They look so simple to humans, and they are considered part of what constitutes the true settlement of a wild region: Wire fences. They outline territories and keep livestock within bounds. Cutting a fence is considered a crime.
Simple as they are, they also block ancient migratory routes. Small animals can go under or through – to large animals, wire fences are often insurmountable.
Case in point: Thousands of miles of ranch wire fencing that delineates the South American continent. British ecologists Katherine and David Lowrie are in the process of their 5000 mile run project, running the length of the continent. They noticed the effect of the fences on mammals and birds during the course of their run. The unbroken fencing is particularly dangerous for young animals unable to jump and follow the mature herd.
It seems like this would be a challenge that wouldn’t be overly difficult to resolve with a bit of attention and compromise.
The Ecologist article