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Climate change is threatening North America's wildflowers, Carnegie Museum research shows

Mason Heberling
Courtesy of the Carnegie Museum of Natural History

Researchers with the Carnegie Museum of Natural History report warming temperatures caused by climate change are putting North American wildflowers, abundant in southwestern Pennsylvania, at risk.

Plants on the forest floor need to get as much light as possible before trees sprout leaves each spring, according to the study, published in the journal Nature Communications last month. Once they do, it’s harder for understory species, like wildflowers, to access sunlight.

But climate-related warming means the seasons change earlier, leading trees to put out their leaves sooner and leaving wildflowers with a shorter window of time in the sunlight.

“If they experience reduced access to light as we project, then they're not going to have the amount of energy from photosynthesis that they need in order to survive and reproduce,” Ben Lee, a post-doctoral fellow at the Museum of Natural History and the lead author of the study.

Scientists surveyed data from 5,522 individual specimens collected from 1901 to 2020, representing 40 species across the three continents. In doing so, they found forest life in North America is more at risk due to this shift in light access than in Europe and northeast Asia.

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That’s because canopy trees in North America were significantly more sensitive to spring temperatures and experience longer springs. At the same time, wildflowers on the continent aren’t as sensitive to these changes, so while the trees’ leaf-out date is shifting earlier, it’s happening faster than wildflowers in North America are able to grow, Lee said.

On the other hand, trees in Europe have a similar temperature sensitivity to that of wildflowers. Since one isn’t changing more or faster than the other, wildflowers are projected to maintain their access to spring light as temperatures rise. Scientists project wildflowers in Asia will not lose access to light for similar reasons.

Forests maintain a delicate balance of species

While wildflowers are just one part of a forest ecosystem, Lee said losing them would disrupt the whole food chain.

“The different colors and the different shapes that they are all coordinate to different pollinators and different organisms that come by and eat the flower, for instance,” Lee explained. “Deer eat a crazy number of wildflowers.”

The understory layer in temperate forests worldwide accounts for about 80% of the ecosystem’s plant species diversity, Lee said. Maintaining the balance between them is critical to the food web that all species--including humans--depend on.

“If you maintain pollinators, you maintain crops, which are vital to humans. So if we lose pollinators, we're not going to do well in agriculture either,” he continued.

While it’s not yet clear to scientists why the disparity across continents exists, Lee said wildflowers face different conditions they must adapt to in each place. Winter and spring temperature variability, for instance, is higher in eastern North America than in Asia and Europe. Lee said scientists think it can also affect plants’ growth patterns and how well they adjust to changing conditions over time.

Courtesy of the Carnegie Museum of Natural History
Ben Lee, a post-doctoral fellow at the Carnegie Museum of Natural History and the lead author of the study, says if wildflowers experience the reduced light access the study predicts, they won't have the energy they need to survive and reproduce.

That includes environmental conditions caused by humans, like acid rain in the eastern United States.

“It’s no longer such an issue, but the legacy effects there might affect what we see,” he added. “But in general, the warming associated with climate change is what's really driving these effects, but it's doing so on all of the continents.”

Conserving biodiversity at home

The threat climate change poses to wildflowers in North America compounds the effects of human-caused risks these plants already face, including habitat loss and soil pollution.

While alleviating these threats and reducing climate change at large requires global cooperation, Lee said there are many things people can do to prevent biodiversity loss at home. That includes swapping out manicured lawns for more native plants and habitats, like pollinator and rain gardens, and helping researchers collect data on how and where species live.

Lee also encourages people to use apps that give everyone the tools they need to collect important ecological data, like iNaturalist. The app was created by graduate students at UC Berkeley in 2008.

“Wherever you are, you take a picture,” he said. “You don't you don't need to be a botanist. You don't need to know what species it is.”

Along with a community of citizen scientists, the app has AI technology that can help identify the species of the plant or animal captured. That information then becomes available to scientists around the world, who need data to track where biodiversity is and how to keep it alive, especially when a broad range of geography is needed.

“The world is changing around us. It's something that we can quantify, that we can measure, but it's also something that you can see in your backyard,” Lee said.

Jillian Forstadt is an education reporter at 90.5 WESA. Before moving to Pittsburgh, she covered affordable housing, homelessness and rural health care at WSKG Public Radio in Binghamton, New York. Her reporting has appeared on NPR’s Morning Edition.