New research suggests that the shrubs that grow in the Arctic may be worsening global warming as shrubs were found to gradually increase across the tundra.

Scientists said that the increasing dominance of shrubs over grasses is a result of climate change. With shrubs taking over, experts said, the amount of sunlight reflected by snow is reduced because shrubs provide a darker surface and alter the temperatures of the soil, which cause the thawing of the permafrost.

For the new study published in the Nature Climate Change on July 6, David Hik, from the University of Alberta, Edmonton, and colleagues looked at nine Arctic countries and data spanning 60 years.

They found that with the increase in the global temperatures, the amount of shrubs has also increased and the type of shrubs in some areas has shifted to taller plants such as willow and alder.

The researchers have likewise found that the distribution of shrubs has moved further north and the changes happen faster in Russia and northern Europe than in North America. The soil moisture and depth were also identified as important contributors to how the shrubs expand in their range.

"Our analyses demonstrate that the sensitivity of shrub growth to climate was: (1) heterogeneous, with European sites showing greater summer temperature sensitivity than North American sites, and (2) higher at sites with greater soil moisture and for taller shrubs (for example, alders and willows) growing at their northern or upper elevational range edges," Hik and colleagues wrote in their study.

The researchers said that these changes could have a crucial impact on the Arctic ecosystem as some animals prefer shrubs while others, such as the caribou, consume lichen and other species of grass that cover the northern parts of the Arctic.

The thawing of the Arctic permafrost, which stores massive amounts of greenhouse gas such as methane, can also worsen global warming since the climate changing effects of methane are more potent compared with carbon dioxide.

"Arctic shrub growth in the tundra is one of the most significant examples on Earth of the effect that climate change is having on ecosystems," said study researcher Isla Myers-Smith, from the University of Edinburgh. "Our findings show there is a lot of variation across this landscape. Understanding this should help improve predictions of climate change impacts across the tundra."

Photo: USFWS | Flickr