How to assess every tree species on Earth

Learn about the Global Tree Assessment (GTA)

Border between Pine plantation and Nothofagus alessandrii forest (2018-05-21) by Cristian EchevirraBotanic Gardens Conservation International

Global tree risk

From the frigid forests of Alaska to the balmy forests of Australia, the world is home to trillions of trees.

This number might seem big—and it is—but Botanic Gardens Conservation International’s Global Tree Assessment found that of approximately 58,000 tree species in existence, at least 30 percent are at risk of extinction.

At least 30 percent of tree species are at risk of extinction.

How do we know this? How was the conservation status of every type of tree evaluated?
The answer: capacity building, innovation, and a vast network of tree experts.

Pepper-Bark tree (Warburgia salutaris) flower by Michele HofmeyrBotanic Gardens Conservation International

The GTA began in 2015

The total number of tree species around the world was unknown. There were only 10,000 assessments for tree species on the IUCN Red List, meaning that it was hard for conservationists to know on which species to focus their efforts.

The first step was to develop a full list of existing tree species. From 2015 to 2017, this was collated using online lists, scientific papers, monographs, etc. The results were published in 2017 in the GlobalTreeSearch database, and the database is continuously being updated to where it is today.

American Ash (Fraxinus americana) autumn purple by The Morton ArboretumBotanic Gardens Conservation International

The starting point for a global network

A network of tree experts and enthusiasts was born. Partners from a wide range of organizations were contacted, including the Global Tree Specialist Group. These groups contributed their own tree lists, and reviewed the master list for accuracy.

Another part of the Global Tree Assessment involved creating the ThreatSearch database, which compiles available conservation information about all plants based on assessments from IUCN Red List, national red lists and other sources. Since it began thousands of additional assessments have been added.

The Loneliest Palm (Hyophorbe amaricaulis) by Paul Smith/BGCIBotanic Gardens Conservation International

Identifying trees that need conservation assessment

So far, more than 47,000 species have a global assessment. Of these, over 16,000 are threatened with extinction.

Many ThreatSearch and GlobalTreeSearch partners went on to aid in the creation of the Global Tree Assessment. The sweeping global program also mobilized a myriad of other actors, often connecting with groups or individuals to gather data on their local tree species. For example, in South America, BGCI worked with organizations such as CNC Flora in Brazil, which are assessing all endemic trees in the country.

Eucalyputs retusa (2016-09-12) by Ian RobertsBotanic Gardens Conservation International

More than 100 partnerships

Partners have supported the Global Tree Assessment through gathering information, drafting tree conservation assessments or reviewing assessments. 

However, much work remains. There are still many trees out there that require assessment. Moreover, some existing assessments require updating, as they are more than 10 years old. Going forward, BGCI will be continuing to train partners, and grow our network.

Karomia gigas seeds by Botanic Gardens Conservation International (BGCI)Botanic Gardens Conservation International

Trees are keystone species in their habitats

They provide food and shelter for wild animals and livelihoods for many millions of humans. 
That’s why the ongoing work of the Global Tree Assessment is an essential part of the future of conservation.

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