Chicago researchers have spent 5 years creating the first-ever inventory of native trees in the United States. Now the real work begins | Chicago News


Bur oak is one of more than 80 species of oak trees native to the United States (Karen Roussel/Flickr Creative Commons)

If asked to quickly jot down a list of American trees, most people could probably name 20 or maybe even 30 off the top of their head.

There are actually 881 native tree species in the 48 contiguous U.S. states, including 85 different types of oak. It took a team of researchers, led by Morton Arboretum, the better part of five years to arrive at that total, drawing data from dozens of disparate sources, including historical logs of field expeditions.

Some of the results match what researchers already know about biodiversity in the United States. science and conservation at Morton Arboretum.

What surprised Westwood was the extent to which the United States is defined by a handful of genres, with oak and hawthorn neck and neck in the lead, far surpassing even the closest as well.

“I think it’s really interesting that we as a country have really iconic and dominant groups of trees,” Westwood said. “We are a land of oaks, hawthorns, willows and pines, it turns out.”

While it seems surprising that prior to 2017 no one thought of creating a single inventory of the state of tree species in the United States, it should be noted that the knowledge gap was global. No one really knew how many species there were in the world.

A collection of botanic gardens and botanical experts, operating under the auspices of the International Union for Conservation of Nature, launched the World Tree Assessment in 2015, with the aim of better understanding the diversity of trees in the planet and their risk of extinction.

The American Project from this larger effort, led by Morton Arboretum, Botanic Gardens Conservation International-US and NatureServe.

More than just a head count (or, perhaps more accurately, a trunk count), the checklist also included a threat assessment for each species, a long and comprehensive process.

“We had to consult people who knew these trees inside out. It was a lot of literature review, it was a lot of contact with experts from different states,” Westwood said.

To arrive at a threat level, the research team took into account several factors: How many individuals of a species are there? Where are they located? Are the populations fragmented from each other? Are they in decline? Are there ongoing conservation actions?

“All of these things are added to this calculation to say, ‘Is this an endangered species or not? “, Westwood said.

This very first comprehensive and standardized checklist and threat assessmentwith Westwood as lead author, was published in the journal “Plants, People, Planet”.

Assessments have found that 11-16% of the country’s native tree species are at risk of extinction, whether due to pests, climate change, habitat destruction, logging or destruction. another hazard.

It’s not exactly a pleasant conclusion to half a decade of work, but Westwood, lead author of the report, sees the findings less as an end and more as a beginning, in that they point the way in which to head. the conversation. efforts.

“The most important thing to note is that our work is not done just because we know what our trees are and we know which ones are at risk,” Westwood said. “It’s not enough to list these things, then we have to act.”


The checklist dataset has been deliberately made available in spreadsheet form so that it can be downloaded and manipulated in multiple ways by anyone interested in taking a deeper dive.

“There are basically a million different ways to use this,” Westwood said. “You can look at the list of threats and say, ‘OK, invasive pests and diseases are a big problem. We may need more investment in early detection and monitoring systems or in research related to how we manage invasive pests and diseases. Or take a look at places like Florida, Texas, California, and the Southeast and say, “Wow, there’s a very high concentration of endangered trees here, let’s take a look at our protected areas. Are there hallways between them? Is the habitat healthy and functional?'”

The project is already bearing fruit.

As the research team was completing some of the oak tree assessments, they noticed a group of very rare and understudied oak trees in southwest Texas.

“We said, ‘We have to go over there and do some studies and send botanists out into the field,'” Westwood recalls.

Morton Arboretum brought together oak experts from across the country and the group traveled to Texas where, as recently announced, they rediscovered the late-leaved oak (quercus tardifolio), one of 17 species of trees native to the United States not found in any botanic garden collection.

“It was a project that we knew we had expertise in, it needed to be done, we have the ability and the interest to do it, and we went out and rediscovered an extinct species,” Westwood said. “Hopefully we can bring him back from the brink.”

More broadly, the checklist has implications outside the walls of botanical institutions.

“I would like the average person to realize they have a role to play,” Westwood said. “Just because you don’t live next to an old growth forest in the Pacific Northwest or Florida doesn’t mean you have nothing to do with it.”

Trees along the North Fork of the Chicago River, October 14, 2021. (Patty Wetli/WTTW News)Trees along the North Fork of the Chicago River, October 14, 2021. (Patty Wetli/WTTW News)

Trees are the foundation on which much of the world’s terrestrial ecosystems and biodiversity depend, and they also play a vital role in public health. They stabilize the soil, recycle nutrients, purify the air, sequester carbon, and provide food and shelter for countless animals, plants, and fungi.

Yet even though trees have been recognized as an essential natural solution to climate change and biodiversity loss, far fewer resources are devoted to their study and conservation.

The amount of federal funding going to plants is about 5% of that going to animals, Westwood said. As a result, many more people and organizations are focusing on the study of animals, even though, she said, there are many more plant species than animals, and animals depend on plants.

“It’s a huge problem,” Westwood said. “Botany programs continue to disappear (from universities). And that just contributes to this “plant blindness” problem where we see trees as that kind of backdrop, they are rarely seen as individuals. They are a bit like the palette on which our animals are painted.

At the most basic level, the checklist and threat assessment serve as the foundation upon which further advocacy and awareness can be built.

This applies to city dwellers living in places like Chicago, even though the checklist only assessed native trees in the wild. People can participate in a day of restoration work in a forest reserve, they can campaign for more protected areas and more green space, they can plant a native oak tree in their backyard, Westwood said.

“You see gardens around (Chicago) where you might have a ton of native species and it’s thriving and the trees are super healthy. It’s a great way for us to support those species at the interface between the natural and built environment,” she said. “We can make our urban areas more like natural areas with native plants and green corridors, and all of that can help wild areas in the long run. “

Contact Patty Wetli: @pattywetli | (773) 509-5623 | [email protected]


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