Credit: © US Fish and Wildlife Service

If the Arctic tundra is invaded by shrubs, the air temperature above the snow could increase by 2.2 °C in the springtime, a new study shows. Shrubs cause deeper snow cover by providing wind breaks. But because they absorb more energy from the sun than snow, which is then radiated back to the air and snow, they can also contribute to warming and melting snow. The overall effect of shrub presence on the Arctic tundra, particularly during the spring melt, is therefore hard to predict.

John Strack from the University of Colorado and colleagues1 studied the impacts of shrub invasion using a regional model of the atmosphere and snowpack of Kuparuk Basin in Alaska that incorporated vegetation, soil, air and snow properties. They found that although there was more winter snow when shrubs were present, the snow melted 11 days earlier than in the absence of shrubs. Also, with shrub coverage, the air temperature above the snow was, on average, 2.2 °C warmer during the spring.

Owing to increasing temperatures, the number and size of deciduous shrubs is growing in Arctic Alaska. The botanical feedback could exacerbate regional climate change.