  The ability to rewire ties in communication networks is vital for large-scale
human cooperation and the spread of new ideas. We show that lack of researcher
co-location during the COVID-19 lockdown caused the loss of more than 4,800
weak ties -- ties between distant parts of the social system that enable the
flow of novel information -- over 18 months in the email network of a large
North American university. Furthermore, we find that the re-introduction of
partial co-location through a hybrid work mode led to a partial regeneration of
weak ties. We quantify the effect of co-location in forming ties through a
model based on physical proximity, which is able to reproduce all empirical
observations. Results indicate that employees who are not co-located are less
likely to form ties, weakening the spread of information in the workplace. Such
findings could contribute to a better understanding of the spatio-temporal
dynamics of human communication networks, and help organizations that are
moving towards the implementation of hybrid work policies evaluate the minimum
amount of in-person interaction necessary for a productive work environment.
