That is a great point . Hopefully the polar bears that are in captivity have good breeding recommendations . Unless an orphaned cub shows up .
The best that can be managed currently, yes.
That is what happened with the sun bears . SDZ was the only successful zoo in AZA to have cubs . They are now a phase out species .
Sun Bears never bred well to begin with - likely due to most of them originating as confiscated bears from poor backgrounds. The population never established and is merely aging out.
Polar Bears are bred with a decent degree of success - the main issue being several valuable bears are legally blocked from breeding and now the population is aging faster than it's growing. The population could probably be salvaged readily enough if the wild-born breeding ban got knocked down.