Red Lists

Conservation assessments of species are often compiled together in what are called Red Lists. The IUCN Red List of Threatened Species is widely recognised as the most authoritative global assessment of the conservation status of species.

Red Lists are a valuable tool to assist conservation planning and decision making. Red Listing involves using available information to assess the conservation status of the taxon in question against the internationally agreed IUCN Red List Categories and Criteria, thus identifying the most rare and threatened species in need of conservation attention. The use of the IUCN Categories and Criteria ensures standardisation and allows comparison not only within trees but also with other groups of plants and animals.

The production of tree Red Lists contributes to achievement of Target 2 of the Global Strategy for Plant Conservation, developed under the Convention on Biological Diversity (CBD). Target 2 calls for ‘an assessment of the conservation status of all known plant species, as far as possible, to guide conservation action’ by 2020.

A tree may also be nationally or regionally threatened, i.e. its populations are threatened within a particular country or region, rather than across its whole range. The IUCN Red List Categories and Criteria can be adapted to perform national or regional assessments, and various national Red Lists also exist. The Global Trees Campaign focuses the majority of its work on globally threatened tree species, but in some cases projects may focus on locally threatened species.

IUCN Red List Categories

Full information about the IUCN Red List Categories and Criteria is available on the IUCN Red List website. The following provides a brief introduction to the Categories. Threatened Categories are highlighted in bold text:

  • Extinct (EX) – no reasonable doubt that the last individual has died
  • Extinct in the Wild (EW) – a taxon known to only survive in cultivation or as a naturalized population well outside of its past range.
  • Critically Endangered (CR) – a taxon that meets any of the criteria for Critically Endangered and is therefore facing an extremely high risk of extinction in the wild.
  • Endangered (EN) – a taxon that meets any of the criteria for Endangered and is therefore considered to be facing a very high risk of extinction in the wild.
  • Vulnerable (VU) – a taxon that meets any of the criteria for Vulnerable and is therefore considered to be facing a high risk of extinction in the wild.
  • Near Threatened (NT) – a taxon that has been evaluated but does not currently meet the criteria to be qualified as Critically Endangered, Endangered or Vulnerable but is close to qualifying or is likely to qualify for a threatened category in the near future.
  • Least Concern (LC) – a taxon has been evaluated and does not qualify for Critically Endangered, Endangered, Vulnerable or Near Threatened. This category covers widespread and abundant taxa.
  • Data Deficient (DD) – a taxon is considered to be Data Deficient when there is inadequate information to make an assessment of its risk of extinction based. A taxon may be well studied, but appropriate data on abundance and/or distribution is lacking. This is not a threat category, but there is a possibility that future research will result in the taxon being classified within a threat category.
  • Not Evaluated (NE) – a taxon that has not yet been evaluated against the criteria.
Tree Red Listing – progress so far

The World List of Threatened Trees (Oldfield, et al., 1998) assessed the conservation status of the world’s trees using version 2.3 of the IUCN Red List Categories and Criteria, which was current at the time. Over 7,400 of the species assessed qualified as globally threatened. For pragmatic reasons, The World List of Threatened Trees did not cover all of the world’s tree species, and there were particularly notable gaps in some taxonomic and geographic areas.

In 2001 a revised version of the IUCN Red List Categories and Criteria was published (version 3.1). Although existing Red List assessments under the old Categories and Criteria are still valid, there is a need to progressively revise assessments using the more recent version.

The IUCN/SSC Global Tree Specialist Group aims to fill the gaps in The World List of Threatened Trees and to revise existing assessments using the most up to date categories and criteria, to produce a Global Conservation Assessment of the world’s trees by 2020.

This is an ambitious target, but good progress is being made.

The assessments included in The World List of Threatened Trees have been added to the IUCN Red List and subsequent assessments have been undertaken.

Currently, more than 9,500 trees have been assessed and published on the IUCN Red List, over 6,400 of which are assessed as globally threatened (CR, EN, VU). Over 1,100 trees are assessed as Critically Endangered (CR) on the IUCN Red List and in urgent need of conservation action.

In 2008, Newton and Oldfield undertook a review of recent progress towards Red Listing the world’s tree species. It is estimated that at least an additional 2,500 trees have been evaluated since 1998, but only a fraction of these have been published on the IUCN Red List.

The total number of trees globally threatened with extinction is therefore higher than the number of threatened tree taxa currently published on the IUCN Red List. Based on this evidence, it is estimated that over 8,000 tree taxa, 10% of the world’s total, are globally threatened with extinction.

GTC contribution to tree Red Listing

Working towards production of a Global Conservation Assessment of the world’s tree species, the GTC is leading Red Listing of trees in taxonomic and geographic groups, depending on conservation priorities and practical opportunities.

GTC Red List publications completed to data are available in the Red List area of our resources section.

Following publication of a tree Red List, the GTC often undertake a survey to determine the presence of threatened species in ex situ collections. Threatened species reported as absent from ex situ collections, or limited to a small number of collections, are highlighted as priority species for conservation concern and recommendations are made for their conservation, incorporating practical action into new or existing GTC projects where possible.

GTC ex situ surveys completed to date are available in the ex situ  survey area of our resources section

Next steps

Work is ongoing on the following tree Red Lists:

  • Betulaceae
  • Hydrangeae
  • Camellia
  • Timber species

Although a lot of information can be gathered through herbaria records and literature, in many cases there is inadequate information on the status of species and further field surveys are urgently needed for many groups and areas. The GTC and GTSG therefore undertake training and support projects which encourage further data collection and Red Listing.

Find out more about the GTSG and its members.