Evolution is just change. Everything is the result of evolution by definition. Including human ability to plan. So we can use that ability to save species. But we should do so according to humanity's best interests first. If we can prevent a species from going extinct we should as that species may turn out to be a valueable resource for ourselves.
Yes, I believe that species loss is a natural result of evolution. However, that doesn't mean that as a more highly evolved species we cant take care to try and preserve those species that are being lost due to the loss of habitat. I don't believe Darwin thought evolution was something that was to happen in a short time, rather something that happened over the course of many years, decades and even centuries, some cases.
Yes, species loss is a mixture of the expansion of a city and the natural result of evolution. Species have always been something temporary. Species are constantly changing and constantly evolving. With the loss of one species, the is always the finding of one or maybe even more new species.
Evolution is a selective process. It looks at what new traits and abilities are needed, and starts the long path to making these changes happen. At the same time, evolution looks at the changes in the world's environment and notes that there are species that will not be capable of changing quickly enough to survive. These species will become extinct.
I believe species loss can be the natural result of evolution. However, there are very few places in the world where humans haven't impacted the natural result of evolution, so theorizing that it may be natural doesn't mean we shouldn't be concerned about this process. Biodiversity is relatively important and the larger our population becomes the more danger comes to biodiversity.
No, I don't believe that species loss is primarily the result of evolution. I believe that much of the species loss is due to man made causes including pollution, global warming and building on the range and land that the animals formerly called home. It is us that is primarily responsible for most of the current species loss.