In 2007 researchers at Zackenberg in high-arctic Greenland reported some of the fastest rates of spring advancement ever observed on the globe. After some 15 years, these researchers now revisit the extended records. They find that the original, extreme rates of phenological change have been replaced by large year-to-year variation in the timing of events. Thus, springs are no longer getting consistently earlier, but one spring may be drastically different from the previous one.

Arctic organisms are well-adapted to life under the extreme climatic conditions found in the region, and the phenology (i.e. timing) of most species track the local climatic conditions closely.
Unfortunately, long-term observation of high-arctic ecosystems are rare. In a report published 2007, researchers recording the timing of spring-time events over a full decade reported extremely rapid rates of phenological advancement in plants, arthropods and birds. In brief, spring was getting very much earlier for most species in the region.
Given the rarity of such data from the high-Arctic, the paper affected the global perception of arctic change.

From rapid advancements to huge fluctuations in onset of spring in the high-Arctic
Today, with 15 more years of data available, researchers have revisited the very same – but now extended – time series. And in contrast to earlier rapid advancements, the researchers found that previously-consistent trends towards earlier timing had turned into erratic variation.
The authors attributed this pattern to a shift in climatic conditions from directional change to a new climatic regime, where conditions vary wildly from one year to the next.

“The lack of directional change in spring phenology across all these distinct taxonomic groups does not mean that the system is stable”, says Niels Martin Schmidt (Aarhus University, Denmark), lead author of the study and responsible for the collection of biological data at Zackenberg as part of Greenland Ecosystem Monitoring (www.g-e-m.dk).
“On the contrary, we see such marked contrasts in climatic conditions from one year to the next that no phenological trends are evident. However, we do also see that some organisms may be close to their phenological limits and thus can’t keep up with the large fluctuations in in particular temperature. Our study shows that climate change is more than “just” continued warming – in many ecosystems, such as the high-Arctic, it’s the climatic variability that determines the dynamics of community over time, and ultimately how this high-arctic community thrives”.

When species meet their phenological limits, they may become decoupled from the climatic drivers, and this may in turn impact interactions between species.

“The delicate interplay between flowering plants and the pollinators very much depends on the timing”, says Tomas Roslin (Swedish University of Agricultural Sciences, Sweden), senior author of the study. “At Zackenberg, the timing of phenological events is driven by climatic conditions. However, if the timing of different species is not responding in the same way to climatic shifts, then they may get mismatched in time. This will be detrimental to for instance plant pollination, which is a key function in any ecosystem”.

“Being able to reevaluate previous findings is pivotal for the way we understand and perceive global change”, says Niels Martin Schmidt. “What our results really show is the importance of keeping a constant eye on nature. We must not assume that current trends will continue forever but should stay vigilant for shifting dynamics and new patterns. Keeping our boots on the ground is then essential – from the high-Arctic to the tropics. Because how could we ever respond to a change that we do not know about?”.

Link to article: Schmidt et al., Little directional change in the timing of arctic spring phenology over the past 25 years, Current Biology (2023), https://doi.org/10.1016/j.cub.2023.06.038

Contact details:
Niels Martin Schmidt
Department of Ecoscience, Arctic Research Centre, Aarhus University, Roskilde, Denmark
E-mail: nms@ecos.au.dk
Cell: +45 4191 5664