Pennsylvania’s Forests: A Wounded Community

Posted: May 29, 2014

In the last twenty or forty years, our forests have experienced a green invasion that does not represent health; the new green shouts to the ecologically educated that all is not well.

In his 1949 A Sand County Almanac, Aldo Leopold, an early environmentalist, wrote, “One of the penalties of an ecological education is that one lives alone in a world of wounds. Much of the damage inflicted on land is quite invisible to laymen.” Leopold was an astute observer of the environment around him and a prolific writer who challenged many norms of his day -- that land and all resources were there for our use without an obligation to the future. He saw that we have an obligation to care for the land and all that depends upon it. He saw humans as part of the ecological community, not separate from it.

In the past few weeks, spring came to Pennsylvania. The forests took on their spring colors -- pastel shades of green and subtle reds, oranges, and pinks. Most noticeable in the spring celebration of colors were early shades of green that only a generation or two ago were not part of our landscape. Back then, the green of spring would have come a little later.

As forests take on their spring green, many people celebrate the end of winter. However, as Leopold noted, those with an “ecological education” see the wounds that are “invisible to laymen.” In the last twenty or forty years, our forests have experienced a green invasion that does not represent health; the new green shouts to the ecologically educated that all is not well.

What is wrong with the new green? If you take the time to look and learn, you would soon learn that much of the earliest green you see, especially in and near the urbanized parts of the state, are exotic invasive plants. Many of these plants were purposefully brought from foreign lands and distant places to decorate our lawns and landscapes or to protect soil and streams. However, in many cases what seemed good has gone strangely awry.

On a recent trip to southeastern Pennsylvania, it was too easy to see all the Norway maples populating the sylvan landscape. Their strong, yet soft, green was pronounced and it was everywhere. Once confined to our lawns and streets, Norway maple is nearly ubiquitous. What is the problem? Well, no insects eat its leaves, so it does not feed birds. It cast heavy shade, and nothing grows under it. When it falls in autumn, its foliage smothers other plants and then quickly decays. It does not protect soil from rain and erosion. It takes away much more than it gives back. We could use native trees for our shade needs.

Look into the edge of woods near you and wonder what plants fill in beneath the forest canopy. Or, consider that abandoned field that has taken on a blanket of shrubs in just a few years. At first, all seems right with the world. If you understand the ecological health, you would wonder about those shades of green. Careful inspection, all too often, finds invasive plants. The strong and vibrant green of Japanese barberry is easy to spot. The winding and twisting vines of Oriental bittersweet reach into tree and forest canopy. Autumn and Russian olive leaves twist in spring breezes and show their silvery and mottled undersides. There are many unwanted newcomers that tell a story about ecological health -- Eurasian privets, Morrow's and Amur bush honeysuckles, Japanese honeysuckle vines, multiflora rose, garlic mustard, Japanese stilt grass, all fill in and compete with our rapidly disappearing native shrubs and vines.

You might wonder how these newcomers achieve ecological success. First, they do green up early. This gives them a jump on native plants. By catching and using light sooner than native plants, they have a chance to expand their leaves and take away light that would benefit native plants. Second, many of them are not palatable to native herbivores (think deer and rabbits) or insects. When nothing chews on the foliage and twigs, but eats the struggling native plants, the invasive species gain an upper hand.

As we lose native plants, our woodlands and forests do suffer wounds. As suggested earlier, many of newcomers give nothing back ecologically. If nothing eats their foliage, then the plants are not part of the food chain. If the foliage does not support an abundance of insects, then many bird species fail to fledge their young. If the foliage decays too quickly or too slowly, it upsets fungal communities. If they cast heavy shade on the forest floor or in old fields, then native plants fail to compete. It is a vicious cycle that is creeping across the landscape.

If you want to improve the health of our woodlands, there are a few things you can do. First, learn about our native plants. Do not plant exotic invasive plants around your home – seek out plants native to where you live. When you find a plant that seems to be gaining an advantage, maybe it greens up way earlier than other plants in your area, identify it. If it is a likely problem, address it early and swiftly. The more you learn and know, the more visible your landscape and its health will become.

Help keep Pennsylvania clean and green with native plants.

The Pennsylvania Forest Stewardship Program provides publications on a variety of topics related to woodland management. For a list of free publications, call 800-235-9473 (toll free), send an email to, or write to Forest Stewardship Program, Natural Resources Extension, The Pennsylvania State University, 416 Forest Resources Building, University Park, PA 16802. The Pennsylvania DCNR Bureau of Forestry and USDA Forest Service, in Partnership with Penn State’s Department of Ecosystem Science and Management, sponsor the Forest Stewardship Program in Pennsylvania.