For decades, retail moguls Kris and the late Douglas Tompkins bought up huge swaths of South American wilderness in hopes of preserving ancient forests and the creatures that live in them and doing so have created Argentina’s latest nature reserve. Now, nearly a year after her husband’s death, Kris, who spent 17 years as chief executive at the outdoor apparel maker Patagonia, is donating enough land to help create what will become Argentina’s largest nature preserve. The donation is part of an ambitious…