A species that has went extinct within the last year for a few reasons:
Easy to bring back.
-We would need alot of biotech equipment and bio-engineers to transplant the extinct DNA into the embryos of a similar extant species.
This species has been gone not too long.
-The habitat it lives in probably still remains or can be copied.
-People still remember it and will advocate for its return.
-A freeze-dried corpse (if animal) or dried specimen (if plant) might remain.
I believe the only animal to be confirmed extinct last year was some sort of whet owl. One could save that species and raise a healthy population (for 3 generations) in captivity and then reintroduce the fourth generation in the wild.
If we are aiming for a more fictional goal, I say the Mammoth.
There are alot of frozen corpses still around with DNA. We could somehow bring them back to existence (using elephants?).
I would place the population on a Northern island, hopefully when the ice freezes they are too heavy to cross into another nation and destroy their ecosystem.
Also a fence could be built. If there is anyway to keep them in one place, we should do it.
My main concern with this is the climate warming. It may not be worth it.
Or perhaps, this could encourage an application to fix environmental misuses?
Lastly, they can be exploited: meats, furs, blubber/fat, and recreation.
Who won't want to have a mammoth coat, during a Maine winter?
Or think of all the meat the thirdworlders or, perhaps, northern natives (like Eskimos) can farm/eat?
We could use their fat for oil and not fossil fuels? (I don't know any of that process so I could be completely wrong).
Personally, I would like to see a Tanzanian wolf, Giant Sloth, or a flock of Passenger pigeons blocking out the sun. It's not a good idea, but it's just a stupid desire.
Picture unrelated: It's an Angel's trumpet. I took this picture when I visited Mexico last year and just learned what it was yesterday. It's poisonous.