Red List Index for European species

Indicator definition

The Red List Index shows trends in the overall threat status of European species.
Specifically the index relates to the proportion of species expected to remain extant in the near future in the absence of additional conservation action.

Units

Values between 0 and 1 - when all species are Least Concern the RLI is equal to 1, and when all species are extinct the RLI is equal to 0.

Policy context and targets

Context description

The RLI measures trends in the threat status (relative projected extinction risk) of European species, indicating the proportion of species expected to remain extant in the next few decades in the absence of additional conservation action. Extinction is a key measure of biodiversity loss that has resonance with the public and decision makers, and which has clear relevance to ecological processes and ecosystem function.

The main pressures affecting the trend in the RLI and biodiversity in general are:
habitat loss, unsustainable exploitation, alien invasive species, pollution and climate change. The precise drivers can be determined from the data used to generate the RLI.

There are two variants of this indicator for which the state of development is different:

(1) An RLI for European species based on global extinction risk (i.e. a European subset of the global RLI);

(2) An RLI based on regional extinction risk at either the pan-European or EU scale. Both variants of the RLI should be developed and could be presented together with appropriate interpretation. However, because of its more direct relevance to European policies, variant (2) is proposed for inclusion here.

Relation of the indicator to the focal area

Extinction is a naturally occurring process, but there is little doubt that humans are increasing the rate of extinctions by 100-1 000 times the historical 'background' rate. Extinction is perhaps the most fundamental form of biodiversity loss. The RLI measures trends in extinction risk for sets of species. In the European context, this indicator will provide a useful measure of the success of the implementation of the EU Birds and Habitats Directives, and the Bern Convention (particularly for threatened birds covered by Species Action Plans, which EU Member States and Convention Parties have endorsed, and thereby agreed to implement specific recovery measures).

Targets

2010 Biodiversity Target

Related policy documents

No related policy documents have been specified

Methodology

Methodology for indicator calculation

Methodology used for the Global Red List Index

The Red List Index (RLI) has been developed by the Red List partnership (IUCN, Species Survival Commission, BirdLife International, Conservation International-Centre of Applied Biodiversity Science and NatureServe).

It uses data from the IUCN Red List of threatened species (www.iucnredlist.org) and shows overall changes in threat status (relative projected extinction risk) of representative sets of species. Red List categories are extinct, extinct in the wild, critically endangered, endangered, vulnerable, near threatened, least concern, data deficient, and not evaluated.

RLIs can be calculated for any set of species for which Red List assessments have been carried out on all species at least twice. To date, a RLI has been developed for all bird species for 1988-2004 (Butchart et al. 2004) and a preliminary RLI has been developed for all amphibian species for 1980-2004 (Butchart et al. 2005). A more recent publication has described revisions and improvements to the RLI formula and its application in response to lessons learned from its initial application (Butchart et al. 2007).

The RLI is related to the rate of biodiversity loss, rather than a measure of the state of biodiversity. Although some of the Red List criteria are based on absolute population size or range size, others are based on rates of decline in these values or combinations of absolute size and rates of decline. These criteria are used to assign species to Red List categories that can be ranked according to relative projected extinction risk, and the RLI is calculated from changes between these categories. Hence, an RLI value relates to the proportion of species expected to remain extant in the near future in the absence of additional conservation action. The timeframe for this cannot be specified exactly, because it depends on generation time (10 years or three generations, whichever is longer) and is calculated over many species with a variety of generation times, but it can be taken to be in the range of 10 - 50 years.

The RLI is based on the proportion of species in each Red List category, and the proportion moving between categories in different assessments owing to genuine improvements and deterioration in status only (i.e. category changes owing to revised taxonomy or improved knowledge are excluded). At any particular point in time, the number of species in each Red List Category is multiplied by a weight (ranging from one for near threatened up to five for extinct and extinct in the Wild) and these products are then summed. The total is then divided by a 'maximum threat score' (the number of species multiplied by the weight assigned to the extinct category). This final value is subtracted from 1 to give the IUCN RLI value, so that when all species are Least Concern the IUCN RLI is equal to 1, and when all species are extinct the IUCN RLI is equal to 0.

It is important to note that the RLI is based on changes in the status of all species (including those classified as Least Concern): a species moving from 'least concern' to 'near threatened' contributes as much to the changing index value as a 'critically endangered' species becoming extinct. Hence this indicator is not based solely on 'changes in the status of threatened species'. Nevertheless, the category 'least concern' is very broad, so a common species may have to undergo quite large changes in status in order to qualify as near threatened and hence influence the RLI trend.

Methodology proposed for the European Red List Index

The IUCN Red List categories and criteria can be applied at regional level to determine categories for regional extinction risk (IUCN 2003). Using assessments of regional extinction risk to construct a European RLI for a particular taxonomic group increases its robustness. This is because more species tend to qualify as 'threatened' or 'near threatened' when assessed for their regional (as compared to global) extinction risk, because of their inherently smaller ranges and population sizes when assessed at this spatial scale. Consequently, more species move between Red List categories in repeated assessments, so the RLI trends are driven by a larger number of species. It may also be the case that less uncertainty is associated with quantitative population size and trends estimates at the European, rather than global, scale leading to greater confidence in the accuracy of Red List categorisations at the European scale.

In Europe, to date, only birds have been assessed for their regional extinction risk using this methodology (BirdLife International 2004a, b). At a pan-European level, 67 species are considered to be 'threatened', 159 'near threatened', and 300 of 'least concern'. At the level of the EU-25, 54 species are considered to be 'threatened', 162 'near threatened', and 232 of 'least concern'.

In 2006, BirdLife International applied the RLI methods retrospectively to published population and range data from 1970-1990 (Tucker and Heath 1994) to calculate the first regional RLI for European birds, with data points in 1994 and 2004. It is currently proposed that more data will be collected and the regional extinction risk of birds in 2007-2009 will be assessed again, yielding three data points before 2010, although this work remains dependent on extra funding.

It should be noted that although many individual European countries have published national Red Data books or lists, these cannot be used directly to calculate pan-European RLIs. Countries often use a variety of different systems to assign categories that cannot be compared directly between countries, and regional extinction risk cannot be determined by simply aggregating national assessments (although national data on population and range sizes and trends are often aggregated in order to determine supranational estimates for these parameters, to which the IUCN Red List criteria are then applied).

Methodology for gap filling

N/A

Methodology references

No methodology references available.

Uncertainties

Methodology uncertainty

No uncertainty has been specified

Data sets uncertainty

No uncertainty has been specified

Rationale uncertainty

 MAIN DISADVANTAGES OF THE INDICATOR

There are two main disadvantages to an RLI for European species based on regional extinction risk:

• RLIs have relatively coarse temporal resolution because species may have to undergo quite significant changes in population and range size/trend in order to qualify for higher or lower Red List categories, and RLIs can only practically be updated every four years (when all species in the taxonomic group are reassessed);
• Within a particular taxonomic group a regional RLI for European species is more robust than an RLI for European species based on global extinction risk; however, suitable data are available currently for birds only.

ANALYSIS OF OPTION

Global population trend-based indicators (such as the Living Planet Index) show higher temporal resolution (being sensitive to relatively small population changes on an annual basis) than the RLI, but are much less geographically representative, as monitoring of species' populations is largely concentrated in developed countries, particularly in northern temperate regions.