Pleistocene Park, Siberia, Russia

Pleistocene Park is the most audacious attempt to resurrect a lost ice-age ecosystem, with the ultimate goal of genetically engineering woolly mammoth traits. Sergey Zimov introduced bison, horses, and musk oxen to compact permafrost and restore grassland, already reducing methane emissions by 30% per hectare compared to untouched tundra. Over 5,000 hectares are now being transformed, and early data show soil temperatures dropped by 2°C in summer, confirming that large herbivores can slow thaw — a concrete result that no other rewilding project on this list can match.