Jennifer Pierce and David Wilkins stand in front of a ponderosa pine forest just outside the city of Boise. They hope to study the relationship between fire and climate here and recreate a snapshot of ancient climate. They are both teach at Boise State University's Geosciences Department. (Photo by Sadie Babits)
Twenty years ago this year, the
country watched its oldest national park
go up in flames. Looking back, scientists
believe the 1988 fires of Yellowstone
National Park were the signal fire of
climate change. Researchers have been
working ever since to understand this
relationship between climate and wildfire.
Sadie Babits reports on two scientists
searching for clues to ancient climates,
using trees as their guide:
Transcript
Twenty years ago this year, the
country watched its oldest national park
go up in flames. Looking back, scientists
believe the 1988 fires of Yellowstone
National Park were the signal fire of
climate change. Researchers have been
working ever since to understand this
relationship between climate and wildfire.
Sadie Babits reports on two scientists
searching for clues to ancient climates,
using trees as their guide:
Jennifer Pierce wears work boots as she plows down a steep slope in a
ponderosa pine forest.
(sound of walking, twigs breaking)
Her blonde hair is tucked up under her Boise State bronco cap, but it keeps
sneaking out. She has to keep brushing it back under. She and her
colleague David Wilkins are professors who work for Boise State
University’s Geosciences Department. They’re in the middle of tall pines in
a forest just outside of Boise, Idaho. Suddenly she’s crashing across the
brambles and heads for this tree.
“Oh that’s a great one! Wow! Sweet!”
She drops to her knees and shows me how this tree has been scarred by
fire.
“You see this little V shaped cat face here at the bottom of the tree that’s
blackened? So during a fire when the bark of the tree gets damaged that
preserves a record of the fire as a scar on the tree.”
Pierce says since the tree has annual growth rings, she can tell when the
tree got burned.
It’s one way Pierce and Wilkins reconstruct the fire history of this forest.
It’s a key to understanding how climate has affected forest fires in the past.
“I think as we move into a likely warmer and drier future, it’s going to be
increasingly important to understand the relationship between climate and
fire.”
She says climate is the primary control for wildfires. As the West warms,
there’s less control. Recently, that’s meant a lot more wildfires.
(popping sound) “There you go!” (sound of a drill bit going through the tree
with sound of birds and forest)
David Wilkins is twisting an auger into the tree.
“It’s a good upper body workout!” (laughs)
It’s a way to take a sample of the rings of this tree. Within a half-minute,
Wilkins’ auger is stuck. The tree is rotten inside. An eight-inch core is all he
gets.
(sound of drill bit coming out of the tree)
Jennifer Pierce takes a look at this sample Wilkins twisted out. The rings –
some light, some dark – reveal just how the tree has responded to moisture
and temperature.
“If you have a tree that kind of is at the edge of its comfort zone so to
speak, it will be more of a sensitive recorder of those environmental
stresses. See this one looks pretty good.”
Tree rings aren’t the only clue these scientists use to reconstruct historic
climates.
(scraping sound)
“I didn’t bring my big shovel. I kind of feel naked without it.”
Pierce scrapes away dirt and she finds bits of charcoal. She can sometimes
use charcoal for radio carbon dating. But these won’t do.
“But, um, I wouldn’t use them for dating because you want to make sure
that the charcoal is stratographicly in place and that you haven’t had
critters burrowing and mixing things up.”
Charcoal can be dated much further back than the tree rings. It helps
Pierce and Wilkins understand what happened here thousands of years
ago. With samples from other scientists, they’ll get a snapshot of ancient
climate and how it affects wildfire.
And possibly determine what climate change will mean for forests in the
future.
For The Environment Report, I’m Sadie Babits.