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.
“Climate change is so widespread across the whole of the Arctic and we’re seeing this magnitude of warming at four times the rate than the rest of the planet. We expected to see very concrete trends and trajectories. Because in other biomes, we are,” said lead author Mariana García Criado, a postdoctoral researcher in tundra biodiversity at the University of Edinburgh. “But the Arctic is a special and often unexpected place.”
The researchers found greater species richness at lower latitudes and warmer sites, while species and the areas with the greatest growth – and loss – were in areas with the largest temperature increase.
In Canada’s western Arctic, for example, Isla Myers-Smith and her “Team Shrub” group of researchers have documented ecosystems rapidly shifting, where the tundra is “greening” at an incredible rate as shrubs such as willow push north and grow taller.
Shrubs are highly competitive: they grow taller and shade out other plants, extracting more resources in the process. As they take over, they push out the cottongrass, mosses and lichens that take hundreds – sometimes thousands – of years to grow. Higher temperatures and lengthened growing seasons mean this trend is unlikely to abate, and more broadly across the Arctic, the number and diversity of plants will keep growing.
“Often when we think about climate change impacts on the planet we think about biodiversity loss, but in the temperature-limited tundra, climate change is multi-faceted,” she said in a news release.
While an increase in biodiversity might seem like a beneficial shift for the region, experts caution those changes come with a steep cost.
“These ecosystems are so fragile and any changes to the species composition can really have strong effects on everything else. Changes start with plants, and if plants move, everything follows, said García Criado, adding that herds of caribou were among the most likely casualties, as bare spots on the tundra, favoured by the lichen that they like to eat, are overtaken by shrubs.
“This has cascading effects for Arctic animals that depend on these plants, also for food security for all the people that live in the Arctic, for local and Indigenous communities, but also for the more ecosystem function,.”
Greg Henry, a geography professor at the University of British Columbia who helped establish the study’s data collection system, said the research involved thousands of hours of fieldwork in remote locations, with teams “enduring extreme weather, clouds of biting insects and even the occasional polar bear encounter”.
But researchers didn’t have enough data to include mosses and lichens in the study. These cryptogams are critical for ecosystem function, particularly in the Arctic where there is a rich diversity in species.
García Criado said the results underscore the deep uncertainty in understanding the effects climate change has on life – and the way in which the Arctic often serves as a harbinger of changes to come.
“All these changes that we’re observing, they’re not limited to the Arctic. We may see them in the Arctic, but the consequences spread far beyond the confines of the region,” she said. “We want to understand these changes. And then we need to prepare for these changes. Because it’s not a question of if they might happen – it is a question of when.”
