ZOOGEOMORPHOLOGY IN THE ANTHROPOCENE

Humans have profoundly altered geomorphic pathways and systems through their near-extirpation of native populations of animal species that strongly influenced hydrology and removal of surface sediment, and through the introduction of now-feral populations of animals that bring to bear a suite of different geomorphic effects on the fluvial system. In the category of effects of extirpation, examples are offered through an examination of the geomorphic effects and former spatial extent of beavers, bison, prairie dogs, and grizzly bears. Beavers entrapped hundreds of billions of cubic meters of sediment in North American stream systems prior to European contact. Individual bison wallows, that numbered in the range of 100 million wallows, each displaced up to 23 m³ of sediment. Burrowing by prairie dogs displaced more than 5000 kg and possibly up to 67,500 kg of sediment per hectare. In the category of feral populations, the roles of feral rabbits, burros and horses, and pigs are highlighted. Work remains to adequately quantify the geomorphic effects animals have on fluvial systems, but the influence is undeniable.

In the mountains of the western U.S.A. and elsewhere, the geomorphic actions of animals are being impacted by climate change. The spatial pattern and intensity of these impacts, associated with activities such as digging for food, burrowing for shelter, and damming of streams, may change as a result of climate change. Food sources utilized will be affected by processes such as meadow infilling with trees, upward advancement of trees, and changes in intensity of other geomorphic processes such as avalanching and glacial action and associated meltwater. As climate change impacts food sources and habitats, some geomorphically active animals may become much more limited in the geographic range and intensity of their influence, and some may disappear altogether if the habitat disappears.