Climate Change

Question 1

How is the climate changing?

Answer 1

Not just temperature increases
* Circulation patterns are changing; e.g.,
Hadley cells get stronger and therefore
larger, causing desert belts shifting poleward
beyond 30 degrees
* Extreme weather events are becoming more
frequent (e.g., hurricanes, droughts, floods,
fires)
* Local climate changes are affecting
organisms

Question 2

Humans impact

Answer 2

Human
activities are
adding more
CO2 to the
atmosphere
This
intensifies
greenhouse
effect and
causes
global
warming

Question 3

What happens to organisms as
the climate changes?

Answer 3

• They can acclimate to new conditions
  (phenotypic plasticity)
• They can adapt to new conditions
  (adaptation)
• They can migrate to suitable conditions
  (range shift)
• They can go extinct globally or locally
  (extirpation)

Question 4

Acclimation

Answer 4

Early or gradual exposure
to environmental stress
can reduce its negative
impacts
* Porcelain crabs
(Petrolisthes) acclimated
to cold temperatures
function better at colder
temperatures
* But acclimation to warm
temperatures increases
high-temperature
tolerance only minimally
Stillman

Question 5

Climate change is more than just
the direct effects of warming

Answer 5

High predation-related mortality (remember those lynx-hare
cycles?); coat colour is important for reducing predation

Question 6

Not enough plasticity to avoid
mismatches

Answer 6

Projections of future snow
duration show there will
be greater mismatch
between snowshoe hare
coat colour and its
background
Plasticity alone in coat
colour change will not
be able to respond to
changes in conditions

Question 7

Plasticity to changing conditions

Answer 7

Mills et al. (2013) studied snowshoe hares in
western Montana over 3 consecutive winters
(2009-2012)
* Radio-collared hares and performed weekly
measurements of coat colour and snow
around each hare

Question 8

Will hares adapt?

Answer 8

There is not enough plasticity in the timing of
coat colour change for snowshoe hares to avoid
coat colour mismatches as snow duration
shortens
* Having the wrong coat colour decreases hare
survival, slowing population growth, but this also
generates strong selection on timing of coat
colour changes
* Open question whether hares will adapt fast
enough to save hare populations from extinction
* Depends on the amount and type of genetic
variation underlying the timing of coat colour
change

Question 9

Are pikas threatened by climate
change?

Answer 9

The elevational range of American pikas in the Great
Basin is getting smaller
* Sites where pikas have gone locally extinct often had
temperatures above 26°C, which can be lethal to
pikas (if they cannot behaviourally thermoregulate)
* The American pika was under consideration to be
listed as an endangered species in the US (but the US
ultimately decided against it)
* On the other hand, American pika populations in the
Rocky Mountains and elsewhere appear to be healthy
(Smith et al. 2020)
* In Canada, the Collared pika (which lives in the
Yukon, Northwest Territories, and BC) is federally
designed as a species of “Special Concern”

Question 10

Extinctions

Answer 10

“The loss of biodiversity is
the most important process
of environmental change.
This is because it is the only
process that is wholly
irreversible. Its
consequences are also the
least predictable, because
the value of the earth’s biota
is largely unstudied and
unappreciated.”