Demystifying the IUCN Red List
Endangered, threatened, vulnerable. These are all words that appear on species information signs at zoos and on information pages online, but where exactly do they mean, and where do they come from? Well, they come from an international system used to classify organisms based on their risk of extinction that is based on data collection and a thorough review process. Perhaps we should now take the time to break this system down into its most basic components and demystify the International Union for Conservation of Nature’s Red List (IUCN Red List).
Hippopotamus sign from the San Diego Zoo. (Credit:Anne Napier asnapier.com)
The IUCN Red List first sprung into existence in 1964 in the attempt to create the most comprehensive conservation list on the planet. In the years since it’s creation, the list has indeed become the most comprehensive list categorizing the conservation status of a wide array of organisms that call the Earth home and is called a “barometer of life” on the IUCN website. It has picked up this barometer of life title because it is said to act as a measure of the pressures affecting the survival of species and measure the overall biodiversity of the planet. This biodiversity measure essentially tracks how many different species exist and about how many members of each species are still alive, which is where the classification system comes into play.
Prior to a classification being assigned to a species, the information that has been collected must first be weighed against a list of five specific criteria that are defined by three specific areas of data, population, geographical range, and projection models. To begin picking this apart, we will start with the data collected on a species’ population.
The population describes how many individuals of a species are currently alive and residing within their natural habitat. While this data can be represented by raw counts, that makes up only a portion of the work that is done to understand and represent the population of a species in question. After years of collection, the data can be compiled and used to look at the overall trends, determine if the numbers are increasing or decreasing, and inform what other information needs to be taken into account. Specifically, the estimate for overall population size, mature individuals (individuals that are capable of breeding), and the decline in population size is observed are what is used to assign a classification. Populations with less than 2500 overall individuals, less than 250 mature individuals, or a greater than 50% reduction in population size over ten years are all eligible to be flagged during the analysis step of the system.
Of course, population size is only a small part of the picture when looking at what is happening with a species, so the geographical range is also taken into account. The geographical range is just a way of saying where the creature in question is found. When looking at the range, researchers take into account how much habitat is available and how fragmented that habit may or may not be. The smaller the geographical range and the more fragmented the available habitat, then the more likely a species is to pick up a more dire classification. If there is not much suitable space available or it is hard to get from one piece of habitat to another, then a species will have a tough time maintaining a stable population as time progresses.
Once population and range are taken into account over a substantial period of time, scientists are able to take the numbers and plug them into mathematical models to project a hypothetical future for the species if the trends remain the same. These models help determine how likely it is for a species to be driven to extinction if their conservation is not prioritized. The models in question are similar to those used in the world of finance to calculate interest rates and are fairly simple to use by plugging in data points collected when surveying for the geographical range and population size points. It is this data that is used to clear away some of the ambiguity in the classification process and officially pick one of those familiar words that show up on plaques in zoos.
IUCN Red List Diagram.
Once the species is identified, there are nine categories that can be applied based on how the collected data weighs up against the criteria. Two of the possible classifications are not technically part of the threatened/not threatened system because they essentially mean that there has not been enough data collected to make a definitive decision. Not evaluated (NE) indicates that the species is known and names, but there is no data available to weigh against the criteria, and data deficient (DD) indicates that there is some data, but not enough to completely evaluate. These two categories essentially allow for the classification of species that there simply has not been enough manpower to completely study without leaving them off the list entirely.
Least concern (LC) and near threatened (NT) are the first two classifications where enough data is available to definitively assign a species to one of the conservation groupings on the IUCN Red List that truly indicates a conservation status. Both classifications mean a species has failed to meet at least two of the five criteria to qualify as threatened, but there is one big difference between the two. Species of least concern are considered to be stable in population with a widespread distribution making it unlikely that they will face a threat of extinction in the near future. Near threatened species are not facing immediate danger of extinction, but there is some data that suggests that this status may change in the near future. This distinction allows for species to be put on a watch list while conservation resources can still be allocated to a species facing a more imminent threat of extinction.
At this point, the classification system enters the world of nuance and technicality until it gets to the extreme end where it ends with extinct. For the time being, we are going to jump to the end and look at the final classifications that can be given to a species extinct in the wild (EW) and extinct (EX) because they are as simple as the non-classifications previously discussed. Extinct in the wild means that the species has been determined through extensive research to no longer be present in their native range and only be living in captivity or highly cultivated populations existing in a sort of pseudo wild state. One step farther is extinct, a classification that means there are no more living specimens of the species, and barring a hidden individual or population it is highly unlikely that the species will ever be present in the natural world again. In general, there is no coming back from extinction, although there is a corner of research exploring the possibility of bringing back species that have been lost to the unforgiving wrath of time.
The three threatened classifications.
The final three classifications all fall under the threatened umbrella, meet at least two of the criteria, and differ mainly in the wording used to describe their threat of extinction. First, there is vulnerable (VU) where a species definitely has a high risk of extinction, but not quite as pressing as the next two classifications. Species with the endangered (EN) are considered to have a “very high” risk of extinction in the near future, while critically endangered (CR) species have an “extremely high” risk of extinction based on the models produced from the available data. The ambiguity in these classifications allows for human error, the changing realities of nature, and a constantly evolving field of research.
Science is constantly evolving, and as a result, so is the IUCN Red List. As new species are discovered, more scientists publish research, and people work tirelessly to assign classifications the list will become more complete and better represent the biodiversity on Earth. Since the list is constantly being updated and there is some necessary ambiguity in the definitions of the classifications, species are moved around from one classification to another. In some cases, it is more helpful to label a species as threatened instead of vulnerable or endangered if they fall somewhere in between the two categories. It is important to note that while there are some conservation success stories, most classification moves tend to be in the extinction direction and result in the incremental reduction of overall biodiversity.
The IUCN Red List, however, does not just serve to paste a label on every species and warn that biodiversity is in decline, it is an important tool that is used in multiple disciplines outside of the realm of conservation. Since the list tracks the geographic ranges of species, it can be used in the medical field to pinpoint areas that are high risk for diseases that can be transmitted to humans and livestock by wild animals and plan for any future outbreaks that may arise from the inevitable overlap of nature with the human world. Policymakers use the list in a similar way to the medical community by utilizing it to plan for the preservation of high-risk species and reasonable allocation of resources while allowing for the expansion of the perpetually expanding human race.
Education may be the most pressing field that the IUCN Red List is used in because it influences not just those in charge of new policies, but the next generations that will one day lead the conservation charge. The website is full of tools and links to publications that can make the list easier to understand and can be introduced at almost any education level from grade school to grad school. The more the IUCN Red List is utilized and broken down into words that anybody can understand, the more people will become involved and hopefully, aid in the classification of the many species that have yet to be completely researched.
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