingly turn our backs of whole swathes of the nation in a quest for short - term advantage in a few marginal seats. (labour-uncut.co.uk)
We're close and loving with whole swaths of my son's family of origin. (openadopt.org)
Ministers who returned from their holiday to attend the emergency Cobra meeting are understood to have been livid about the police's failure to secure the streets on Monday night, when whole swathes of London fell into the control of rioting mobs. (politics.co.uk)