September/October 2002
War on Weeds
by
Bonnie Harper-Lore
Anyone
who has swatted mosquitoes buzzing around a patio or pulled weeds
in a vegetable garden knows that nature often does not obey human
or political boundaries, even those between countries. And nature's
weeds find the roadsides along highways particularly attractive.
Invasive
plant species, otherwise known as non-native weeds, can be accidentally
or intentionally introduced into a landscape. Invasives can have a
devastating impact on native ecosystems, out-competing native plants
and crops for space, light, water, and nutrients. Scientists blame
invasive plants for a variety of environmental and economic ills,
including the loss of wildlife habitat, grazing lands, agricultural
crops, land values, biodiversity, wetland function, and recreational
use.
In May
2002, to help combat the continent-wide problem of invasive plant
species, the Federal Highway Administration (FHWA) sponsored an interagency
international conference on invasive plants. The "Weeds across
Borders" conference in Tucson, AZ, brought together approximately
100 vegetation management professionals from Canada, Mexico, and the
United States to share their experiences managing invasive plants
along roadsides.
![Photo of purple loosestrife Photo: Bonnie Harper-Lore, FHWA](images/01loosestrife.jpg)
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The
majority of attendees noted that purple loosestrife is a wetland
pest in their country, although few reported it in Mexico
at this time.
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All
photos by Bonnie Harper-Lore, FHWA unless otherwise noted. |
Highways
crisscross and connect all three countries, and the transport of people,
plants, animals, and products along the roads serves as a conduit
for introducing invasive plants. As Roy Reichenbach, weed and pest
program coordinator at the Wyoming Department of Agriculture, says,
"Most weeds left to their own devices don't really travel, but
once they enter interstate commerce, they can go a long way."
A recent
increase in the coordination of Federal and State efforts to control
weeds led to interest in what Canada and Mexico are doing to manage
the threat of invasive plants. The Weeds across Borders conference
provided a forum to learn about our neighbors' activities, as well
as to explore common weed problems, applied research, best management
practices, and opportunities for international cooperation.
Invasive Plants 101
When
invasive plant species—also called exotics or aliens—are
accidentally or intentionally introduced into a new environment, they
are free from the natural competitors that existed in their places
of origin. They can adapt to their new environments quickly and proliferate
aggressively—often at the expense of native plants and wildlife
in the area.
Documented
conduits for accidental introductions include agricultural seed, livestock,
packing materials, immigrants, and ship ballasts. Leafy spurge and
spotted knapweed are common examples of accidentally introduced weeds.
![Photo of spotted knapweed Photo: Bonnie Harper-Lore, FHWA](images/01napweed.jpg)
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The
spotted knapweed is an invasive plant found throughout the
West.
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Many
intentional introductions occur when horticulturists or farmers import
nonnative plants from other countries to solve agricultural problems
such as the need for rigorous and hardy pasture grasses (e.g., reed
canary grass) or for use as ornamental plants (e.g., Russian olive).
Although
many invasive plants travel to their new environments from other countries
or continents, some plants that Americans consider "native"
are actually invasive. The black locust, Robinia pseudoacacia,
for example, is native to the Appalachian Mountains, but it became
invasive in other regions of the United States when farmers and other
landowners began transplanting the trees for use as windbreaks or
to cut for fence posts.
Controlling Weeds in the United States
Most
States have noxious weed laws listing the plants that are most troublesome
to agriculture, human health, and the environment. State weed lists
may contain as few as 4 plants, or as many as 124 species, that State
and county weed inspectors monitor or control. Eleven States do not
have specific weed laws at all.
![Photo of raised bank covered with reed canary grass along road Photo: Bonnie Harper-Lore, FHWA](images/03canarygrass.jpg)
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Reed
canary grass, shown here growing on a raised bank along a
highway, is an example of an intentionally introduced invasive
plant.
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Recently,
the Western Governors' Association called for a list that their States
could use for targeting improvements for the prevention and control
of invasive plants.
Since
1993, 16 Federal agencies have pooled their resources to deal with
invasive plants. In 1994, the agencies signed a memorandum of understanding
that created the Federal Interagency Committee for the Management
of Noxious and Exotic Weeds (FICMNEW) as a mechanism to share information
and resources in what the committee refers to as the "war on
weeds."
By 1999,
scientists at every level of government and land management recognized
the costly economic and environmental impacts of uncontrolled invasive
plants. A letter signed by 500 scientists prompted then-President
Bill Clinton to issue Executive Order 13112 on invasive plants, announced
on Earth Day 1999. The executive order, which defined invasive species
as "an alien species whose introduction does or is likely to
cause economic or environmental harm or harm to human health,"
directed all Federal agencies to review the issue of invasive plants
and attempt new levels of cooperation, communication, and information-sharing.
The order
also created the National Invasive Species Council to write a national
plan and oversee efforts to control invasive plants and animals. The
council published its plan in 2001, and, since then, individual States
have begun establishing stakeholder councils to address local concerns.
These councils connect with the national council for support and information
exchange.
In 2002,
when Cornell University reported that the annual economic impact of
invasive plants in the United States exceeded $37 billion—including
crop and forage losses, property devaluation, and control costs—the
National Invasive Species Council began seeking congressional action
to support a national war on weeds and funding for research, prevention,
control, and public education.
Applied
Research along the Borders
The Weeds
across Borders conference offered a forum for representatives from
Canada, Mexico, and the United States to open a dialogue on invasive
plants. During one plenary session, researchers from each country
shared the results of applied studies dealing with invasive plants
along the U.S. borders.
At the
U.S.-Canadian border, the Canadians want to stop the northward migration
of the saltcedar tree, a common invasive tree in the western
United States. According to research conducted by Cheryl Pearce at
the University of Western Ontario, the common saltcedar, or Tamarix
ramosissima, continues to adapt and move northward, now taking
root within 100 miles of the Canadian border. Pearce's research found
that one source plant in Montana has been linked to 30,000 saltcedar
seedlings.
At the
U.S.-Mexican border, the U.S. Department of Agriculture is considering
introduction of the alien buffelgrass as a pasture grass. But vegetation
managers in Mexico are monitoring the spread of this invasive plant,
which has proved to be a costly problem on the Mexican side of the
Sonoran desert. Alejandro Castellanos, a professor at the University
of Sonora in Mexico, has documented the introduction of this grass
from Africa and its movement through arid lands in northern Mexico.
Originally introduced to improve rangelands, buffelgrass has a propensity
to burn easily. Historically, fire is uncommon in the desert because
sparsely growing plants cannot carry a fire, but after the introduction
of buffelgrass, fires have become more common. Because most desert
plant communities cannot tolerate this kind of burn, they consequently
decline, resulting in diminished plant diversity and wildlife habitat.
![Photo of leafy spurge Photo: Bonnie Harper-Lore, FHWA](images/03leafyspurge.jpg)
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The
Wyoming Department of Agriculture uses biocontrols to manage
the invasive leafy spurge.
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Cornell
University's Tony DiTomasso, who researches roadside management issues
in Quebec, explained how electing not to manage one particular invasive
plant actually caused problems in protecting human health. After Quebec
banned the use of herbicides in urban corridors, common ragweed—an
invasive plant whose seeds remain viable for 40 years and whose pollen
can travel as far as 250 miles in the wind—increased dramatically,
creating severe medical problems for individuals with allergies. While
eliminating the use of herbicides, vegetation managers actually exacerbated
the ragweed problem.
Ultimately,
DiTomasso's example illustrates the need for additional research,
information-sharing, and consideration of multiple strategies for
invasive plant control.
Attendees
Share Best Practices
Another
session of the Weeds across Borders conference focused on the prevention
and control of invasive plants. Representatives from each country
described their best practices in preventing the spread of invasives.
Geographic information system (GIS) mapping, the use of biocontrols,
and weed-free forage and mulch were among the management strategies
shared by attendees.
Ira
Bickford, maintenance chief with the Utah Department of Transportation
(UDOT), reported on UDOT's innovative Roadveg system, which uses GIs
to inventory invasive plants. By mapping the location of invasive
plants along with other standard transportation-related data, vegetation
management professionals can track the spread of invasives or monitor
the progress of mitigation strategies. UDOT also included invasive
species in its decision-making process mandated by the National Environmental
Policy Act. The agency documented potential environmental impacts
and listed appropriate best management practices as mitigation commitments
for all projects that have the potential to spread or introduce listed
weeds.
![Photo of kudzu, Russian Olive, Tree of Heaven Photos: Bonnie Harper-Lore, FHWA](images/03weeds.jpg)
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A
few invasive weeds: Kudzu (left), Russian Olive (below center),
and Tree of Heaven (right).
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![Photo of salt cedar, black locust, star thistle Photos: Bonnie Harper-Lore, FHWA](images/03plants.jpg)
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Salt
Cedar (left), Black Locust (center), and Star Thistle (right).
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The State
of Wyoming found that biocontrols (natural insect enemies of weeds)
are highly effective in controlling certain pesky plants. Roy Reichenbach,
weed and pest program coordinator at the Wyoming Department of Agriculture,
reported that biocontrols helped the State manage two invasive plants,
the musk thistle and leafy spurge.
"Thanks
to two insects, Rhinocyllus conicus and Trichosirocalus
horridus, we have seen the musk thistle population collapse,"
Reichenbach said. "We used to have hundreds of thousands of acres
of it in Wyoming, but the biocontrols have been so effective we are
thinking of removing musk thistle from the designated weed list."
Wyoming,
nine other States, and a Canadian province are participating in a
certified weed-free forage and mulch program sponsored by the North
American Weed Management Association. "Forage," which is
vegetation fed to livestock, also is a term used to certify mulches
in many western States. The certification process involves a certifier
walking the fields of origin and surveying the field boundaries for
evidence of noxious plants. Once certified, the forage or mulch can
be baled and marked with color twine, or otherwise tagged as certified.
The Wyoming
Department of Transportation uses certified weed-free seed and mulch
to keep weeds from entering the environment at construction projects.
Seed packers use different screens and blowers in the packaging process
to remove weed seeds, and laboratory analyses help ensure the purity
of the final seed product. Many State departments of transportation
(DOTs) now specify weed-free seeds and mulches on construction and
reseeding projects.
Montana
State agencies, including the Montana Department of Transportation
(MDT), also participate in weed-free forage programs. The Montana
Department of Agriculture now monitors and certifies forages as "weed-free,"
while MDT specifies the use of weed-free mulches on all of its highway
projects. This interagency cooperation provides farmers with a more
pure feed option and
promises to help MDT avoid inadvertently introducing weed seeds during
construction projects.
![Photo of man speaking to crowd in the Santa Rita Experimental Range Photo: Faith Campbell](images/03inthefield.jpg)
Photo
by: Faith Campbell
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In
the field, the Canadian, Mexican, and U.S. attendees witnessed
invasive plants spreading across the Santa Rita Experimental
Range.
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Information
Exchange
In the
course of the discussions, conference attendees provided updates on
current projects and offered recommendations on strategies for sharing
information. Shaffeek Ali, head of pest risk management with Alberta
Agriculture, Food, and Rural Development in Alberta, Canada, noted
that his country, like the United States, historically tended to be
more reactive in dealing with invasive plants. He recommended that
vegetation managers focus more on preventative and proactive measures.
In the interest of sharing information, he told attendees that the
invasive plant, scentless chamomile, is a widespread problem in Alberta
and advised that measures be taken to prevent this weed from becoming
established in the United States. Canada already has developed containment
programs to control the weed.
"By
alerting each other to certain weed species that have become problems
in certain areas, and sharing control strategies," Ali said,
"we can avoid recreating the wheel and save resources as well.
Alberta, for example, undertook an eradication program for diffuse
and spotted knapweed to avoid the large infestations that are present
now in Montana and British Columbia."
Richard
D. Lee, an extension weed scientist at New Mexico State University,
pointed to rapid response as a highly effective tactic for controlling
invasives. "If, while working in the field, traveling down a
road, or even walking to a favorite camping site, you recognize an
invasive weed, then pull it up, bag it, and dispose of the culprit,
and notify the landowner of your find," he said. "Taking
a few minutes and eliminating a single plant could prove to be much
more effective than attending a dozen weed meetings."
Bruce
Eilerts of the Arizona Department of Transportation (ADOT) reported
to attendees on one of the first international roadside vegetation
agreements on the control of invasive plants. Vegetation managers
from ADOT, following in the footsteps of highway design and construction
engineers when they go across the border, will begin demonstrating
management methods to their colleagues in Sonora, Mexico. With this
precedent established, other border States could consider similar
information exchange partnerships.
John
Randall, director of The Nature Conservancy's wildland invasive species
team, discussed the results of a recent workshop in St. Louis, MO,
aimed at exploring new ways to stop the introduction and spread of
unwanted plant species. Botanical garden representatives, nursery
professionals, landscape architects, garden clubbers, and government
experts put their heads together to produce the St. Louis Declaration
on Invasive Plant Species, a document listing findings from the
workshop.
Be
Alert for These Roadside Invasive Top 10
1.
Kudzu, Pueraria lobata—spreads from Washington,
DC, to Portland, OR.
2.
Purple loosestrife, Lythrum salicaria—invades wetlands
in all 50 States.
3.
Leafy spurge, Euphorbia esula—compromises grazing
and Western State economies.
4.
Spotted knapweed, Centaurea maculosa—moves throughout
the West and eastward.
5.
Star thistle, Centaurea solstitialis—degrades natural
areas and rangeland.
6.
Giant phragmites, Phragmites australis—reduces diversity
in wetlands.
7.
Reed canary grass, Phalaris arundinacea—infests
wetlands across the country.
8.
Russian olive, Elaeagnus angustifolia—dominates
lowland forests and pasture meadows.
9.
Tree of heaven, Ailanthus altissima—appears from
coast to coast.
10.
Black locust, Robinia pseudoacacia—decreases biodiversity
in deciduous forests.
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The declaration
contains a set of draft voluntary professional codes of conduct one
produced by each professional or interest group at the workshopdesigned
to curb the use and distribution of invasive plant species through
self-governance and self-regulation. The American Nursery and Landscape
Association, the American Society of Landscape Architects, and the
Garden Club of America already have endorsed the codes of conduct
designed for their groups.
According
to Ron Hiebert, research scientist with the U.S. National Park Service,
100 highways go across the U.S.-Canadian border and 20 cross the U.S.-Mexican
border. In order to monitor these borders effectively, Hiebert recommended
that agencies agree on a risk assessment model to determine priorities
for which weeds to watch. Hiebert discussed how he and colleagues
at The Nature Conservancy are collaborating to design such a model.
Continental
Cooperation
Following
a day-long field trip to the Mexican border and group discussions
at weed-infested stops along the way, the conference concluded with
a review of existing international frameworks to support further cooperation.
Each framework offers a piece of the puzzle that can help control
invasive species in the Western Hemisphere and beyond.
The Global
Invasive Species Programme (GISP) serves as an umbrella organization,
facilitating the operation of the Global Invasive Species Information
Network. Currently GISP is focused on aquatic nuisance species, and
it will be 3 years before GISP begins work on invasive terrestrial
plant species.
One of
GISP's 10 strategic responses to the problem is to promote information-sharing.
Already, 120 major sources of information on invasives are available
electronically. Among GISP's projects to improve the exchange of information
are linking regional and national databases, developing an early warning
system to share alerts of new threats,
and establishing a database of case studies detailing successful control
methods.
The Comisión
Nacional para el Conocimiento y Uso de la Biodiver-sidad (CONABIO)
is an organization dedicated to building a national database for all
biological resources in Mexico (www.conabio.gob.mx). The group uses
the data to understand biogeographical patterns and
centers of biodiversity and to make more informed conservation choices.
So far, CONABIO has developed a GIS database for invasive species
in Mexico and most of South America (14 countries), enabling it to
predict future hot spots and distribute warnings about invasives based
on a plant's biological characteristics and the biogeography of regions
south of the equator. CONABIO also is contributing to the development
of an information hub for all of North America.
Established in 1993, the North American Weed Management Association
(NAWMA) is a network of public and private professional weed managers
who are involved in implementing any phase of a local, State, or Federal
noxious weed law (www.nawma.org). NAWMA meets the needs of on-the-ground
vegetation managers, offering educational opportunities, regulatory
direction, professional development, and environmental awareness geared
toward preserving and protecting the continent's natural resources
from exotic, invasive, and noxious weeds. NAWMA's current goals include
establishing
and maintaining standards for North American weed-free forage (mulch),
developing international mapping and data standards for invasive plants,
and defining a certification program for invasive plant managers.
The World
Conservation Union (IUCN), founded in 1948, brings together States,
government agencies, and diverse nongovernmental organizations from
nearly 140 countries into a global partnership to protect biodiversity
and manage habitats and natural resources (www.iucn.org). IUCN believes
that improved education within the international community is essential
to stopping the spread of alien species, and the organization recently
finalized a set of guidelines for preventing biodiversity loss due
to invasive species. Another IUCN concern is the buying, selling,
and shipping of plants globally through e-commerce.
Since
its creation in 1951, The Nature Conservancy's (TNC) mission has been
to preserve the plants, animals, and natural communities that represent
the diversity of life on Earth by protecting the lands and waters
they need to survive (www.tnc.org).
Because invasive species are among the gravest threats to TNC's mission,
eradicating non-native weeds is now one of the organization's five
goals for the Western Hemisphere.
"We
need to have a system to better understand where invasives are and
where they are coming from," says Ann Bartuska, executive director
for the invasive species initiative at The Nature Conservancy. "When
we see new invasives, we need to be able to identify them quickly
and mobilize a rapid response tocontrol them before they become established."
![Photo of thistle along roadway Photo: Bonnie Harper-Lore, FHWA](images/03thistle.jpg)
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The
Canadian thistle threatens croplands nationally.
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Established
in 1952, the North American Plant Protection Organization (NAPPO)
is a partnership of Canada, Mexico, and the United States to protect
North American plant resources from the entry, establishment, and
spread of regulated plant pests, while facilitating intra/interregional
trade (www.nappo.org). Because
key stakeholders include a much broader audience than environmentalists,
policy decisions take
into account economic and trade issues in addition to environmental
issues.
Tying It All Together
After
representatives from each country and various agencies reported on
the status of their weed problems, highlighted ongoing research, and
presented best management practices, the attendees had established
a common ground for discussion using a broad North American focus.
At the close of the
conference, the attendees had the opportunity to use a new keypad
technology for completing an opinion survey to learn more about each
other.
Attendees
learned, for example, that 53 percent of their peers had traveled
more than 1,600 kilometers (1,000 miles) to attend the conference,
demonstrating truly continent-wide interest in the subject matter.
The majority—73 percent of attendees—had come from various
regions and agencies in the United States, not surprising given the
home-court advantage. Canadian and Mexican attendees were equally
divided in the remaining 27 percent. The make-up of the participants
included 47 percent scientists and 22 percent policy-makers.
Major
findings revealed through the opinion survey include:
1. Most
attendees (92 percent) agree that they do not have adequate funding
for invasive plant prevention and control.
2. Attendees
strongly support a North American information exchange.
3. Attendees
believe that an international agreement would be helpful in establishing
uniform goals and making funding a higher priority.
4. Workers
at all levels in Canada, Mexico, and the United States have access
to the Web, indicating that the Internet is a logical means for sharing
information.
5. Attendees
agree that early detection is the highest priority for controlling
invasive species.
6. State,
Federal, and university representatives prefer biocontrols to other
available vegetation management tools.
7. Attendees
believe that road-building and housing developments surpass overgrazing
as the most common activities that lead to plant invasions.
The attendee
responses to question 7 about road-building's contribution to spreading
invasive plants highlights the importance of raising awareness of
invasives within the transportation industry and confirms the value
of continent-wide cooperation, especially along interstates.
"Even
though invasive species represent a huge problem, it is one that we
can do something about," says The Nature Conservancy's Ann Bartuska.
"You can see the results of your success right in front of you,
whether it's watching native prairie plants come back inTexas after
Chinese tallow was eradicatedorseeing hikers clean off their boots
to prevent spreading seeds on their next hike."
As State
DOTs explore ways to implement Executive Order 13112 by reviewing
internal policies, vegetation management practices, and construction
processes, FHWA will continue fostering cooperation with the Nation's
neighbors to the north and south. In the war on weeds, your neighbors
are your allies, and information is your best artillery.