Three million observations over twenty years put land use ahead of temperature for butterflies, birds and small mammals, which was not what the Helsinki team expected to find.

When a species turns up somewhere it did not used to be, or disappears from somewhere it used to live, climate is now the first explanation reached for. It is often right, and it has the advantage of being measurable on a map at continental scale.

A study in Nature Communications from the University of Helsinki tested it against the alternative across an entire country and found climate coming second for most of the animals examined — a result the researchers say ran contrary to their expectations.

The analysis covered 503 terrestrial animal species across all of Finland and its climatic zones over twenty years, drawing on more than three million observations. Habitat composition explained occurrence and abundance better than climate for most groups.

Which animals, and by how much

The effect was not uniform. “The habitat proved to be of special importance to butterflies, birds, and small mammals,” said Emy Guilbault, the study’s lead author and a Humboldt Foundation Research Fellow.

“As for large mammals and moths, the relative importance of the habitat and climate were equal,” she said.

That grouping has a logic to it. Butterflies are closely tied to particular host plants, and a host plant’s presence is a function of land use. Small mammals live at scales where a hedgerow or a drained wetland is the whole world. Large mammals range over distances that average across many habitat types, so for them the broader climatic setting carries proportionally more weight.

Finland is a useful place to run this comparison. It spans a substantial climatic gradient from the Baltic south to the Arctic north, so there is real variation in temperature to detect, and it has the kind of long-running, volunteer-supported biological recording that makes three million observations possible.

Different questions, different answers

The most useful thing in the study is not which factor won but the finding that each one explains a different kind of variation.

Climate best explains the differences between northern and southern Finland, and the year-to-year variation in communities. Habitats best explain local and regional variation.

Stated that way the apparent conflict with other research largely dissolves. A continental-scale study comparing Spain with Finland is asking a question climate answers; a study comparing two valleys in the same region is asking one habitat answers. Much of the disagreement in this literature may be about the scale of the question rather than about the world.

“In many cases, land use can have an even more decisive impact on species, especially locally and regionally,” Guilbault said.

She is also careful not to let the finding be read as a dismissal of climate change. “At the same time, climate change and habitats cannot be completely separated from each other,” she said, and the study reports that climate and habitat have significant combined effects on biodiversity.

The entanglement runs in both directions. Climate shapes which habitats exist in a place over time, and land use alters local climate directly — a cleared field is warmer and drier at ground level than the forest it replaced, which is why habitat loss and warming often act on a species through the same physiological channel.

Which species feel the climate

One pattern ran across nearly every group. Species with slow reproductive cycles were more sensitive to climate than faster-reproducing species.

The reason is adaptive capacity measured in generations rather than years. A species producing several generations annually gets many rounds of selection and many chances to shift its timing or range within a decade of warming. One that breeds once a year, or less, experiences the same change with far fewer opportunities to respond.

Among small mammals the pattern had a further wrinkle: those with a specific habitat or food preference depended on climate, while habitat mattered more for larger, less specialised mammals. For birds, butterflies and moths, body size and degree of specialisation made no difference to whether climate or habitat dominated.

The inconsistency across groups is itself informative, and it is the kind of detail that gets lost when results are summarised as a single ranking. Whatever makes a small specialist mammal climate-sensitive does not operate the same way in birds, and a conservation rule of thumb built on one taxon will not transfer.

What follows for conservation

Professor Jarno Vanhatalo of the University of Helsinki draws the practical conclusion.

“To preserve biodiversity, we should put greater effort into the protection and restoration of the remaining habitats,” he said. “Maintaining habitat diversity is an action that also helps species cope with climate change.”

The second sentence is the one that resolves the apparent tension. Habitat and climate are not competing policy priorities in the way they are competing statistical predictors: a landscape with varied habitats offers more microclimates, more refuges and more routes to move through, which is precisely what a species needs when the regional climate shifts underneath it.

Vanhatalo adds that conservation efforts should take species characteristics, regional differences and temporal variation into account — a recommendation that follows directly from the study’s structure, since those are the three dimensions along which its answers changed.

There is also a political reading worth naming. Habitat protection is a local decision with identifiable costs and identifiable beneficiaries, which makes it contestable but also actionable by a national or regional government. Climate is neither. A finding that local land-use decisions carry as much weight as global temperature, at the scales where most conservation actually happens, returns some agency to the people making those decisions.

The study’s co-authors include L.H. Antão and A. Santangeli; the release does not name the remainder or state the study’s funding sources.

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Notes

1. Guilbault, E., et al. Nature Communications, 2026. DOI: 10.1038/s41467-026-78359-2.
2. University of Helsinki. “Habitat quality accounts for shifts in Finnish species more than the climate.” EurekAlert!, 22 October 2026. https://www.eurekalert.org/news-releases/1148818.

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