Inroad

[Sarah]

The entrance of an enemy into a country with purposes ofhostility; a sudden or desultory incursion or invasion; raid;encroachment.The loss of Shrewsbury exposed all North Wales to the daily inroadsof the enemy. Clarendon.With perpetual inroads to alarm, Though inaccessible, his fatalthrone. Milton.

[Agnes]

An instance of something being encroached on or reduced by something else.

[Becky]

to start to have a direct and noticeable effect (on something):