Natural Perspectives: Losing forests to pests in the East

Wherever Vic and I travel, we study the area, searching for environmental stories. Our recent trip to Tennessee yielded a number of interesting tales about eastern forests.

First, we learned that the magnificent forest that we saw in Great Smoky Mountains National Park was fairly recent re-growth. The original forest had been almost all clear-cut by the lumber industry. By the time the park was created in 1934, 80% of the original forest was gone. The lumber went to build the rapidly growing cities of Memphis, Nashville, Indianapolis, Chicago, etc.

Most of the remaining 20% of the forest had been selectively cut, with only the steepest, most inaccessible portions left untouched. The venerable forest giants that would make you marvel at the magnificence of their height and girth were gone by the time the national park was created. While our visit there was a wonderful experience, the knowledge of what was no longer there was sad.

While the forest that we saw was beautiful, it wasn’t the way the early settlers found it. One missing tree species in particular is the American chestnut. Once a dominant species of the Appalachian Mountains, its nuts fed bears, deer, passenger pigeons, Native Americans and early pioneers. Chestnuts were so plentiful that this species comprised 40% of eastern forests.

But in 1904, a fungus from Asia was discovered infecting American chestnuts growing in New York’s Central Park. The fungus was thought to have come into the U.S. in the late 1800s with imported Japanese chestnut trees.

The blight spread rapidly, infecting the bark and killing the trees. From 1900 to 1940, an estimated 3.5 billion American chestnut trees succumbed to the blight. By the 1950s, the American chestnut was functionally extinct. A few surviving trees still sprouted shrubby growth from the base of stumps, but the stems soon became infected. No new nuts formed, and no new trees grew in their original range.

Vic and I lived in a historic house in Connecticut in the 1970s. The house had been built in 1710. It had huge oak beams in the ceiling and chestnut paneling on the walls. The lumbered slabs were 3 and 4 feet across for each panel. Living in a house with nearly 300-year-old wooden chestnut paneling was awesome. It stimulated our interest in the American chestnut tree.

Lumbermen of the 1800s favored American chestnut trees because they grew straight and reached heights of 50 feet before branching out. Many of the trees were 100 feet tall with 10-foot diameters. The boards cut from a single tree could fill an entire railroad car. Chestnut wood was as resistant to rot as redwood, and was more easily worked than oak. The loss of the American chestnut from eastern forests was an economic and environmental catastrophe.

But the chestnut may not be entirely lost. Scientists at the American Chestnut Foundation have been cross-breeding American chestnuts with Chinese chestnuts, a species that is resistant to the blight. There are now hybrids that are seven-eighths American chestnut and one-eighth Chinese chestnut. These hybrids appear to have resistance to the blight. Other scientists are working on isolating the gene that confers resistance to the blight so that it can be inserted into the genome of the American chestnut and save the species.

Another group working to save the tree is the American Chestnut Cooperators’ Foundation. Their approach is to select trees that have more resistance to the blight than others. Trees growing in the northern U.S. and Canada outside the range of the blight have escaped infection. By selective breeding and grafting, they hope to be able to revive the American chestnut. They have planted nearly 200,000 seedlings, some of which they hope will show resistance to the disease.

But chestnut blight isn’t the only imported problem of eastern forests. A more recent invasion is the balsam wooly adelgid, a tiny, wingless, non-native insect that is decimating fir trees in the East. This insect, discovered in the U.S. in 1957, attacks both balsam and Fraser firs. To date, 95% of the Fraser firs within the park have been lost.

The Fraser fir is a species that grows only in the higher elevations of the Smokies and nearby mountains. A number of different mosses and liverworts grow only on Fraser firs, and a particular species of spider lives only on those mosses. If Fraser firs are lost to the adelgids, then the species that live on the firs will also go extinct. The small ecosystem that depends on Fraser firs is at risk.

Crews are hand-spraying trees with a soap emulsion that specifically kills the basalm wooly adelgid, but it is impossible to save an entire forest that way. Biologists are raising seedlings to plant outside the range of the introduced adelgid and freezing other seeds to plant after — or if — the adelgid has been eradicated.

Biologists in the park are battling yet another introduced pest in the eastern forests. In 2002, the hemlock wooly adelgid was discovered there. It has already killed 80% of the hemlocks in the Smokies. When Vic and I visited Clingmans Dome, the highest point in the park, we were struck by the large number of dead trees all around us, all firs and hemlocks killed by invasive pests.

Today’s textbooks no longer use the term “virgin forest” because so little uncut original forest remains. The term “old growth” is used instead. This includes forest that has been logged and that has since re-grown.

America has lost most of its original habitats. Whether that habitat is coastal wetland, prairie, chaparral or old growth forest, the few remnants that have survived need to be protected.

Our habitats are under seemingly constant attack these days from introduced pests and diseases, as well as pressure from humans and global climate change.

There is always an environmental story out there. Sadly, it isn’t usually a happy one.

VIC LEIPZIG and LOU MURRAY are Huntington Beach residents and environmentalists. They can be reached at LMurrayPhD@gmail.com.