Mountain Refugia and the Velocity
of Climate Change
Solomon Dobrowski
Dept. Forest Management
College of Forestry and Conservation
University of Montana
Motivation
Ok….but??
Are mountain systems more or
less vulnerable to climate change?
Can complex terrain buffer against
climate change exposure?
How did species cope with past
climate changes?
What about the rate of change?
Outline
Part 1. Climate refugia
Part 2. Climate change velocity
Part 3. Role of scale
Part I. Climate Refugia
What are climate refugia?
sites that support locally
favorable climates amidst
unfavorable regional
climates, which allow
populations of species to
persist during periods of
adverse conditions
Support relict climates
that were once more
prevalent
Climate Refugia
Why are climate refugia
important?
1. Reid’s Paradox
2. Patterns of genetic
diversity
3. Conservation interest
Pearson 2006
Vitals of climate refugia
For climate refugia to exist requires climatic
conditions that differ from their regional
surroundings. (spatial variability)
For climate refugia to persist they should
buffer against rapid climatic changes or
they will be short lived. (temporal stability)
Climate experienced in-situ
 Sum of regional advective
influences and local terrain
influences.
 Known as topo-climate, mesoclimate, terrain climate.
 Terrain affects the level of coupling
between the free atmosphere and
the boundary layer
Spatial Variability
Recent studies suggest that spatial climatic variability
driven by topography may may allow for species to
mitigate climate-change exposure through shortdistance dispersal to more favorable climates.
Scherrer & Korner 2010; Dobrowski 2011; Dobrowski et al. 2013; Lenoir et al. 2013
“Microtopography can mimic temperature differences of large
elevational (or latitudinal) gradients over very short horizontal
distances. This is important in the context of climate change because
it shows that species do not necessarily need to climb several
hundred meters in elevation to escape the warmth. Quite often, a few
meters of horizontal shift will do”
Scherrer and Koerner 2010
Rate of climate change through time
Climate Refugia
(Climate refugia)
Spatial climate variability
Part II. Climate Change Velocity
What is climate change velocity?
 Climate change velocity describes the rate and
direction which an organism would need to
migrate to maintain an isocline of a given climate
variable.(Loarie et al. 2009)
 It takes into account change in climate in time
and the ability of topographic heterogeneity to
buffer biota against changes in climate
Calculated as:
Climate Change Velocity
 Tmin, AET, Deficit
 monthly timestep from 1916-2005
 PRISM 30 arc-second data inputs
 PET based on Penman Monteith
 terrain and cloud corrected
radiation data
 wind from NLDAS-2
 soil available water from STATSGO
 snowmelt model accounts for
temperature and radiation
Observations:
• Greatest velocities in the plains
states
• Patterns of climate velocity are
driven by physiography in the
west and climate dynamics in
the east
• Direction of velocity vectors
often differ between
temperature and water balance
Dobrowski et al. 2013
Climate Divergence
Velocity (km/yr)
tmin
AET
deficit
19162005
19161945
19461975
19762005
19162005
19161945
19461975
19762005
19162005
19161945
19461975
19762005
0.081
0.284
0.183
0.505
0.098
0.226
0.267
0.216
0.084
0.180
0.311
0.247
Mountains put the brakes on velocity
Migration Rates
Recent observations of elevational and latitudinal shifts
(Chen et al. 2011):
 1.6 km/year latitude (not including plants)
Paleorecord for trees (Clark 1998, Malcolm et al. 2002):

0.1-1 km/year
Part III. Scale
Part III. Scale
Potential Climate Refugia?
Velocity and Endemism
Sandel et al. 2011
Recap
Are mountain systems more or
less vulnerable to climate change?
Can complex terrain buffer against
climate change exposure?
How did species cope with past
climate changes?
What about the rate of change?
Acknowledgements
Thanks to
 Colleagues: John
Abatzoglou; Alan
Swanson; Alison
Mynsberge; Zack Holden
 PRISM Group
 USFS Region 5 Ecology
Paying the bills:
Lets eat grandma.
Lets eat, grandma.
--------------------------Commas save lives.