The CNPS Ranking Working Group was formed to review the ranking system in the
CNPS Inventory of Rare and Endangered Plants (Inventory) and discuss needed
modifications. This group decided to discontinue the use of the R-E-D
(Rarity-Endangerment-Distribution) Code and to instead convey this information
in a clearer way through modifying the CNPS List and including other information
in the Inventory. This decision and the associated modifications were approved
by the CNPS Board of Directors at their August 2005 meeting. The following
information is intended to provide an explanation of and rationale for this new
change to the CNPS ranking system.
Background
The R-E-D Code contains information on Rarity,
Endangerment, and Distribution, ranked as a 1, 2, or 3 for each value (as
below). This code was originally known as the R-E-V-D Code (through the 3rd
edition 1980), and the V (Vigor) was removed in the 4th edition (1984).
R - Rarity
1 – Rare, but found in sufficient numbers and distributed widely enough that
the potential for extinction is low at this time
2 – Distributed in a
limited number of occurrences, occasionally more if each occurrence is
small
3 – Distributed in one to several highly restricted occurrences, or
present in such small numbers that it is seldom reported
E - Endangerment
1 – Not very endangered in California
2 – Fairly endangered in
California
3 – Seriously endangered in California
D - Distribution
1 – More or less widespread outside California
2 – Rare outside
California
3 – Endemic to California
Modifications Associated with R-E-D Code
Discontinuation
The information contained in the R-E-D Code remains
in the Inventory, but the following new modifications express it more
clearly:
- A new Threat Code extension has been added following the CNPS List (e.g.
1B.1, 2.2 etc.). This extension replaces the E (Endangerment) value from the
R-E-D Code. The main difference is that the number coding is now reversed to
reduce confusion and represent this information in parallel with the threat
rankings that the California Natural Diversity Database (CNDDB) uses. Therefore
the logic is reversed so that the lower the number, the higher the corresponding
threat level.
New Threat Code extensions and their meanings:
.1 -
Seriously endangered in California (over 80% of occurrences threatened / high
degree and immediacy of threat)
.2 – Fairly endangered in California
(20-80% occurrences threatened)
.3 – Not very endangered in California
(<20% of occurrences threatened or no current threats known)
Note that all List 1A (presumed extinct in California) and some List 3 (need
more information- a review list) plants lacking any threat information receive
no threat code extension. Also, these Threat Code guidelines represent a
starting point in the assessment of threat level. Other factors, such as habitat
vulnerability and specificity, distribution, and condition of occurrences, are
also considered in setting the Threat Code.
- A “CA Endemic” entry is displayed in the Inventory entries for those taxa
that only occur in California. This clearly highlights endemic taxa.
- Information contained in the R (rarity) value of the RED Code is expressed
by displaying the state rank (S-rank) of the CNDDB.
- Out-of-state distribution information is retained by displaying the global
rank (G-rank) of the CNDDB.
- With the addition of G- and S-ranks, the following explanation of CNDDB
ranking will be included in the Inventory as explanatory material.
CNDDB ELEMENT RANKING
Global Ranking
The global rank (G-rank) is a reflection
of the overall condition of an element throughout its global range.
Species or Community Level
G1 = Less than 6 viable
element occurrences (EOs) OR less than 1,000 individuals OR less than 2,000
acres.
G2 = 6-20 EOs OR 1,000-3,000 individuals OR 2,000-10,000 acres.
G3
= 21-80 EOs OR 3,000-10,000 individuals OR 10,000-50,000 acres.
G4 =
Apparently secure; this rank is clearly lower than G3 but factors exist to cause
some concern; i.e., there is some threat, or somewhat narrow habitat.
G5 =
Population or stand demonstrably secure to ineradicable due to being commonly
found in the world.
Subspecies Level
Subspecies receive a T-rank attached to
the G-rank. With the subspecies, the G-rank reflects the condition of the entire
species, whereas the T-rank reflects the global situation of just the subspecies
or variety. For example: Chorizanthe robusta var. hartwegii. This plant is
ranked G2TI. The G-rank refers to the whole species range i.e., Chorizanthe
robusta. The T-rank refers only to the global condition of var. hartwegii.
State Ranking
The state rank (S-rank) is assigned much
the same way as the global rank, except state ranks in California often also
contain a threat designation attached to the S-rank.
S1 = Less than 6 EOs OR less than 1,000 individuals OR less than 2,000
acres
S1.1 = very threatened
S1.2 = threatened
S1.3 = no
current threats known
S2 = 6-20 EOs OR 1,000-3,000 individuals OR 2,000-10,000 acres
S2.1 =
very threatened
S2.2 = threatened
S2.3 = no current threats
known
S3 = 21-80 EOs or 3,000-10,000 individuals OR 10,000-50,000 acres
S3.1
= very threatened
S3.2 = threatened
S3.3 = no current threats
known
S4 = Apparently secure within California; this rank is clearly lower than S3
but factors exist to cause some concern; i.e. there is some threat, or somewhat
narrow habitat. NO THREAT RANK.
S5 = Demonstrably secure to ineradicable in California. NO THREAT RANK.
Notes:
- In reality, more factors are reviewed than just numbers of element
occurrences. Other considerations used when ranking a species or natural
community include the pattern of distribution of the element on the landscape,
fragmentation of the population/stands, condition of the individual populations,
and historical extent as compared to the plant’s modern range. It is important
to take a bird’s eye or aerial view when ranking sensitive elements rather than
simply counting Eos.
- Uncertainty about the rank of an element is expressed in two major
ways:
By expressing the rank as a range of values: e.g., S2S3 means the rank
is somewhere between S2 and S3. By adding a ? to the rank: e.g., S2? This
represents more certainty than S2S3, but less than S2.
- Other symbols: GH All sites are historical; the element has not been seen
for at least 20 years, but suitable habitat still exists (SH = All California
sites are historical).
- GX All sites are extirpated; this element is extinct in the wild (SX = All
California sites are extirpated).
- GXC Extinct in the wild; exists in cultivation.
- G1Q The element is very rare, but there are taxonomic questions associated
with it.
- T Rank applies to a subspecies or variety
Rationale for the Modifications
Though the R-E-D Code has
a long tradition within CNPS, it has caused confusion for users of the Inventory
and results in duplication of CNPS and CNDDB staff effort. These modifications
clearly highlight the threat component within the ranking system. This is
beneficial because the CNPS List is now a more effective prioritization tool for
conservation planning. Additional rationale for discontinuation of the R-E-D
Code is given below:
- The R value is mostly redundant vs. CNPS List (i.e. R=2 or 3, List 1B or 2;
R = 1, List 4) and not as useful as a ranking tool as CNDDB G- and S-ranks. G-
and S- ranks should be used as a finer cut for conservation prioritization (e.g.
S1 = 1-5 occurrences, S2 = 6-20 occurrences). As CNDDB tracks individual
occurrences, rarity values should come from them, not CNPS (who track by quad).
It is difficult for CNPS to keep the R values “correct” and seems to be needless
duplication of effort.
- The E value seems the most important for conservation ranking, and the
utility of this code is obfuscated by its placement in the poorly understood
R-E-D Code. It is highlighted by being extracted from the R-E-D Code and
incorporated as a Threat Code extension to the CNPS List. CNPS List is based on
rarity, and thus the Threat Code extension clearly highlights the endangerment
factor, and allows prioritization based on it. For example, a listing of 1B.1
indicates a taxon is very rare and very endangered, while a listing of 1B.3
indicates a taxon is very rare, but not endangered.
- The D value primarily indicates whether the plant is a California endemic,
or more or less widespread outside the state. The former can easily be
determined from the distributional information, but distribution outside the
state can be difficult and/or time-consuming to make objective and keep current.
Adding the “CA Endemic” entry and displaying G-ranks conveys this information in
a more efficient and accurate way.
