Humboldt County Weed Management Area Questionnaire
by Liz McGee
In the plant world invasive weeds and native plants generally do not thrive
together. However, in the human realm, the Northcoast chapter of the CNPS and
the Humboldt County Weed Management Area (HWMA) have developed a mutually
beneficial partnership. With the support of CNPS, the HWMA has been able
to secure funding and complete an initial report on invasive weeds in Humboldt County.
The HWMA is a consortium of public agencies,
organizations and private landowners committed to controlling weed species
throughout the county. A Memorandum of Understanding (MOU) between several agencies
and organizations, including the BLM, US Forest Service, US Fish and
Wildlife Service, CalTrans, UC Extension, and CNPS. The purpose of the MOU is
to formalize the cooperative relationship among these agencies and
organizations in order to effectively manage and implement invasive species
programs. With a formal agreement in place the HWMA has been applying for
funding from the State.
The North Coast Chapter has been the main cooperating organization that has made
it possible for the HWMA to receive funding from the California Department of
Food and Agriculture (CDFA). The CDFA grants are contingent on matching funds
or in-kind support from any entity that has signed the MOU. Through our
president and board, chapter agreed to provide matching support and
the personnel to complete a survey of the invasive weed species found throughout
A questionnaire was sent to seventeen agencies and organizations in spring 2000.
This questionnaire is the beginning of the development of a
comprehensive database and map of invasive weeds within the HWMA area. A
description and the results are provided here to show how
our chapter has contributed to the effort to control invasive weeds.
The HWMA steering committee decided to send out a questionnaire in order to
find out what is known and what we do not know about individual weed species in
the county. A list of 48 species was compiled and combined with 11 questions.
Each land manager or representative filled in the appropriate box on a
spreadsheet to provide vital information about each species. The information
sheet was mainly sent to public land agencies because they have compiled the most
information about weed species. The topics covered in the questionnaire
included presence, control methods, rate of spread, economic impact, whether or not
the species was mapped, and a rank of dominance. Thirteen of the seventeen
questionnaires were returned. It
is estimated that the information in the responses
covers almost half of the county lands.
Besides the initial 48 species, many agencies had additional species impacting their
lands, which brought the total to 62. The most frequently reported
species were Pampas grass (Cortaderia jubata), Scotch broom
(Cytisus scoparius), Himalaya berry (Rubus discolor), and English ivy
(Hedera helix). According to questionnaire responses, dogtail grass
(Cynosurus echinatus) had the highest number of acres, followed by
yellow star thistle ( Centaurea solstitalis).
Other species that had high acres were some of the annual
grasses, Scotch broom and French broom ( Genista monspessulana). These acres
were estimated and should not be used as actual size of the infestations.
The responses from the questionnaire showed that only 16 of the 62 species have
populations that are mapped. There are more maps of yellow bush lupine (Lupinus
arboreus) than of any other species. Four agencies have maps of this species.
The lack of maps is clearly a data gap in our information on invasive weeds.
There is a need to do more inventory and mapping on a county-wide scale.
The land managers who completed the questionnaire were asked how each species
ranked in terms of aggressiveness or dominance over other species. Most species
were ranked as low to moderate in dominance. Twenty-three species (37%) were
ranked as severe threats to ecological stability. Some species fit within
several categories depending on which agency was responding. This
type of response was expected and indicates areas within the county where
certain species could be easily controlled or areas that need to be protected
from further infestation.
"Other" was the most common response to the impact a weed species may have on a
natural resource. There are 33 species in this category. Twenty
species are threats to Threatened and Endangered species, and 17 impact system
processes. Only 8 species were reported to be threats to range value. They include
several annual grasses, yellow star
thistle, bull thistle (Cirsium vulgare), Canada thistle (Cirsium arvense),
and tansy ragwort (Senecio jacobaea). Yellow star thistle
was reported to impact all of these resource categories.
The majority of the species are controlled manually or with chemicals. Three
species were controlled using biological methods, and three using other methods.
Further information could be obtained about which chemical, biological and
other methods are being used to control noxious species.
A date for the first sighting of an infestation was provided for twelve species.
The USFWS and
the BLM were the only agencies that reported these dates. European beachgrass
(Ammophila aranaria), dense-flowered cordgrass (Spartina densiflora), and yellow
star thistle all were reported as first sighted in 1900. Most of the other species
were sighted before 1970. The latest initial sighting was of purple ragwort
Most species are spreading at a medium to fast rate according to the survey
responses. As with the ranking question, these responses varied with agency.
Several species were reported to be spreading slow, steady or fast, depending on
the reporting agency. This would indicate that some areas of the county are at
decreased threat from some species.
Three species were reported to have an economic impact to the County. These
are yellow star thistle, medusa-head rye, (Taeniatherum caput-medusae),
and tansy ragwort.
The information garnered from this questionnaire has been used to compile a list of
the most invasive species in the County (see side boxes). With continued support from
CNPS and funding from the CDFA, the HWMA will begin to inventory and map invasive species
and produce a weed management plan within the next year. If you would like more
information about the HWMA or how you can become more involved in this effort you can call
Lisa Hoover at 441-3612 or Jennifer Wheeler at 825-2316.