MICHAEL MILSTEIN
The Oregonian
The mystery arose from the depths of Hells Canyon on the Oregon-Idaho
border.
Native American artwork -- shapes, birds and human figures etched into or
painted onto stone -- had survived there, along the Snake River, for as long
as 7,100 years. What was eating it away?
The answer would take about five years to unravel. It would hinge on some of
the isolated canyon's most primitive and little-noticed life-forms: lichens,
a blend of fungi and algae. And it would tell scientists that booming
populations in the West are flushing corrosive pollution through Hells
Canyon's central artery, the Snake River itself.
Now they figure that invisible ammonia gas, spewed by a river laden with
livestock waste and fertilizer, is probably ruining the rock art. It is a
more insidious form of pollution than a power plant, where filters can be
clamped onto a smokestack. Here, there is no easy fix because the problem is
as expansive as people are.
Their discovery may help decipher air pollution problems in other parts of
the Pacific Northwest, such as the Columbia River Gorge.
The first clue something was wrong in Hells Canyon, a national recreation
area, came from archaeologists who knew its nooks and crannies as one of the
richest troves of ancient art in the West. Its desertlike depths provide a
warm refuge from the winters of Northeast Oregon, and Native Americans left
their mark by etching rocks or painting them with colored clay.
More than 200 rock art sites from 200 to 7,100 years old in Hells Canyon are
listed on the National Register of Historic Places.
In his nearly 20 years as a U.S. Forest Service archaeologist based in
Enterprise, Bruce Womack realized the ancient patterns were fading. Rocks
polished smooth by water had become pitted and pocked, and colored lichens
were shrouding the native insignias.
"It's kind of pretty, but not when it's covering over rock art that had been
there for 2,000 years," said Womack, who retired in 1999 and now is a
paramedic at Wallowa Memorial Hospital in Enterprise.
They wondered whether air pollution could be the culprit. Maybe acid rain?
Linda Geiser, a lichen specialist in the air quality division of the Forest
Service, found it hard to believe anything could be wrong in Hells Canyon.
It's hundreds of miles from the nearest industrial plants. Few roads reach
down its steep walls, and most of its 150-mile length is reachable only by
boat. If anything, it seemed unusually pristine.
Could the petrogylphs and pictographs just be weathering away?
"We didn't take it too seriously at first," said Geiser, based at the
Siuslaw National Forest in Corvallis.
But in 1998 she and a few others took a look. They took a jet boat up the
canyon and stopped at little-known petroglyphs that should be undisturbed by
the vandalism that has taken a toll elsewhere in the West.
A striking finding
What struck Geiser was not so much the ancient symbols, although they
fascinate her, but the hackberry trees that are almost the only trees along
the river.
They were orange.
It was as if they had been painted with a brightly colored layer of living
lichens called Xanthomendoza and Xanthoria. Other lichens were virtually
absent.
"I'd never seen anything like that," she recalled.
The two species are well-known weeds of the lichen world. They flourish
around farm fields and under bird perches -- places loaded with nitrogen, a
common element of most fertilizers and animal droppings.
Add fertilizer, and the orange lichens take over.
Geiser built her career around using lichens as living air samplers across
the West and in Alaska. They absorb whatever's in the air almost as
effectively as fancy and costly electronic devices.
"Lichens are great," she said. "You don't have to go out there for a whole
year. You just grab a sample, and you get a snapshot."
On to greenish lichen
So she grabbed samples of another lichen, greenish Xanthoparmelia, spreading
over the canyon's rocks and petroglyphs.
Basic tests showed it had soaked up nitrogen and sulfur, hinting at dirty
air from sources as varied as auto exhaust, power plants and livestock
manure. Nitrogen levels, especially, were striking.
"It was higher than anything we had seen before," Geiser said.
That finding offered more questions than answers. What was the pollution,
and where was it coming from? How bad was it? Was it only along the river --
or spread across the rugged cliffs and peaks that strike off to the east and
west?
A year later, Geiser and her team returned. They examined trees and lichens
at various distances from the river. And answers began to take shape. Next
to the river, orange lichens covered about half the exposed surface of tree
trunks and branches. But a quarter mile or more from the water, only about
10 percent was covered.
A dousing of nitrogen
Something along the Snake River was dousing the trees with nitrogen, sending
lichens growing out of control.
Nitrogen levels in lichen tissue right next to the river were off the
charts -- about 60 percent higher than usual levels in places such as
Central Oregon's Deschutes National Forest. They were higher, even, than
measured in lichens Geiser had gathered from the polluted Columbia River
Gorge and from Colorado mountains in the shadow of two large coal-burning
power plants.
Lichens farther from the river also held extra nitrogen, but not nearly as
much. Sulfur levels were slightly high, as well, but not as far out of line.
Nitrogen pollution comes from two leading sources. One is nitrogen oxides
from the exhaust of vehicles and power plants. It joins with moisture in the
air to form acid rain. But it's declining nationally as engines and fuels
burn more cleanly.
The other is ammonia, a common source of nitrogen that plants need. It comes
mainly from decomposing manure and fertilizer, and it can rise into the air
or wash into rivers. More ammonia is being released as industrial farms and
feedlots multiply to feed a growing population.
Feedlots cluster on Idaho's southern plains that drain to the Snake River.
The number of cattle has more than doubled in the past 15 years in some
counties along the Snake, according to federal statistics.
Geiser continued her detective work. She seized on a key difference between
ammonia and nitrogen oxides: Ammonia is not acidic.
Acidity of tree bark
Geiser seized on that. She tested the acidity of tree bark in Hells Canyon.
The readings showed that whatever was at work along the river, it wasn't
acid. Ammonia became the likely suspect.
Geiser wondered whether manure from cattle in the canyon could be driving up
nitrogen levels. But she found no extra nitrogen in lichens where cattle had
grazed recently.
The nitrogen was coming from somewhere else.
In 2002, Forest Service researchers installed air monitors at five spots in
the canyon to nail it down. Local staff took boats up the canyon every few
weeks for a year to collect filters and send them to the laboratory.
The ammonia couldn't hide.
Its concentrations spiked as high as five times normal during spring and
early summer, climbing halfway to where it would burn plant leaves, Geiser
said.
"We had begun to suspect ammonia, but I was surprised to see these very high
values," said Andrzej Bytnerowicz, a Forest Service ecologist and senior
scientist at the Pacific Southwest Research Station in Riverside, Calif.
The river's role
They turned to the river. The Snake collects fertilizers and runoff from the
farm belt of Southern Idaho and Eastern Oregon. The region releases more
ammonia per acre than almost anyplace else in the West outside Central
California, according to U.S. Environmental Protection Agency figures.
The Snake River is highly polluted, violating several state water standards
as it heads toward Hells Canyon.
"There's a huge amount of ammonia going into the Snake River, and that's the
same water that's running through Hells Canyon," Geiser said.
All the extra nitrogen feeds blooms of slimy algae when water warms in the
summer.
The explosion of algae starts a chain reaction, shifting the river chemistry
and freeing ammonia gas, researchers now suspect. Gas rises from the river,
enveloping trees, rocks and the age-old petroglyphs.
It also may combine with sulfur in the air, forming particles that collect
on trees and lichens.
More to study
Ammonia, though not acidic, is toxic at high levels and corrosive enough to
burn skin. It's logical it would dissolve the rock etchings, though there
has been little study of that process directly, Geiser said.
No one knows what else the ammonia might be affecting in the canyon.
Invasive cheatgrass is thick on the canyon floor and is known to thrive with
the kind of extra nitrogen the ammonia would supply. It also fuels severe
wildfires.
Algae blooms also release ammonia in Upper Klamath Lake near Klamath Falls,
sometimes killing fish, said Dick Nichols of the Oregon Department of
Environmental Quality. A ring of orange lichens encircles the lake.
A joint Oregon-Idaho effort to clean up the Snake River is under way.
However, results will take years, and the effort does not specifically
target the deluge of nitrogen.
At least Geiser's team now has a good idea what's doing in the petroglyphs.
"It's really a function of our population," she said, "and it's hard to see
that change."