Presumably, we have (near future) the capacity to bring species such as the one named back. I also assume we will eventually if we are not to be totally fatalistic about human prospects. The question, then, really is whether resources should be put to the task more or less immediately, assuming the cost not exorbitant.

The problem is - are the factors different now than when the species went extinct? If not, what's the point of bringing it back?

As much as I detest our slow destruction of planetary diversity, I just don't think we can hope to save many animals in their natural settings. It's no good, for example, saving tigers if they are expected to live in little forest islands and have nothing to hunt.

If we set up wildlife reserves, then we are tampering with the species ongoing survival anyway with respect to a lack of gene transmission between isolated populations.

As much as I'd like to wave a magic wand and make this all better, I think the chances are that a significant percentage of biodiversity will be lost through our population explosion and exploitation of the world's resources. It's the price we, and they, have to pay for our success.

I agree that any attempt to 'fix' this problem has to be a package deal addressing others that appear even more difficult on their face. Off-topic, but I think the key is for all cities to be move toward modernity as quickly as possible, with those in underdeveloped places getting more attention from outsiders than would normally be the case merely on account of commerce and tourism. Higher healthy dense cities allow more space for wildlife. The problem of restoring the Western Black Rhino, e.g., then becomes very indirectly one of civil engineering and the capacity of humans to translate successes in this field down economically to less intrinsically (historically) advanced societies.
Obviously, still, population growth of humans has to be cut by societal means wherever it is. I think the factor of most importance on this latter subject is the characterization of the child adoption process in the minds of economic elites and in the law. Children born into poverty--and their often young parents included--are not less, but probably actually more, capable of making familial and societal contributions than prospective children born of the wealthy. No child wants to live believing it is in some sense an error of its parents, so simple awareness of this fact and the fact the world is already overpopulated (along with the absurdity of other means of addressing this issue, like deliberate warring or poisoning people through their diets and other means of vice) could probably make 'Brangelina'-type parental arrangements common, though really the support of young adults and not just children is even more critical.

I don't believe that would be fair to Rex unless we terraform Mars or something.

We're fucking up the planet anyway. We may as well make life interesting for those who find themselves in the post-apocalyptic wasteland. Bring on the killer crocoducks!

We should at least 'bank' tissue samples from as many endangered species as possible - so that bringing them back is at least an option on the table.

That actually raises an interesting issue: Insects (and arachnids, myriapods, etc.) in small niches are probably the least documented species--on land, at least. Many soon-to-be-extinct species are highly likely to never be known, as when some portion of a rainforest is cleared or suffers a fire. So, a side issue is whether resources should be put to research that would make the OP possible for such species.

It is very easy to 'bank' tissue specimens. Simply store them in alcohol. We cannot use the old traditional formalin, since that destroys DNA, but apparently alcohol does not. So, as a simple precaution, it would cost very little to bank as many tissue samples in alcohol as possible. Even if we never resurrected the specimens involved, it would cost little to make this much effort at least.

PS : one of the extinct species that could be done this way is the Tasmanian Wolf, where a museum already holds several embryos in alcohol. Worth doing?

Well, it is not a good response on my post preceding yours, the cost there having more to do with extensive land surveillance in extremely difficult terrain to acquire tissue samples. It is a partial answer, of course, to say that locals without much external knowledge or access to chemicals/equipment could do it, however.

Someone wrote:That actually raises an interesting issue: Insects (and arachnids, myriapods, etc.) in small niches are probably the least documented species--on land, at least. Many soon-to-be-extinct species are highly likely to never be known, as when some portion of a rainforest is cleared or suffers a fire. So, a side issue is whether resources should be put to research that would make the OP possible for such species.

Fungi beat insects by a long shot. Every known insect has at least ONE parasitic fungus which only grows on that species. Some insects like beetles have fungus that grow only on the second joint of the third leg. And there are multiples of those types! If you go into your back yard and grab a handful of soil, you are guaranteed to have 10+ species of fungi (mostly glomeromycota, a mycorrhizal group) undescribed by science.

Then we have bacteria and protists which we know even LESS about!