What is meant by topographic barrier? There are three types of barriers, physical , climatic and biological barriers that can prevent the dispersal of organisms. Topographic barrier falls in the category of physical barrier but exactly what should be considered as topographic barriers is not clear to me. The source from which I actually came across the term says that mountain range is a topographic barrier like the Himalayan range separating the North-asian fauna (partly Palearctic fauna) from the Oriental fauna. But what else falls under topographic barriers is my question?

Topograhpy refers to earth's physical features and a topographic barrier refers to physical features that prevent free movement from one position to another. As GForce pointed out, whether or not something is a barrier can depend heavily on the animal in question. A long, wide canyon can be a barrier for squirrels, but not for birds.

Think of topographic as referring to features on a map, which is a type of topological graph.