The evolution of nature in Southwestern Pa.

When I was a boy, my dad, knowing my infatuation with the Disney Davy Crockett TV series would take me for walks in the woods and tell me, “It was just like this when ol’ Davy went through here!” My dad’s enthusiasm for history far exceeded his knowledge.

It wasn’t until years later that I learned that Davy Crockett never set foot in Western Pennsylvania until he was a middle-aged congressman. I also learned that our local woods were very different in Crockett’s times.

This month’s column will look at some of the differences between the forest and rivers of the Mon Valley today and 250 years ago when the first European pioneers settled here.

One of the things I like about living in Southwestern Pennsylvania is how green this area is. Our hillsides and valleys are blanketed with trees. Our contemporary woods make it hard to believe that, at one time, almost every inch of Pennsylvania’s original forests were clear-cut. The land was cleared for farming, and many trees were cut to make charcoal for the state’s early iron furnaces. In addition to lumber, potash was a major export of our state. Potash, the ashes created by burning wood from our forests, was shipped to Europe to fertilize its worn-out soils.

Vintage photos of the Mon Valley dating from the early 1900s to the 1950s show barren hillsides and eroded soil.

Foresters estimate that less than one-half of 1% of Pennsylvania’s trees predate the 20th century. In the life cycle of the forest, our local woods are in their “adolescence.” To get a sense of what the “old growth” forests that greeted the pioneers were like, one can visit one of the few forest groves that escaped the loggers’ axes. These include the “Forest Cathedral” in Cook’s Forest State Park, and “Heart’s Content” in the Allegheny National Forest.

Visiting these places, the first thing you notice is the size of the trees. Many are 140 feet tall and 40 or more inches in diameter. This is representative of the trees that were here in the 1770s.

The average age of the trees in Heart’s Content is around 400 years old. Walking through the area felt stepping on a mattress; the ground was covered with thick layers of forest loam that built up over the centuries. Early settlers in this area talked about the richness of the soil in their nearly cleared fields and that one could easily push their arms into the untilled soil up to the elbow. Much of this richness was lost over the centuries to poor agricultural practices and erosion.

Whenever I visit one of the old-growth forest remnants I always stop and take a deep breath. Old-growth forests have a deep, earthy and rich aroma that is invigorating.

The virgin forests were a mix of hardwood and softwood species These included white pines, hemlocks, oaks, chestnuts, beeches, maples, poplars, gum trees, yellow pine and pitch pine. The forests the early settlers found here were the result of 8,000 years of evolution. The forest was comprised of trees of many ages that had evolved together over the centuries.

The wholesale cutting of trees changed the mix of trees in the forest. Fastergrowing trees like black cherries took over from the slower-maturing species like hemlocks. Meanwhile, imported trees like sumacs forced out native species. In recent years, local conservation groups have been trying to reverse this trend. The Allegheny County Land Trust which manages the Deadman’s Hollow Conservation area along the GAP trail, has been removing invasive species from its property and replacing them with native hemlocks in an attempt to return the hollow to its original balance.

Over the years, many varieties of trees have disappeared from our forests.

Early pioneers relied on native chestnut trees for food and lumber. Rot-resistant chestnut wood was used to build log cabins and barns, and the nuts were consumed by both humans and livestock. In the early 1900s, chestnut blight began killing off the American chestnut.

It is believed that wooden crates made from European chestnut lumber brought the disease to North America.

Lacking resistance to the blight, the native chestnut virtually disappeared from the entire continent.

In later years, similar diseases wiped out or severely limited the number of many native tree species such as ash trees, beeches, hemlocks and butternuts. Over the decades, our ash trees were attacked by the emerald ash borer, the woolly adelgid attacked the needles of our state tree, the hemlock.

Beech leaf disease caused by a parasitic nematode virtually wiped out that species in the state, and gypsy moth infestations have killed many native oak species. Growing up, my grandfather’s property was covered with butternut trees and my mother made good use of the fall nut crop in her baking. Today, butternuts are virtually extinct, falling victim to butternut canker, a fungal disease.

A number of other factors have impacted the biodiversity of our forests. Over browsing by uncontrolled deer herds limits the types of trees growing in our woodlands. Like humans, deer are picky eaters. Their selective browsing can eliminate their favorite species from the forest and can prevent young trees from reaching maturity.

Climate changes are also presenting challenges to many of our trees. Reduced rainfall affects the health of the forest, leaving the trees even more vulnerable to insect attack and diseases.

Drier forests also increase the risk of brush and forest fires. The Pennsylvania State Department of Conservation and Natural Resources has developed a Climate Change Adaptation and Mitigation plan to deal with an ever more challenging environment. Fortunately, Western Pennsylvania is home to a very resilient ecosystem — if we fail to mow our lawns for a few weeks, it begins to revert to a forest. While our forests will change and evolve, our hillsides and valleys are likely to remain green well into the future.

The rivers that define our area have also undergone significant changes over the last two centuries. George Washington would not recognize the rivers he saw as a highway to the west. The Army Corps of Engineers has transformed our river system into a series of lakes suitable for navigation by building locks and dams. Prior to the construction of these dams in the mid-19th century, our rivers would ebb and flow through the seasons, flooding in the spring and shrinking in the hot summer months.

Early Mon Valley residents could easily walk across the Monongahela and Youghiogheny Rivers in the summertime.

The steamboats that played a big part in the local economy spent months at a time stuck in the mud along the river’s edge. As early as 1817, the Pennsylvania House authorized the building of dams on the Monongahela to improve navigation.

Nine dams were completed in the 19th century, and the Corps of Engineers finally completed the system in 1904. The dams maintain a minimum depth of 9 feet from West Virginia to Pittsburgh.

After the devastating 1936 floods, the Army Engineers took on a new challenge, flood control. Structures like the Yough Dam not only allowed the Corps of Engineers to hold back flood waters, but also gave them the power to maintain a consistent depth in the rivers throughout the year. All this construction and changes in the environment, of course, had a big impact on the riverine ecosystem. Improvements in navigation spurred the growth of industry along our rivers, many of which used them as a sewer where they dumped all manner of toxic substances. Environmental regulations in recent years have cleaned up the rivers.

Rivers that were once “dead” now teem with aquatic life.

In 2005, the Pennsylvania Fish Commission discovered a paddlefish in the Monongahela near Grays Landing in Greene County during a survey of river life. This prehistoric-looking species had not been seen in the river in over a century.

The “hydrology” of the Mon Valley has changed in many other smaller ways.

This area was much swampier than it is today. For centuries, farmers and land developers have been draining marshy areas and burying and channeling streams in the region.

In White Oak where I live, workers building a shopping center unearthed a millstone from the site of a waterdriven mill where no stream now exists. As odd as it may seem, the leading cause of death of early pioneers in Western Pennsylvania was malaria carried by the mosquitoes that bred in the area’s bogs and swamps.

Though the woods and water have undergone many changes over the centuries, some constants remain — they always remain beautiful, interesting and resilient. In my 70-plus years, I have watched a hillside near my home change from a sheep pasture to a field thick with blackberry bushes to a young forest. I find these changes fascinating to watch.

Next month: Changes in the wildlife living in the Mon Valley forests.

Jim Busch of White Oak is a freelance writer for the Mon Valley Independent.