Old military air samples turned out to contain a hidden DNA archive showing that northern mosses now release spores much earlier than in the past.
By examining DNA preserved in decades-old air samples collected by the Swedish Armed Forces, scientists at Lund University in Sweden have found clear evidence that northern mosses now release their spores much earlier in the year than they once did. The shift spans several weeks, offering a striking example of how quickly seasonal patterns can adjust as the climate warms.
When the Swedish military began gathering air samples in the 1960s to monitor radioactive fallout from nuclear weapons tests, the focus was entirely on radiation, not plant life. Yet the glass fibre filters used to store the samples also trapped unexpected material. They held DNA traces from pollen, spores and other biological particles. Researcher Per Stenberg of Umeå University was the first to recognize the scientific value of this overlooked genetic record.
“The samples have proved to be an unexpected, unique and very exciting archive of DNA from wind-dispersed biological particles,” says Nils Cronberg, researcher in botany at Lund University.
Using this archive, the research team examined changes in the timing of airborne moss spore release across 16 species and species groups over a 35-year span. Their analysis shows that, on average, the start of spore dispersal now occurs four weeks earlier than it did in 1990, and peak release happens six weeks earlier.
“It’s a considerable difference, especially considering that summer is so short in the north,” says Nils Cronberg.
Climate’s Delayed Influence
Warmer autumns mean that the mosses’ spore capsules have a longer time to develop before the onset of winter – a biological kick-start that enables the spores to be released earlier in the spring. But perhaps what is most surprising is that it is not the current spring weather that controls the timing of spore dispersal.
“We had expected that snow thaw or air temperature in the same year as spore dispersal would be crucial, but climate conditions the year before were shown to be the most important factor,” says Fia Bengtsson, formerly a researcher in botany at Lund University, who is now at the Norwegian Institute for Nature Research.
In addition to showing how fast climate change affects ecosystems, the study paves the way for a completely new method for understanding biological changes over time. The same type of DNA analysis can also be conducted for other plant and animal groups. As the collection points are all over Sweden, the researchers can follow developments back in time through the decades – from north to south.
“We anticipate that our results and knowledge about how nature has changed from the 1970s onwards will be part of the next report by the Intergovernmental Panel on Climate Change (IPCC) on the documented effects of climate change,” concludes Nils Cronberg.
Reference: “Rapid shifts in bryophyte phenology revealed by airborne eDNA” by Fia Bengtsson, Nils Cronberg, Jose Antonio Lozano Villegas, Abu Bakar Siddique, Per Stenberg and Johan Ekroos, 15 October 2025, Journal of Ecology.
DOI: 10.1111/1365-2745.70180
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1 Comment
“… Unexpected Changes in Nature’s Seasonal Rhythms”
Why would that be unexpected? We know that the dates for the first and last severe frosts have been changing over past decades. Clearly, this isn’t the first time that plants have been exposed to changes in the length of the growing season and they have adapted to the changes. They are doing what plants do, which is maximizing their opportunity to use the available resources to improve their potential for successfully surviving and expanding their biological niche. Why is it that changes in the climate are implied to have potential negative changes instead of just being a window into understanding how life adapts to changes?