Islands in the Air: The Spruce-Fir Forests of the Great Smoky Mountains

The spruce-fir forest of the southern Appalachians is one of the rarest ecosystems in North America, occurring only at elevations above 4500 feet. Over 70 percent of this ecosystem’s worldwide range exists within the Great Smoky Mountains National Park.

Ten thousand years ago, North America was frozen in an ice age. Mile-thick ice sheets stretched as far south as Ohio and Pennsylvania. Northern species migrated south, into the area around the Smokies. When temperatures warmed, some of these plants and animals moved back north, while others shifted to higher altitudes.

Today, the southern Appalachians are dotted with high-elevation islands of spruce-fir forests, surrounded by an ocean of lowland hardwood forest. Because of this isolation, the spruce-fir forests are home to a number of very rare species, including the red-cheeked salamander and the Rugel’s ratwort, both of which live only in the Smoky Mountains. The peaks of the Smokies also shelter the endangered Carolina northern flying squirrel, as well as the world’s smallest tarantula, the spruce-fir moss spider, measuring about one-eighth inch in length.

Trees damaged by wooly adelgids, near Clingmans Dome

The unique location of the southern spruce-fir forests also presents some unique challenges to their flora and fauna. Species like the Carolina northern flying squirrel, which soars from tree to tree like a hang glider, are completely dependent on the Appalachian highlands. A northward shift in its habitat would be blocked by the central Appalachian area, where peaks are too low to support spruce-fir forests.

Prior to the park’s establishment in the early twentieth century, the old-growth forests were considered prime timber resources. If the land had not been protected, it is possible that most of the spruce and fir trees would have been cut down.

Although the Smoky Mountains are now safe from logging, other factors are threatening the ecosystem. One particularly dangerous problem is the influx of non-native species. For example, the balsam wooly adelgid (ah-DEL-jid), an aphid-like European insect, entered the United States by accident around 1900. Although the adelgid does not greatly harm its European hosts, it devastates trees in North America. The adelgid has killed 95 percent of Fraser firs in the Smoky Mountains. The good news is that the few surviving trees were able to regenerate, and the young firs seem to be thriving.

Pollutants from automobiles and power plants—sulfur dioxide and nitrogen oxides—cause acid deposition, in which precipitation is overly acidic. When water in a stream or lake becomes too acidic, many plants and animals cannot survive. The state of Tennessee lists twelve Smoky Mountain streams as being excessively acidic because of acid rain, fog, and snow. Brook trout have been lost from six streams since 1980 because of acidity.

In 1990, an amendment to the Clean Air Act set up a cap-and-trade program to reduce pollution from coal-burning power plants. The federal government gave companies permits to release a certain amount of pollution. Power plants that produced less pollution could sell extra permits to plants that needed more of them. The goal was to make it profitable for businesses to reduce pollution.

Since the EPA started its Acid Rain Program, acid deposition has become less of a problem. The program reached its goal for reducing sulfur dioxide emissions three years ahead of schedule and at one-fourth of the predicted cost.

Middle Prong of Little River, Great Smoky Mountains National Park, TN


Despite ongoing challenges, the spruce-fir forest of the Smoky Mountains remains one of the most biologically rich habitats in North America. The variety of ecosystems in the park makes it ideal for many plants and animals (in twelve years of studying the Smokies, researchers identified more than 900 new species). Through these discoveries, we can glimpse the sheer scale of biodiversity in North America, and even in the entire earth. Maybe this is one of the most compelling reasons to preserve earth’s life—so we can be spared the tragedy of losing species before we have a chance to appreciate them.


Images © David Rickless. All Rights Reserved.


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