The Plant Press

From The Plant Press, Vol. 23, No. 2, April 2020.

Analyzing tree data to prevent extinctions

Sara Oldfield, Co-Chair IUCN SSC Global Tree Specialist Group

This year biodiversity and climate change will be in the headlines as politicians take stock of progress towards global targets and make plans for increasing concerted action. Tree species are of fundamental importance both as elements of biodiversity and in adaptation and mitigation measures addressing climate change. One way botanists around the world are contributing their expertise to support scaled-up environmental action is through the Global Tree Assessment (GTA). This is a global effort to assess the risk of extinction faced by each and every tree species by the end of 2020. The goal is to pull together all existing data on the conservation status of tree species and add conservation assessments to the IUCN Red List of Threatened Species for all previously unassessed tree species. This is a huge collaborative effort, managed and coordinated by Botanic Gardens Conservation International (BGCI) and the IUCN Global Tree Specialist Group (GTSG) working together with many national and local institutions and individuals. The Smithsonian Institution is contributing significantly to this global initiative which will be used to prioritize and significantly increase conservation efforts to ensure that no tree species goes extinct.

An initial task in the GTA was to produce the first global checklist of the world's tree species. This in itself was no easy feat given that plant habit is not routinely recorded in taxonomic checklists. The list of around 60,000 tree species with accepted names and country level distribution took two years to produce by consulting a range of plant databases, over 500 scientific references, and working with around 80 tree experts. The list is maintained online by BGCI as the GlobalTreeSearch database. It remains a dynamic resource reflecting taxonomic and nomenclatural changes and is a baseline for monitoring progress towards the GTA. GlobalTreeSearch has also been connected to the World Flora Online, which is being developed as the open-access, web-based compendium of all the world’s plant species.

Evaluating the conservation status of tree species for the GTA follows the guidelines for applying the IUCN Red List Categories and Criteria. Each species is assessed by considering information on its area of distribution, population size and trend, habitat, uses, and threatening factors. Herbarium specimens and collection data continue to be of primary value in carrying out conservation assessments. Wherever possible these are combined with field knowledge of botanical experts. Often there is limited information on individual tree species and further fieldwork would greatly enhance our knowledge. Nevertheless, we need to use what information is currently available rather than waiting and, at the same time, identify those species which are poorly known and in need of further research. Concerns about loss of particular areas of forest and similar indirect information can form part of the species assessment process.

A species distribution map is required for each assessment and is very important in determining whether a species falls within the thresholds for IUCN threat categories. The Smithsonian’s National Museum of Natural History (NMNH) has pioneered using plant specimen data to calculate distribution range for rapid conservation assessments, for example in published research on Caribbean species, and this work is taken fully into account by the GTA.

One particular approach taken by the GTA has been a rapid assessment of tree species considered to be Least Concern at a global level. These are species with a widespread distribution, not known to be exploited on a large scale as timbers or for other products such as medicines, and not known to be declining because of other significant threats. Lists of candidate species thought to meet these criteria have been sent to experts for review and/or reviewed through regional workshops. It is expected that around 20,000 tree species will be evaluated as Least Concern by the end of this year. Each species published as Least Concern on the IUCN Red List will meet the minimum required documentation standards for IUCN assessments.

Assessments of tree species more likely to be at risk because of their restricted distribution, inclusion in national or regional red lists, or known targeted use have been undertaken in more depth than those that fall into the Least Concern category. A major priority has been to assess national endemics for countries which have particularly rich tree floras. Partnerships have been established with national organizations to undertake the tree assessments. Brazil has the most tree species of any single country, with over 9,000 species, and the most endemic trees. Currently over 3,000 endemic species are being assessed by Centro Nacional de Conservação da Flora (CNC Flora), a unit of the Rio de Janeiro Botanic Garden, and will be published on the IUCN Red List later this year. Over 20 other national partnerships are in place to help deliver the GTA. In Madagascar, the country with the highest percentage of endemic tree species, a collaborative effort over the past three years is yielding great results. The Red List of Dry Forest Trees of Madagascar is due for publication in April 2020 and all Madagascan tree species will be included on the IUCN Red List by the end of 2020.

In January this year a meeting was held at NMNH to plan an assessment for the trees of the Guianas. A rapid review of around 200 Least Concern tree species was initiated and a plan developed to assess 377 endemic trees of the Guiana Shield with no previous assessment using maps produced by NMNH’s Department of Botany.

Some countries already have well-developed lists of threatened tree species. These are being incorporated into the GTA. The Smithsonian has been involved in assessing the conservation status of U.S. species since the 1970s contributing data from the US National Herbarium to both federal and non-governmental organization (NGO) efforts. Now this data for all tree species of the continental US is being converted for inclusion on the IUCN Red List for the first time. This initiative is being undertaken through a partnership, coordinated by the Morton Arboretum who are working with NatureServe and BGCI US. Linking back to GlobalTreeSearch, this work builds on the first definitive list of the native tree species of the continental US. Some of the US species assessed as part of the GTA are the Fraxinus (ash) species devastated by the Emerald Ash Borer. Six widespread and previously abundant North American Fraxinus spp. are now listed as Critically Endangered as a result of predation by this beetle which was accidentally introduced through infested shipping pallets. 

The results of the GTA will allow us to gain a clearer understanding of the threats faced by tree species on a global scale. It will be possible to analyze which species are in trouble through overexploitation for resources, general deforestation and the growing risk from climate change and exotic pests or diseases. Then it should be possible to plan for action. Conservation assessments for specific groups of trees are already guiding coordinated efforts to safeguard trees in well-managed ex situ collections providing materials for ecological restoration and helping to meet UN biodiversity targets. Ideally in situ protection for tree species can also be scaled up as part of conservation of healthy forests and other habitats, contributing for example to the planning of protected areas and sustainable forest management. 

The GTA is the biggest species conservation assessment ever undertaken. It will summarize the best available information on tree species, highlight the gaps that need to be filled, and place tree diversity center stage in global discussions on biodiversity and climate change. For more information please visit www.globaltreeassessment.org.