[APWG] Invasive Chinese brake fern - Environmental custodian or environmental catastrophe?

[Patricia_DeAngelis at fws.gov]

It appears that Washington state is taking a sound approach to potentially
using Pteris vittata in phytoremediation - interesting that the last
paragraph on the article was left out of the summary.  I've pasted it at
the end of the summary...

Read on...

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From the latest NWFP-Digest-L (No. 9/05):

Back issues of the Digest may be found on FAO's NWFP home page:
www.fao.org/forestry/site/12980/en


7.         Ferns: Arsenic-eating fern holds hope for tainted soils
Source: Environmental News Network, 21 June 2005 CFRC Weekly Summary
6/30/05

Tacoma, Washington, USA.– State pollution fighters planted a small patch of
pitiful-looking plants inside a wire cage in Tacoma's Point Defiance Park
and labelled them poison.
            The 100 subtropical ferns inside the test plot near Fort
Nisqually are part of a two-year, $30,000 experiment in pollution control
that began in April on Vashon and Maury islands. "We just want to know
whether it's taking arsenic from the soil. We're watching for other things,
but that's our primary objective," said Norm Peck, a state Department of
Ecology investigator.
            Four years ago, scientists in Florida found that Chinese brake
ferns (Pteris vittata) thrive on arsenic, sucking the poison out of soil
and concentrating it in their fronds. A company now markets the ferns as a
pollution solution for arsenic-plagued communities.
            Ecology Department officials decided to test whether the ferns
will grow locally and reduce soil contamination in areas affected by
windborne arsenic from the former Asarco smelter. Its smokestack and
buildings have been demolished, but the site, adjacent neighbourhoods and
nearby shoreline are the focus of a federal Superfund cleanup. Beyond that,
elevated concentrations of arsenic, lead and cadmium still taint soils in a
1,000-square-mile area around Puget Sound.
            Health officials have cautioned residents in many parts of
Pierce and King counties to limit exposure to contaminated dirt because of
the risks of long-term arsenic exposure. Children are particularly
vulnerable. Earlier this year, Metro Parks agreed to allow the
Tacoma-Pierce County Health Department to sample soils at about a dozen
sites at Point Defiance and other Tacoma parks. So far, about half --
including those in Point Defiance -- have been sampled. Detected arsenic
concentrations have not been high enough to warrant alarm, said Glenn
Rollins, a health department environmental health specialist.
            As for the ferns, scientists in the Florida laboratory
experiments measured arsenic concentrations in them that were as much as
200 times higher than in the soil where the plants grew. "The fronds
themselves will become poisonous," said Marian Abbett, an environmental
engineer who oversees the Ecology Department's Tacoma smelter project.
            Pteris vittata, as scientists call the ferns, looks a lot like
native sword ferns. But Chinese brake ferns are considered invaders in
Florida, where they dominate their habitat. "We don't think it will be an
invasive here. In fact, we're concerned whether we're going to keep it
alive," Abbett said. "They like the warmer, tropical climate."
            Bhaskar Bondada, a Washington State University plant
physiologist who studied the fern in Florida, said that the beauty of this
plant is it only accumulates arsenic in the fronds, which are easily
picked. But in the process, the fern also converts arsenate to arsenite,
which is more toxic, he said.
            In all, Ecology Department officials bought 750 plants for $5
each.
            Rita Schenck, who runs the Institute for Environmental Research
and Education on Vashon Island, said she thinks the ferns should be
studied, but she urged caution. They could prove to be invasive, she said.
Besides that, the fronds might have to be buried in a hazardous waste
repository.
            "We have to harvest the leaves," Abbett said. "They can't just
fall back on the ground." Nor does the Ecology Department plan to compost
them, she said. The plan is to test the arsenic concentrations and decide
whether the fronds are hazardous before dumping. Regular soil testing also
is planned.
For full story, please see: www.enn.com/today.html?id=8014

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The final (and important) paragraph that was left off the above summary:

Lois  Stark, a Metro Parks planner, said she's confident Ecology Department
officials  will  make sure the plant doesn't prove to be a problem in Point
Defiance.
"They're not just planting them and walking away," she said.



Patricia S. De Angelis, Ph.D.
Botanist - Division of Scientific Authority
Chair - Plant Conservation Alliance - Medicinal Plant Working Group
US Fish & Wildlife Service
4401 N. Fairfax Dr., Suite 750
Arlington, VA  22203
703-358-1708 x1753
FAX: 703-358-2276
Working for the conservation and sustainable use of our green natural
resources.
<www.nps.gov/plants/medicinal>