The datasets below provide information on biotic and climatic velocity for North and South America for the period 1961-2100 under the SRES A2 scenario (as shown summarized by ecoregion in Figure 1 below). The velocity of climate change was originally proposed as a metric used to evaluate the exposure of organisms to climate change. In its original form, one divides the rate of climate change by the rate of spatial climate variability to obtain a speed at which species must migrate over the surface of the earth to maintain constant climate conditions (Figure 2a below). Here, we provide data from an improved algorithm that conforms to standard velocity calculations if climate equivalents are nearby. Otherwise, the algorithm extends the search for climate refugia globally (Figure 2b). We also provide a related metric, termed "biotic velocity" (Figure 2d), which is based on projections of shifts in species' climatic niche in response to climate change, for ~3000 species of birds, mammals, and amphibians. Whereas climatic velocity assumes narrow climatic tolerances, biotic velocity assumes local populations can adapt to any climatic conditions encountered within the full range of the species distribution. Together, these two assumptions inform estimates of upper and lower bounds on actual migration rates.

We also distinguish forward and backward velocities, allowing useful inferences about conservation of species (present-to-future velocities) and management of species populations (future-to-present velocities). For the forward calculation we ask: what is the rate at which an organism in the current landscape has to migrate to maintain constant climate conditions? Conversely, in the backward calculation we ask: given the projected future climate habitat of a grid cell, what is the minimum rate of migration for an organism from equivalent climate conditions to colonize this climate habitat?

The "GIS Data" link below provides a zipfile containing ASCII (.asc) format files that can be imported into ArcGIS or other GIS applications.

For gridded climatic velocity data for North America at 1km resolution, see this page.