Winds Strengthened by Global Warming May Disperse Seeds, Pollen Farther

October 18, 2009
Contact:

Gabriel Katul, (919) 613-8033, gaby@duke.edu, Note: For help reaching Katul, contact Tim Lucas, (919) 613-8084, tdlucas@duke.edu

DURHAM, N.C. – Increased updrafts induced by rising global temperatures may disperse seeds and pollen over greater distances, according to findings from a recent study by an international team of scientists including a Duke University micrometeorologist.

The study, published in September in the peer-reviewed journal Proceedings of the Royal Society B, found that an increase of air temperature of only a couple of degrees may increase the buoyant production of turbulent kinetic energy leading to increases in dispersal distances of plants in northern forests and the spread of plant species into forest clearings after logging or forest fires.

Gabriel Katul, professor of hydrology and micrometeorology at the Nicholas School of the Environment at Duke University, was second author on the study, which was headed by University of Helsinki researcher Anna Kuparinen and co-authored by Ran Nathan of the Hebrew University of Jerusalem and Frank Schurr of the University of Potsdam. The study used meteorological data gathered over the course of a decade at the Hyytiälä Forestry Field Station, located about 210 kilometers northwest of Helsinki. Much of the analysis was conducted at the University of Potsdam in Germany.

Kuparinen, Katul and their Israeli and German colleagues found that a temperature rise of only three degrees Celsius increased the dispersal distances of seeds and the speed at which plant populations spread throughout the growing season. The effect was most pronounced for plants with lightweight seeds.

Seed and pollen dispersal profoundly affects the spread and genetic variation of plant populations. Spreading into more favorable areas can help plants survive in a warming climate. Wind conditions play a key role in this process, as turbulent eddies or gusts in particular spread seeds efficiently even over long distances, Katul explains.

Based on the study’s results, the team concluded that global warming can accelerate the spread of plants in the northern forests but will not alone be enough to help plant populations relocate to new vegetation zones. On a local level, however, global warming-strengthened winds may have a significant impact as original and newly introduced species spread faster from one place to another and take over new patches of habitat.

The findings illustrate the complexity of ways in which increased temperatures associated with climate change may affect plants in northern forest habitats, and underscore the fact that the combined effects of global warming are difficult to predict.

Katul is widely cited for his work to develop mathematical models that emulate how far and high seeds and pollen can be carried by winds at various heights in forest canopies. He has authored or co-authored more than 195 peer-reviewed papers, including a seminal study, published in 2002 in the journal Nature, demonstrating that mechanistic models can be used to provide accurate probabilistic descriptions of long-distance dispersal of seeds by wind.