What makes a weed stand out as an early detection target
in a certain area?
In broad strokes, it is a
combination of high potential impact, low current distribution, and high feasibility of control.
While the Bay Area Early Detection Network (BAEDN) was active,
Calflora worked to support their efforts to collect
observations of plants on the
Bay Area Early Detection Weeds list.
How the BAEDN folks came up with their list is fascinating,
and is described in detail in
Once the BAEDN list was made public, it had the effect of
catalyzing the data collection efforts of many individuals and agencies in
the Bay Area. As a result, we know much more now about
where those weeds are growing and spreading in Bay Area counties.
For instance, there were 20 records of
Rytidosperma penicillatum (purple awned wallaby grass)
reported in the Bay Area before June 1, 2011. Since that date,
an additional 1150 records have been reported in the Bay Area.
As it turned out, this weed is much more widespread than expected,
so widespread that it does not really qualify as an early detection target.
But, nobody knew how widespread it was before the data collection
effort inspired by the BAEDN list.
© 2010 Robert Steers/NPS
Choosing Target Weeds
In 2009, when Andrea Williams worked for the National Park Service,
she wrote the following in her description of
a volunteer based protocol
Detection of Invasive Plant Species in
the San Francisco Bay Area Network):
"The list of target species for each park was based on current knowledge and rankings, summing
recognized invasiveness and biological ease of control and stratifying into priorities by feasibility
of control based on species' infested acreage in the park." (pg. xvii)
National Park Service Resource Brief
further explains the protocol:
exotic plants on SFAN land
are classified into four lists, from high to low priority.
The point of invasive plant early detection is to
find potentially problematic invasive plants ...
while they can still be easily controlled ...".
Collecting adequate data is fundamental, and is used
- To determine the distribution and abundance of target invasive plant species
- To measure the success of removal activities
- To understand how different invasive plants threaten local ecosystems
- To re-prioritize which species and locations to target on future surveys
- To determine the factors that
lead to new infestations