Judging from this article on Wikipedia, work is underway in this field, although it hasn't been too fruitful yet.
https://en.wikipedia.org/wiki/Cloning#Cloning_extinct_and_en...
Simply cloning one of these animals and dumping it into the ocean reminds me of seal conservation efforts where seals were rehabilitated and then basically dumped into the ocean and swiftly eaten by orcas. A naïve approach is unlikely to work.
We don’t care for the whales we have now.
> Not to take away from any conservation efforts to reduce or reverse these extinctions,
Presumably one reason the loss of species is bad because it lessens biodiversity. If extinct species could be re-introduced in a more amenable future, then that would be a good thing, no?
Even then, on a human timeline a thousand years is nothing. We still have buildings that are 3x as old.
Specially with those huge animals. Would need incredibly complex and humongous laboratories just for trying to hold each 3000 Kg newborn. Avoiding contamination and making the embryo cameras sterile for months would be a real headache.
We must forget the idea that cloning will save the day someday, be smart and use our narrow and shrinking interval of opportunity to act now.
Pushing solutions into the future is exactly why we ended up with this mess in the first place.
Similarly, governments right now are competing with each other who declares the most ambitious climate plan to be realised by 2050, instead of doing something right now.