How could organisms be harmed by high levels of salt from roadways?

Salt tends to dehydrate plants and animals that come in contact with it in large quantities. Most plants that are not growing in the salt marches have a relatively low tolerance for salt and will die. You can see the brown grass in the spring time along the roads and sidewalks. Small organisms, bacteria and small animals can be dehydrated to the point of death. Preserving with salt has been a preservative for many centuries, because it prevents the bacteria from growing.