Forests Affect the Amount of Mercury Pollution in Fish

The amount of tree cover around a lake may be more responsible for mercury in fish than contaminated rain or snow.

By the editors of Park Science magazine

About this article

This article was originally published in the "Research Roundup" section of Park Science magazine, Volume 39, Number 1, Winter 2024-25 (January 15, 2025).

Mills Lake in Rocky Mountain National Park.

Image credit: © Jessica Weinberg McClosky. Used by permission.

Mercury is a natural element, but excess levels can enter the environment through air pollution or industrial discharges. Mercury can build up to toxic levels in animals like insects and fish, affecting human and ecosystem health. A team of scientists from the U.S. Department of the Interior studied mercury levels in fish from lakes in high-elevation U.S. national parks. They reported their results in the December 2024 issue of Science of the Total Environment. They found evidence that something else besides pollution through precipitation was influencing how much mercury ended up in these lakes.

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The researchers discovered that fish in lakes with more evergreen forests around them had more mercury. This suggests that the forest surrounding a lake can influence how much mercury gets into the lake. How this happens isn’t yet clear. But the study authors think the amount of tree cover may be more responsible for mercury in fish than contaminated rain or snow. This means that forces that change the forest, like wildfires and beetle kill, could change how mercury affects aquatic life.

Flanagan Pritz and others. 2024. Forest Cover Influences Fish Mercury Concentrations in National Parks of the Western U.S. Science of The Total Environment 955: 176936.