Unlike animals, plants are rooted to a place and don’t have the ability to get away when things take a turn for the worse. This can pose great challenges when a changing climate makes certain areas less suitable.
Yet while individual plants cannot migrate, plant species can. They do this by having their seeds spread in the hope that some of them will land in hospitable terrain. And as plants migrate in this way over time, entire ecosystems might need to migrate with them in a process that is being studied by scientists.
“Plants are shifting their geographic ranges, and this is happening whether we realize it or not,” observes Jenny McGuire, an assistant professor at the Schools of Biological Sciences and Earth and Atmospheric Sciences at Georgia Tech in the United States who co-authored a study on investigating how and why plants moved over geographic time in North America and where they are heading.
“As seeds fall or are transported to distant places, the likelihood that the plant’s seed is going to be able to survive and grow is changing as climates are changing,” McGuire explains. “Studying plants’ niche dynamics over thousands of years can help us understand how species adapt to climate change and can teach us how to protect and maintain biodiversity in the face of rapid climate change to come.”
If a plant has “climate fidelity,” it adheres to its preferred climatic niche even if that entails migrating across geographic areas over thousands of years to keep up with its ideal habitat. Plants that don’t have this feature prefer instead to adapt locally in the face of climate change, McGuire eludicates.
The scientist and a colleague examined data from more than 13,000 fossil pollen samples taken from 337 locations across North America and divided the pollen data into six distinct periods of time of 4,000 years, starting from 18,000 years ago. Their aim was to see how each tree species’ climatic conditions have changed from one period to the next over time.
“This process allowed us to see the climate fidelity of these different plant taxa, showing that certain plants maintain very consistent climatic niches, even when climate is changing rapidly,” says Yue Wang, an associate professor at the School of Ecology at Sun Yat-sen University in China who worked with McGuire.
For example, when glaciers in North America were retreating 18,000 years ago, spruce and alder trees migrated northward to maintain the cool temperatures of their habitats. In fact, most plant species in North America have shown a tendency for climate fidelity over the past 18,000 years, Wang says.
However, some species are inherently better able to migrate than others. Willows, for instance, have small seeds that can stay airborne over long distances, enabling the trees to travel farther faster over a relatively short period. The large seeds of ash trees, however, can be dispersed only over short distances, hindering the trees’ ability to migrate in lockstep with changing temperatures.
“Habitat disruptions from humans could make it even more difficult for ash trees to be able to take hold in new regions. If there are no adjacent habitats for ash trees, their seeds are under pressure to move even farther — a particular challenge for ash, which slows their migration movements even more,” the scientists note in a statement on their findings.
A better understanding of plant migration could help us adjust conservation efforts, the experts say,
“I think that understanding climate fidelity, while a new and different idea, will be very important going forward, especially when thinking about how to prioritize protecting different plants in the face of climate change,” McGuire says.
“It is important to be able to see that some plants and animals are more vulnerable to climate change, and this information can help build stronger strategies for protecting the biodiversity on the planet.”
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