Scientists studying Arctic plants say the ecosystems that host life in some of the most inhospitable reaches of the planet are changing in unexpected ways in an “early warning sign” for a region upended by climate change.

In four decades, 54 researchers tracked more than 2,000 plant communities across 45 sites from the Canadian high Arctic to Alaska and Scandinavia. They discovered dramatic shifts in temperatures and growing seasons produced no clear winners or losers. Some regions witnessed large increases in shrubs and grasses and declines in flowering plants – which struggle to grow under the shade created by taller plants.

Those findings, published in Nature, fill key knowledge gaps for teams on the frontlines of a changing climate.