Barrier and Bridge - Decoding the Obstacles of Movement

Barrier is an obstacle that prevents movement. Similarly, bridge is a connection between two systems. A forest has series of barriers for certain inhabitants as well as number of connections for the others. A stream stops the Chitals, but creates a thoroughfare for the fishes. My idea is to identify major physio-graphic systems inside the forest, which act as barriers for the terrestrial fauna. If they want to move through their habitat patches, they find some way to circumnavigate or cross the barrier. That way, the weakest part of the obstruction becomes a connecting corridor or a bridge.