For seven years entomologist Jack DeLoach had searched, like a driven cancer doctor, for a cure to one of the American West's most widespread plagues. It was no ordinary ailment that sent the Texas-based Department of Agriculture scientist to places like Kazakhstan, China, Italy and Israel. It was a subtle affliction, a green rash moving quietly - and unnoticed by most Westerners - up the rivers and streams of California, Arizona, Texas, New Mexico, and later into Colorado, Utah and Wyoming.
With its billowy pink flowers and bright
green foliage, the woody tamarisk, or saltcedar, seemed a beautiful
addition to the flora that survives along the waterways of the
West. But DeLoach, along with a growing number of ecologists,
understood there was more to the plant than met the eye.
The Eurasian native was naively introduced into
Southern California and Arizona as a streambank stabilizer and
ornamental shrub back in the early 1800s. It had no predators or
diseases and it spread rapidly - more than 12 miles a year by one
estimate - into virtually every river system in the West. Wherever
it colonized, it choked out native plants, provided scant habitat
for wildlife, sucked up inordinate amounts of precious water,
concentrated salt on the soils beneath it, and spread damaging
fires through riparian areas.
Federal and state
land managers tried cutting down tamarisk and burning it, but that
only strengthened its hold. Chemical poisoning worked better, but
the plant was so ubiquitous that managers needed a vast and
well-supplied army - one that lawmakers would never fund - to
tackle the thousands of miles of infested rivers.
After traveling the temperate world, DeLoach
thought he had finally found a better weapon. But today the weapon
- two species of insects - sits, quarantined, in a lab in Temple,
These are not just any bugs. They evolved
in Eurasia with the same species of tamarisk that was loosed upon
North America. The Israeli mealybug and Chinese leafbeetle were the
best prospects out of several dozen insect predators. The larvae of
the beetle attack the tamarisk's foliage, while the mealybug larvae
eat the stems.
"We believe we can get 80-85
percent control of tamarisk," DeLoach says. "We might get more in
some areas and less in others."
With that kind
of miracle cure on hand, land managers in the West should have
lined up at his door with open bug jars. But none have. As DeLoach
has discovered, not everyone likes the idea of releasing exotic
bugs to fight an exotic plant. One critic said, "There's no telling
what the insects will do once they eat through the tamarisk."
DeLoach says that fear is unfounded because
rigorous tests ensure that the insects will eat only target plants.
But behind the fear stands another and larger obstacle: a
contentious debate over the ecological demise of Western rivers -
and the role played by tamarisk. Some scientists think the whole
notion of wiping out tamarisk is wrongheaded. The plant, they say,
is a symptom of a sick system. Focusing on it distracts from the
real causes of the West's damaged rivers - human-constructed dams,
desert agriculture and livestock grazing.
are two opinions out there about tamarisk," says Mike Scott, a
biologist with the United States Geological Survey based in Fort
Collins, Colorado. "One camp says it is an aggressive invader that
is vigorously displacing natives and must be eradicated. The other
says it is more passive, that it is an opportunist that has taken
advantage of man-made changes to the rivers."
This intellectual squabble rolled along quietly
for years, surfacing from time to time in scientific journals. But
in 1995, something brought it to a loud and roiling
A bird in the
At the time, DeLoach was eagerly moving
toward a real-world test of his insects. He had received permission
from the U.S. Department of Agriculture to release the insects in
nine locations, including sites in Wyoming, Colorado, Utah, Nevada,
Arizona and New Mexico.
In the spring of "95, he
returned to Israel to do the final insect collecting. It was there
that he got the bad news.
"I had just finished
packing the insects for shipment," DeLoach recalls, "when a fax
came in from the states. It said that I might have a problem with
the Endangered Species Act."
willow flycatcher, a small native songbird, had just been declared
an endangered species by the U.S. Fish and Wildlife Service. The
bird was hanging on by a thread along Southwestern rivers and
reservoirs. By law, DeLoach now needed to prepare a biological
assessment to demonstrate that eliminating the tamarisk would not
harm the flycatcher.
It took him two years to
complete. Today, three years later, and ready to retire at age 65,
DeLoach still awaits a final decision on his five-inch-thick,
"It's frustrating," he says.
"When I got started on this, there wasn't any endangered species
listing. If I had gotten done earlier, we could have already
released the bugs and been on our way."
On the surface, the conflict between
the insects and the bird is simple. A significant number of the
remaining 400 pairs or so of willow flycatchers have taken to
nesting in tamarisk. The attraction is proximity to water, shade
and a branching structure that apparently reminds the birds of the
native willow trees they historically nested in. If DeLoach's
insects ate up all of the tamarisk, the reasoning went, an
important chunk of nesting habitat would disappear, pushing the
bird closer to extinction.
This line has been
pushed hardest by Bob Ohmart, an ecologist with an activist bent
who teaches at Arizona State University.
have any great love for tamarisk," says Ohmart. "It provides poor
habitat for wildlife compared to our native plants. But we're stuck
For Ohmart to resist tamarisk control
seems almost odd. He did pioneering studies in the 1970s showing
that tamarisk supports less animal life - from insects to birds and
mammals - than native vegetation. But Ohmart argues that tamarisk
has merely taken advantage of our sick, static river systems, and
that removal of it will leave next to no habitat for the willow
flycatcher and other riparian-dependent species. Dams and water
diversions have permanently altered river corridors in the West, he
says, rendering many inhospitable to native cottonwoods and
"If you wipe out saltcedar, what will
replace it? Not much," says Ohmart. "I'd rather see a monoculture
of saltcedar than bare dirt. At least it holds in soil and provides
a little habitat. We're damn lucky tamarisk came along when it
Backing up Ohmart is Bertin Anderson, an
ornithologist turned soil scientist based in Blythe, Calif..
"Removing tamarisk and replacing it with native vegetation isn't
going to happen on any major river in the Southwest," says
Anderson, who has spent the last 25 years restoring native
vegetation to sites along the lower Colorado River for the Bureau
of Reclamation, various Indian tribes and other
Rivers and their banks have become
saltier and drier since irrigated agriculture and dams came in more
than 50 years ago, he says, and these conditions favor the hardier
saltcedar over the cottonwoods and willows. Anderson says that dams
have prevented the nurturing floods that wash salts out of the soil
and moisten it to sustain native plants.
Anderson says he analyzed a large portion of the
Southwest's rivers, looking at soil conditions, and found that 75
percent of the area is no longer suitable for natives. "But a large
percentage of the area is still suitable for tamarisk," he says.
"In some places, the conditions are so bad that even tamarisk can't
Ohmart's and Anderson's viewpoints
have elicited visceral reactions from those involved with tamarisk
"I had one scientist in their camp come
up to me and say that we should start considering tamarisk a
naturalized plant in North America," says Jeff Lovich, an ecologist
with the U.S. Geological Survey in Riverside, Calif. "I thought,
what are we going to do, give it a green card?"
Lovich says he understands the river degradation
wrought by dams and irrigation, but he still can't stomach the idea
of sitting idly by while tamarisk takes over the West. "Tamarisk
has caused severe ecological problems and it needs to be
"I think Ohmart has forgotten one
of his basic principles from Ecology 101: Nature abhors a vacuum,"
says Keith Duncan, a weed specialist from New Mexico State
University. "Something is going to come in when we take out the
tamarisk, especially if we give it a little help."
Duncan and a coalition of water conservation
districts and irrigation companies are trying to do just that on
5,000 acres along the Pecos River in southern New Mexico. The
members of the Pecos River Native Riparian Restoration Organization
have raised nearly $1 million to manually and aerially spray a
mixture of herbicides Arsenal and Rodeo or Roundup on the tamarisk.
"It's the biggest project I know of," says Duncan (see story on
After three years of spraying, the
tamarisk is mostly dead now, says Duncan. The next step is getting
something else to grow.
"We're going to get
something back in there this summer, especially with the help of
some El Niûo moisture," says Duncan. "The skeletons of the
tamarisk will remain for a long time, providing some soil retention
and a nursery bed for other plants. It won't be like a parking lot
As for DeLoach, he can't help but
note the irony of being held up by a bird that could ultimately
benefit from his insects.
"I don't want to damage
the willow flycatcher, but it's clear that the willow flycatcher
has been hurt by saltcedar," says DeLoach. "There are 50 other
endangered riparian species that could benefit from biocontrol of
saltcedar. The Fish and Wildlife Service needs to look at the
benefits to the whole ecosystem, not just the willow flycatcher."
Curt Deuser could really use DeLoach's
insects. He heads an elite, 10-person tamarisk control team for the
National Park Service out of Nevada's Lake Mead National Recreation
Deuser's team uses a two-step approach:
One person chainsaws a tamarisk tree at the base and another
quickly sprays on a chemical called Garlon before - within 30
seconds - the tree's cells close.
This method is
pretty effective for the side canyons and streams where tamarisk is
just getting established, says Deuser, whose team has cut and
sprayed in Arches National Park and Colorado National Monument, as
well as at Lake Mead. But it is no threat to tamarisk in the larger
scheme of things.
"I was driving along the lower
Colorado the other day, and I just couldn't believe how much
tamarisk is out there," Deuser says. "We need biological control
(insects) to knock back the immense tamarisk seed source along the
mainstem rivers. Otherwise, whatever areas we clear will be
reinvaded, and we might as well just resign ourselves to living
with tamarisk monocultures along every river in the West."
That's no overstatement. Tamarisk is notoriously
fecund; it can reproduce vegetatively, growing shoots from its
extensive root system, or sexually, sending pinhead-sized seeds
into the air or water by the hundreds of thousands. The seeds
sprout wherever they encounter moist soil. Once established,
tamarisk resists drought better than native cottonwoods.
In Arizona, The Nature Conservancy has battled
tamarisk for more than a decade on its 333-acre Hassayampa River
Preserve. Every summer weekend, a crew of volunteers - self-dubbed
Tamiwhackers - breaks out the chainsaws and the backpack sprayers
and goes at it, says preserve manager Greg Gamble.
"They've knocked out the biggest stuff on
two-thirds of the preserve," says Gamble, "but it's a treadmill.
New tamarisk seeds are always coming in and re-establishing
themselves. We feel we have a leg up on the problem, but it's never
going to go away."
Despite the difficulties in
attacking tamarisk, practitioners such as Deuser maintain that
their efforts can still pay big ecological dividends, especially in
areas where humans have not disrupted the natural hydrology. He
points to a place called Sacatone Springs in southern Nevada, where
his team began cutting and spraying in 1991, when tamarisk started
taking over a riparian area once dominated by willows, cottonwoods,
mesquite and other natives.
"The invasion there
had nothing to do with dams or anything else," he says. "Tamarisk
was just plain outcompeting the natives."
the tamarisk has all but disappeared and the natives have
vigorously reclaimed their turf. "We've seen the whole drainage -
maybe four miles long - come back with natives," says
Even Ohmart believes that getting rid of
tamarisk makes sense in places where the conditions are right - in
his book, where there is a natural flooding cycle and the absence
of bank-trampling, cottonwood-eating cows.
likes to cite Grand Gulch, Utah, where cows and tamarisk once ruled
an undammed river corridor below ancient Anasazi ruins. Twelve
years ago, the Bureau of Land Management removed the cows, and now
the tamarisk is dying back and the cottonwoods and willows are
returning, he says. "Last time I was there, I pulled out a
four-foot-tall tamarisk - by hand. You can't do that unless its
roots are weak," he says.
Ohmart speculates that,
absent the cows, the stream has begun to flood over the banks more
regularly, giving native vegetation a competitive
Still, he is skeptical about restoring
habitat along rivers such as the Colorado, the Rio Grande and the
Gila. "We'll never get rid of tamarisk along the mainstems, because
they are just too heavily managed."
The timing is
If anyone knows about fighting tamarisk along
a large Western river, it is Phil Norton, manager of the Bosque del
Apache National Wildlife Refuge in southern New Mexico. Norton
manages 13 miles of habitat along the Rio Grande near the town of
The refuge's primary mission is to
accommodate thousands of snow geese and sandhill cranes during the
winter, but for the past decade Norton has also tried to return
native vegetation to the tamarisk-choked banks of the river. His
work gained urgency two years ago, when a dense tamarisk patch
beneath a gallery of ancient cottonwoods caught fire and burned
eight miles of riverfront.
"We lost a couple of
thousand acres of cottonwoods and what has come back is tamarisk,
not cottonwoods," he says.
Over the years, Norton
has used every control method, including bulldozers and chemicals.
Each has its downside and none of them is cheap. "Bulldozing runs
about $500 an acre, and chemicals $100 an acre or more," he says.
Though Norton says introducing insects could
help reduce the cost of control, he is pinning his hopes on another
tool that most managers lack: a senior water right. With plenty of
water available, Norton tried to mimic the floods of a natural
river last year to see if that would give cottonwoods and willows
an advantage over tamarisk. He inundated a section of cleared
bottomland so that he would have a mudflat at the exact time that
cottonwood seed flies in May. Then he dropped the water back in the
weeks that followed.
"I thought we'd just grow
tamarisk, but we got stands of baby cottonwoods without any
tamarisk," Norton says.
Why did it work? Timing.
The cottonwood trees let their seeds fly a week before the
tamarisk. By wetting the mudflat and slowly drying it out right
after cottonwood germination, the managers didn't give tamarisk a
chance to get established, he says. "You've got to remember that
the cottonwoods evolved to release their seeds right at the peak of
spring runoff from the mountains," says
Norton hopes his experiments will
eventually prod water management agencies around the West to try
their own experiments.
"My argument is that the
river was never static," says Norton. "You don't want to manage for
a particular tree or simply because a flycatcher has been seen in a
particular tree. You want to manage for flux."
A tale of two
For most of its 96-year history, the
federal Bureau of Reclamation has built dams to subdue those wild
swings of water. Today, the agency no longer builds big dams, and
its leaders proclaim a new mission: water management for both
ecological and economic health. Releasing water from Glen Canyon
Dam to flood Grand Canyon two years ago (HCN, 7/22/96) symbolized
the agency's transformation. But the persistence of tamarisk is a
stark reminder that it will take much more than an occasional flood
to undo the ecological havoc wrought by
That stark truth is not lost on Debra
Eberts, a botanist and biocontrol expert for the Bureau based in
Denver, Colo. Eberts has secured money for much of Jack DeLoach's
work, even as the willow flycatcher issue has heated up. She says
people who believe the Bureau is merely looking at the
tamarisk-eating insects as a silver bullet to destroy the
ecological sins of its past are mistaken.
understand that revegetation is the big issue," she says. The
insects shouldn't be released until everyone has agreed on a set of
stipulations regarding how revegetation will be accomplished,
Eberts says. Hand-planting cottonwood plugs beneath the surface
layer of salty soil along rivers may be one way, she
But some biologists say they don't see
the Bureau making any real commitment to revegetation. "If the
Bureau said it was going to throw in $100 million over the next 20
years to change flow regimes from its dams and protect new
vegetation, then I'd feel a lot better about this (DeLoach's
insect) proposal," says Mark Sogge, a Flagstaff biologist who
studies the willow flycatcher for the United States Geological
Meanwhile, another agency in the
Department of Interior, the U.S. Fish and Wildlife Service, seems
hesitant to attack DeLoach's proposal. "It sounds like a valid
proposal," says Ron McClendon, an Endangered Species Act specialist
for the Service, based in Phoenix. "It might be that we could allow
the insects to be released outside flycatcher habitat in Wyoming or
Nevada. I just can't say." Because DeLoach has requested an
informal Endangered Species Act consultation, the agency has no
time limit on making a decision. Agency officials plan to meet in
early June to further discuss the proposal.
is going to be a tough call for the Service," says former agency
biologist Rob Marshall, who now works for The Nature Conservancy in
Tucson, Ariz. "You can't really do controlled experiments in the
wild, because there may be limited ability to control the insects
after they are released."
DeLoach says he could
live with a limited release. But even loosing the insects in prime
willow flycatcher habitat would not be a problem, he maintains,
because they would not immediately kill all of the tamarisk in the
"Biocontrol itself is not total," says
DeLoach. "There's never been a case of biocontrol eradicating
anything. We just see reductions."
A silver lining?
It seems that almost everyone involved in the
tamarisk debate understands that getting rid of tamarisk cannot be
separated from the task of restoring rivers and streams.
"We need to resist taking a classic USDA
approach to the tamarisk: "It's an alien bolshevik invader that we
need to crush before it crushes us," "''''says biologist Michael
Scott with the USGS. "This plant causes problems, but it hasn't
created them. We've dammed and diverted flows, irrigated saline
soils and cleared the land. Just talking about getting rid of
tamarisk is playing around the edges."
says getting serious about addressing riparian restoration will
require fundamental changes. "Are we willing to do the things it
takes to bring back riparian areas - buy easements, move people out
of the floodplains and retire irrigation from saline soils?" he
Ohmart, for one, doubts it. "When all is
said and done, more will be said than done," he says. "Maybe 50
years from now, when our water is so salty and filled with selenium
that it is unusable, the public will finally say, "let's take out
the dams." But it won't happen in my lifetime."
But the tamarisk debate has started a long
overdue public dialogue that could lead to substantial changes.
Says Mark Sogge, "This proposal to introduce
insects has forced us to ask whether there is something we, as a
society, want to do about our riparian areas."
Paul Larmer is the editor at
High Country News' syndicate, Writers on the Range. Reach him by
e-mail at firstname.lastname@example.org.
can contact ...
* Bob Ohmart at the Center for
Environmental Studies, Arizona State University,
* Jack DeLoach, U.S.D.A.
Agricultural Research Service, 817/770-6531 or email:
* Scott Stenquist,
Regional Integrated Pest and Weed Management Coordinator, U.S. Fish
and Wildlife Service, Portland, Ore.,
* Or, for a detailed scientific
discussion of the tamarisk management controversy, check out the
proceedings of the 1996 Saltcedar Management and Riparian
Restoration Workshop held in Las Vegas, Nev., placed on the Web by
the U.S. Fish and Wildlife Service: