The text starts with explaining to the readers the danger which highways and busy roads present to animals. It is done on purpose, to draw the readers' attention to the problem and to effect their feelings. The readers should already feel sorry for the dead animals and condemn the often reckless drivers.
Next, the purpose of building a wildlife overpass is explained. The reader begins to feel better, knowing there is a way to stop the pointless massacre and save entire populations of wildlife. By telling the readers that the overpasses often connect habitats, the author strengthens his point that the humans are doing something beneficial to nature.
The following part of this writing is the answer to the question of the overpasses' direct benefits to humans. The author prepared the readers for this questions, giving them plenty of facts and explanations about overpasses before. The main purpose for overpasses apart from saving the wildlife is to provide additional recreational space for humans. They help them to discover places they would have not discovered previously.
The next part and the conclusion are about being sensitive to the animals' needs, and they imply again the benefits of the passes for humans.
The text is structured in a way that does not make the readers see the overpasses' benefits for humans immediately. It builds up to it bit by bit, in a more general manner, making the readers think and draw their own conclusions.