title: Biotic and Climatic Velocity Identify Contrasting Areas of Vulnerability to Climate Change.
abstract: Metrics that synthesize the complex effects of climate change are essential tools for mapping future threats to biodiversity and predicting which species are likely to adapt in place to new climatic conditions, disperse and establish in areas with newly suitable climate, or face the prospect of extirpation. The most commonly used of such metrics is the velocity of climate change, which estimates the speed at which species must migrate over the earth's surface to maintain constant climatic conditions. However, "analog-based" velocities, which represent the actual distance to where analogous climates will be found in the future, may provide contrasting results to the more common form of velocity based on local climate gradients. Additionally, whereas climatic velocity reflects the exposure of organisms to climate change, resultant biotic effects are dependent on the sensitivity of individual species as reflected in part by their climatic niche width. This has motivated development of biotic velocity, a metric which uses data on projected species range shifts to estimate the velocity at which species must move to track their climatic niche. We calculated climatic and biotic velocity for the Western Hemisphere for 1961-2100, and applied the results to example ecological and conservation planning questions, to demonstrate the potential of such analog-based metrics to provide information on broad-scale patterns of exposure and sensitivity. Geographic patterns of biotic velocity for 2954 species of birds, mammals, and amphibians differed from climatic velocity in north temperate and boreal regions. However, both biotic and climatic velocities were greatest at low latitudes, implying that threats to equatorial species arise from both the future magnitude of climatic velocities and the narrow climatic tolerances of species in these regions, which currently experience low seasonal and interannual climatic variability. Biotic and climatic velocity, by approximating lower and upper bounds on migration rates, can inform conservation of species and locally-adapted populations, respectively, and in combination with backward velocity, a function of distance to a source of colonizers adapted to a site's future climate, can facilitate conservation of diversity at multiple scales in the face of climate change.
authors.affiliation: Klamath Center for Conservation Research, Orleans, CA 95556, United States of America.
authors.forename: Carlos
authors.initials: C
authors.lastname: Carroll
authors.affiliation: School of Environmental and Forest Sciences, University of Washington, Seattle, WA, 98195, United States of America.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Lawler
authors.affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G2H1, Canada; Department of Biometry and Environmental System Analysis, University of Freiburg, 79106, Freiburg, Germany.
authors.forename: David R
authors.initials: DR
authors.lastname: Roberts
authors.affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G2H1, Canada.
authors.forename: Andreas
authors.initials: A
authors.lastname: Hamann
mesh_terms: D044822:Biodiversity; D057231:Climate Change; D017753:Ecosystem