Dear Conchlers,
I am back after a few days' absence. My computer is so full of unread email
messages that the electrons are dripping onto the floor, and I am sitting
in the slop.
The following message is from the Taxacom listserve. Basically, it
recommends not collecting any specimens (of rare plants) until the
collector has seen 20 specimens at the same location. Obviously,
paleontologists do not generally follow this kind of rule, except sometimes
at sites that are reserved for student use. What about collectors of living
shells? Would this sort of rule make a useful guideline, or is it
unworkable?
Andrew K. Rindsberg
Geological Survey of Alabama
Tuscaloosa, Alabama, USA
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David Wagner published his "Rule of thumb" in Oregon Flora On-line
Newsletter and elsewhere. This is a version from BEN (Botanical Electronic
News) # 180 (Dec. 12, 1997):
A RULE OF THUMB FOR BOTANISTS: THE 1 IN 20 RULE
From: Dr. David H. Wagner <[log in to unmask]>
originally published in the Oregon Flora On-Line Newsletter
Volume 1 Number 3 - Oregon State University - July 1995
There have apparently been instances in the past where well-meaning
botanists have destroyed plant populations through over
zealous collecting. The case most familiar to me concerns one of the
world's rarest ferns, the pumice grape-fern, Botrychium
pumicola. A student searching for new sites found two individuals of
this species on Oregon's Tumalo Mountain in 1954
which he collected to make herbarium specimens. In the late 1970s I
searched the top of Tumalo Mountain with friends. We
were experienced fern hunters, but we found no Botrychium. I strongly
suspect that the two plants removed in 1954 eliminated
the population at this location. Today we would hope that botanists
finding only one or two plants at a site would docu-
ment their discovery with photographs and notes. Good
photographs and careful field notes are increasingly acceptable
for recording plant discoveries.
Nevertheless, from time to time, a field worker may encounter a small
population of a plant and feel it is necessary to collect
a bit of it for positive identification and documentation. The Native
Plant Society of Oregon's Guidelines and Ethical Codes
for botanists urges that a collector use good judgement and rules of
thumb when deciding whether or not to collect. But in
this case, what is a good rule of thumb? During the past 10 years, I
have been using what I call the "1-in-20 Rule."
The 1-in-20 Rule dictates that a botanist never collect more than one
out of twenty plants. It means NOT collecting ONE plant
UNTIL you have found at least TWENTY. Only if twenty are found should you
consider collecting one plant. And forty should be
present before two are taken, and so on. The rule applies to parts of
plants, also: remove no more than five percent (one-
twentieth) of a shrub, one fern frond from a clump of twenty, 5% of a patch
of moss, 5% of seeds from a plant. I use the 1-in-20
Rule whether I am collecting voucher specimens for the herbarium,
doing rare plant work, or gathering common species for
classroom use.
The 1-in-20 Rule does not obviate the need for good judgement. Only when
a botanist has the knowledge to assess whether col-
lecting is both ecologically justified and legally permitted should a
specimen be taken. Any pertinent factor relating to the
survival of a population needs to be superimposed on the 1-in-20 Rule. The
main value of this rule of thumb is to provide a clear
point of reference from which to begin assessing a situation. It helps a
botanist determine how much time should be spent inven-
torying before sampling is appropriate. I suggest the 1-in-20 Rule as
a minimal criterion to be met before any taking of a
plant be considered.
There is at least a modicum of scientific logic behind this rule.
Statistically, a population sample of nineteen is not
significantly different from a sample of twenty. One population geneticist
I consulted advised me that contemporary statistical
theory would support the 1-in-20 Rule. Another pointed out, however,
that repeated collecting would tend to reduce every
population to nineteen individuals. This caution serves to emphasize
that the 1-in-20 Rule is a rule of thumb, not a
license to ravage.
An interesting line of argument in support of the 1-in-20 rule has
developed since I first published the idea in the Bulletin
of the Native Plant Society of Oregon in 1991. First, I received a letter
from James Grimes of the New York Botanical Garden
querying whether or not I had picked up the idea from a similar article he
and others had published in the newsletter of the
Idaho Native Plant Society a few years before. I honestly cannot recall
seeing their note. Then, last year, four botanists from
Australia and New Zealand published an article in the international
journal, Taxon, which made essentially the same recommen-
dation. Thus, three botanists or groups of botanists, deliberating
independently, have arrived at the same standard. I submit
that this concurrence from three separate sources speaks strongly
for the sensibility of the 1-in-20 Rule.
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