Trees need wind to reproduce. Climate change is messing that up. Popular Science

Trees may seem sedentary, but movement is a big part of their lives. To reproduce, many trees rely on wind to move their pollen and seeds around, says Matthew Kling, a postdoctoral researcher in plant biogeography at the University of California, Berkeley. 

A study led by Kling, published on April 27 in the journal Proceedings of the National Academy of Sciences, examines how wind patterns affect the exchange of DNA between populations of trees. Their findings suggest that factors such as wind strength and direction can help mold the genetic makeup of forested landscapes. 

As the climate heats up, some plants won’t thrive as well in their current environments, and will need to be in historically cooler locations to stay within a comfortable temperature range, says Kling (for many plants, this is already happening). But plenty of questions remain around precisely how the plants will get there, he says, “and one of the biggest areas of uncertainty in plant movement is related to wind,” because wind dispersal can be tricky to measure at large scales. 

Kling and his coauthor David Ackerly, a professor of integrative biology at UC Berkeley used 72 previously published scientific papers to gather genetic data on nearly 2,000 populations of trees belonging to nearly 100 different tree species around the globe. The researchers took this genetic data and compared it to a “windscape” model they developed, which pulls from three decades of hourly wind data.

The wind model provides a prediction for the way we would expect dispersal of seeds and pollen to take place across large geographic scales and long time periods, says Kling. “And the genetic data provides a measured estimate, totally independent of the wind data, of the way that the seeds and pollen have dispersed across large landscapes in the past.” The authors then compared the predictions made by the wind model to the observed genetic patterns, allowing them to test whether the wind was actually driving them. 

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“We found evidence that migration of seeds and pollen tends to happen preferentially in the direction of the prevailing wind,” says Kling. In other words, the seeds and pollen are carried downwind more often than they’re carried upwind. They also found that populations located downwind—or in the direction the wind is blowing—were typically more genetically diverse overall. In addition, they found that distinct tree populations connected by stronger winds were more similar to one another than populations connected by weaker winds, suggesting that migration is happening between those populations. 

“In many ways the findings of the paper are predictable—many plant-focussed researchers have understood the links between wind dispersal of pollen and seed, and how those factors can contribute to or limit reproduction, dispersal, connectivity, and genetic diversity,” wrote Jasmine Janes, an evolutionary biologist at Vancouver Island University who was not involved in the research, in an email to Popular Science. “What’s interesting about this paper is that it brings many of these ideas together and tests them on a range of data sets,” so that scientists and forest managers can gain a deeper understanding of broad patterns. 

Understanding how quickly the location range of a species of trees can migrate in response to climate change is important, says Kling, but it’s also important to consider how different genetic adaptations may be able to travel between populations of a given tree species. “We can imagine that over time, perhaps populations in different climates and different parts of the species range have evolved different adaptations to survive better in those particular climates,” says Kling. 

“As climate warms, it’s going to be important for those genetic variants to be able to move around different populations in the species range, to help those other populations be better adapted to the warmer conditions of the future.”