In 1802, the great scientist and explorer,
Alexander von Humboldt, went up a mountain
and came down with an idea that changed ecology.
Humboldt was determined to reach the summit
of Chimborazo, a 6300 meter high volcano in
Ecuador, which at the time was thought to be
the highest mountain in the world.
A chasm prevented the explorer from reaching
the peak, but ever the naturalist, all the
way up and all the way back down, Humboldt
dutifully collected measurements.
5 years later, he published his findings from Chimborazo
and other mountains in an epic drawing.
Tableau Physique, as he called it, depicts
what was then a novel concept: that climate
is an organizing principle of life, shaping
the distinct communities of plants and animals
found at different altitudes and latitudes.
Climate change affects all kinds of aspects of the world.
It affects water, it affects ice, it affects
communities of plants and animals.
And scientists who are studying the impact
of climate change are finding that Humboldt’s
holistic approach⁠—drawing on many different disciplines
to understand how the physical and biological
worlds interact is really the key to understanding
how climate change is transforming our world.
Even without the historical perspective from Humboldt,
it’s plain to see that global
warming is laying siege to Chimborazo.
The volcano’s glaciers overall have lost
20% of their surface area since the 1980’s.
Retreating ice reveals soil, rock, and gravel
ready to be colonized by vegetation.
Newly verdant slopes are popping up higher
and higher on tropical mountains like Chimborazo
throughout the world.
So a team decided to use Humboldt’s data,
as he mapped it on Tableau Physique, to figure
out how much plants have migrated up the slope
of Chimborazo over the past 200 years.
The team selected 51 high-altitude plant taxa
that Humboldt described in his Tableau Physique
and other works from the Andes,
and climbed much of the way up the mountain
themselves to see where those plants now grow.
While Humboldt had recorded an upper limit
for seed plants of 4600 meters, in 2012
the scientists found that the upper limit
was nearly 5200 meters.
Other lower-living species had moved upslope
by an average of more than 500 meters since
Humboldt’s climb.
But not everyone thinks Humboldt’s data
is reliable enough to base new research on.
One group notes that Humboldt spent
just a few hours on Chimborazo, that he didn’t
collect above 3600 meters, and his sampling
wasn’t systematic.
In fact, they argue that Humboldt transposed
measurements he made on a nearby volcano,
Antisana, because, well, Chimborazo, was the
more famous mountain.
So was Humboldt wrong?
To reconcile the measurements, scientists
recently went to Antisana, and using Humboldt’s
data from the Tableau Physique mapped how
much the plants on Antisana had moved upslope.
So far, they found that one species, Senecio Nivalis,
climbed more than 200 vertical meters
in step with the rising snow line.
So the rise is perhaps not as dramatic as
originally thought based on Humboldt’s Tableau,
but it still clearly shows a steep jump.
Well climate change is also affecting water
that flows down the mountain to communities
downslope.
In some of the communities in Chimborazo,
the flow in the main irrigation channel on
the side of the mountain has fallen by about 50%.
in the last couple of decades.
On other parts of the mountain, wells have
dried up, and there’s at least a suspicion
that this has a lot to do with the shrinking
of the glaciers.
Researchers hope to take their updated understanding
of Chimborazo ’s glaciers and vegetation
into a predictive model, which would forecast
how continuing glacial retreat will make water
scarcer and less reliable for downstream users⁠—
not just on Chimborazo, but on glacial mountains
everywhere.
To accurately reflect the effect of climate change on
Chimborazo, Humboldt’s classic drawing
needs a revision.
But his findings continue to energize the latest group of
researchers following in his footsteps.