OK, clickbait titles abound. It's actually about the characteristic ecosystem known as the mammoth steppe, although the people involved have repeatedly stated their willingness to deploy mammoths or even a cheap gene-spliced knock-off.
https://translate.google.com/translate?sl=auto&tl=en&u=https%3A%2F%2Fwww.kommersant.ru%2Fdoc%2F3819067
http://www.pleistocenepark.ru/en/background/
And... err... their Kickstarter (mods, don't kill me).
TL;DR: unlike the modern moss and tree-dominated tundra, the mammoth steppes covered much of the Northern Hemisphere during the last Ice Age, mutually supported by large grazers - such as the mammoth. The hypothesis here is that the biosphere was a massive boon to carbon sequestering, and there was an additional benefit of all the trampled snow being a better insulator, further fortifying the permafrost. So now, all of that is gone except for two tiny enclaves deep in the Eurasian interior, while global temperatures rise and threaten to launch a vicious cycle of permafrost thaw.
And the counterplan is to aggressively reintroduce as many grazers as possible to restore the ecosystem. The Pleistocene Park is currently a chunk of some 160 km2 with a bunch of imported bison and deer. Their claims of ongoing overt environmental transformation are hard to independently verified - for once, they did pick the cheeks end of nowhere for their park.
But the only thing most people care are the mammoths, and it helps that Republic of Yakutia now has a gene lab dedicated solely to working with animals conserved in permafrost.