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. This experimental reserve outperforms #6 Lynx Reintroduction in scale and ambition, though critics argue it risks diverting funds from climate mitigation. 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.