lower, most of what used to be up in his research area shifted a little bit
lower. We think that has something to do with temperature changes,
because as it warms up, everything at low tide becomes a little warmer
and dryer. So it sort of makes sense that things would tend to shift a lit-
tle bit lower so they’re exposed to air for shorter periods of time.”
The snails, sea stars, and anemones Gilman and Sagarin counted
were all small. But the shifts they recorded—and the implications of
those changes—were anything but.
These were “massive community reorganizations,” Sagarin says.
And the implication of such a finding is that “it seems that species
respond to climate change in the present day. It’s not just going to hap-
pen at some point in the future.”
“It was one of the first studies to suggest that you could go out and
find [climate-related] changes already,” Gilman adds. “But it was com-
pletely unexpected to me. I thought I was just counting snails for a
summer project.”
The results have held up over time. Sagarin, who received his
Ph.D. from the University of California at Santa Barbara in 2001, has
resampled the Hewatt line regularly. And while he has not found new
changes with the same kind of drama as those he and Gilman found
in 1993, he also has not found anything to indicate that the species are
shifting back.
“Changes in the short term—every few years—are much smaller
than the dramatic, aggregate changes that we saw when we looked 60
years later,” he says. “So it just suggests that, even though each of these
organisms is changing in its own time frame, real ecosystem evolution
takes a long time.”
Baxter points out that what his students found in the intertidal area
by Hopkins are the same kinds of community changes one observes
climbing up into the Sierra Nevada mountains. And if climate is affect-
ing the globe, and therefore the Sierras, the same kinds of changes are
happening there on a different scale. Scientists believe it takes some-
thing on the order of 300 years to see the tree line shift; with
Endocladia, the timeline is probably about 10 years. That, he says,
makes studying intertidal areas ideal for observing the ways a commu-
nity of plants and animals responds to a warming world.
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