Influence of landslides on biophysical diversity — A perspective from British Columbia

Landslides have long been overlooked or underestimated as important natural disturbance agents. In particular the ecological role of landslides in maintaining biological diversity has been largely ignored. Here we provide a western Canadian (British Columbian) perspective on the influences of landslides on biophysical diversity, which is related in several ways to biological diversity. We recognize several types of biophysical/ecological diversity: site diversity, soil diversity, and the derivative habitat or ecosystem (including aquatic ecosystems) diversity. There are also a variety of landslide types, depending on materials and on the rate and style of movement. We discuss the roles of different landslide types on various aspects of terrestrial diversity. Landslides are simultaneously depositional and erosional processes that influence sites by redistributing materials and changing surface expression — usually creating a complex microtopography that can include very dry ridges and hummocks, and sometimes depressions with standing water. Landslide impacts to site also influence soil and soil development. Portions of landslides with exposed parent material are set back to the initial stages of soil development and ecological succession. Landslides can also change soil density, structure, porosity, surface texture, chemistry and microclimate. By changing site and soil, landslides also influence habitat. Landslides influence habitat diversity by engendering a mosaic of seral stages (often both primary and secondary), and in overwhelmingly forested landscapes often create nodes or hotspots of non-forested habitat and biota. In some areas, like the boreal forest, there is an important interplay between landslides and fire, while on the coast of British Columbia debris and snow avalanches can be the dominant disturbance agent. Low-gradient and deep-seated landslides are often opportunistically colonized by beaver and other water and shrub-loving fauna. Sag ponds and impounded streams provide aquatic habitat — often with standing dead trees. Landslide rubble and scarps provide denning/nesting habitat, escape terrain, and cliff habitat for vertebrates.