system
Given the following post, respond as if you're commenting on Reddit:
human
Why aren't certain endangered species that are now limited to a single site, such as the large mason bee, just reintroduced to areas where they used to be common, when they've been limited to a single site for years. Is there some scientific reason for this?

You can buy mason bee cocoons and keep them in your garden, so I'm just wondering why nobody's done this with that species. If they had, it'd no longer be limited to a single site, so its population, distribution and genetic diversity would increase, reducing its risk of extinction. Is there some good reason this can't be done, or has it just not happened because nobody's bothered doing it yet? Surely the population can't be so unstable that at least one or two cocoons can't be safely taken to another site and raised there?
gpt
In many cases they are trying to reintroduce them but either the climate is no longer suitable, their particular food source is no longer sufficient, the area has somehow changed in possibly an imperceptible way that we have yet to grasp that it doesn’t like, a new predator has moved in, a competing species is consuming its resources, pollution… or a mix. Sometimes species just reproduce at too slow a rate to get their numbers back up to spread out again.