The Return of the mammoths

In the early years of the 20th century, a dazzling discovery was made - time travel. Scholars, scientists, and visionaries alike found the potential to not merely observe history unfold but actively participate in it, an irresistible opportunity. After numerous ethical and practical deliberations, the decision was made that the immense power time travel provided should be used to right a series of historical wrongs: the extinction of some magnificent species native to North America's environmental canvas. In this scenario, the methodology of time travel does not permit paradoxes, making the retrieval of extinct species possible without any deleterious effects on the timeline. Careful measures were established to ensure that the chain of events leading to the present wouldn't be disrupted. Four species were chosen for this unique revival: the Columbian mammoth, the woolly mammoth, the American mastodon, and the Pacific mastodon, each iconic in their majesty and critical to the ecological balance of the time. Each species was painstakingly reintroduced into its respective and known prehistoric ranges, mirroring their habitats as closely as possible to ensure the greatest chances of survival. In the heartland of America, the Columbian mammoths again roamed, their thunderous steps resonating across the land and their long tusks gleaming in the sunlight. In the colder northern realms, the woolly mammoths returned, their thick coats shielding them from the harsh weather, their presence adding a note of vividness to the austere landscape. Mastodons, both American and Pacific, dotted the Eastern and Western coasts respectively, uniquely adapted to the humid, semi-arid, forested and open environments - their massive stature yet gentle nature becoming a cherished part of the North American wildlife. As the mid-20th century approached, these efforts bore fruit - reintroduced populations started breeding successfully, ensuring their survival. These giants of the past began forming an integral part of the landscape, influencing the ecosystem in their unique ways. The revival of these heroic species not only offered a glimpse into the magnificent past of natural America but also served as a listener's note on our stewardship of the earth and its creatures - past, present, and future.