Global Tree Conservation

IUCN Red List Threat Assessments for Priority Tree Species

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In a rapidly changing world, it is crucial for conservationists, policymakers, and communities to have accurate, up-to-date information on the threats that face global plant diversity, since all life depends on plants. The International Union for Conservation of Nature (IUCN) Red List of Threatened Species is the globally recognized and standardized system for assessing the extinction risk of the world’s plant, animal, and fungal species.

Since 2015, The Morton Arboretum has worked in partnership with IUCN, the IUCN SSC Global Tree Specialist Group, and Botanic Gardens Conservation International (BGCI) to assess, review, contribute to, and facilitate IUCN Red List threat assessments for priority tree species globally. 

In 2021, BGCI released the first State of the World’s Trees report, which found at least 30% of tree species worldwide are threatened with extinction. The report was a major milestone for the Global Tree Assessment initiative and is the result of five years of research among more than 60 institutions to identify major gaps in tree conservation efforts.

The Project’s Mission

  • Strengthen connections within the global conservation world.
  • Provide leadership in the conservation and protection of threatened tree species.
  • Improve knowledge of the prevalent threats facing trees.
  • Prioritize species for conservation and policy-based action.

The Project’s Process

  • Research: Gather scientific literature on a tree species, consult with experts, determine the most serious threats, determine the species’ range size and attributes.
  • Assess: Use the information generated by research to assess the species for threat status based on the categories and criteria set by IUCN.
  • Review: Consult a species expert for review of the threat assessment.
  • Submit: Submit the assessment to IUCN for approval.
  • Publish: Publish all approved assessments on the IUCN website.

Flagship IUCN Red List Projects

Red List of U.S. Trees: The Arboretum is working in partnership with NatureServe and Botanic Gardens Conservation International-US to create the first definitive list of the native tree species of the continental U.S. and complete threat assessments for all of the tree species that have not been evaluated for the Red List. 

The Fagaceae Family: The Arboretum is completing assessments for all Fagaceae species of the world. As Asia hosts the largest number of Fagaceae species, it is our priority to work with partners in this region to assess this family and identify species in need of conservation. 

Oaks: The genus Quercus: The Arboretum has been assessing the world’s 450 oak species (Quercus) to the IUCN Red List by partnering with experts in Latin America, Asia, and Europe. In 2017, this project completed assessments for all 91 native species of US oaks and published The Red List of US Oaks Report 2017. This was subsequently updated in 2020 and published in The Red List of Oaks Report 2020.

Ashes: The genus Fraxinus: In 2017, the project completed assessments for the eastern US species of ash (Fraxinus) in light of the renowned and quickly established invasive beetle, the emerald ash borer (EAB). In 2018, in partnership with BGCI, the project published The Red List of Fraxinus and identified, for the first time, that five species of ash are endangered and one critically endangered.  


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