[dividedbyzero]

Bringing back beaver and wolves to areas where they've been wiped out is functionally the same and shows that often such niches don't get filled all that fast. The replacement for wolves has been hunters, beavers had no replacement. Usually when either gets reintroduced, the local ecosystem functions quite a bit better, there has been quite a bit of backlash by hunters because it turns out wolves do a substantial part of their work and there is less need to control deer populations. Might not work in all cases, but even if partial restoration is an option, having that genome around is a good thing in itself, as life thrives off diversity. Reducing genetic diversity hampers an ecosystem's ability to adapt to change. We have a lot of ecosystems that have been decimated to the point of being close to unviable, and we're losing keystone species all the time. Fixing what drove them over the cliff (hard if it's feral cats, easier if it's a specific pesticide, disease, hunting, or habitat fragmentation) and subsequent reintroduction may well prove a pretty important strategy to keep the world a place that humans can thrive in, especially given the predicted decrease in world population by the end of the century which may result in renaturation of swathes of land.