Ranking Systems

An important responsibility of ORBIC is to review and rank rare, threatened, and endangered species of Oregon. We assign Heritage Ranks to animals, plants, and fungi that are or may become rare in Oregon. Heritage Ranks are decided through expert review, discussion, input from interested parties, and trends in sightings and population data.

Heritage Ranks

The Heritage Ranks are a part of an international ranking system first developed by The Nature Conservancy and now managed by NatureServe. This system is used by Heritage programs in all 50 states in the USA, at the 8 Canadian Conservation Data Centres, and network partners in several Latin American countries. A brief definition of these ranks can be found below. You can find more detailed discussion of these ranks at NatureServe's Conservation Status page.

In addition to ranking each species' conservation status, Heritage programs also rank each occurrence, or population group, of species that are found in each state. If you are interested in learning how we rank occurrences, see the Ranking Species Occurrences - A Generic Approach article by NatureServe, updated in January 2008. More background information on occurrence ranking can be found in the NatureServe Ranking Methodology publication from April 2009.

State and Federal Ranking Systems

In addition to our Heritage Ranks, the Oregon Department of Fish and Wildlife (ODFW), the United States Fish and Wildlife Service (USFWS), and the Oregon Department of Agriculture (ODA) also rank species. We include these rankings in our publication, Rare,Threatened and Endangered Species of Oregon.

You can view the current ODFW and USFWS rankings for vertebrates at ODFW's Wildlife Division. ODFW has also compiled a Sensitive Species list to address species which are not currently considered threatened but which may need proactive protection to maintain their populations. Current ODA plant listings are found at their Plant Conservation pages.

Rare, Threatened, and Endangered Species of Oregon

ORBIC publishes this book every two or three years with updated ranks for rare species in Oregon. The latest version of the RTE book is available as a PDF file at our Rare Species Lists page. Archived PDF versions of the RTE books are also available on this page. Paper copies of older editions of the book may be available. If you are interested in these paper editions, please contact [email protected]. Future editions of the RTE book will be available as a PDF file only.

Ranking Definitions 

ORBIC participates in an international system for ranking rare, threatened and endangered species throughout the world. The system was developed by The Nature Conservancy and is now maintained by NatureServe in cooperation with Heritage Programs or Conservation Data Centers (CDCs) in all 50 states, 9 Canadian provinces, and in 13 Latin American countries. The ranking is a 1-5 scale with 1 being critically imperiled and 5 being secure. When determining species rank many factors are taken into account, including the number of known occurrences, threats, inherent sensitivity, area occupied, and other biological and anthropogenic factors. Documentation for several species ranking decisions are available on our Ranking Documentation information (see below).

Global Ranks

Ranks are developed for different portions of a species range. The first and most critical rank describes the species status globally, and best describes the risk of extinction. This is called the Global Rank and begins with a "G". If the taxon has a trinomial (a subspecies, variety or recognized race), this is followed by a "T" rank indicator. A "Q" at the end of this line indicates the taxon has taxonomic questions. National Ranks beginning with the letter "N" describe a species' status in specific nations such as the United States, Mexico, or Canada, but are not often used in the US.

State Ranks

The most widely used NatureServe rank in the United States are the State Ranks, which describe the rarity of a species within each state's boundary. These State Ranks begin with the letter "S". Global, National, and State ranks all use a 1-5 ranking system, summarized below:

1 = Critically imperiled because of extreme rarity or because it is somehow especially vulnerable to extinction or extirpation, typically with 5 or fewer occurrences.

2 = Imperiled because of rarity or because other factors demonstrably make it very vulnerable to extinction (extirpation), typically with 6-20 occurrences.

3 = Rare, uncommon or threatened, but not immediately imperiled, typically with 21-100 occurrences.

4 = Not rare and apparently secure, but with cause for long-term concern, usually with more than 100 occurrences.

5 = Demonstrably widespread, abundant, and secure.

H = Historical Occurrence, formerly part of the native biota with the implied expectation that it may be rediscovered.

X = Presumed extirpated or extinct.

U = Unknown rank.

? = Not yet ranked or assigned rank is uncertain.

More details on the Heritage Ranking system and more definitions can be found at the NatureServe Web site and on their Conservation Status page. A complete description of the ranking process is available from Natureserve's Methodology for Assigning Ranks.

Heritage Lists

ORBIC evaluates the NatureServe ranks and further refines the data for state application through placing species on their Lists 1 through 4. The fact that Oregon and California have such high rates of species endemism was the reason for the implementation of the 1-4 Heritage Listings in Oregon and California. In particular, most heritage programs consider all G1, G2 or G3 taxa as needing protection. Based on a snapshot search of NatureServe explorer, 1138 taxa in Oregon are ranked G1-G3 (or T1-T3). Of these, 615 taxa ranked as a G3 (or T3, excluding taxa with G3 in range ranks). Many of these are rare endemics which have few documented threats. Because of this, ORBIC evaluates G3 taxa individually based the significance of the species Oregon distribution, and overall threats to the taxa. This evaluation is the primary analysis used to determine which ORBIC list they are placed on.

Brief Summary of ORBIC Lists:

List 1 contains taxa that are threatened with extinction or presumed to be extinct throughout their entire range. These are the taxa most at risk, and should be the highest priority for conservation action. Includes many rare Oregon endemic species.

List 2 contains taxa that are threatened with extirpation or presumed to be extirpated from the state of Oregon, but are secure or abundant elsewhere. These are often peripheral or disjunct species which are of concern when considering species diversity within Oregon's borders. They can be very significant when protecting the genetic diversity of a taxon. ORBIC regards extreme rarity as a significant threat and has included species which are very rare in Oregon but secure elsewhere on this list.

List 3 contains species for which more information is needed before status can be determined, but for which there is reason to believe they may be threatened or endangered in Oregon or throughout their range. Many taxa on this list may eventually be determined to belong on List 1 or List 2, so it is important that they be looked for.

List 4 contains taxa which are of conservation concern but currently do not meet the criteria for begin considered threatened or endangered. This includes taxa which are very rare but are currently secure, as well as taxa which are declining in numbers or habitat but are still too abundant to be proposed as threatened or endangered. While these taxa currently may not need the same active management attention as threatened or endangered taxa, they do require continued monitoring.

List 4 includes species that may be of conservation concern from a global or state perspective.

Ranking Documentation 

Tables of Results:

Vascular Plants  
Fungi and Lichen  

Introduction to Natural Heritage Ranks

One of the Oregon Biodiversity Information Center's tasks is to rank rare species in Oregon according to how at risk they are in Oregon. For endemic species and those for which we have ranking responsibility, we also assess species' status on a global scale. The conservation status ranks for the species on the linked pages below were assigned following NatureServe's protocol on species assessment. An explanation of the methodology, a description of the factors being assessed, and the spreadsheet calculator tool can be viewed and downloaded from NatureServe's Rank Calculator website. The calculator version used for these evaluations is noted in the footer of the document; if there is no footer the version was 2.0. For a brief description of the meaning of the rank codes, see our Rare Species Ranking Definitions (section above).

Ranks are assigned as a couplet, one for the global level and one for the state/Oregon level. If only the global ranking form is available, then the species is an Oregon endemic and the state rank and information will be the same. If only the state ranking form is available, then the species occurs outside of Oregon as well and Oregon does not have global ranking authority. The global ranks for these species therefore reflect the published values in the current Rare, Threatened, and Endangered Species of Oregon list, and global ranking authority rests with another state or with NatureServe.

Many of the vascular plant species have also been assessed for vulnerability to climate change using NatureServe's Climate Change Vulnerability Index calculator. Where it has been calculated, the score from the CCVI is listed in the "Climate Vulnerability" column of the table. This rank informs the "threats" section of the Element Rank Calculator, and provides a measure of how vulnerable a species is to negative impacts from predicted climate change. See NatureServe's Climate Change Vulnerability Index page for more information or to download a copy of the calculator.

The element ranks assigned to the species under the Survey and Manage Assessment project (completed in 2004) followed a similar protocol as the NatureServe Element Ranking methodology but the calculator tool had not been developed at that time. The ranks in the tables linked above supercede all other previous ranks for a given species.

As time allows more species will have their ranks documented and published in these tables, please check back periodically for updates.