Given our previous fairly mixed results with introducing foreign species into new habitats where they can flourish, this sounds like it'd most likely be pretty bad for the current ecosystems there.

While I generally agree, as far as I’m not mistaken they are not foreign to these regions at all - on the grand scheme of things they just disappeared from there very recently

I would expect that the current ecosystems there have adapted to Mammoths no longer existing?

Maybe, though I doubt it would have had long enough time to alter too much - so I don’t think it would be anything similar to introducing an invasive species.

I'm not sure that the Arctic needs "rewilding", it is still a wild environment. What's definitely needed is protecting it.

Mammoths were adapted to the ice age while we are in a climate warming crisis... apparently they lived in steppes called "mammoth steps" that are very rare today [1]. So realistically this would just be a tourist attraction a la Jurassic Park.

[1] https://en.wikipedia.org/wiki/Mammoth_steppe

> If these revived woolly mammoths eventually repopulate the Arctic, they would take down small trees and help repopulate the grasses they thrive on, Church said. Those grasses reflect sunlight better than the dark trunks of the conifer trees that live there. In addition, the woolly mammoths tamp down the snow, making it less insulating.

Those grasses would cool the ecosystem, in turn reducing the release of trapped methane gas from melting permafrost, a major contributor to global warming.