ORBIC participates in an international system for ranking rare, threatened and endangered species throughout the world. The system is maintained by NatureServe in cooperation with a network of Heritage Programs and Conservation Data Centers (CDCs) across North America. The ranking is a 1-5 scale with 1 being critically imperilied 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 page.
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.
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.
Breeding birds may have separate ranks for Breeding (B) and Nonbreeding (N) populations.
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.
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.
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.