The NatureServe conservation status system, maintained and presented by NatureServe

NatureServe

NatureServe is a non-profit conservation organization whose mission is to provide the scientific basis for effective conservation action. NatureServe and its network of natural heritage programs are the leading source for information about rare and endangered species and threatened ecosystems in...

 in cooperation with the Natural Heritage Network, was developed in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 in the 1980s by The Nature Conservancy

The Nature Conservancy

The Nature Conservancy is a US charitable environmental organization that works to preserve the plants, animals, and natural communities that represent the diversity of life on Earth by protecting the lands and waters they need to survive....

 (TNC) as a means for ranking or categorizing the relative imperilment of species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of plant

Plant

Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s, animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s, or other organism

Organism

In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

s, as well as natural ecological communities

Community (ecology)

In ecology, a community is an assemblage of two or more populations of different species occupying the same geographical area. The term community has a variety of uses...

, on the global, national and/or subnational levels. These designations are also referred to as NatureServe ranks, NatureServe statuses, or Natural Heritage ranks. While The Nature Conservancy is no longer substantially involved in the maintenance of these ranks, the name TNC ranks is still sometimes encountered for them.

NatureServe ranks indicate the imperilment of species or ecological communities as natural occurrences, ignoring individuals or populations in captivity

Captivity

Captivity or Captive may refer to:*Imprisonment or hostage, the state of being confined to a space from which it is difficult or impossible to escape**Captive company...

 or cultivation, and also ignoring non-native occurrences

Introduced species

An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...

 established through human intervention beyond the species' natural range (as, for example, with many invasive species

Invasive species

"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

).

NatureServe ranks have been designated primarily for species and ecological communities in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 and Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, but the methodology is global, and has been used in some areas of Latin America

Latin America

Latin America is a region of the Americas where Romance languages  – particularly Spanish and Portuguese, and variably French – are primarily spoken. Latin America has an area of approximately 21,069,500 km² , almost 3.9% of the Earth's surface or 14.1% of its land surface area...

 and the Caribbean

Caribbean

The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

. The NatureServe Explorer web site presents a centralized set of global, national, and subnational NatureServe ranks developed by NatureServe or provided by cooperating U.S. Natural Heritage Programs and Canadian and other international Conservation Data Centers.

Introduction

Most NatureServe ranks address the conservation status of a plant or animal species or a natural ecological community using a one-to-five numerical scale (from most vulnerable to most secure), applied either globally (world-wide or range-wide) or to the entity's status within a particular nation or a specified subnational unit with a nation. Letter-based notations are used for various special cases to which the numerical scale does not apply, as explained below. Ranks at various levels may be concatenated to combine geographical levels, and also to address infraspecific taxa (subspecies and plant varieties).

Global, national, and subnational levels

NatureServe conservation statuses may be applied at any or all of three geographical levels:

• G - Ranks designated at the global (or range-wide) level (G-rank),
• N - Ranks designated at a national level (N-rank) for a particular nation, and
• S - Ranks designated at a subnational level (S-rank) for a particular next-lower geographical unit within a nation, such as a state within the United States or a province or territory within Canada.

Commonly encountered ranks

The most commonly encountered NatureServe conservation statuses at the G-, N-, or S-level are:

Numbers

• 1 - Critically imperiled (typically having five or fewer occurrences, or 1,000 or fewer individuals).
• 2 - Imperiled (typically having six to twenty occurrences, or 1,000 to 3,000 individuals).
• 3 - Vulnerable (rare; typically having 21 to 100 occurrences, or 3,000 to 10,000 individuals).
• 4 - Apparently secure (uncommon but not rare, but with some cause for long-term concern, usually having more than 100 occurrences and 10,000 individuals).
• 5 - Secure (common, widespread, abundant, and lacking major threats or long-term concerns).

Letters

• X - Presumed extinct
  Extinction
  In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
  
   or extirpated (not located despite extensive and intensive searches, with rediscovery not reasonably expected). Note that extinction is here considered a global (range-wide) phenomenon, while extirpation applies to loss within a particular national or subnational area, with the entity still extant elsewhere.
• H - Possibly extinct or extirpated (of historical occurrence but not known recently extant, with some reasonable hope of rediscovery).
• R or ? - Recorded within a nation or subnation, but local status not available or not yet determined. When combined with a global rank of G1 to G3, local status is 'Indeterminate,' but the entity is nevertheless presumed vulnerable, if still extant.

Thus, for example, a G3 species is "globally vulnerable", and an N2 species is "nationally imperiled" for the particular country the rank is assigned. Species with G, N, or S rankings of 4 or 5 are generally not the basis for major conservation actions.

Ranks for additional cases

Several less frequent special cases are addressed through other notation in the NatureServe ranking system, including:

Subspecies and plant varieties

• T - When desired, infraspecific taxa (subspecies, plant varieties, and other designations below the level of the species) may be assigned global T-ranks. A T-rank is appended to the G-rank for the including species. N-ranks and S-ranks presented with T-ranks apply to the particular infraspecific taxon, not its including species. Most taxa given such ranks have trinominal (three-word) rather than binominal (two-word) scientific names.

Non-Native (Exotic) Taxa

• E - Used at the national or subnational levels, E indicates taxa not native in the specified area, even historically, but currently or historically present there due to direct or indirect human intervention; such taxa are often termed exotic, escaped, non-native, adventive, or waif.

Note, however, that regionally native species or other taxa that have recently arrived in the area of interest by natural means (such as wind, floods, or birds), without direct or indirect human intervention, are ranked by the same methodology and notation as for other native taxa.

Interspecific hybrids

• HYB - Modern interspecific hybrids, typically encountered as isolated individuals, are rarely themselves targets of conservation attention, are generally given a placeholder global rank of HYB, and not ranked at the national or subnational levels.

However, reproducing or other self-maintaining, population-forming species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 known or suspected to be of hybrid origin are ranked using the same methodology and notation as for other species. For example, many fertile polyploid

Polyploidy

Polyploid is a term used to describe cells and organisms containing more than two paired sets of chromosomes. Most eukaryotic species are diploid, meaning they have two sets of chromosomes — one set inherited from each parent. However polyploidy is found in some organisms and is especially common...

 species of ferns formed by interspecific hybridization followed by chromosome

Chromosome

A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

doubling. Some of these hybrid-derived species are quite rare (ranked G1), but others are so widespread, abundant, and secure as to deserve a G5 rank.

Taxa extant only in captivity or cultivation

• C - When appended to X or H, the letter 'C' indicates species or other taxa extant in captivity or cultivation, although otherwise extirpated or extinct.

Combinations of ranks

Any NatureServe rank may be used alone, or G-, T-, N-, and S- ranks may be combined in that sequence, such as a G5N3S1 rank for a particular species (or ecological community) within a particular subnational unit of a particular nation. An entity has only a single global rank (G-rank alone, or G-rank and T-rank combination), but may have different N-ranks or S-ranks for different nations or subnations within its geographical range.

External link and references

• http://www.natureserve.org/explorer
• http://www.unep-wcmc.org/species/plants/status_tnc.htm