If a Tree Falls: Human Impacts on Forest and Park Trees

Forests are natural, wild places. Trees burn, blow down, mature, and regenerate on their own.

At the same time, forests have fingerprints of Homo sapiens all over them. If you know how to look, a stroll through Frick Park’s shady paths can highlight just how human actions have molded one very visible part of the park forests: the trees.

eastern hemlock magnified

An eastern hemlock attacked by hemlock woolly adelgid.

Dude, where’s my hemlock?

You could scour Frick Park and never come across white pine (Pinus strobus) or our state tree, the eastern hemlock (Tsuga canadensis). Until the 19th century both species were common throughout the state, but as the region industrialized, lumber companies prized these trees for their uses in tanning and construction and they disappeared from much of their former ranges. The result? The number of places in Pennsylvania where massive old-growth stands of white pine persist can be counted on your two hands. Afterwards, when forests began to regenerate, conditions did not always favor the return of these former giants.

If you do see a white pine or eastern hemlock in Frick (and there are a few of each), it was likely planted relatively recently by Parks Conservancy staff and volunteers. Much like logging these species, reforesting requires human labor.

A century later: Cherries

Though white pine and eastern hemlock have fared poorly in our forests over the last 200 years, the forests that regenerated after logging actually benefited other trees. Black cherry (Prunus serotina) is one of these. North of Pittsburgh, in the Allegheny Plateau, it is estimated that black cherry trees made up less than 1% of the pre-logging forest. After extensive clear-cutting in the late 19th century, however, black cherry became a common part of the new forest that regrew there thanks to preference for sunny conditions and fast growth.

The same is true in Frick Park. Easily identifiable by their dark bark that looks like burnt potato chips or corn flakes, black cherries are common these days. You can find a large number of them where there once was a country club (now in the area where Riverview and Bench trails run). After the club’s annexation to Frick in the 1920s, forests regrew on these lands with black cherries. Some of these trees are actually now dying, as the species’ mortality typically increases after 80-100 years.

Tagging Tree 2

Phil Gruszka, Parks Management and Maintenance Director, tagging a dead ash tree.

Invasive species, world travelers

Dead trees can also illustrate how humans have shaped our forests. Since 2007 when it was first detected in Pennsylvania, emerald ash borer (EAB), a tiny green invasive insect, has left a path of destruction across Allegheny County, killing nearly all area ash trees (Fraxinus var.) in just a few years. The evidence is all over Frick Park, with standing and fallen dead ash trees exhibiting the tell-tale scars where EAB larva chewed through the trees’ energy-rich cambium, girdling them.

Globalization not only redistributes products, money, and people around the world, but also non-native plants, animals, and fungi, sometimes in ways that reshape our parks. EAB, for example, likely arrived in the U.S. in a shipping pallet from Asia. This pest, however, is not the first invasive species to change our forests. In the early 20th century, chestnut blight, a fungus accidentally introduced from Asia, killed virtually all American chestnut trees, a species then common throughout the eastern U.S.

Trees on the move (and we’re not talking Ents)

Frick Park’s forests will keep changing as a result of human influence. In addition to the risk of future invasive species, anthropogenic (human-induced) climate change promises big shifts for park trees. Just walk Rollercoaster Trail on the hills between Fern Hollow and Falls Ravine and look out on the sea of young sugar maples (Acer saccharum) that dominate the forest understory.

According to the U.S. Forest Service’s Climate Change Atlas, sugar maples will likely become significantly less important across Pennsylvania as the climate warms and stresses this species, eliminating it from the southerly parts of its range. More heat-tolerant trees may ultimately replace sugar maples in Frick Park and elsewhere in the state.

Learning from the past

Recognizing human fingerprints on our forests gives us opportunity to learn from the mistakes and successes of past generations. How can we leave fingerprints that will improve forest health? Parks are planned spaces, cared for by the people that use them. The team at the Pittsburgh Parks Conservancy is constantly on the watch for invasives like the Asian longhorned beetle and oak wilt and replanting diverse, resilient species of trees to create strong forests that will be around for generations to come.

Kevin C. Brown is an educator with the Parks Conservancy, and a researcher-writer of a National Park Service-funded history of the Devils Hole pupfish, an endangered desert fish that lives in Death Valley National Park. You can read more about his work here.

11 Things You Didn’t Know About Mellon Square: Part 1

Walking into Downtown Pittsburgh’s “elegant outdoor living room,” as Mellon Square was called by architectural historian James van Trump, it’s easy to see why it’s such a well-loved greenspace. Sixty years after it’s original opening, Pittsburghers are just as excited for the grand reopening next week.

Beyond the welcoming feel of this vibrant park, Mellon Square has an exceptionally unique history. Did you know that the Square is located over a prehistoric stream? That it’s a Mad Men masterpiece? That sea lions were a part of some of the early plans?

As we count down the days to the Square’s grand rededication, join us in digging into historic Mellon Square. (Many thanks to Parks Curator Susan Rademacher for providing the information below!)

1. Mellon Square was radical green infrastructure

Image from www.lifeprint.com.

Pittsburghers, sorry to tell you, but the American Sign Language sign for our city was decided during some of our filthiest years. The sign for Pittsburgh is the gesture for dusting dirt off of your shoulder — and we don’t mean in the Jay-Z kind of way. Presumably, in the way that steel workers, city workers, and just about everyone dusted themselves off after a day in the sooty air.

In addition to the dismal air quality, Pittsburgh had the kind of traffic that would turn the Golden Triangle into a nightmare on the daily. A comprehensive traffic study identified the block that now houses Mellon Square as an ideal location for a parking garage. Thinking big, Richard K. Mellon had a better idea — put those unsightly parking spaces underground, and give the people of Pittsburgh greenery, space, and a place to enjoy their city. With Mellon’s decision, the first modern garden plaza on a parking garage was born.

before Mellon Square

Existing buildings and parking had to be removed for the construction of Mellon Square. Photo courtesy Historic Pittsburgh Image Collections, circa 1951.

aerial MlSq

An aerial shot of the completed Mellon Square. Photo courtesy Historic Pittsburgh Image Collections, circa 1955.

2. Strong women shaped the Square

Like so much of Pitttsburgh’s park history, wise women played an influential role in shaping Mellon Square. Two in particular — Sarah Mellon Scaife and Constance Mellon — had a direct pipeline to Richard King Mellon while he was dreaming up Mellon Square.

the girls

Sarah Mellon Scaife (left). Constance and Richard K. Mellon (right).

While staying at the William Penn Hotel on one trip to Pittsburgh, Constance Mellon, Richard’s wife, couldn’t even see the Mellon Bank Building across the street because of the smog. She urged him to do something, or no businessperson (or his wife, for that matter) would want to live in a city that was so heavily polluted.

Sarah Mellon Scaife, Richard’s sister, was not impressed with the initial paving design — a plain rectangular pattern — for the Square. After visiting Venice’s St. Mark’s Square, she returned to challenge the Mellon Square designers to come up with a more intriguing pattern. And thus, the iconic terrazzo pavement that resonated with the nearby ALCOA building (now the Regional Enterprise Tower) came to be.

3. What lurks beneath…

Fundamentally, the six stories of parking was built atop a prehistoric stream bed. The stream bed predicated where all of the support structures were placed and determined where to put the trees and heavy loads on the plaza. Looking at the Square from a birds-eye vantage, you can get a rough sense of where the stream was by where the trees are planted.


Construction of the garage and Square. Photo courtesy Historic Pittsburgh Image Collections, circa 1954.


The Square at the time of restoration groundbreaking. Photo by John Altdorfer, 2011.

4. Nine-of-a-kind basins

Have you ever taken a good hard look at the nine gorgeous bronze basins in the Square? These 3,500-pound behemoths are reportedly the largest basins cast as one single piece. It’s common in bronze casting to create pieces in multiple casts before welding them all together. The basins in the Square were made up of one cast, which by today’s safety standards would not be allowed. And so, these are reportedly the largest single bronze basins ever cast.

Refurbishing these basins during the Square’s restoration was no small feat. Moved with great care to Matthews International where they were cast, all nine basins are back to their original splendor. Read more about that here.

Bronze Basins from Matthews_3

Finishing the surface of one of the nine bronze basins for Mellon Square. Image courtesy Matthews International.


Positioning the last basin after its repair and refinishing by Matthews International.

5. Classy and sophisticated

When opened, Mellon Square had a quintessential Mad Men style. A promenade for men in flat-brimmed fedoras and ladies in white gloves, Mellon Square provided the perfect backdrop for classy Downtown gentlepeople. Designed by the distinguished firms Mitchell & Ritchey and Simonds & Simonds, Mellon Square has been named one of America’s Ten Great Public Spaces.


Mellon Square after opening. Photo courtesy Historic Pittsburgh Image Collections.

With the rededication of the Square next week, we’re looking forward to this restored image of classic glamour, Downtown’s emerald oasis. We hope you’ll join us in celebrating this gem being polished back to its dazzling splendor!

For more information about the rededication, visit our website and check back here next week as we finish off the list of Mellon Square things to know!

Content for this blog was adapted from a presentation by Parks Curator Susan Rademacher.

From Hill to Hollow: The Evolution of Panther Hollow Watershed

This guest post comes from Krissy Hopkins, a graduate student in the Department of Geology and Planetary Science at the University of Pittsburgh. Krissy has been getting her feet wet in the Panther Hollow Watershed and contributing her research skills to the Pittsburgh Parks Conservancy  for years.

Krissy exploring Panther Hollow Run in Schenley Park.

For the past three years I’ve fixated on learning as much as I can about the Panther Hollow Watershed, which includes parts of Schenley Park and Squirrel Hill. How many people live in the watershed? How many buildings are there and when were they built? When rain falls on the watershed where does it go? Where does the water in Panther Hollow Lake go? I want to know how this landscape changed over the last century.

This may seem like an odd fascination. However, to a graduate student studying how urbanization impacts aquatic ecosystems it is spot on. My research uses a bit of detective work to understand how people change the land and how our decisions impact the health of local streams and rivers.

Pittock Street at Phipps Avenue in Squirrel Hill was built in 1910. Today, houses and large trees line the same stretch of street. Krissy’s research found that Panther Hollow’s residential tree canopy expanded from 21% canopy cover in 1938 to 40% canopy cover in 2010.

My latest research project reconstructs the expansion of development in Panther Hollow since 1870 and estimates how this development has impacted Schenley Park’s streams. Using historical maps, aerial photographs, and U.S. Census records, I created a series of maps for each decade since 1900 showing the location of roads, buildings, and sewer lines in the Panther Hollow Watershed. To assess the impact of development on the streams, I developed a simple model to predict changes in the amount of water flowing through the streams in Panther Hollow since 1900. Results from this project were recently published in the journal Landscape Ecology.

The Panther Hollow watershed has changed dramatically over the last century. In 1987, just five families owned land in the watershed. Today, about 3,400 people call the watershed home.

My research shows that roads and rooftops covered only 3% of the watershed area in 1900. These surfaces now cover 27% of the land area — a big change! Prior to 1900, the watershed was an agricultural landscape with seven large lots containing only 29 buildings. Panther Hollow’s streams flowed west through the Squirrel Hill neighborhood into Schenley Park, eventually draining through Junction Hollow to the Monongahela River. Two main dirt roads (Forbes and Shady) ran through the eastern portion of the watershed. Residents disposed of sewage in pit-style outhouses and obtained drinking water from local streams.

A transition from agriculture to urban land use occurred between 1890 and 1920. Development was concentrated in the eastern half of the Panther Hollow Watershed, while the lower watershed remained part of Schenley Park. Between 1890 and 1911, approximately 10 miles of brick and clay sewer pipes and 6.5 miles of roads were installed in the watershed.

Workers building a 36-inch brick sewer in Schenley Park in 1911. Photo courtesy Pittsburgh City Photographer Collection.

To make room for development, the streams through Squirrel Hill were piped into the sewer system and diverted out of the watershed through a sewer main along Greenfield Avenue. As a result, the streams in the eastern half of the watershed no longer feed the Schenley Park streams. The watershed was cut in two! The remaining above-ground streams in Schenley Park have about 50% less water flowing through them every year. Sometimes in the summer months these streams have little to no water flowing through them — bad news for aquatic life that call the stream home.

Panther Hollow Lake drains into the combined sewer systems. In 2012, 82 million gallons of water from Panther Hollow Lake drained into the sewer system.

Schenley Park has also changed. Around 1904, Panther Hollow Lake and a pipe connecting the lake to the sewer system were constructed. Now, even the remaining above-ground streams eventually flow into Pittsburgh’s combined sewer system. The system channeled raw sewage, street runoff, and stream water directly into the Monongahela River until 1959. That year, the city installed sewer mains along the river to collect sewage to be sent to the new treatment plan along the Ohio River. However, when it rains the pipes are too small to hold all the water, causing excess water and sewage to flow into the rivers to this day. In 2010, 11 billion gallons of sewage and stormwater flowed into the Pittsburgh’s rivers!

As the Pittsburgh Parks Conservancy continues to work on restoring the Panther Hollow Watershed, research like mine helps them better understand how development impacts the ecosystem. Knowledge of past impacts can help better target restoration efforts in the future and restore this watershed back to health.

Krissy Hopkins

To learn more about Krissy’s research in Panther Hollow, visit her blog. For more information on Panther Hollow Watershed restoration, visit our website

Give Me Shelter: Riverview Park Evolves

Since I have fun compiling them and it seems like you folks have fun reading them, today it’s time for another history post.  This time we’re shining a spotlight on the development of Riverview Park.  In looking back through old photos and documents, it seems that in some ways the story of Riverview is a story of shelters.  Many of the buildings in the park either started as or became shelters, with a common thread of people using the park to gather together.  Here’s a look at some of those shelters (with some other buildings thrown in for good measure).  Click the photos for larger versions.

Perhaps the building we talk about most in Riverview Park is the Chapel Shelter, which was at the top of our priority list for quite a while thanks to our 2008 restoration project.  It was likely one of only two buildings within the park’s boundaries on July 4, 1894, when Riverview Park was officially dedicated (only a few days after the land had been acquired).  1894 was the year that a new Watson Presbyterian Church was built on the site of the present-day Riverview Presbyterian Church; thus, it’s probably the year that the original church building was moved and converted into a picnic shelter. 

This undated photo was given to us by a woman who attended the rededication ceremony of the Chapel Shelter, and it shows the building in its original location.  You can see the familiar steeple and dormers in the small building in the right foreground of the photo.  I’ve always wondered what those two other magnificent-looking buildings are in the background, and whether the smaller building at left is the new church under construction.

Chapel Shelter original

As you can tell from this photo we recently unearthed, the Chapel Shelter’s longtime status as the most popular building in the Pittsburgh park system has been thanks to the many groups who have embraced it as a gathering space.

Chapel Shelter gathering 1930s

Before the restoration project converted it back into a lawn, the area behind the Chapel was home to some rundown tennis courts.  Recreation was a little more active in the Chapel’s earlier years too, although technically this area was still a lawn—it was just referred to as a “play terrace” with swings!

Chapel Shelter Play Terrace

The other building that existed when Riverview Park was dedicated was Watson’s Cabin.   This log cabin probably dates back to the early 1800s.  Like much of the land in Riverview Park, the cabin was owned by Samuel Watson, a member of one of the original families of the City of Allegheny (which was annexed by Pittsburgh in 1907).  Before it was a park, the property was largely open land that Watson rented to  dairy farmers—a far cry from the current forested landscape!  The log cabin eventually was converted into the Girl Scout Headquarters and into a shelter, and it played host to small groups of Scouts on overnight camping trips.  Eventually, it was destroyed by fire but its ruins remain on site. 

Watson's Cabin

The first structure to actually be built within the park was likely the zoo, which went up sometime around 1896 at the foot of what would come to be known as Observatory Hill.  Coming up Riverview Avenue into the park, visitors would pass refreshment stands, and further down the slope was an aviary.  The zoo itself featured a flying cage, an elk paddock, and other native animals.  It also had a bear pit, whose floors were later used in the construction of a picnic shelter, aptly named “The Bear Pit.”  After 1910 the Highland Park Zoo began drawing crowds away, and the zoo was eventually shut down.

Riverview Zoo

The next construction project brought Riverview Park its signature structure: the Allegheny Observatory.  Begun in 1900, the building was constructed because the original observatory along Perrysville Avenue was having its views blocked by Pittsburgh’s industrial pollution.  With its new position atop the park’s natural hill, the visibility was better.  Thorsten Billquist was the architect for the new building, incorporating Greek Ionic columns and Roman balustrades.  This early-20th-century postcard shows a view from behind the Observatory, one that’s hard to envision for those of us who have visited this century and know this area as densely forested.  I wonder if, standing in the same spot today, you’d even be able to make out the top of the building over the trees.

Allegheny Observatory

Another postcard from this era shows a more-familiar view from the front side of the building.  The entrance steps were simpler then, but otherwise the basic layout resembles what you’d see today.

Allegheny Observatory

You can read more about the history of the Observatory and the many research advancements made there at this website.    

1913 was a boom year for construction in Riverview Park.  A cabin shelter was built that year in the northern end of the park, but its location made it difficult for planned gatherings because of poor vehicular access.  In the early 1920s, it was converted into the Wissahickon Nature Museum and was a highly popular attraction until it was eventually lost to arson. 

Wissahickon Nature Center

Here’s a view of the cabin from the inside.

Wissahickon Nature Center interior

Also in 1913, a building housing a carousel was built.  Designer Thomas Scott was at work in many of Pittsburgh’s parks around this time, and based this design on his work on the Schenley Park merry-go-round across town.  The carousel was used until 1938, when the machinery became too old to be serviced.  The building was later used as a shelter and game room.


This earlier view shows the carousel’s location, close to where today’s Activities Building sits.

Carousel 1915

Another period of wide park improvement was in the late 1930s and early 1940s, when Ralph Griswold was Pittsburgh’s Parks Director and funds for construction were available through the Works Progress Administration.  Griswold was the first landscape architect hired by the City of Pittsburgh, and he served as the Superintendent of the Bureau of Parks in this era while independently working to develop plans for Point State Park.  One of the projects he spearheaded was the main park entrance, which was completed in 1941.  Griswold designed the entrance garden and stone fountain, and a park office (today’s Visitor Center) was built alongside.

Riverview entrance

Other features dating back to the WPA era include the two bus shelters (originally trolley shelters) along Perrysville Avenue and their accompanying stone stairways that lead into the park’s trail system.

Have any Riverview memories to share?  Feel free to post a comment!