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Stochasticity
Abundance

Latitudinal and Elevational Range Shifts under Contemporary Climate Change

Latitude/altitude

March
Abundance

(a)

Latitude/altitude

Lean
Abundance

(b)

Latitude/altitude

Crash
Abundance

(c)

(d)

Latitude/altitude

601

locations within the peripheral area of a species’ range that
were too cold and therefore less suitable might become more
suitable in a warmer climate, thus turning sink populations
into source populations with higher growth and colonization
rates. On the other hand, locations within the core area of a
species’ range that were highly suitable might become too
warm and therefore less suitable, turning source populations
into sink populations with higher decline and extinction rates.
Across species ranges, the net result of these changes in
growth, decline, colonization, and extinction processes will
affect their geographic distribution in different ways. However,
an increase in temperature is likely to have an overall directional impact on species range shifts, because temperatures
are autocorrelated in space, linking warmer conditions at
lower latitudes and elevations with cooler conditions at higher
latitudes and elevations. Therefore, one expects to observe
poleward and upward range shifts as climate warms, even after
accounting for dispersal limitations (Engler et al., 2009) or
biotic interactions (Arau´jo and Luoto, 2007). Accordingly,
poleward and upward range shifts in the warming climates
following the glacial recessions of the past interglacial periods
have been widely reported for plants, birds, and mammals
(Brown and Lomolino, 1998). For instance, Pleistocene fossils
of several species of rodents have been found several thousand
kilometers southward of the southern limit of their modern
distribution in northern America (Graham, 1986), suggesting
strong poleward shifts during the Holocene. Similarly, Pleistocene macrofossils of Podocarpus have been found c. 1000 m
below the lower limit of their contemporary distribution on
the Andean flank in western Amazonia (Ca´rdenas et al., 2011),
thus suggesting a large upward shift during the current interglacial period.

Although the expectations given temperature increase
alone are relatively straightforward, it is difficult to predict
how concurrent changes in other climatic factors, especially
precipitation, will affect species ranges. Temperatures are
negatively correlated along the latitudinal and elevational
gradients and have risen globally over the past decades (IPCC,
2007b). In contrast, precipitation changes are more heterogeneous across space and time (IPCC, 2007b), leading to
strong regional differences. Such regional variation in climate
change, mainly due to the effect of precipitation changes on
the water balance equation (balance between evapotranspiration and precipitation), may affect species ranges as
well, leading to unexpected regional range shifts as climate
warms globally (Crimmins et al., 2011). Additionally, biotic
interactions may also affect the magnitude of species range
shifts as climate warms (Arau´jo and Luoto, 2007) with some
suggestions that interactions could explain unexpected range
shifts as well (Lenoir et al., 2010a). Therefore, at global to
continental scales, poleward and upward range shifts are likely
Figure 2 Conceptual representations of latitudinal and elevational
range shifts and their mechanics under a steady-state environment
(a) and under climate warming (b)–(d). In each case, the
figure shows the relative importance of growth, decline, colonization,
and extinction processes across the species range. For the march-,
lean-, and crash-range shifts, gray shades represent conditions
before a climate warming event whereas overlaying transparent
colors represent shifting conditions under a climate warming event.