Moss spores are now launch weeks earlier due to climate warming

Air carries more than dust and pollen – it carries a biological archive. For decades, tiny moss spores drifted across northern skies, quietly capturing how seasons shifted as the climate warmed.

Scientists can now read that airborne record by pulling DNA from old monitoring filters, revealing changes no one could see at the time.

The results are striking. Mosses are moving their reproductive schedules forward by weeks, reshaping their life cycles in response to warmer falls and shorter winters.

Many species now release spores long before they once did, showing just how quickly these small, ancient plants react to seasonal disruption

Moss spore timing leaps forward

Early work with Swedish air filters showed moss spores now rise weeks earlier. The new research expands that picture.

The study reveals that most moss and liverwort groups have advanced their early season by three to six weeks over recent decades. Some groups also show changes in the peak of their spore release. A few even disperse later in the year.

These results match a clear trend. Northern temperatures have climbed steadily. Many moss species react more quickly than flowering plants. Their simple structure and strong climate dependence allow rapid shifts.

“The samples have proved to be an unexpected, unique, and very exciting archive of DNA from wind-dispersed biological particles,” said study co-author Nils Cronberg, a researcher at Lund University.

Moss biology drives quick shifts

Bryophytes lack the water transport systems that vascular plants use. They grow only when moisture is present. They also rely on water for fertilization.

The male cells need a thin film of water to reach the female parts. Temperature, humidity, and light shape their entire reproductive cycle.

These traits help explain why moss spores respond so quickly to warmer seasons. Warmer falls let spore capsules grow further before winter.

Many species pause development over winter, but that pause varies among them.

Some hold mature capsules under snow. Others rely on early spring cues. In warmer years, this rest period shifts, allowing earlier spring release.

Climate cues shift cycles

The researchers expected current spring weather to drive spore timing. Instead, the key driver turned out to be the climate of the previous year.

Warm late-season conditions appear to let sporophytes mature more before winter. This supports earlier spring release once light and temperature return.

Different species respond in different ways. Some shift sharply, while others show little change. One liverwort group exhibits almost no shift at all.

This suggests that some species rely more on day length than temperature. The mix of strategies reveals how diverse bryophytes are in their climate responses.

“It’s a considerable difference, especially considering that summer is so short in the North,” said Cronberg.

The survival of moss spores

Most moss groups now experience longer spore seasons overall. Their release period has expanded by several weeks.

Some groups exhibit double peaks in activity, likely caused by mixed species within a genus or shifts in weather-driven cues.

A few groups cluster strongly in early summer. Others wait for drier periods when capsule teeth can open.

Spore travel also adds complexity. Most spores fall close to their parent plants, but some travel many miles under the right conditions.

Their survival in air depends on humidity and UV exposure. Many remain viable long enough to reach new ground.

“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,” said Fia Bengtsson, an ecologist at Lund University and the study’s corresponding author.

Airborne clues mark warming

Airborne environmental DNA gives scientists a way to study plant cycles without long field surveys. This method captures moss spores, pollen, and even fragments missed by traditional tools.

The results show how timing shifts vary between species. The findings also suggest that some moss groups may expand into new habitats as warming reshapes microclimates.

These rapid shifts matter for ecosystems. Mosses influence soil insulation, moisture, carbon storage, and nutrient cycles.

Their timing affects grazers, plant competitors, and the structure of northern landscapes. Their changing schedules mark clear signals of climate change.

Ultimately, the research shows that even the smallest plants track climate shifts with remarkable speed. Their spores drift through the air as tiny timekeepers, recording the pace of a warming world.

The study is published in the Journal of Ecology.

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