  Circumstellar discs are the precursors of planetary systems and develop
shortly after their host star has formed. In their early stages these discs are
immersed in an environment rich in gas and neighbouring stars, which can be
hostile for their survival. There are several environmental processes that
affect the evolution of circumstellar discs, and external photoevaporation is
arguably one of the most important ones. Theoretical and observational evidence
point to circumstellar discs losing mass quickly when in the vicinity of
massive, bright stars. In this work we simulate circumstellar discs in
clustered environments in a range of stellar densities, where the
photoevaporation mass-loss process is resolved simultaneously with the stellar
dynamics, stellar evolution, and the viscous evolution of the discs. Our
results indicate that external photoevaporation is efficient in depleting disc
masses and that the degree of its effect is related to stellar density. We find
that a local stellar density lower than 100 stars pc$^{-2}$ is necessary for
discs massive enough to form planets to survive for \SI{2.0}{Myr}. There is an
order of magnitude difference in the disc masses in regions of projected
density 100 stars pc$^{-2}$ versus $10^4$ stars pc$^{-2}$. We compare our
results to observations of the Lupus clouds, the Orion Nebula Cluster, the
Orion Molecular Cloud-2, Taurus, and NGC 2024, and find that the trends
observed between region density and disc masses are similar to those in our
simulations.
