Climate change is shifting the Earth’s coldest forest northward

New research led by Northern Arizona University has found that global warming is causing the Earth’s coldest forests to shift northward. This phenomenon raises concerns about biodiversity, increased risks of wildfires, and mounting impacts of climate change on northern communities. 

The boreal forest is a belt of cold-tolerant conifer trees stretching nearly 9,000 miles across North America and Eurasia. It accounts for almost a quarter of our planet’s forest area and is the coldest forest biome.

In order to assess climate change’s impact on the boreal forest, researchers used 40 years of moderately fine resolution satellite observations and a variety of geospatial climate-related datasets of this forest. They found that vegetation became greener across most of the cold northern margins of the boreal forest, and browner along parts of the warm southern margins of this biome due to hotter and drier conditions which increased tree stress and death.

“There is emerging evidence that climate change is causing boreal trees and shrubs to expand into arctic and alpine tundra, while at the same time causing trees to become more stressed and die along the warm southern margins of the boreal forest,” said study lead author Logan Berner, an assistant professor of Forest Ecology and Ecoinformatics at the Northern Arizona University.

“These dynamics could lead to a gradual northward shift in the geographic extent of the boreal forest biome, but the extent to which such changes are already underway has remained unclear.”

Intriguingly, vegetation seems more likely to become greener in regions with high soil nitrogen, suggesting that soil nutrient availability is an important constraint on the response of boreal vegetation to global warming.

These changes could affect local plant and animal biodiversity, especially species such as caribou and moose that have highly specific foraging preferences (deciduous shrubs and trees), as well as impact wildfire regimes, most likely increasing the risks of more frequent and severe fires. Moreover, changes in vegetation will affect carbon-rich permafrost soils and the absorption of solar energy by the land surface in ways that can accelerate global warming.

 “To minimize adverse impacts of climate change, efforts are needed to dramatically reduce greenhouse gas emissions, especially related to fossil fuel consumption and deforestation. Furthermore, northern communities need to plan for potential changes in vegetation that could impact resource availability (e.g. wildlife, timber) and wildfire risk,” Professor Berger concluded. 

The study is published in the journal Global Change Biology.

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By Andrei Ionescu, Earth.com Staff Writer