So, e.g., the Cultural Assimilation event tells you to replace a Dahan that's adjacent to a City. If either the land with the City or the land with the Dahan were Isolated, the players could nullify the adjacency. If every possible
City - lone Dahan pair were separated this way, the players could thwart the Event on that board.
(Discussion elsewhere) Tags: Isolate, Cultural Assimilation