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.

Sex and occupation time influence niche space of a recovering keystone predator

“…Although niche space has not been thoroughly examined in sea otters (but see Silliman et al, ), sea otter diets have been well studied. In British Columbia (Breen, Carson, Foster, & Stewart, ; Hessing‐Lewis et al, ; Honka, ), Washington (Laidre & Jameson, ; Hale et al, in press), California (Estes et al, ; Tinker, Doak et al, ; Tinker et al, ), and Alaska (Hoyt, ; Kvitek, Oliver, DeGange, & Anderson, ; Weizman, ), sea otter diets have been found to differ among recently and long‐occupied areas.…”

“…Understanding how prey selection and the range of habitats used by sea otters vary over the course of recovery has important implications for sea otter conservation and affects our understanding of the recovery process in a predator that has traditionally been studied in a limited context (Silliman et al, ). Although dietary changes have been noted within and among sea otter populations, only limited research has examined niche variation across space and time.…”

“…Recently, the role of sea otter predation on crabs in seagrass communities has been shown to initiate a trophic cascade that increases seagrass biomass (Hughes et al, ). These studies show that sea otter community interactions are context‐dependent and that the ecological consequences of alternative niche‐use patterns may be important to consider in terms of beneficial conservation impacts, fisheries interactions, and other management and conservation priorities (Silliman et al, ).…”

“…Most of the world's large predators have suffered widespread extirpation, limiting our understanding of how ecological communities function with intact predator populations (Estes et al, ; Jackson, ; Silliman et al, ). Thus, the interactions among predators, herbivores, and primary producers, and the habitat and food requirements of recovering predators, are difficult to predict.…”

Land‐use and climatic causes of environmental novelty in Wisconsin since 1890

“…, Silliman et al. ), placing ecosystem services at risk. The predictive ability of ecological forecasting models is typically low when future conditions are outside of the range of observations used to test and calibrate such models (Veloz et al.…”