“The beauty is that we have scientists
and citizen volunteers all using the same
protocols to collect the information,” says
Jake Weltzin, the network’s executive
director. This process creates a seamless
dataset on a wide variety of organisms
across the nation that researchers, conservation groups and others can use to
piece together the big picture.
In addition to monitoring what’s going
on right now, the organization is tracking down and organizing records of what
has happened in the past. “About 10 percent of the people in any audience I’m
talking to have some kind of phenology
records they’ve been keeping on anything from when maple syrup comes to
when they applied insecticide on their
grapes,” Weltzin says. “We want to create a clearinghouse for these kinds of
historical datasets.”
Establishing cause
From the earliest studies through the
current efforts, a major challenge has
been verifying that observed changes in
animal distribution, seasonal activities
and so on are actually linked to climate
change, and then disentangling the rela-
tive contributions of natural tempera-
ture fluctuations and human-caused
temperature increases.
Speed game A recent study analyzed how quickly climate change would move across the
world during the 21st century, depicted below as the velocity one would have to move along
Earth’s surface to maintain a constant local temperature. Different ecosystems show varying
average velocities (examples at bottom). SOURCE: S. LOARIE E T AL/NATURE 2009
1.00
10
Speed of
temperature
change
(km/year)
0.1
0.01
0.08 km/yr
Tropical or subtropical
coniferous forests
0.29 km/yr
Tundra
1. 26 km/yr
Flooded grasslands and
savannas
sayers,” Root says, “so in 2005 I looked
at species change in relation to actual
temperatures recorded at the particular study sites.” The study that she and
her coauthors published that year in the
Proceedings of the National Academy of
Sciences showed a strong link between
local temperatures and the timing of
biological events. The researchers then
looked to see how the observed biological changes fit various climate scenarios
generated from three different versions
of global climate models: one based only
on natural climate variability, one based
only on human-caused climate change
and one that factored in both natural and
human-caused changes. The best fit was
with the combined model; the worst was
with natural climate variation alone.
“That was just a way of showing that
yes, indeed, humans are a part of this,”
says Root, who endorses efforts to fur-
ther clarify the relative contributions
of natural and anthropogenic climate
change, while conceding that it makes no
difference to plants and animals what’s
causing the warming. “From a species
perspective, it does not matter why the
climate is changing, just that it is. From
a human perspective, it does matter a lot,
because knowing the reason can help us
to stop our behavior that is driving the
rapid changes.”
Parmesan, however, thinks the pur-
suit amounts to unproductive hair-
splitting. In a commentary published
last year in Nature Climate Change, she
and coauthors argued that the whole
picture is too complex to ever say with
certainty that a particular response in
a given animal species is due to human-
induced climate change. For one thing,
animals respond to local climate, but
human-caused climate change can be
detected only on a larger spatial scale.
What’s more, other factors can inter-
act with climate change, enhancing or
masking its effects.
“Changes at the local level are going
to be a complete mix of interactions
among regional climate, habitat loss and
local pollution sources,” Parmesan says.
Assessing and seeking to understand
these interactions is a better use of time
MAP: S. R. LOARIE ET AL/NATURE 2009; IMAGES, FROM LEFT: © JEAN-PAUL FERRERO/AUSCAPE/MINDEN PIC TURES/CORBIS;
PI-LENS/SHUTTERSTOCK; JACQUES JANGOUX/PHOTO RESEARCHERS, INC.
