Survival of species
The act of natural selection I think is the same as “survival of the fitness”. That being said, there are circumstances that interfere with that process. What about the Rhinos that can adapt to his environment and survive but then there is a little thing like Rhino horns being used for potions by certain cultures. They are killed for that one item and eventually the decline becomes noticeable and then before you know it they are no more (hopefully this will not happen). This happened to the Carolina Parakeets which were killed for their feathers during the 19th century. This was a sudden man made extinction and there was no way to adapt to it.
If it was a simple change in environment and gradual enough, perhaps the species could and would adapt. The coyote is adapting to urban living now and the Opossum adapted as the cities grew up around it. I am not sure that I see this as natural selection though it is a type of adaptation and is defiantly survival of the fitness as they have learned how to live in a world that is totally different from the world they were designed to survive in. I think that for a species to become extinct it must have outside interference. That interference could be anything; a natural disaster (volcanic, earthquake, storm), another species, climatic, or man himself but it would have to be combined with the factor of time. It would have to be done suddenly not giving a chance for adaptation.