If you wanted to point to a tree that can handle climate change, you might start with the bur oak.
When the Earth cooled millions of years ago and tropical species started to die off, the oaks began diversifying and moving southward. New species emerged and spread across North America, down into Mexico, and in time diversified further — giving rise to the nearly 300 oak species in North America.
A warming planet will reshape the range where oaks will and can grow. As the giant trees lurch northward, a multi-state investigation into the future of oak trees and American forests is underway at the Morton Arboretum in west suburban Lisle.
“This study can give us a good idea of how the most foundational species of our forests are going to evolve as conditions change. And with the evolution of the oaks with the migration of the oaks, those will shape the composition of the entire forest in our region,” said Andrew Hipp, a senior scientist at Morton Arboretum.
Walking past row after row of young bur oaks inside the botanic garden’s private research field, Hipp shows off the experiment in the common garden. One thousand bur oaks have been planted.
Back in 2021, Hipp said three identical gardens were seeded simultaneously across the bur oaks native range in Illinois, Minnesota and Oklahoma.
The goal is to see if different populations of bur oaks perform better in their current environment than in environments within the species range but still hundreds of miles away. Scientists want to know how the oaks will respond to different climates, and how that could affect forests in the future.
“It’s raining right now, as we talk, we all put on a raincoat. Oaks can’t do that. So they have to be able to respond to the climate that they find themselves in.” Hipp said.
To measure how the oaks respond, the team of scientists planted offspring from a single tree into three states across the oaks range.
The trees from Oklahoma should be adapted to the droughts and the ones from northern Minnesota should be adapted to freezing conditions. The expectation is that the oaks would do better in their home environments because they have had generations to adjust.
“If it turns out that oaks are strongly adapted to the local environment, that means they’ve had potentially thousands of years to evolve gene combinations that may prove advantageous in the future as climates change,” Hipp said.
Oaks dominate North American forests – approximately 30% of American forests, which means that this single group of trees provides a scaffolding critical for ecosystem services and diversity of other life forms. What happens to oaks, and how they respond to a warming planet will be profound.
Earlier this year, the Species Survival Commission of the International Union for Conservation of Nature designated the Morton Arboretum as the Center for Species Survival: Trees. It’s one of 11 research institutions worldwide, with only five in North America.
Morton Arboretum’s director of global tree conservation, Silvia Alvarez-Clare, said nearly a third of the more than 400 oak species around the world are at risk of extinction. This experiment could help scientists determine if the oaks need help migrating to preserve climate-adapted genotypes.
“These types of experiments can help us predict where we should be helping these trees move since change is happening so fast,” Alvarez-Clare said. “They may not have time to move through evolutionary time in thousands of years. It’s all happening so fast that we may have to help them and plant some of them.”
Across the three gardens, Jeannine Cavender-Bares, a plant physiological and evolutionary ecologist at the University of Minnesota, said that some overall results are becoming increasingly clear at the drier, hotter southernmost range of the experiment.
“So in a warming world, how do we maintain healthy forests?” said Cavender-Bares. “We need trees that are adapted, have the right genes, that are adapted to the environments of the future.”
Juanpablo Ramirez-Franco covers climate change and the environment for WBEZ and Grist. Follow him on X at @__juanpab.