From that angle, it sounds strange. However, if you talk about colonizing other planets, it's not "preserving natural life" anymore, it's establishing several i

From that angle, it sounds strange. However, if you talk about colonizing other planets, it's not "preserving natural life" anymore, it's establishing several invasive species by either creating an ecosystem where there is none or (even worse) destroying a (hypothetical) extraterrestrial ecosystem to establish one that would be useful to humans. There are definitely some people who would refuse extending their own lifespan beyond its natural limits, so it's not surprising that some have the same opinion for the species as a whole...