Trees for 2050

A study of suitable trees for a warming midwestern climate

Andrew Bell —  September 4, 2013 — 9 Comments

A living museum presents special challenges to its curators.

At the Chicago Botanic Garden, we not only acquire and display our collections, but we must also keep them alive and healthy. As curator of the Garden’s collection of woody plants, I’m responsible for the welfare of more than 13,000 trees. Disease, infestations, and extreme weather events are the kinds of things that keep me awake at night.

If you have recently lost a tree to emerald ash borer, you may wish to view our short list of ash replacement selections. Our full list of suggested trees for adaptive planting is linked below.

As you may know, the Garden is undertaking a ten-year plan to remove about 400 trees due to the emerald ash borer. It’s up to me to suggest suitable replacements to continue our tree legacy. To do so, I first needed to know which of the trees now growing in the Garden would continue to thrive in a warming urban environment. Thanks to a $120,000 research grant from the U.S. Institute of Museum and Library Services, we’ve been able to undertake an adaptive planting study to identify which trees will continue to thrive in Chicago’s urban forests under worst-case carbon-emissions scenarios.

Climate-change modeling indicates that some trees—those currently growing at the northern edge of their hardiness—will actually do a little bit better in slightly warmer conditions around 2020, but by 2050, ten of the 50 trees under study—20 percent—will no longer find the metropolitan area a welcoming habitat. The real concern sets in when we look at the data for 2080, which projects that only 11 of the initial trees would continue to do well in Chicago and the upper Midwest.

The trees growing along our city streets, parks, residences, and public gardens enhance the quality of metropolitan living and also play an important role in reducing greenhouse gas emissions. The cooling summer leaf canopy reduces our energy needs, and the trees themselves store significant amounts of carbon.

Our adaptive planting study suggests two key calls to action: drastically reducing carbon emission to slow climate change and help protect existing trees, and carefully selecting the trees we plant for future generations. To help both public officials and private property owners in their tree selections, the Garden has created an Adaptive Planting page on our website. There you’ll find information on a selection of 60 suitable trees for 2050.

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This project is made possible in part by a grant from the Institute of Museum and Library Services (IC-01-11-0145-11)
©2013 Chicago Botanic Garden and my.chicagobotanic.org

Andrew Bell

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Andrew C. Bell, Ph.D., serves as curator of woody plants and is responsible for managing the development of the Garden's tree and shrub collections. Dr. Bell's work includes evaluating and promoting woody plants for sustainable landscapes and studying the effects of climate change on urban street trees.

9 responses to Trees for 2050

  1. What can be done for the lifeforms which feed exclusively on Ash seeds, such as those listed here… http://ashalert.osu.edu/userfiles/EAB%20impact%20on%20forests.pdf

    • For those species that are dependent exclusively on ash for their survival, there is not much we can do to help them. Because the ash decline is occurring so rapidly, there is not much likelihood that those species will be able to adjust or evolve to utilize new host plants. For those species which utilize ash, but do not have an exclusive relationship with them (such as spiders), they will switch to alternative plant species and do OK. Canopy gaps which are created by the loss of the ash trees, and that may affect other plant and animal species, will likely be short-term impacts that will be filled-in by other tree species. In our oak woodland at the Garden, the gaps created by the missing ash trees contain sapling and seedling oak trees which will do better now that they are receiving more light and will fairly quickly close those canopy gaps. This is not to suggest that the loss of the ash trees is not a serious problem. Any time you reduce the species diversity in a system, the system is less resilient, less able to adjust to environmental changes, both natural and man caused. As an ecologist, the next question is – what happens to those species that are dependent on the first wave of species to be lost? In nature, no species exists unto itself.

  2. Elizabeth Sorkin September 7, 2013 at 4:08 pm

    Thanks for your list of trees for the future. It has been most informative. We are replacing two lost elms on the sunny, west side of our house in Evanston and are considering the Silver Leaf Linden Tree. Is this tree going to have a long, sustainable life under the changing environmental conditions? We have already lost elms am now the ash trees are showing signs of dying.

    Many thanks, we appreciate all of your work in putting together this list.

    • We did not include silver linden (Tilia tomentosa) in our study so I can not say for sure how it will respond to climate change but the silver linden has demonstrated greater adaptability to heat and drought than other species of Tilia. I would not be surprised it if continues to perform well in the mid-century decades and beyond.

  3. I was considering the state street maple for a replacement of an ash tree. Is this tree going to be okay in 2050?

    • Like the silver linden, we were not able to include this tree in our modeling but it’s definitely one we should look at as we continue the research; it’s a really great tree for the urban landscape. The climate change modeling that we conducted is very time consuming thus we were only able to include 50 trees at this time but we hope to include more in the near future.

  4. Looks like a great study. Thanks for sharing this. I conducted a multi-year study to find the most appropriate trees for our city (Kansas City) by asking local experts to numerically rate each tree cultivar for different attributes and averaging all submitted ratings. You might find it interesting. Of all the trees that you mention in this post, only hackberry performed poorly in my study. Feel free to contact me if you would like more information on the study. I hope to conduct similar studies for other metropolitan areas.

    http://www.gouldevans.com/studio/pl/treelist/

  5. Hi Andy — I had hoped to chat with you about this at the urban tree conference a couple of weeks ago but I had to leave after my own presentation. Like you, I have been observing hundreds ot tree species for their responses to our increasingly unstable climate here in the Midwest. I am about 200 miles southwest of you. I’m curious about your methodology because I have reached some conclusions that substantially mesh with yours, but with notable exceptions. For example, Ostrya virginiana has been stalwart through our record heat and drought here during 2012 and continuing into 2013, as well as the notable drought years (in my area) of 2006-07, 1988, 1983, and 1977-78. It also fares better than many others during the ice storms that are becoming (or in your area, are likely to become) more frequent and severe, and it resists wind damage as well as opportunistic insects and diseases. This tree has a huge natural range, extending into very hot areas in Central America, with a broad diversity in site adaptability. Thus, you and I obviously are looking at different parameters. How did you reach the conclusion that this species would not be able to adapt even to the less severe climate expected up there when it does so well down here in central Illinois and points to the south?
    Thanks for any insights or references you can provide —
    Guy S.

  6. Similar question as Guy’s for shagbark hickory. Curious if, or how, you account for seed source. Shagbark hickory is native all the way to Texas. Why would you consider it unsuitable under a warmer climate in Chicago?

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