“Habitat fragmentation occurs when human-made barriers such as roads, railroads, canals, electric power lines, and pipelines penetrate and divide wildlife habitat.
This affects biodiversity by reducing the amount of available habitat in an ecological niche. It invariably involves some habitat destruction. Plants are usually destroyed directly; then animals retreat into remnant patches of habitat.
This can lead to crowding, increased competition, and speciation – a process in which isolated populations evolve in response to their new habitat, separately from their ancestors.
Wildlife crossings are structures that allow animals to cross human-made barriers safely. They may include: underpasses, viaducts, and overpasses; amphibian tunnels; fish ladders; tunnels and culverts; as well as green roofs.
The crossings also assist in avoiding collisions between vehicles and animals which, in addition to killing or injuring wildlife, cause injury to humans and property damage.” – adapted from Wikipedia
Read more and see other examples, including two in NJ: