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In the Arctic, Extreme Air Pollution Kills Trees, Limits Growth by Reducing Sunlight

Study area of high tree mortality associated with industrialization at Norilsk.  Photo courtesy of Alexander Kirdyanov. Madison, WI, September 29, 2020 - An international team of scientists that includes a USDA Forest Service scientist based in New Hampshire used tree rings to document how “Arctic dimming,” the interference with sunlight caused by extreme pollution such as that at an industrial complex in northern Siberia, is killing trees and possibly affecting how trees respond to climate change.

The study, “Arctic Dimming and the Divergence Problem,” was published this week by the journal Ecology Letters. Kevin T. Smith, a supervisory plant physiologist with the Forest Service’s Northern Research Station, is the sole North American co-author of the study; lead author is Alexander V. Kirdyanov of the University of Cambridge in the United Kingdom.

The research team used dendroecology, dendrochemistry, and process-based forward modelling to explore the relationship of tree growth and mortality with industrial pollution at the Norilsk mining complex in northern Siberia; the complex is regarded as the most heavily polluted site on Earth. Their study describes the spatial and temporal dimensions of massive tree mortality associated with development of the industrial complex.

The study also sought to explain “The Divergence Problem,” a phenomenon in which scientists observed a surprising decline in tree growth despite increasing temperatures – normally a positive catalyst for tree growth – in the Arctic. They attribute the breakdown of the correlation between tree growth and climate in northern latitudes to “Arctic dimming,” the loss of direct sunlight available for photosynthesis due to interference by aerosol pollutants from Norilsk and other industrial centers in the Northern Hemisphere.

“Forests encircling the Arctic are important for a number of reasons, including their role in shaping the planet’s carbon cycle and climate system,” Smith said. “This study demonstrates the enormous scale of forest-atmosphere-industrial interactions, and it also demonstrates how much we can learn about trees and future of forests from the ecological and chemical history we find in tree rings.”


The mission of the Northern Research Station is to improve people's lives and help sustain the natural resources in the Northeast and Midwest through leading-edge science and effective information delivery.


The mission of the U.S. Forest Service, an agency of the U.S. Department of Agriculture, is to sustain the health, diversity and productivity of the nation's forests and grasslands to meet the needs of present and future generations. The agency manages 193 million acres of public land, provides assistance to state and private landowners, and maintains world-renowned forestry research and wildland fire management organizations. National forests and grasslands contribute more than $30 billion to the American economy annually and support nearly 360,000 jobs. These lands also provide 30 percent of the nation's surface drinking water to cities and rural communities; approximately 60 million Americans rely on drinking water that originated from the National Forest System.


USDA is an equal opportunity provider and employer. To file a complaint of discrimination, write to USDA, Assistant Secretary for Civil Rights, Office of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, S.W., Stop 9410, Washington, DC 20250-9410, or call toll-free at (866) 632-9992 (English) or (800) 877-8339 (TDD) or (866) 377-8642 (English Federal-relay) or (800) 845-6136 (Spanish Federal-relay).

Last modified: September 29, 2020