At the Kevo Research Station in Utsjoki, perched in the northernmost corner of Finland's Lapland, researchers have been trapping moths under ultraviolet light since the early 1970s—and what 45 years of data reveals is a landscape in flux, where ocean rhythms thousands of kilometers away beat out the pulse of life on land.
Oceanic regime shifts in the Atlantic and Baltic seas are reshaping subarctic moth communities in ways that divide species into clear winners and losers, according to a new study from the University of Turku published in Insect Conservation and Diversity. The findings matter because they illustrate an overlooked truth: climate change doesn't affect all creatures equally, and sometimes, paradoxically, the global picture includes unexpected bright spots.
Between 1972 and 2017, researchers tracked how moth populations fluctuated and which climate variables drove those shifts. The headline finding was counterintuitive: total moth biomass at Kevo had moderately increased over the four decades—a result that stands in stark contrast to alarming global trends of collapsing insect populations. "We discovered that total moth biomass and biomass of different moth groups are clearly connected to the regime shifts in the Atlantic Ocean and the Baltic Sea," explains postdoctoral researcher Julia Fält–Nardmann. Regime shifts are abrupt transitions in marine ecosystems where they move from one stable state to another, triggered by changes in salinity, temperature, or other large-scale ocean dynamics. Two such shifts occurred during the study period, and the same climate systems that regulate the Baltic Sea's marine environment also govern the terrestrial ecosystems of Lapland.
The story becomes more complex, however, when zooming in on individual moth groups. Local weather variables—minimum and maximum seasonal temperatures, frost patterns—shaped which species thrived and which struggled. Larvae that overwinter underground can suffer from repeated freezing and thawing of soil; the timing of their host plants' budbreak matters enormously. Specialized species dependent on certain plant hosts have declined, while generalists feeding on multiple plant species have become more common. Moths that overwinter as eggs fare better in warming conditions than those wintering as larvae.
This patchwork of winners and losers reflects a deeper principle: climate change is rewriting ecological relationships in ways that are seldom uniform or simple. In Lapland and beyond, specialist insects are losing ground while generalists gain it. The implications ripple through subarctic food webs. Moth larvae, especially during their cyclical peak years when populations can surge thousands of times above background levels, are crucial prey for insectivores and drivers of defoliation events in mountain vegetation. Every ten years or so, massive outbreaks occur, creating feast-or-famine cycles that shape predator populations for decades.
The remote location of Kevo itself helps explain why these results differ from global doom-and-gloom narratives. "Elsewhere, the negative impact of human activities can obscure the results of corresponding studies. Kevo is far away from cultivated land and urban areas, which makes it an ideal place to study the impact of climate change on organisms," Fält–Nardmann notes. Moreover, polar regions have warmed faster than anywhere else on Earth, amplifying climate signals that might be muted elsewhere. The same research team previously documented that Atlantic regime shifts also drive changes in Baltic zooplankton biomass—but with opposite results: those tiny marine arthropods have declined, triggering cascading effects on fish like Baltic herring that depend on them.
The Kevo data thus offers a rare window into how distant ocean rhythms orchestrate changes in terrestrial life, and how the same warming can bring gain for some and loss for others.