Swedish researchers recently accidentally opened a "hidden DNA archive" using aerial samples collected by the Swedish military decades ago. They found that mosses in northern areas are now releasing spores weeks earlier than in the past, showing that nature's seasonal rhythms are rapidly being rearranged.
As early as the 1960s, the Swedish military began to systematically collect air samples in order to monitor radioactive fallout produced by nuclear tests. The goal at that time was entirely radiation monitoring and had nothing to do with plant ecology. However, these samples stored on glass fiber filters also captured a large number of biological particles such as pollen and spores from the air, and were "frozen" in time together with their DNA, until their value was rediscovered by scientists many years later.
A team of researchers from Lund University and other institutions conducted DNA analysis on this batch of aerial samples spanning 35 years, focusing on changes in the timing of spore release in 16 moss species and species groups. The results show that compared with 1990, moss spore dispersal begins on average about four weeks earlier, and spore release peaks a full six weeks earlier, which is particularly significant at high latitudes where summers are already short.
The study pointed out that this "significant shift" in time is closely related to climate warming, especially the warmer autumn, which provides moss sporangia with a longer development window, giving them a "starting advantage" to release spores earlier in the following spring. Even more unexpectedly, the key to determining when the spores are dispersed is not the current spring temperature or the timing of snowmelt, but the climate conditions from the previous year, which had a "delayed effect" on the growth and development of the moss.
Scientists involved in the study emphasized that this result is not only a clear example of how climate change can rapidly reshape ecosystems, but also provides a new method for tracking long-term changes in biological phenomena. The same air DNA (eDNA) analysis technology can also be extended to other plant and animal taxa. Because these sample collection points are spread across northern and southern Sweden, researchers can trace the trajectory of ecological changes along the temporal and geographical axes simultaneously.
The team expects these quantifications of how the state of nature has changed since the 1970s will provide an important basis for "observed climate impacts" in future reports from the United Nations Intergovernmental Panel on Climate Change (IPCC). The related paper, entitled "Aerial environmental DNA reveals rapid shifts in moss phenology", was published in the Journal of Ecology in October 2025.