BOISE - John Thornton, a hydrologist for the Boise National Forest, remembers staring out of the helicopter in disbelief.
Below him, a major wildfire was
raging, devouring trees and brush.
caught his eye was the black volcanic rock along the South Fork of
the Boise River. On both sides of the canyon, the rock was on fire.
Then, it came to him. It wasn't the rock that was on fire. It was
lichen. Even the tiny rock-hugging lichen were
That is how it went with the 1992
Foothills fire - one of the most savage and memorable blazes to
sear Idaho in years.
"That fire was like a
blowtorch," said Stephen Mealey, supervisor of the Boise Forest
from 1991 to 1994. "It traveled 18 miles in 10 hours. That's an
incredible rate. And it went with incredible force and incredible
Today, the Foothills fire has become a
textbook example of the environmental damage inflicted by
modern-day, super-hot wildfires.
across a quarter million acres, reached temperatures of more than
2,000 degrees - hot enough to melt glass bottles and metal culverts
- and triggered horrific soil and stream damage. The largest
ponderosa pine in Idaho, one that had survived centuries of natural
fire, was fried by the Foothills fire.
Foothill's footprints remain painfully visible from the air.
Charred hillsides seem to roll on forever. Ghostly white-ash images
of trees linger on the blackened ground - a signature of the fire's
fury. Damage was so extensive that "it will impose limits on forest
ecosystems for centuries," the National Commission on Wildfire
Disasters - a panel of fire specialists - said in a report last
One especially hard-hit piece of scorched
earth lies near the headwaters of the South Fork of Sheep Creek - a
tributary of the Middle Fork of the Boise.
burned so fiercely it stripped steep slopes of soil-gripping
vegetation. The area was reseeded but - for reasons still unknown -
seedlings didn't grow. For two years, the area remained barren, as
vulnerable "as a crab out of its shell," said
Then, on July 31, 1994, disaster
A thunderstorm pounded the area. It
wasn't a big storm but it did a lot of damage. Up to 3.5 inches of
soil washed away in a few hours - soil that had taken 1,500 years
to form. Steep parts of the creek were scoured by mud and ash;
gentler sections were buried by them. Many aquatic species
perished, including an entire spawning class of rare bull trout.
No one knows why the area suffered so
extensively. But it may be due to a freakish phenomenon called
"hydrophobic soil" that can be caused by very hot fires.
"You literally get an impermeable waxlike layer
below the surface," said Mealey. "It resists water. If you were to
scratch the surface of the soil and pour water on it, the water
would bead up and run off just like the hood of your car."
On the South Fork of Sheep Creek, the waxlike
layer may have prevented young trees from growing. Almost
certainly, it hastened erosion. "When water doesn't penetrate, it
runs off," said Mealey. "And as it runs off, it takes everything
that's loose. And there's a lot that's loose."
Sheep Creek is no isolated incident. Similar
fire-related damage is happening throughout the
After the Tanner Gulch fire in Oregon in
1989, mudslides occurred along a pair of creeks so small they
didn't have names. That was just the
The erosion led to a very major
"debris torrent" in the Grand Ronde River which was measured 36
miles downstream, said Oregon fisheries biologist V.K.
It loaded the river with sediment,
increased the temperature of the water, and depleted it of oxygen,
Kaczynski added. The result: "A total fish kill in that stretch of
river, including the endangered spring chinook salmon. I was up
there in 1993, and you still had excessive sediments in spawning
"Something is crazily out of kilter,"
said Mealey, who now heads the Upper Columbia River Basin project,
a long-range federal land-management plan for a huge chunk of the
Northern Rockies and Pacific Northwest.
problem is we've interrupted the natural processes. We've altered
fire regimes which were nature's way of portioning out limited
water and nutrients," Mealey said.
"Over so many
acres, much of the coniferous vegetation has been removed. It's
difficult to make the argument there's going to be much
biodiversity. Most of the vegetation will all be the same age. And
because of that, there won't be much variety. That's a frightening
prospect: to see that much of this forest in such a monotonous
ecological condition. It didn't evolve that way."
* Tom Knudson