Are the ghosts of nature's past haunting ecology today?

Abstract

Humans have decimated populations of large-bodied consumers and their functions in most of the world's ecosystems. It is less clear how human activities have affected the diversity of habitats these consumers occupy. Rebounding populations of some predators after conservation provides an opportunity to begin to investigate this question. Recent research shows that following long-term protection, sea otters along the northeast Pacific coast have expanded into estuarine marshes and seagrasses, and alligators on the southeast US coast have expanded into saltwater ecosystems, habitats presently thought beyond their niche space. There is also evidence that seals have expanded into subtropical climates, mountain lions into grasslands, orangutans into disturbed forests and wolves into coastal marine ecosystems. Historical records, surveys of protected areas and patterns of animals moving into habitats that were former hunting hotspots indicate that - rather than occupying them for the first time - many of these animals are in fact recolonizing ecosystems. Recognizing that many large consumers naturally live and thrive across a greater diversity of ecosystems has implications for setting historical baselines for predator diversity within specific habitats, enhancing the resilience of newly colonized ecosystems and for plans to recover endangered species, as a greater range of habitats is available for large consumers as refugia from climate-induced threats.