The stories told about the wolves of Yellowstone have changed over the last 100 years. Once portrayed as the scourge of wildlife, they’re now viewed as a force for good. The presence of wolves has divided opinion over the years and continues to do so today.

Yellowstone includes lakes, geysers, bubbling mudpots, canyons, rivers and mountain ranges, with forests covering 80% of the land. Most of the rest is grassland and valleys where visitors to the park can observe large, iconic mammals like bison. After decades of decline, Yellowstone biodiversity is recovering.

Many places are missing important species due to changing climates, environments or human impacts. Similar to the reintroduction of wolves to Yellowstone, wild habitats can be restored by returning key species to an area. People have to decide on what baseline time to refer back to. In Russia, Pleistocene Park aims to recreate a vision of the Siberian steppe in the Last Ice Age which includes the revival of the extinct woolly mammoth. How far back would you go?