We're getting to the point now in our response to climate change where prevention is losing importance as a subject in favor of managing it as best we can. Some suggestions have included introducing wildlife in areas where it will have an easier time adapting or strategically expanding protected areas, but one of the more intriguing is the idea of cloning extinct animals and plants from their preserved DNA, a process referred to as de-extinction (if you've seen Jurassic Park, you have the basic concept).
As with any promising new technology, voices have risen in opposition to it, and there are some valid concerns. One, for example, is that it could lead to a false sense that we can restore any damage we do without worry; another is that reintroducing a single species in a significantly altered environment could do harm to both. These are certainly legitimate worries, but I, for one, take some comfort in the thought that at least we're in a position to make an attempt, even if it's a failed one.
We are faced with losing a lot of precious life on this planet at an alarming rate -- that has only been seen a handful of times in the past half billion years.
With regards to the objection that we might be "playing God," this is in my view a particularly specious one. Any time we act to enforce our will we "play God," If you want to get strict about it, and it would only be through enterprises as grand as this that we'd ever get any good at it.
There are undoubtedly all kinds of mistakes we'd make on the road to restoring vanished ecosystems, but if we have to play one of them -- and it might eventually come to that -- I feel much more comfortable playing the God who oversaw Genesis than the God of Armageddon.