Evolution is a wonderful thing. Any time there is a niche or an opportunity there will be species that evolves to take advantage of it. Everywhere you look there are myriad examples of evolutionary adaptation. For example, new medicines are constantly developed to stay ahead of adapting microbes.
Eventually scientists developed sophisticated computer models to predict evolutionary adaptation by many species to a human modified Earth. This, coupled with genetically modified strains, allowed us to turn the tables on many of humanity's oldest foes.
Still, nobody considered the possibility of carbon nanotube eating bacteria when they built the space elevator.